Journal articles on the topic 'Northern Diurnal variations'
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He, Huizhong, and Fuqing Zhang. "Diurnal Variations of Warm-Season Precipitation over Northern China." Monthly Weather Review 138, no. 4 (April 1, 2010): 1017–25. http://dx.doi.org/10.1175/2010mwr3356.1.
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Abstract This study examines the diurnal variations of the warm-season precipitation over northern China using the high-resolution precipitation products obtained from the Climate Prediction Center’s morphing technique (CMORPH) during May–August of 2003–09. The areas of focus are the Yanshan–Taihangshan Mountain ranges along the east peripheries of the Loess and Inner Mongolian Plateaus and the adjacent North China Plains. It is found that the averaged peak in local precipitation begins early in the afternoon near the top of the mountain ranges and propagates downslope and southeastward at a speed of ∼13 m s−1. The peak reaches the central North China Plains around midnight and the early morning hours resulting in a broad area of nocturnal precipitation maxima over the plains. The diurnal precipitation peak (minimum) is closely collocated with the upward (downward) branch of a mountain–plains solenoid (MPS) circulation. Both the MPS and a low-level southwesterly nocturnal jet are likely to be jointly responsible for the nighttime precipitation maxima over the plains.
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Huang, Fangfang, and Weiqiang Ma. "Analysis of Long-Term Meteorological Observation for Weather and Climate Fundamental Data over the Northern Tibetan Plateau." Advances in Meteorology 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/4878353.
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Meteorological observation plays a critical role in climatic study, and in situ measurements are the foundation of meteorological observation, especially in the Tibetan Plateau, the surface of which is fairly complex. Several field stations in the Northern Tibetan Plateau, which features relatively homogeneous surface, were selected as the study area. A detailed description on the significance of site observation for climate prediction was given in this paper. Data from weather stations can be used to verify satellite data and provide parameters for initial mode field in the study of weather and climate changes. The field observation data in the Northern Tibetan Plateau from 2001 to 2013 is analyzed. The results show that in El Nino year, values of land surface temperature (Ts), air temperature (Ta) and wind speed are all greater than their mean values and that soil moisture values are lower than the averaged, while the opposite is the case in La Nina year. The warming rate in the Northern Tibetan Plateau is greater than that in global areas. The diurnal variations ofTsandTaare various in different seasons and underlying surfaces, with the diurnal variations greater in spring, and less in summer and autumn. Furthermore, the diurnal variation in the area with drier underlying surface is more obvious than that in area with moist surface.
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Cheng, Yueming, Tie Dai, Jiming Li, and Guangyu Shi. "Measurement Report: Determination of aerosol vertical features on different timescales over East Asia based on CATS aerosol products." Atmospheric Chemistry and Physics 20, no. 23 (December 10, 2020): 15307–22. http://dx.doi.org/10.5194/acp-20-15307-2020.
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Abstract. The Cloud-Aerosol Transport System (CATS) lidar, on board the International Space Station (ISS), provides a new opportunity for studying aerosol vertical distributions, especially the diurnal variations, from space observations. In this study, we investigate the seasonal variations and diurnal cycles in the vertical aerosol extinction coefficients (AECs) over East Asia by taking advantage of 32 months of continuous and uniform aerosol measurements from the CATS lidar. Over the Tibetan Plateau, a belt of AECs at approximately 6 km between 30 and 38∘ N persistently exists in all seasons with an obvious seasonal variation. In summer, the aerosols at 6 km are identified as a mixture of both anthropogenic aerosols transported from India and coarse dust particles from Asian dust sources. In addition, the high AECs up to 8 km in summer over the Tibetan Plateau are caused by smoke aerosols from thermal dynamic processes. In fall and winter, the northern slope of the plateau is continuously influenced by both dust aerosols and polluted aerosols transported upslope from cities located at lower elevations in northwestern Asia. The diurnal variation in AECs in North China is mainly related to the diurnal variations in the transported dust and local polluted aerosols. Below 2 km, the AEC profiles in North China at 06:00 and 12:00 CST (China standard time) are significantly higher than those at 00:00 and 18:00 CST, reaching a maximum at midday. The aerosol vertical profiles over the Tarim Desert region in summer have obvious diurnal variations, and the AECs at 12:00 and 18:00 CST are significantly higher than those at 00:00 and 06:00 CST, which are induced by the strong diurnal variations in near-surface wind speeds. In addition, the peak in the AEC profiles has a significant seasonal variation, which is mainly determined by the boundary layer height.
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Zhang, X., K. R. Gurney, P. Rayner, D. Baker, and Y. P. Liu. "Sensitivity of simulated CO2 concentration to sub-annual variations in fossil fuel CO2 emissions." Atmospheric Chemistry and Physics Discussions 15, no. 14 (July 31, 2015): 20679–708. http://dx.doi.org/10.5194/acpd-15-20679-2015.
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Abstract. Recent advances in fossil fuel CO2 (FFCO2) emission inventories enable sensitivity tests of simulated atmospheric CO2 concentrations to sub-annual variations in FFCO2 emissions and what this implies for the interpretation of observed CO2. Six experiments are conducted to investigate the potential impact of three cycles of FFCO2 emission variability (diurnal, weekly and monthly) using a global tracer transport model. Results show an annual FFCO2 rectification varying from −1.35 to +0.13 ppm from the combination of all three cycles. This rectification is driven by a large negative diurnal FFCO2 rectification due to the covariation of diurnal FFCO2 emissions and diurnal vertical mixing, and a smaller positive seasonal FFCO2 rectification driven by the covariation of monthly FFCO2 emissions and monthly atmospheric transport. The diurnal FFCO2 emissions are responsible for a diurnal FFCO2 concentration amplitude of up to 9.12 ppm at the grid cell scale. Similarly, the monthly FFCO2 emissions are responsible for a simulated seasonal CO2 amplitude of up to 6.11 ppm at the grid cell scale. The impact of the diurnal FFCO2 emissions, when only sampled in the local afternoon is also important, causing an increase of +1.13 ppmv at the grid cell scale. The simulated CO2 concentration impacts from the diurnally and seasonally-varying FFCO2 emissions are centered over large source regions in the Northern Hemisphere, extending to downwind regions. This study demonstrates the influence of sub-annual variations in FFCO2 emissions on simulated CO2 concentration and suggests that inversion studies must take account of these variations in the affected regions.
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Zhang, Xia, Kevin R. Gurney, Peter Rayner, David Baker, and Yu-ping Liu. "Sensitivity of simulated CO<sub>2</sub> concentration to sub-annual variations in fossil fuel CO<sub>2</sub> emissions." Atmospheric Chemistry and Physics 16, no. 4 (February 19, 2016): 1907–18. http://dx.doi.org/10.5194/acp-16-1907-2016.
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Abstract. Recent advances in fossil fuel CO2 (FFCO2) emission inventories enable sensitivity tests of simulated atmospheric CO2 concentrations to sub-annual variations in FFCO2 emissions and what this implies for the interpretation of observed CO2. Six experiments are conducted to investigate the potential impact of three cycles of FFCO2 emission variability (diurnal, weekly and monthly) using a global tracer transport model. Results show an annual FFCO2 rectification varying from −1.35 to +0.13 ppm from the combination of all three cycles. This rectification is driven by a large negative diurnal FFCO2 rectification due to the covariation of diurnal FFCO2 emissions and diurnal vertical mixing, as well as a smaller positive seasonal FFCO2 rectification driven by the covariation of monthly FFCO2 emissions and monthly atmospheric transport. The diurnal FFCO2 emissions are responsible for a diurnal FFCO2 concentration amplitude of up to 9.12 ppm at the grid cell scale. Similarly, the monthly FFCO2 emissions are responsible for a simulated seasonal CO2 amplitude of up to 6.11 ppm at the grid cell scale. The impact of the diurnal FFCO2 emissions, when only sampled in the local afternoon, is also important, causing an increase of +1.13 ppmv at the grid cell scale. The simulated CO2 concentration impacts from the diurnally and seasonally varying FFCO2 emissions are centered over large source regions in the Northern Hemisphere, extending to downwind regions. This study demonstrates the influence of sub-annual variations in FFCO2 emissions on simulated CO2 concentration and suggests that inversion studies must take account of these variations in the affected regions.
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Pham Thi Thu, H., C. Amory-Mazaudier, and M. Le Huy. "Time variations of the ionosphere at the northern tropical crest of ionization at Phu Thuy, Vietnam." Annales Geophysicae 29, no. 1 (January 26, 2011): 197–207. http://dx.doi.org/10.5194/angeo-29-197-2011.
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Abstract. This study is the first which gives the climatology of the ionosphere at the northern tropical crest of ionization in the Asian sector. We use the data from Phu Thuy station, in Vietnam, through three solar cycles (20, 21 and 22), showing the complete morphology of ionosphere parameters by analyzing long term variation, solar cycle variation and geomagnetic activity effects, seasonal evolution and diurnal development. Ionospheric critical frequencies, foF2, foF1 and foE, evolve according to the 11-year sunspot cycle. Seasonal variations show that foF2 exhibits a semiannual pattern with maxima at equinox, and winter and equinoctial anomalies depending on the phases of the sunspot solar cycle. ΔfoF2 exhibits a semiannual variation during the minimum phase of the sunspot solar cycle 20 and the increasing and decreasing phases of solar cycle 20, 21 and 22. ΔfoF1 exhibits an annual variation during the maximum phase of solar cycles 20, 21 and 22. Δh'F2 shows a regular seasonal variation for the different solar cycles while Δh'F1 exhibits a large magnitude dispersion from one sunspot cycle to another. The long term variations consist in an increase of 1.0 MHz for foF2 and of 0.36 MHz for foF1. foE increases 0.53 MHz from solar cycle 20 to solar cycle 21 and then decreases −0.23 MHz during the decreasing phase of cycle 21. The diurnal variation of the critical frequency foF2 shows minima at 05:00 LT and maxima around 14:00 LT. foF1 and foE have a maximum around noon. The diurnal variation of h'F2 exhibits a maximum around noon. The main features of h'F1 are a minimum near noon and the maximum near midnight. Other minima and maxima occur in the morning, at about 04:00 or 05:00 LT and in the afternoon, at about 18:00 or 19:00 LT but they are markedly smaller. Only during the maximum phase of all sunspot solar cycles the maximum near 19:00 LT is more pronounced.
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Meng, Z. Y., X. B. Xu, P. Yan, G. A. Ding, J. Tang, W. L. Lin, X. D. Xu, and S. F. Wang. "Characteristics of trace gaseous pollutants at a regional background station in Northern China." Atmospheric Chemistry and Physics 9, no. 3 (February 5, 2009): 927–36. http://dx.doi.org/10.5194/acp-9-927-2009.
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Abstract. Measurements of trace gaseous pollutants were taken at the Shangdianzi site, a WMO Global Atmosphere Watch (GAW) background station in Northern China. The results are presented for the period from September 2003 to December 2006. Seasonal and diurnal variations of the O3, NOx, SO2, and CO concentration are characterized and possible causes for them are discussed. The observed levels of the trace gases are comparable to those at some other background sites in polluted regions inside and outside of China. It was shown that the seasonal variation of O3 can change slightly from year to year due to the year-to-year alternation in the meteorological conditions. Higher CO concentrations were observed in some warmer months, particularly in June and July, 2006. Intensive biomass burning in the North China Plain region, in combination with the transport of regional pollution by more frequent southwesterly winds, is believed to be responsible for the elevated CO concentrations. The diurnal variation of O3, with delayed peaking times, suggests that the transport of photochemical aged plume is an important source for O3 at Shangdianzi. The diurnal variations of SO2 in all seasons show higher values during daytime, contradicting the common view. An explanation for this unusual phenomenon is hypothesized. To gain an insight into the impact of transport on the trace gases levels at Shangdianzi, air mass backward trajectories were calculated and analyzed in combination with corresponding pollutant concentrations. The results indicate that the transport of air masses from the North China Plain region and from the major coal mining regions west of Shangdianzi is responsible for the high concentrations of the gaseous pollutants.
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Verma, Santosh Kumar, Kimitaka Kawamura, Fei Yang, Pingqing Fu, Yugo Kanaya, and Zifa Wang. "Measurement report: Diurnal and temporal variations of sugar compounds in suburban aerosols from the northern vicinity of Beijing, China – an influence of biogenic and anthropogenic sources." Atmospheric Chemistry and Physics 21, no. 6 (March 30, 2021): 4959–78. http://dx.doi.org/10.5194/acp-21-4959-2021.
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Abstract. Sugar compounds (SCs) are major water-soluble constituents in atmospheric aerosols. In this study, we investigated their molecular compositions and abundances in the northern receptor site (Mangshan) of Beijing, China, to better understand the contributions from biogenic and anthropogenic sources using a gas chromatography–mass spectrometry technique. The sampling site receives anthropogenic air mass transported from Beijing by southerly winds, while northerly winds transport relatively clean air mass from the forest areas. Day- and nighttime variations were analyzed for anhydrosugars, primary sugars, and sugar alcohols in autumn 2007. We found that biomass burning (BB) tracers were more abundant at nighttime than daytime, while other SCs showed different diurnal variations. Levoglucosan was found to be dominant sugar among the SCs observed, indicating an intense influence of local BB for cooking and space heating at the surroundings of the Mangshan site. The high levels of arabitol and mannitol in daytime suggest a significant contribution of locally emitted fungal spores and long-range-transported bioaerosols from the Beijing area. The plant emissions from Mangshan forest park significantly control the diurnal variations of glucose, fructose, and mannitol. The meteorological parameters (relative humidity, temperature, and rainfall) significantly affect the concentrations and diurnal variations of SCs. Sucrose (pollen tracer) showed a clear diurnal variation, peaking in the daytime due to higher ambient temperature and wind speed, which influences the pollen release from the forest plants. We found the contribution of trehalose from soil dust in daytime, while microbial and fungal spores were responsible for nighttime. Anhydrosugar and primary sugars are prime carbon sources of the Mangshan aerosols. The high ratios of levoglucosan in organic carbon and water-soluble organic carbon at nighttime suggest a significant contribution of BB to organic aerosols at night. Levoglucosan / mannosan ratios demonstrate that low-temperature burning of hardwood is dominant in Mangshan. The positive matrix factorization analysis concluded that forest vegetation, fungal species, and local BB are the significant sources of SCs.
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Lu, Zhongming, Jianping Gan, and Minhan Dai. "Modeling seasonal and diurnal pCO2 variations in the northern South China Sea." Journal of Marine Systems 92, no. 1 (April 2012): 30–41. http://dx.doi.org/10.1016/j.jmarsys.2011.10.003.
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Tu, Qianguang, Yun Zhao, Jing Guo, Chunmei Cheng, Liangliang Shi, Yunwei Yan, and Zengzhou Hao. "Spatial and Temporal Variations of Aerosol Optical Thickness over the China Seas from Himawari-8." Remote Sensing 13, no. 24 (December 14, 2021): 5082. http://dx.doi.org/10.3390/rs13245082.
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Six years of hourly aerosol optical thickness (AOT) data retrieved from Himawari-8 were used to investigate the spatial and temporal variations, especially diurnal variations, of aerosols over the China Seas. First, the Himawari-8 AOT data were consistent with the AERONET measurements over most of the China Seas, except for some coastal regions. The spatial feature showed that AOT over high latitude seas was generally larger than over low latitude seas, and it is distributed in strips along the coastline and decreases gradually with increasing distance from the coastline. AOT undergoes diurnal variation as it decreases from 9:00 a.m. local time, reaching a minimum at noon, and then begins to increase in the afternoon. The percentage daily departure of AOT over the East China Seas generally ranged ±20%, increasing sharply in the afternoon; however, over the northern part of the South China Sea, daily departure reached a maximum of >40% at 4:00 p.m. The monthly variation in AOT showed a pronounced annual cycle. Seasonal variations of the spatial pattern showed that the largest AOT was usually observed in spring and varies in other seasons for different seas.
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Xu, C., Y. M. Ma, K. Yang, Z. K. Zhu, J. M. Wang, P. M. Amatya, and L. Zhao. "Similarities and differences of aerosol optical properties between southern and northern slopes of the Himalayas." Atmospheric Chemistry and Physics Discussions 13, no. 8 (August 13, 2013): 20961–1002. http://dx.doi.org/10.5194/acpd-13-20961-2013.
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Abstract. The Himalayas is located at the southern edge of the Tibetan Plateau, and it acts as a natural barrier for the transport of atmospheric aerosols, e.g. from the polluted regions of South Asia to the main body of the Tibetan Plateau. In this study, we investigate the seasonal and diurnal variations of aerosol optical properties measured at the three Aerosol Robotic Network (AERONET) sites over the southern (Pokhara station and EVK2-CNR station in Nepal) and northern (Qomolangma (Mt. Everest) station for Atmospheric and Environmental Observation and Research, Chinese Academy of Sciences (QOMS_CAS) in Tibet, China) slopes of the Himalayas. While observations at QOMS_CAS and EVK2-CNR can generally be representative of a remote background atmosphere, Pokhara is an urban site with much higher aerosol load due to the influence of local anthropogenic activities. The annual mean of aerosol optical depth (AOD) during the investigated period was 0.06 at QOMS_CAS, 0.04 at EVK2-CNR and 0.51 at Pokhara, respectively. Seasonal variations of aerosols are profoundly affected by large scale atmospheric circulation. Vegetation fires, peaking during April in the Himalayan region and northern India, contribute to a growing fine mode AOD at 500 nm at the three stations. Dust transported to these sites results in an increase of coarse mode AOD during the monsoon season at the three sites. Meanwhile, coarse mode AOD at EVK2-CNR is higher than QOMS_CAS from July to September, indicating the Himalayas blocks the coarse particles carried by the southwest winds. The precipitation scavenging effect is obvious at Pokhara, which can significantly reduce the aerosol load during the monsoon season. Unlike the seasonal variations, diurnal variations are mainly influenced by meso-scale systems and local topography. In general, precipitation can lead to a decrease of the aerosol load and the average particle size at each station. AOD changes in a short time with the emission rate near the emission source at Pokhara, while does not at the other two stations in remote regions. AOD increases during daytime due to the valley winds at EVK2-CNR, while this diurnal variation of AOD is absent at the other two stations. The surface heating influences the local convection, which further controls the vertical aerosol exchange and the diffusion rate of pollutions to the surrounding areas. The Himalayas blocks most of the coarse particles across the mountains. Fine and coarse mode particles are mixed to make atmospheric composition more complex on the southern slope in spring, which leads to the greater inter-annual difference in diurnal cycles of Ångström exponent (AE) at EVK2-CNR than that at QOMS_CAS.
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Xu, C., Y. M. Ma, A. Panday, Z. Y. Cong, K. Yang, Z. K. Zhu, J. M. Wang, P. M. Amatya, and L. Zhao. "Similarities and differences of aerosol optical properties between southern and northern sides of the Himalayas." Atmospheric Chemistry and Physics 14, no. 6 (March 31, 2014): 3133–49. http://dx.doi.org/10.5194/acp-14-3133-2014.
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Abstract. The Himalaya mountains along the southern edge of the Tibetan Plateau act as a natural barrier for the transport of atmospheric aerosols from the polluted regions of South Asia to the main body of the Tibetan Plateau. In this study, we investigate the seasonal and diurnal variations of aerosol optical properties measured at two Aerosol Robotic Network (AERONET) sites on the southern side of the Himalaya (Pokhara, 812 m above sea level (a.s.l.) and EVK2-CNR, 5079 m a.s.l. in Nepal) and one on the northern side (Qomolangma (Mt. Everest) station for Atmospheric and Environmental Observation and Research, Chinese Academy of Sciences (QOMS_CAS) in Tibet, 4076 m a.s.l. in China). While observations at QOMS_CAS and EVK2-CNR can generally be representative of a remote background atmosphere, Pokhara is a lower-elevation suburban site with much higher aerosol load due to both the influence of local anthropogenic activities and to its proximity to the Indo-Gangetic Plains. The annual mean aerosol optical depth (AOD) during the investigated period was 0.05 at QOMS_CAS, 0.04 at EVK2-CNR and 0.51 at Pokhara, respectively. Seasonal variations of aerosols are profoundly affected by large-scale atmospheric circulation. Vegetation fires, peaking during April in the Himalayan region and northern India, contribute to a growing fine mode AOD at the three stations. Dust transported to these sites, wind erosion and hydrated/cloud-processed aerosols lead to an increase in coarse mode AOD during the monsoon season at QOMS_CAS and EVK2-CNR. Meanwhile, coarse mode AOD at EVK2-CNR is higher than at QOMS_CAS in August and September, indicating that the transport of coarse mode aerosols from the southern to the northern side may be effectively reduced. The effect of precipitation scavenging is clearly seen at Pokhara, which sees significantly reduced aerosol loads during the monsoon season. Unlike the seasonal variations, diurnal variations are mainly influenced by meso-scale systems and local topography. The diurnal pattern in precipitation appears to contribute to diurnal changes in AOD through the effect of precipitation scavenging. AOD exhibits diurnal patterns related to emissions in Pokhara, while it does not at the other two high-altitude sites. At EVK2-CNR, the daytime airflow carries aerosols up from lower-altitude polluted regions, leading to increasing AOD, while the other two stations are less influenced by valley winds. Surface heating influences the local convection, which further controls the vertical aerosol exchange and the diffusion rate of pollution to the surrounding areas. Fine and coarse mode particles are mixed together on the southern side of the Himalaya in spring, which may lead to the greater inter-annual difference in diurnal cycles of Ångström exponent (AE) at EVK2-CNR than that at QOMS_CAS.
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Arnup, Sarah J., and Michael J. Reeder. "The Diurnal and Seasonal Variation of the Northern Australian Dryline." Monthly Weather Review 135, no. 8 (August 1, 2007): 2995–3008. http://dx.doi.org/10.1175/mwr3455.1.
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Abstract The diurnal and seasonal variations of the northern Australian dryline are examined by constructing climatologies of low-level dynamic and thermodynamic variables taken from the high-resolution Australian Bureau of Meteorology’s Limited Area Prediction Scheme (LAPS) forecasts from 2000 to 2003. The development of the dryline is analyzed within the framework of the frontogenesis function applied to the mixing ratio and the airstream diagnostics of Cohen and Schultz. A case study of 12–13 October 2002 illustrating the airmass boundaries over the Australian region is also examined. Daytime surface heating produces sea-breeze circulations around the coast and a large inland heat trough that extends east–west along northern Australia. At night, air parcels accelerate toward low pressure, increasing convergence and deformation within the heat trough. This sharpens the moisture gradient across the tropical and continental airmass boundary into a dryline. This is different than the dryline of the Great Plains in the United States, which generally weakens overnight. The Australian dryline is strongest in spring just poleward of the Gulf of Carpentaria, where the moisture gradient across the heat trough is enhanced by the coast, and the axis of dilatation is closely aligned with mixing ratio isopleths. The dryline is weakest in winter, when the heat trough is weak. The LAPS 3-h forecasts are in good agreement with observations obtained from the Automatic Weather Station network. The 3-h forecasts capture the observed diurnal and seasonal cycle of the airmass boundaries. However, the sea-breeze circulation and ageostrophic flow into the surface heat trough is limited by the model resolution. The LAPS 3-h forecasts may therefore underestimate the nocturnal intensification of the dryline, especially since the inland moisture content is overestimated.
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Moerman, Jessica W., Kim M. Cobb, Jess F. Adkins, Harald Sodemann, Brian Clark, and Andrew A. Tuen. "Diurnal to interannual rainfall δ18O variations in northern Borneo driven by regional hydrology." Earth and Planetary Science Letters 369-370 (May 2013): 108–19. http://dx.doi.org/10.1016/j.epsl.2013.03.014.
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Chen, Guixing, Yu Du, and Zhiping Wen. "Seasonal, Interannual, and Interdecadal Variations of the East Asian Summer Monsoon: A Diurnal-Cycle Perspective." Journal of Climate 34, no. 11 (June 2021): 4403–21. http://dx.doi.org/10.1175/jcli-d-20-0882.1.
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AbstractThis study revisits the long-term variabilities of the East Asian summer monsoon (EASM) in 1958–2017 through examination of diurnal cycles. We group monsoon days into four dynamic quadrants (Q1 to Q4), with emphasis on the strong daily southerlies coupled with a large (Q1) or small (Q4) diurnal amplitude over Southeast China. The occurrence day of Q1 increases in June–July with the seasonal progress of the EASM. It is most pronounced in the 1960s to the 1970s and declines to the lowest in the 1980s to the 1990s, whereas the Q4 occurrence increases notably from the 1970s to the 1990s; both groups return to normal in recent years. The interdecadal decrease (increase) of Q1 (Q4) occurrence corresponds well to the known weakening of EASM in the twentieth century, and it also coincides with the rainfall anomalies over China shifting from a “north flooding and south drought” to a “north drought and south flooding” mode. The rainfall under Q1 (Q4) can account for ~60% of the interannual variance of summer rainfall in northern (southern) China. The contrasting effects of Q1 and Q4 on rainfall are due to their remarkably different regulation on water vapor transport and convergence. The interannual/interdecadal variations of Q1 (Q4) occurrence determine the anomalous water vapor transports to northern (southern) China, in association with the various expansion of the western Pacific subtropical high. In particular, Q1 conditions can greatly intensify nighttime moisture convergence, which is responsible for the long-term variations of rainfall in northern China. The results highlight that the diurnal cycles in monsoon flow act as a key regional process working with large-scale circulation to regulate the spatial distributions and long-term variabilities of EASM rainfall.
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Chen, Tianmeng, Zhanqing Li, Ralph A. Kahn, Chuanfeng Zhao, Daniel Rosenfeld, Jianping Guo, Wenchao Han, and Dandan Chen. "Potential impact of aerosols on convective clouds revealed by Himawari-8 observations over different terrain types in eastern China." Atmospheric Chemistry and Physics 21, no. 8 (April 26, 2021): 6199–220. http://dx.doi.org/10.5194/acp-21-6199-2021.
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Abstract. Convective clouds are common and play a major role in Earth's water cycle and energy balance; they may even develop into storms and cause severe rainfall events. To understand the convective cloud development process, this study investigates the impact of aerosols on convective clouds by considering the influence of both topography and diurnal variation in radiation. By combining texture analysis, clustering, and thresholding methods, we identify all convective clouds in two warm seasons (May–September, 2016/17) in eastern China based on Himawari-8 Level 1 data. Having large diurnally resolved cloud data together with surface meteorological and environmental measurements, we investigate convective cloud properties and their variation, stratified by elevation and diurnal change. We then analyze the potential impact of aerosol on convective clouds under different meteorological conditions and topographies. In general, convective clouds tend to occur preferentially under polluted conditions in the morning, which reverses in the afternoon. Convective cloud fraction first increases then decreases with aerosol loading, which may contribute to this phenomenon. Topography and diurnal meteorological variations may affect the strength of aerosol microphysical and radiative effects. Updraft is always stronger along the windward slopes of mountains and plateaus, especially in northern China. The prevailing southerly wind near the foothills of mountains and plateaus is likely to contribute to this windward strengthening of updraft and to bring more pollutant into the mountains, thereby strengthening the microphysical effect, invigorating convective clouds. By comparison, over plain, aerosols decrease surface heating and suppress convection by blocking solar radiation reaching the surface.
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Chen, Y., L. Liu, H. Le, W. Wan, and H. Zhang. "Dusk-to-nighttime enhancement of mid-latitude <i>Nm</i>F2 in local summer: inter-hemispheric asymmetry and solar activity dependence." Annales Geophysicae 33, no. 6 (June 10, 2015): 711–18. http://dx.doi.org/10.5194/angeo-33-711-2015.
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Abstract. In this paper ionosonde observations in the East Asia–Australia sector were collected to investigate dusk-to-nighttime enhancement of mid-latitude summer NmF2 (maximum electron density of the F2 layer) within the framework of NmF2 diurnal variation. NmF2 were normalized to two solar activity levels to investigate the dependence of the dusk-to-nighttime enhancement on solar activity. The dusk-to-nighttime enhancement of NmF2 is more evident at Northern Hemisphere stations than at Southern Hemisphere stations, with a remarkable latitudinal dependence. The dusk-to-nighttime enhancement shows both increasing and declining trends with solar activity increasing, which is somewhat different from previous conclusions. The difference in the dusk-to-nighttime enhancement between Southern Hemisphere and Northern Hemisphere stations is possibly related to the offset of the geomagnetic axis from the geographic axis. hmF2 (peak height of the F2 layer) diurnal variations show that daytime hmF2 begins to increase much earlier at low solar activity level than at high solar activity level at northern Akita and Wakkanai stations where the dusk-to-nighttime enhancement is more prominent at low solar activity level than at high solar activity level. That implies neutral wind phase is possibly also important for nighttime enhancement.
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Chen, Guixing. "Diurnal Cycle of the Asian Summer Monsoon: Air Pump of the Second Kind." Journal of Climate 33, no. 5 (March 1, 2020): 1747–75. http://dx.doi.org/10.1175/jcli-d-19-0210.1.
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AbstractDiurnal variations of rainfall and winds are pronounced over the Asian summer monsoon region, but their activities under different monsoon conditions are not clarified. Here, the diurnal cycle of monsoon flow and its influence are examined using 20-yr satellite rainfall and reanalysis data. A total of 1840 summer days are partitioned into four dynamic groups of strong or weak background flows with large or small diurnal amplitudes of low-level meridional wind. Large-scale southerly wind is found to be strongest after midnight, with a large diurnal amplitude on strong monsoon days over central-north India and southeast China. Such a nocturnal speed-up is closely associated with the Blackadar boundary layer inertial oscillation due to the diurnal heating over low-lying landmass. It acts like a large air pump that injects moisture poleward at night and strengthens monsoonal circulation with anomalous rising motion at the northern rainband of the Asian monsoon. In particular, monsoon southerlies with large nighttime speed-up converge with downslope winds from the Himalayas or northerly anomaly from midlatitudes. Enhanced water vapor convergence facilitates the growth of organized convection, producing substantial rainfall at the Himalayan foothills in predawn hours and at the mei-yu–baiu zone from predawn to noon. When monsoon flow undergoes a small diurnal cycle, rainfall is instead displaced south and mostly recorded in daytime. Both the daily mean and morning peak of rainfall are suppressed on land under weak monsoon southerlies. Moreover, the monsoon diurnal cycle exhibits evident intraseasonal/interannual variations and contributes to rainfall variability. The results highlight that monsoon flow couples with subdaily forcings to strongly regulate the detailed patterns of rainfall and moisture budget over the Asian monsoon regions.
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Lee, Myong-In, Siegfried D. Schubert, Max J. Suarez, Isaac M. Held, Ngar-Cheung Lau, Jeffrey J. Ploshay, Arun Kumar, Hyun-Kyung Kim, and Jae-Kyung E. Schemm. "An Analysis of the Warm-Season Diurnal Cycle over the Continental United States and Northern Mexico in General Circulation Models." Journal of Hydrometeorology 8, no. 3 (June 1, 2007): 344–66. http://dx.doi.org/10.1175/jhm581.1.
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Abstract The diurnal cycle of warm-season rainfall over the continental United States and northern Mexico is analyzed in three global atmospheric general circulation models (AGCMs) from NCEP, GFDL, and the NASA Global Modeling Assimilation Office (GMAO). The results for each model are based on an ensemble of five summer simulations forced with climatological sea surface temperatures. Although the overall patterns of time-mean (summer) rainfall and low-level winds are reasonably well simulated, all three models exhibit substantial regional deficiencies that appear to be related to problems with the diurnal cycle. Especially prominent are the discrepancies in the diurnal cycle of precipitation over the eastern slopes of the Rocky Mountains and adjacent Great Plains, including the failure to adequately capture the observed nocturnal peak. Moreover, the observed late afternoon–early evening eastward propagation of convection from the mountains into the Great Plains is not adequately simulated, contributing to the deficiencies in the diurnal cycle in the Great Plains. In the southeast United States, the models show a general tendency to rain in the early afternoon—several hours earlier than observed. Over the North American monsoon region in the southwest United States and northern Mexico, the phase of the broad-scale diurnal convection appears to be reasonably well simulated, though the coarse resolution of the runs precludes the simulation of key regional phenomena. All three models employ deep convection schemes that assume fundamentally the same buoyancy closure based on simplified versions of the Arakawa–Schubert scheme. Nevertheless, substantial differences between the models in the diurnal cycle of convection highlight the important differences in their implementations and interactions with the boundary layer scheme. An analysis of local diurnal variations of convective available potential energy (CAPE) shows an overall tendency for an afternoon peak—a feature well simulated by the models. The simulated diurnal cycle of rainfall is in phase with the local CAPE variation over the southeast United States and the Rocky Mountains where the local surface boundary forcing is important in regulating the diurnal cycle of convection. On the other hand, the simulated diurnal cycle of rainfall tends to be too strongly tied to CAPE over the Great Plains, where the observed precipitation and CAPE are out of phase, implying that free atmospheric large-scale forcing plays a more important role than surface heat fluxes in initiating or inhibiting convection.
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He, Jianjian, Pengyan Zhang, Wenlong Jing, and Yuhang Yan. "Spatial Responses of Net Ecosystem Productivity of the Yellow River Basin under Diurnal Asymmetric Warming." Sustainability 10, no. 10 (October 11, 2018): 3646. http://dx.doi.org/10.3390/su10103646.
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The net ecosystem productivity (NEP) of drainage basins plays an important role in maintaining the carbon balance of those ecosystems. In this study, the modified CASA (Carnegie Ames Stanford Approach) model and a soil microbial respiration model were used to estimate net primary productivity (NPP) and NEP of the Yellow River Basin’s (YRB) vegetation in the terrestrial ecosystem (excluding rivers, floodplain lakes and other freshwater ecosystems) from 1982 to 2015. After analyzing the spatiotemporal variations in the NEP using slope analysis, the coefficient of variation, and the Hurst exponent, precipitation was identified as the main factor limiting vegetation growth in the YRB. Hence, precipitation was treated as the control variable and a second-order partial correlation method was used to determine the correlation between diurnal asymmetric warming and the YRB’s NEP. The results indicate that: (i) diurnal asymmetric warming occurred in the YRB from 1982 to 2015, with nighttime warming (Tmin) being 1.50 times that of daytime warming (Tmax). There is a significant correlation between variations in NPP and diurnal warming; (ii) the YRB’s NEP are characterized by upward fluctuations in terms of temporal variations, large differences between the various vegetation types, high values in the western and southeastern regions but low values in the northern region in terms of spatial distribution, overall relative stability in the YRB’s vegetation cover, and changes in the same direction being more dominant than those in the opposite direction (although the former is not sustained); and (iii) positive correlations between the NEP and nighttime and daytime warming are approximately 48.37% and 67.51% for the YRB, respectively, with variations in nighttime temperatures having more extensive impacts on vegetation cover.
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Wang, Bing, Xinqing Lee, Benny K. G. Theng, Jianzhong Cheng, and Fang Yang. "Diurnal and spatial variations of soil NOx fluxes in the northern steppe of China." Journal of Environmental Sciences 32 (June 2015): 54–61. http://dx.doi.org/10.1016/j.jes.2014.11.011.
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Fiedler, J., G. Baumgarten, and G. von Cossart. "Mean diurnal variations of noctilucent clouds during 7 years of lidar observations at ALOMAR." Annales Geophysicae 23, no. 4 (June 3, 2005): 1175–81. http://dx.doi.org/10.5194/angeo-23-1175-2005.
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Abstract. From 1997 to 2003, noctilucent clouds (NLC) were observed by lidar above the ALOMAR observatory in Northern Norway (69° N) during a total of 1880 measurement hours. This data set contains NLC signatures for 640h, covering all local times, even during the highest solar background conditions. After data limitation imposing a threshold value of 4x10-10m-1sr-1 for the volume backscatter coefficient of the NLC particles, a measure for the cloud brightness, local time dependencies of the NLC occurrence frequency, altitude, and brightness were determined. On average, over the 7 years NLC occurred during the whole day and preferably in the early morning hours, with a maximum occurrence frequency of ~40% between 4 and 7 LT. Splitting the data into weak and strong clouds yields almost identical amplitudes of diurnal and semidiurnal variations for the occurrence of weak clouds, whereas the strong clouds are dominated by the diurnal variation. NLC occurrence, altitude, as well as brightness, show a remarkable persistence concerning diurnal and semidiurnal variations from 1997 to 2003, suggesting that NLC above ALOMAR are significantly controlled by atmospheric tides. The observed mean anti-phase behavior between cloud altitude and brightness is attributed to a phase shift between the semidiurnal components by ~6h. Investigation of data for each individual year regarding the prevailing oscillation periods of the NLC parameters showed different phase relationships, leading to a complex variability in the cloud parameters.
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Sharifnezhadazizi, Zahra, Hamid Norouzi, Satya Prakash, Christopher Beale, and Reza Khanbilvardi. "A Global Analysis of Land Surface Temperature Diurnal Cycle Using MODIS Observations." Journal of Applied Meteorology and Climatology 58, no. 6 (June 2019): 1279–91. http://dx.doi.org/10.1175/jamc-d-18-0256.1.
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AbstractDiurnal variations of land surface temperature (LST) play a vital role in a wide range of applications such as climate change assessment, land–atmosphere interactions, and heat-related health issues in urban regions. This study uses 15 years (2003–17) of daily observations of LST Collection 6 from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on board the Aqua and the Terra satellites. A spline interpolation method is used to estimate half-hourly global LST from the MODIS measurements. A preliminary assessment of interpolated LST with hourly ground-based observations over selected stations of North America shows bias and an error of less than 1 K. Results suggest that the present interpolation method is capable of capturing the diurnal variations of LST reasonably well for different land-cover types. The diurnal cycle of LST and time of occurrence of maximum temperature are computed from the spatially and temporally consistent interpolated diurnal LST data at a global scale. Regions with higher variability in the timing of maximum LST hours and diurnal amplitude are identified in this study. The global desert regions show generally small variability of the monthly mean diurnal LST range, whereas larger areas of the global land exhibit rather higher variability in the diurnal LST range during the study period. Moreover, the changes in diurnal temperature range for the study period are examined for distinct land-cover types. Analysis of the 15-yr time series of the diurnal LST record shows an overall decrease of 0.5 K in amplitude over the Northern Hemisphere. However, the diurnal LST range shows variant changes in the Southern Hemisphere.
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Chen, Guixing, Ruoyu Lan, Wenxin Zeng, He Pan, and Weibiao Li. "Diurnal Variations of Rainfall in Surface and Satellite Observations at the Monsoon Coast (South China)." Journal of Climate 31, no. 5 (March 2018): 1703–24. http://dx.doi.org/10.1175/jcli-d-17-0373.1.
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The complex features of rainfall diurnal cycles at the south China coast are examined using hourly rain gauge data and satellite products (CMORPH and TRMM 3B42) during 1998–2014. It is shown that morning rainfall is pronounced near the coasts and windward mountains, with high rainfall in the summer monsoon season, while afternoon rainfall is dominant on land, and nocturnal rainfall occurs at northern inland sites. Both satellite products report less morning rainfall and more afternoon rainfall than the rain gauge data, and they also miss the midnight rainfall minimum. These errors are mainly attributable to an underestimation of morning moderate and intense rains at coasts and an overestimation of afternoon–evening light rains on land. With a correction of the systematic bias, satellite products faithfully resolve the spatial patterns of normalized rainfall diurnal cycles related to land–sea contrast and terrains, suggesting an improved data application for regional climate studies. In particular, they are comparable to the rain gauge data in showing the linear reduction of morning rainfall from coasts to inland regions. TRMM is marginally better than CMORPH in revealing the overall features of diurnal cycles, while higher-resolution CMORPH captures more local details. All three datasets also present that morning rainfall decreases from May–June to July–August, especially on land; it exhibits pronounced interannual variations and a decadal increase in 1998–2008 at coasts. Such long-term variations of morning rainfall are induced by the coastal convergence and mountain liftings of monsoon shear flow interacting with land breeze, which is mainly regulated by monsoon southwesterly winds in the northern part of the South China Sea.
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Zhao, Hui, Youfei Zheng, and Chen Li. "Spatiotemporal Distribution of PM2.5 and O3 and Their Interaction During the Summer and Winter Seasons in Beijing, China." Sustainability 10, no. 12 (November 30, 2018): 4519. http://dx.doi.org/10.3390/su10124519.
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This study analyzed the spatiotemporal variations in PM2.5 and O3, and explored their interaction in the summer and winter seasons in Beijing. To this aim, hourly PM2.5 and O3 data for 35 air quality monitoring sites were analyzed during the summer and winter of 2016. Results suggested that the highest PM2.5 concentration and the lowest O3 concentration were observed at traffic monitoring sites during the two seasons. A statistically significant (p < 0.05) different diurnal variation of PM2.5 was observed between the summer and winter seasons, with higher concentrations during daytime summer and nighttime winter. Diurnal variations of O3 concentrations during the two seasons showed a single peak, occurring at 16:00 and 15:00 in summer and winter, respectively. PM2.5 presented a spatial pattern with higher concentrations in southern Beijing than in northern areas, particularly evident during wintertime. On the contrary, O3 concentrations presented a decreasing spatial trend from the north to the south, particularly evident during summer. In addition, we found that PM2.5 concentrations were positively correlated (p < 0.01, r = 0.57) with O3 concentrations in summer, but negatively correlated (p < 0.01, r = −0.72) with O3 concentrations in winter.
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Bonne, Jean-Louis, Hanno Meyer, Melanie Behrens, Julia Boike, Sepp Kipfstuhl, Benjamin Rabe, Toni Schmidt, Lutz Schönicke, Hans Christian Steen-Larsen, and Martin Werner. "Moisture origin as a driver of temporal variabilities of the water vapour isotopic composition in the Lena River Delta, Siberia." Atmospheric Chemistry and Physics 20, no. 17 (September 9, 2020): 10493–511. http://dx.doi.org/10.5194/acp-20-10493-2020.
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Abstract. In the context of the Arctic amplification of climate change affecting the regional atmospheric hydrological cycle, it is crucial to characterize the present-day moisture sources of the Arctic. The isotopic composition is an important tool to enhance our understanding of the drivers of the hydrological cycle due to the different molecular characteristics of water stable isotopes during phase change. This study introduces 2 years of continuous in situ water vapour and precipitation isotopic observations conducted since July 2015 in the eastern Siberian Lena delta at the research station on Samoylov Island. The vapour isotopic signals are dominated by variations at seasonal and synoptic timescales. Diurnal variations of the vapour isotopic signals are masked by synoptic variations, indicating low variations of the amplitude of local sources at the diurnal scale in winter, summer and autumn. Low-amplitude diurnal variations in spring may indicate exchange of moisture between the atmosphere and the snow-covered surface. Moisture source diagnostics based on semi-Lagrangian backward trajectories reveal that different air mass origins have contrasting contributions to the moisture budget of the Lena delta region. At the seasonal scale, the distance from the net moisture sources to the arrival site strongly varies. During the coldest months, no contribution from local secondary evaporation is observed. Variations of the vapour isotopic composition during the cold season on the synoptic timescale are strongly related to moisture source regions and variations in atmospheric transport: warm and isotopically enriched moist air is linked to fast transport from the Atlantic sector, while dry and cold air with isotopically depleted moisture is generally associated with air masses moving slowly over northern Eurasia.
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Buriti, Ricardo A., Wayne Hocking, Paulo P. Batista, Igo Paulino, Ana R. Paulino, Marcial Garbanzo-Salas, Barclay Clemesha, and Amauri F. Medeiros. "Diurnal mesospheric tidal winds observed simultaneously by meteor radars in Costa Rica (10° N, 86° W) and Brazil (7° S, 37° W)." Annales Geophysicae 38, no. 6 (December 17, 2020): 1247–56. http://dx.doi.org/10.5194/angeo-38-1247-2020.
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Abstract. This paper presents a study of diurnal tidal winds observed simultaneously by two meteor radars located on each side of the Equator in the equatorial region. The radars were located in Santa Cruz, Costa Rica (10.3∘ N, 85.6∘ W) (hereafter CR) and São João do Cariri, Brazil (7.4∘ S, 36.5∘ W) (hereafter CA). The distance between the sites is 5800 km. Harmonic analysis has been used to obtain amplitudes and phases (hour of peak amplitude) for diurnal, semidiurnal and terdiurnal tides between 82 and 98 km altitude, but in this work we concentrate on the diurnal component. The period of observation was from April 2005 to January 2006. The results were compared to the Global Scale Waves Model (GSWM-09). Magnitudes of zonal and meridional amplitudes from November to January for CR were quite different from the predictions of the model. Concerning phases, the agreement between model and radar meridional tidal phases at each site was good, and a vertical wavelength of 24 km for the diurnal tide was observed practically every month, although on some occasions determination of the vertical wavelength was difficult, especially for the zonal component, due to nonlinear phase variations with height. For the diurnal zonal amplitude, there were notable differences between the two sites. We attribute this site-to-site difference of the diurnal zonal amplitude to the nonmigrating component of the tide and propose that an anomaly was present in the troposphere in the winter (Northern Hemisphere) of 2005–2006 which produced substantial longitudinal variation.
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Singer, W., U. von Zahn, and J. Weiß. "Diurnal and annual variations of meteor rates at the arctic circle." Atmospheric Chemistry and Physics 4, no. 5 (August 23, 2004): 1355–63. http://dx.doi.org/10.5194/acp-4-1355-2004.
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Abstract. Meteors are an important source for (a) the metal atoms of the upper atmosphere metal layers and (b) for condensation nuclei, the existence of which are a prerequisite for the formation of noctilucent cloud particles in the polar mesopause region. For a better understanding of these phenomena, it would be helpful to know accurately the annual and diurnal variations of meteor rates. So far, these rates have been little studied at polar latitudes. Therefore we have used the 33 MHz meteor radar of the ALOMAR observatory at 69° N to measure the meteor rates at this location for two full annual cycles. This site, being within 3° of the Arctic circle, offers in addition an interesting capability: The axis of its antenna field points (almost) towards the North ecliptic pole once each day of the year. In this particular viewing direction, the radar monitors the meteoroid influx from (almost) the entire ecliptic Northern hemisphere. We report on the observed diurnal variations (averaged over one month) of meteor rates and their significant alterations throughout the year. The ratio of maximum over minimum meteor rates throughout one diurnal cycle is in January and February about 5, from April through December 2.3±0.3. If compared with similar measurements at mid-latitudes, our expectation, that the amplitude of the diurnal variation is to decrease towards the North pole, is not really borne out. Observations with the antenna axis pointing towards the North ecliptic pole showed that the rate of deposition of meteoric dust is substantially larger during the Arctic NLC season than the annual mean deposition rate. The daylight meteor showers of the Arietids, Zeta Perseids, and Beta Taurids supposedly contribute considerably to the June maximum of meteor rates. We note, though, that with the radar antenna pointing as described above, all three meteor radiants are close to the local horizon but all three radiants were detected.
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Duvel, Jean Philippe. "Analysis of Diurnal, Interdiurnal and Interannual Variations during Northern Hemisphere Summers Using METEOSAT Infrared Channels." Journal of Climate 1, no. 5 (May 1988): 471–84. http://dx.doi.org/10.1175/1520-0442(1988)001<0471:aodiai>2.0.co;2.
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Waqas, A., and H. Athar. "Observed diurnal temperature range variations and its association with observed cloud cover in northern Pakistan." International Journal of Climatology 38, no. 8 (March 23, 2018): 3323–36. http://dx.doi.org/10.1002/joc.5503.
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Shimada, Teruhisa, Masahiro Sawada, Weiming Sha, and Hiroshi Kawamura. "Low-Level Easterly Winds Blowing through the Tsugaru Strait, Japan. Part I: Case Study and Statistical Characteristics Based on Observations." Monthly Weather Review 138, no. 10 (October 1, 2010): 3806–21. http://dx.doi.org/10.1175/2010mwr3354.1.
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Abstract This study has investigated structures and diurnal variations of the easterly surface winds blowing throughout the east–west passage comprising the Tsugaru Strait, Mutsu Bay, and circumjacent terrestrial gaps in northern Japan during the summer months. Based on observational and reanalysis data, a representative case study in June 2003 and supplemental statistical analyses are presented. The cool easterly winds accompanied by clouds and fog are blocked by the central mountain range. This condition increases an along-strait sea level pressure (SLP) gradient, which induces strong winds in the west of the strait. The along-strait SLP gradient is enhanced by the developed Okhotsk high and by low pressure systems passing along the southern coast of Japan or over the Japan Sea. Stronger (weaker) and easterly (east-northeasterly) winds are observed during the nighttime (daytime), corresponding to the cool air intrusion from the east (retreat from west). Differences in SLP observed at meteorological observation stations on the east and west can be a good indicator of wind speed in the west of the strait. Meanwhile, the winds over the land also show diurnal variations specific to the times of the prevailing cool easterly winds. The easterly winds over the land are stronger and more divergent across the strait during the daytime than nighttime. This indicates the possibility that the diurnal wind variations are thermally induced. Reduction of diurnal air temperature changes in the east increases east–west thermal contrast. Additionally, the cool air over the strait and the bay can enhance land–sea thermal contrast across the coast.
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Mao, Huiting, Irene Cheng, and Leiming Zhang. "Current understanding of the driving mechanisms for spatiotemporal variations of atmospheric speciated mercury: a review." Atmospheric Chemistry and Physics 16, no. 20 (October 19, 2016): 12897–924. http://dx.doi.org/10.5194/acp-16-12897-2016.
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Abstract. Atmospheric mercury (Hg) is a global pollutant and thought to be the main source of mercury in oceanic and remote terrestrial systems, where it becomes methylated and bioavailable; hence, atmospheric mercury pollution has global consequences for both human and ecosystem health. Understanding of spatial and temporal variations of atmospheric speciated mercury can advance our knowledge of mercury cycling in various environments. This review summarized spatiotemporal variations of total gaseous mercury or gaseous elemental mercury (TGM/GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM) in various environments including oceans, continents, high elevation, the free troposphere, and low to high latitudes. In the marine boundary layer (MBL), the oxidation of GEM was generally thought to drive the diurnal and seasonal variations of TGM/GEM and GOM in most oceanic regions, leading to lower GEM and higher GOM from noon to afternoon and higher GEM during winter and higher GOM during spring–summer. At continental sites, the driving mechanisms of TGM/GEM diurnal patterns included surface and local emissions, boundary layer dynamics, GEM oxidation, and for high-elevation sites mountain–valley winds, while oxidation of GEM and entrainment of free tropospheric air appeared to control the diurnal patterns of GOM. No pronounced diurnal variation was found for Tekran measured PBM at MBL and continental sites. Seasonal variations in TGM/GEM at continental sites were attributed to increased winter combustion and summertime surface emissions, and monsoons in Asia, while those in GOM were controlled by GEM oxidation, free tropospheric transport, anthropogenic emissions, and wet deposition. Increased PBM at continental sites during winter was primarily due to local/regional coal and wood combustion emissions. Long-term TGM measurements from the MBL and continental sites indicated an overall declining trend. Limited measurements suggested TGM/GEM increasing from the Southern Hemisphere (SH) to the Northern Hemisphere (NH) due largely to the vast majority of mercury emissions in the NH, and the latitudinal gradient was insignificant in summer probably as a result of stronger meridional mixing. Aircraft measurements showed no significant vertical variation in GEM over the field campaign regions; however, depletion of GEM was observed in stratospherically influenced air masses. In examining the remaining questions and issues, recommendations for future research needs were provided, and among them is the most imminent need for GOM speciation measurements and fundamental understanding of multiphase redox kinetics.
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Zhao, Jie, Kunlun Xiang, Zhitao Wu, and Ziqiang Du. "Varying Responses of Vegetation Greenness to the Diurnal Warming across the Global." Plants 11, no. 19 (October 8, 2022): 2648. http://dx.doi.org/10.3390/plants11192648.
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The distribution of global warming has been varying both diurnally and seasonally. Little is known about the spatiotemporal variations in the relationships between vegetation greenness and day- and night-time warming during the last decades. We investigated the global inter- and intra-annual responses of vegetation greenness to the diurnal asymmetric warming during the period of 1982–2015, using the normalized different vegetation index (NDVI, a robust proxy for vegetation greenness) obtained from the NOAA/AVHRR NDVI GIMMS3g dataset and the monthly average daily maximum (Tmax) and minimum temperature (Tmin) obtained from the gridded Climate Research Unit, University of East Anglia. Several findings were obtained: (1) The strength of the relationship between vegetation greenness and the diurnal temperature varied on inter-annual and seasonal timescales, indicating generally weakening warming effects on the vegetation activity across the global. (2) The decline in vegetation response to Tmax occurred mainly in the mid-latitudes of the world and in the high latitudes of the northern hemisphere, whereas the decline in the vegetation response to Tmin primarily concentrated in low latitudes. The percentage of areas with a significantly negative trend in the partial correlation coefficient between vegetation greenness and diurnal temperature was greater than that of the areas showing the significant positive trend. (3) The trends in the correlation between vegetation greenness and diurnal warming showed a complex spatial pattern: the majority of the study areas had undergone a significant declining strength in the vegetation greenness response to Tmax in all seasons and to Tmin in seasons except autumn. These findings are expected to have important implications for studying the diurnal asymmetry warming and its effect on the terrestrial ecosystem.
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Wu, Y. W., R. Y. Liu, B. C. Zhang, Z. S. Wu, J. S. Ping, J. M. Liu, and Z. J. Hu. "Variations of the ionospheric TEC using simultaneous measurements from the China Crustal Movement Observation Network." Annales Geophysicae 30, no. 10 (October 1, 2012): 1423–33. http://dx.doi.org/10.5194/angeo-30-1423-2012.
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Abstract. Variations of the ionospheric Total Electron Content (TEC) over China are investigated using the TEC data obtained from China Crustal Movement Observation Network in the year 2004. The results show a single-peak occurred in post-noon for the diurnal variation and two peaks exit around two equinox points, respectively, for the seasonal variation. Overall, the values of TEC increased from the north to the south of China. There were small but clear longitudinal differences in both sides of the longitudes with zero magnetic declination. The intensity of the day-to-day variation of TEC was not a monotonic change along the latitudes. It was usually weaker in the middle of China than that in the north or south. Comparing with the maximum F-layer electron density (NmF2) derived from the ionosonde stations in China, it is found that the day-to-day variation of TEC was less significant than that of NmF2, and that the northern crest of the equatorial anomaly identified from the NmF2 data can reach Guangzhou-region. While, the TEC crest was hardly observed in the same location. This is probably caused by the tilt of topside ionosphere near the northern anomaly crest region at lower latitudes.
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Zhang, Chunxi, Qinghong Zhang, and Yuqing Wang. "Climatology of Hail in China: 1961–2005." Journal of Applied Meteorology and Climatology 47, no. 3 (March 1, 2008): 795–804. http://dx.doi.org/10.1175/2007jamc1603.1.
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Abstract A previous hail climatology of China was based upon observations during 1951–60. An effort has been made in this study to update this hail climatology in China with the use of a much longer record of observations from 1961 to 2005. This is made possible with the release of a new, comprehensive collection of hail observational data in May 2006 by the National Meteorological Information Center of China. The focus herein is to document the mean annual geographical distribution of hail frequency and seasonal and diurnal variations of hail occurrence. The results show that hail occurs most frequently in the high mountainous areas and northern plains. As a result, hail frequency is generally higher in northern China than in southern China. The hail frequency is highest over the central Tibetan Plateau. Hail seasons start in late spring and end in early autumn in northern and western China; they start mainly in spring in southern and southwestern China. On the diurnal time scale, hail events occur mainly between 1500 and 2000 local time in most of China except in Guizhou and Hubei Provinces (central western China), where hail events often occur during nighttime.
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Eriksson, P., B. Rydberg, M. Johnston, D. P. Murtagh, H. Struthers, S. Ferrachat, and U. Lohmann. "Diurnal variations of humidity and ice water content in the tropical upper troposphere." Atmospheric Chemistry and Physics 10, no. 23 (December 6, 2010): 11519–33. http://dx.doi.org/10.5194/acp-10-11519-2010.
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Abstract. Observational results of diurnal variations of humidity from Odin-SMR and AURA-MLS, and cloud ice mass from Odin-SMR and CloudSat are presented for the first time. Comparisons show that the retrievals of humidity and cloud ice from these two satellite combinations are in good agreement. The retrieved data are combined from four almost evenly distributed times of the day allowing mean values, amplitudes and phases of the diurnal variations around 200 hpa to be estimated. This analysis is applied to six climatologically distinct regions, five located in the tropics and one over the subtropical northern Pacific Ocean. The strongest diurnal cycles are found over tropical land regions, where the amplitude is ~7 RHi for humidity and ~50% for ice mass. The greatest ice mass for these regions is found during the afternoon, and the humidity maximum is observed to lag this peak by ~6 h. Over tropical ocean regions the variations are smaller and the maxima in both ice mass and humidity are found during the early morning. Observed results are compared with output from three climate models (ECHAM, EC-EARTH and CAM3). Direct measurement-model comparisons were not possible because the measured and modelled cloud ice masses represent different quantities. To make a meaningful comparison, the amount of snow had to be estimated from diagnostic parameters of the models. There is a high probability that the models underestimate the average ice mass (outside the 1-σ uncertainty). The models also show clear deficiencies when it comes to amplitude and phase of the regional variations, but to varying degrees.
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Shevchenko, I. V. "Influence of solar activity on water clusters. Annual variations 2015—2019." Reports of the National Academy of Sciences of Ukraine, no. 3 (July 2, 2022): 51–57. http://dx.doi.org/10.15407/dopovidi2022.03.051.
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The variations of solar activity and distribution of solar energy due to the rotation of the Earth around its axis and around the Sun exert a strong influence on water clusters, as a result of which their chemical reactivity in hydrolytic processes can vary in a very wide range. This phenomenon is well manifested in the hydrolysis of the phosphoric acid esters. The 5-year regular investigations (2015—2019) of the hydrolysis of triethylphosphite in acetonitrile show that the rate of this reaction with all other conditions being equal displays diurnal, very large annual variations, and is also modulated by the 11-year cycles of solar activity. Since water is a necessary constituent in all forms of life, the discovered diurnal and annual variations of water clusters’ reactivity may underlie the biological circadian and circannual rhythms. The results obtained also point to the fact that the chemical reactivity of water clusters depends on the geographic latitude, and, in summer and winter, it can be significantly different at the same time in the Northern and Southern hemispheres. At the equator, where there should be no seasonal differences, measurements of the rate of triethylphosphite hydrolysis may become an independent method for assessing the solar activity.
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Gomes, Marcelo Paes, Miguel Siano Cunha, and Ilana Rosental Zalmon. "Spatial and temporal variations of diurnal ichthyofauna on surf-zone of São Francisco do Itabapoana beaches, Rio de Janeiro State, Brazil." Brazilian Archives of Biology and Technology 46, no. 4 (December 2003): 653–64. http://dx.doi.org/10.1590/s1516-89132003000400020.
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Spatial and temporal variations of diurnal ichthyofauna and the environmental variables influences on its distribution were studied at the surf-zone of three beaches of São Francisco do Itabapoana, northern coast of Rio de Janeiro, Brazil. From August/1999 to August/2000, three beach seine hauls were made monthly, and environmental variables were recorded. A total number of 4,562 fishes (74,155g) were sampled at the three beaches, where estuarine-dependent species prevailed (44%), followed by marine (31%), estuarine (19%) and freshwater species (3%). Species richness, number of individuals and wet weight were significantly higher at Gargaú, followed by Manguinhos and Barra do Itabapoana, respectively. Canonical Correspondence Analysis highlighted influences of the rivers flushing, salinity and plant abundance on the diurnal ichthyofauna distribution and dynamics of São Francisco do Itabapoana surf-zone.
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Wu, Ruoting, and Guixing Chen. "Contrasting Cloud Regimes and Associated Rainfall over the South Asian and East Asian Monsoon Regions." Journal of Climate 34, no. 9 (May 2021): 3663–81. http://dx.doi.org/10.1175/jcli-d-20-0992.1.
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AbstractThe Asian monsoon has large spatial and temporal variabilities in winds and precipitation. This study reveals that the Asian monsoon also exhibits pronounced regional differences in cloud regimes and cloud–rainfall relationship at a wide range of time scales from diurnal to seasonal to interannual. Over South (East) Asia, the convectively active regime of deep convection (CD) occurs frequently in June–September (March–September) with a late-afternoon peak (morning feature). The intermediate mixture (IM) regime over South Asia mainly occurs in summer and maximizes near noon. It develops as CD at late afternoon and dissipates as convective cirrus (CC) after midnight, showing a life cycle of thermal convection in response to solar radiation. Over East Asia, IM is dominant in cold seasons with a small diurnal cycle, indicating a prevalence of midlevel stratiform clouds. Further analyses show that CD and CC contribute 80%–90% of the rainfall amount and most of the intense rainfall in the two key regions. The CD-related rainfall also accounts for the pronounced diurnal cycles of summer rainfall with a late-afternoon peak (morning feature) over northern India (Southeast China). The afternoon CD-related rainfall mainly results from thermal convection under the moderate humidity but warm conditions particularly over northern India, while the morning CD-related rainfall over Southeast China is more related to the processes with high humidity. The CD/CC-related rainfall also exhibits large interannual variations that explain ~90% of the interannual variance of summer rainfall. The interannual variations of CD/CC occurrence are positively correlated with the moist southerlies and induced convergence, especially over Southeast China, suggesting a close relationship between cloud regimes and monsoon activities.
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Singer, W., J. Weiß, and U. von Zahn. "Diurnal and annual variations of meteor rates at the Arctic circle." Atmospheric Chemistry and Physics Discussions 4, no. 1 (January 6, 2004): 1–20. http://dx.doi.org/10.5194/acpd-4-1-2004.
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Abstract. Meteors are an important source for (a) the metal atoms of the upper atmosphere metal layers and (b) for condensation nuclei, the existence of which are a prerequisite for the formation of noctilucent cloud particles in the polar mesopause region. For a better understanding of these phenomena, it would be helpful to know accurately the annual and diurnal variations of meteor rates. So far, these rates have been little studied at polar latitudes. Therefore we have used the 33 MHz meteor radar of the ALOMAR observatory at 69° N to measure the meteor rates at this location for two full annual cycles. This site, being within 3° of the Arctic circle, offers in addition an interesting capability: The axis of its antenna field points (almost) towards the North ecliptic pole once each day of the year. In this particular viewing direction, the radar monitors the meteoroid influx from (almost) the entire ecliptic Northern hemisphere. We report on the observed diurnal variations (averaged over one month) of meteor rates and their significant alterations throughout the year. The ratio of maximum over minimum meteor rates throughout one diurnal cycle is in January and February about 5, from April through December 2.3±0.3. If compared with similar measurements at mid-latitudes, our expectation, that the amplitude of the diurnal variation is to decrease towards the North pole, is not really borne out. Observations with the antenna axis pointing towards the North ecliptic pole showed that the rate of deposition of meteoric dust is substantially larger during the Arctic NLC season than the annual mean deposition rate. The daylight meteor showers of the Arietids, Zeta Perseids, and Beta Taurids supposedly contribute considerably to the June maximum of meteor rates. We note, though, that with the radar antenna pointing as described above, all three meteor radiants are close to the local horizon. This radiant location should cause most of these shower meteors to occur above 100 km altitude. In our observations, the June maximum in meteor rate is produced, however, almost exclusively by meteors below 100 km altitude.
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Meskhidze, N., L. A. Remer, S. Platnick, R. Negrón Juárez, A. M. Lichtenberger, and A. R. Aiyyer. "Exploring the differences in cloud properties observed by the Terra and Aqua MODIS sensors." Atmospheric Chemistry and Physics Discussions 9, no. 1 (January 16, 2009): 1489–520. http://dx.doi.org/10.5194/acpd-9-1489-2009.
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Abstract. The aerosol-cloud interaction in different parts of the globe is examined here using multi-year statistics of remotely sensed data from two MODIS sensors aboard NASA's Terra (morning) and Aqua (afternoon) satellites. Simultaneous retrievals of aerosol loadings and cloud properties by the MODIS sensor allowed us to explore intra-diurnal variation of liquid cloud fraction (CF) and optical thickness (COT) for clean, moderately polluted and heavily polluted clouds in different seasons. Data analysis for six-years of MODIS retrievals revealed strong temporal and spatial patterns in intra-diurnal variation of cloud fraction and optical thickness over different parts of the global oceans and the land. For the vast areas of stratocumulus cloud regions, the data shows that the presence of aerosols can more than double afternoon reduction of CF and COT pointing to the possible predominance of semi-direct over the indirect effects of aerosols in stratocumulus clouds. A positive relationship between AOD and morning-to-afternoon variation of trade wind cumulus cloud cover was also found over the northern Indian Ocean, though no clear correlation between the concentration of Indo-Asian haze and intra-diurnal variation of COT was established. Over the Amazon region during wet conditions, aerosols are associated with an enhanced convective process in which morning shallow warm clouds are organized into afternoon deep convection with greater ice cloud coverage. Analysis presented here demonstrates that the new technique for exploring intra-diurnal variability in cloud properties by using the differences in data products from the two daily MODIS overpasses is capable of capturing some of the major features of morning-to-afternoon variations in cloud properties and can be used for improved understanding of aerosol radiative effects.
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Hajkowicz, L. A. "Longitudinal (UT) effect in the onset of auroral disturbances over two solar cycles as deduced from the AE-index." Annales Geophysicae 16, no. 12 (December 31, 1998): 1573–79. http://dx.doi.org/10.1007/s00585-998-1573-9.
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Abstract. Statistical study on the universal time variations in the mean hourly auroral electrojet index (AE-index) has been undertaken for a 21 y period over two solar cycles (1957–1968 and 1978–1986). The analysis, applied to isolated auroral substorm onsets (inferred from rapid variations in the AE-index) and to the bulk of the AE data, indicates that the maximum in auroral activity is largely confined to 09–18 UT, with a distinct minimum at 03–06 UT. The diurnal effect was clearly present throughout all seasons in the first cycle but was mainly limited to northern winter in the second cycle. Severe storms (AE > 1000 nT) tended to occur between 9–18 UT irrespective of the seasons whereas all larger magnetic disturbances (AE > 500 nT) tended to occur in this time interval mostly in winter. On the whole the diurnal trend was strong in winter, intermediate at equinox and weak in summer. The implication of this study is that Eastern Siberia, Japan and Australia are mostly at night, during the period of maximum auroral activity whereas Europe and Eastern America are then mostly at daytime. The minimum of auroral activity coincides with near-midnight conditions in Eastern America. It appears that the diurnal UT distribution in the AE-index reflects a diurnal change between interplanetary magnetic field orientation and the Earth's magnetic dipole inclination.Key words. Ionosphere (auroral ionosphere) · Magnetospheric physics (auroral phenomena; storms and substorms).
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Cui, Xiaoyong, Song Gu, Xinquan Zhao, Jing Wu, Tomomichi Kato, and Yanhong Tang. "Diurnal and seasonal variations of UV radiation on the northern edge of the Qinghai-Tibetan Plateau." Agricultural and Forest Meteorology 148, no. 1 (January 2008): 144–51. http://dx.doi.org/10.1016/j.agrformet.2007.09.008.
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Eriksson, P., B. Rydberg, M. Johnston, D. P. Murtagh, H. Struthers, S. Ferrachat, and U. Lohmann. "Diurnal variations of humidity and ice water content in the tropical upper troposphere." Atmospheric Chemistry and Physics Discussions 10, no. 5 (May 3, 2010): 11711–50. http://dx.doi.org/10.5194/acpd-10-11711-2010.
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Abstract. Observational results of diurnal variations of humidity from Odin-SMR and AURA-MLS, and cloud ice mass from Odin-SMR and CloudSat are presented for the first time. Comparisons show that the retrievals of humidity and cloud ice from these three satellite instruments are in good agreement. The retrieved data are combined from four almost evenly distributed times of the day allowing mean values, amplitudes and phases of the diurnal variations around 200 hPa to be estimated. This analysis is applied to six climatologically distinct regions, five located in the tropics and one over the subtropical northern Pacific Ocean. The strongest diurnal cycles are found over tropical land regions, where the amplitude is in the order of 6 %RHi for humidity and 50% for ice mass. The greatest ice mass is for these regions found during the afternoon, and the humidity maximum is observed to lag this peak by ~6 h. Over tropical ocean regions the variations are smaller and the maximum in both ice mass and humidity are found during the early morning. Observed results are compared with output from three climate models (ECHAM, EC-EARTH and CAM3). Direct measurement-model comparisons were not possible because the measured and modelled cloud ice masses represent different quantities. To make a meaningful comparison, the amount of snow had to be estimated from diagnostic parameters of the models. There is a high probability that the models underestimate the average ice mass (below the 1-σ uncertainty). The models show also clear deficiencies when it comes to amplitude and phase of the regional variations, but to a varying degree.
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Rauniyar, Surendra P., and Kevin J. E. Walsh. "Scale Interaction of the Diurnal Cycle of Rainfall over the Maritime Continent and Australia: Influence of the MJO." Journal of Climate 24, no. 2 (January 15, 2011): 325–48. http://dx.doi.org/10.1175/2010jcli3673.1.
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Abstract The influence of the MJO on the phase and amplitude of the diurnal cycle of rainfall during Australian summer [December–February (DJF)] over the Maritime Continent (MC) and northern Australia is investigated using the Tropical Rainfall Measuring Mission (TRMM) 3B42 and 3G68 datasets. The gridded rainfall was partitioned into MJO categories (active, suppressed, and weak) based on their longitudinal position and by utilizing the real-time multivariate MJO (RMM) index of Wheeler and Hendon. The diurnal cycles were composited and an empirical orthogonal function (EOF) analysis was applied to extract the spatial and temporal variability. Distinct variations in the rainfall distribution pattern among categories of the MJO over land and ocean are seen. The result of the composite-mean rainfall distribution shows that the average daily rainfall rate over islands is higher during suppressed MJO days, while for surrounding oceans and northern regions of Australia, more rainfall occurs during MJO active days. The normalized relative amplitude (NRA) of the diurnal cycle of rainfall shows that morning rainfall near coastal areas during active days of the MJO is 1.5 times greater than the climatological-mean rainfall but is less than or equal to the climatological mean during other phases of the MJO. Similarly, during the suppressed phase of the MJO evening rainfall is greater over the islands than in other MJO phases. The first two modes of the EOF alone explain more than 88% (65%) of the variance for the 3B42 (3G68) rainfall, and the corresponding principal component time series show a marked diurnal cycle. The results show that both the amplitude and phase of the diurnal cycle of rainfall are modulated by the categories of the MJO. In general, the peak in the diurnal cycle for active (suppressed/weak) days of the MJO lags (leads) the peak in the diurnal cycle for total rainfall by 2 h. Over Darwin and its adjacent regions, the active phase of the MJO is responsible for the occurrence of maximum rainfall after midnight, which is unusual in this region.
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Beavis, Nick K., Timothy J. Lang, Steven A. Rutledge, Walter A. Lyons, and Steven A. Cummer. "Regional, Seasonal, and Diurnal Variations of Cloud-to-Ground Lightning with Large Impulse Charge Moment Changes." Monthly Weather Review 142, no. 10 (September 19, 2014): 3666–82. http://dx.doi.org/10.1175/mwr-d-14-00034.1.
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Abstract The use of both total charge moment change (CMC) and impulse charge moment change (iCMC) magnitudes to assess the potential of a cloud-to-ground (CG) lightning stroke to induce a mesospheric sprite has been well described in the literature, particularly on a case study basis. In this climatological study, large iCMC discharges for thresholds of >100 and >300 C km in both positive and negative polarities are analyzed on a seasonal basis. Also presented are local solar time diurnal distributions in eight different regions covering the lower 48 states as well as the adjacent Atlantic Ocean, including the Gulf Stream. The seasonal maps show the predisposition of large positive iCMCs to dominate across the northern Great Plains, with large negative iCMCs favored in the southeastern United States year-round. During summer, the highest frequency of large positive iCMCs across the upper Midwest aligns closely with the preferred tracks of nocturnal mesoscale convective systems (MCSs). As iCMC values increase above 300 C km, the maximum shifts eastward of the 100 C km maximum in the central plains. Diurnal distributions in the eight regions support these conclusions, with a nocturnal peak in large iCMC discharges in the northern Great Plains and Great Lakes, an early to midafternoon peak in the Intermountain West and the southeastern United States, and a morning peak in large iCMC discharge activity over the Atlantic Ocean. Large negative iCMCs peak earlier in time than large positive iCMCs, which may be attributed to the growth of large stratiform charge reservoirs following initial convective development.
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Dong, Manyu, Bingqin Wang, Yuan Jiang, and Xinyuan Ding. "Environmental Controls of Diurnal and Seasonal Variations in the Stem Radius of Platycladus orientalis in Northern China." Forests 10, no. 9 (September 9, 2019): 784. http://dx.doi.org/10.3390/f10090784.
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Fine-resolution studies of stem radial variation over short timescales throughout the year can provide insight into intra-annual stem dynamics and improve our understanding of climate impacts on tree physiology and growth processes. Using data from high-resolution point dendrometers collected from Platycladus orientalis (Linn.) trees between September 2013 and December 2014, this study investigated the daily and seasonal patterns of stem radial variation in addition to the relationships between daily stem radial variation and environmental factors over the growing season. Two contrasting daily cycle patterns were observed for warm and cold seasons. A daily mean air temperature of 0 °C was a critical threshold that was related to seasonal shifts in stem diurnal cycle patterns, indicating that air temperature critically influences diurnal stem cycles. The annual variation in P. orientalis stem radius variation can be divided into four distinct periods including (1) spring rehydration, (2) the summer growing season, (3) autumn stagnation, and (4) winter contraction. These periods reflect seasonal changes in tree water status that are especially pronounced in spring and winter. During the growing season, the maximum daily shrinkage (MDS) of P. orientalis was positively correlated with air temperature (Ta) and negatively correlated with soil water content (SWC) and precipitation (P). The vapor pressure deficit (VPD) also exhibited a threshold-based control on MDS at values below or above 0.8 kPa. Daily radial changes (DRC) were negatively correlated with Ta and VPD but positively correlated with relative air humidity (RH) and P. These results suggest that the above environmental factors are associated with tree water status via their influence on moisture availability to trees, which in turn affects the metrics of daily stem variation including MDS and DRC.
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Kostsov, Vladimir S., Anke Kniffka, and Dmitry V. Ionov. "Cloud liquid water path in the sub-Arctic region of Europe as derived from ground-based and space-borne remote observations." Atmospheric Measurement Techniques 11, no. 10 (October 5, 2018): 5439–60. http://dx.doi.org/10.5194/amt-11-5439-2018.
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Abstract. Tropospheric clouds are a very important component of the climate system and the hydrological cycle in the Arctic and sub-Arctic. Liquid water path (LWP) is one of the key parameters of clouds urgently needed for a variety of studies, including the snow cover and climate modelling at northern latitudes. A joint analysis was made of the LWP values obtained from observations by the SEVIRI satellite instrument and from ground-based observations by the RPG-HATPRO microwave radiometer near St Petersburg, Russia (60∘ N, 30∘ E). The time period of selected data sets spans 2 years (December 2012–November 2014) excluding winter months, since the specific requirements for SEVIRI observations restrict measurements at northern latitudes in winter when the solar zenith angle is too large. The radiometer measurement site is located very close to the shore of the Gulf of Finland, and our study has revealed considerable differences between the LWP values obtained by SEVIRI over land and over water areas in the region under investigation. Therefore, special attention was paid to the analysis of the LWP spatial distributions derived from SEVIRI observations at scales from 15 to 150 km in the vicinity of St Petersburg. Good agreement between the daily median LWP values obtained from the SEVIRI and the RPG-HATPRO observations was shown: the rms difference was estimated at 0.016 kg m−2 for a warm season and 0.048 kg m−2 for a cold season. Over 7 months (February–May and August–October), the SEVIRI and the RPG-HATPRO instruments revealed similar diurnal variations in LWP, while considerable discrepancies between the diurnal variations obtained by the two instruments were detected in June and July. On the basis of reanalysis data, it was shown that the LWP diurnal cycles are characterised by considerable interannual variability.
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Nambiar, Manoj K., Françoise R. Robe, Alison M. Seguin, Matthew Endsin, and Amir A. Aliabadi. "Diurnal and Seasonal Variation of Area-Fugitive Methane Advective Flux from an Open-Pit Mining Facility in Northern Canada Using WRF." Atmosphere 11, no. 11 (November 14, 2020): 1227. http://dx.doi.org/10.3390/atmos11111227.
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Greenhouse Gas (GHG) emissions pose a global climate challenge and the mining sector is a large contributor. Diurnal and seasonal variations of area-fugitive methane advective flux, released from an open-pit mine and a tailings pond, from a facility in northern Canada, were simulated in spring 2018 and winter 2019, using the Weather Research and Forecasting (WRF) model. The methane mixing ratio boundary conditions for the WRF model were obtained from the in-situ field measurements, using Los Gatos Research Ultra-Portable Greenhouse Gas Analyzers (LGRs), placed in various locations surrounding the mine pit and a tailings pond. The simulated advective flux was influenced by local and synoptic weather conditions in spring and winter, respectively. Overall, the average total advective flux in the spring was greater than that in the winter by 36% and 75%, for the mine and pond, respectively. Diurnal variations of flux were notable in the spring, characterized by low flux during thermally stable (nighttime) and high flux during thermally unstable (daytime) conditions. The model predictions of the methane mixing ratio were in reasonable agreement with limited aircraft observations (R2=0.68). The findings shed new light in understanding the area-fugitive advective flux from complex terrains and call for more rigorous observations in support of the findings.
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Liu, Yu, Nicolas Gruber, and Dominik Brunner. "Spatiotemporal patterns of the fossil-fuel CO<sub>2</sub> signal in central Europe: results from a high-resolution atmospheric transport model." Atmospheric Chemistry and Physics 17, no. 22 (November 28, 2017): 14145–69. http://dx.doi.org/10.5194/acp-17-14145-2017.
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Abstract. The emission of CO2 from the burning of fossil fuel is a prime determinant of variations in atmospheric CO2. Here, we simulate this fossil-fuel signal together with the natural and background components with a regional high-resolution atmospheric transport model for central and southern Europe considering separately the emissions from different sectors and countries on the basis of emission inventories and hourly emission time functions. The simulated variations in atmospheric CO2 agree very well with observation-based estimates, although the observed variance is slightly underestimated, particularly for the fossil-fuel component. Despite relatively rapid atmospheric mixing, the simulated fossil-fuel signal reveals distinct annual mean structures deep into the troposphere, reflecting the spatially dense aggregation of most emissions. The fossil-fuel signal accounts for more than half of the total (fossil fuel + biospheric + background) temporal variations in atmospheric CO2 in most areas of northern and western central Europe, with the largest variations occurring on diurnal timescales owing to the combination of diurnal variations in emissions and atmospheric mixing and transport out of the surface layer. The covariance of the fossil-fuel emissions and atmospheric transport on diurnal timescales leads to a diurnal fossil-fuel rectifier effect of up to 9 ppm compared to a case with time-constant emissions. The spatial pattern of CO2 from the different sectors largely reflects the distribution and relative magnitude of the corresponding emissions, with power plant emissions leaving the most distinguished mark. An exception is southern and western Europe, where the emissions from the transportation sector dominate the fossil-fuel signal. Most of the fossil-fuel CO2 remains within the country responsible for the emission, although in smaller countries up to 80 % of the fossil-fuel signal can come from abroad. A fossil-fuel emission reduction of 30 % is clearly detectable for a surface-based observing system for atmospheric CO2, while it is beyond the edge of detectability for the current generation of satellites with the exception of a few hotspot sites. Changes in variability in atmospheric CO2 might open an additional door for the monitoring and verification of changes in fossil-fuel emissions, primarily for surface-based systems.