Academic literature on the topic 'Meteorology Australia, Northern Diurnal variations'
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Journal articles on the topic "Meteorology Australia, Northern Diurnal variations"
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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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Bochníček, J., P. Hejda, V. Bucha, and J. Pýcha. "Possible geomagnetic activity effects on weather." Annales Geophysicae 17, no. 7 (July 31, 1999): 925–32. http://dx.doi.org/10.1007/s00585-999-0925-4.
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Abstract. Tropospheric temperature and pressure fields on the Northern Hemisphere in the winter periods 1952-1996 were investigated. Composite maps of those fields, created for the high and low geomagnetic activity and individual quasi-biennial oscillation (QBO), phases show clear differences not only between different levels of geomagnetic activity, but also between the two phases of QBO. Special attention was given to the behaviour of the lower troposphere in January and February 1982.Key words. Geomagnetism and paleomagnetism (time variations · diurnal to regular). Meteorology and atmospheric dynamics (general circulation; middle atmosphere dynamics)
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Feng, Ming, Yongliang Duan, Susan Wijffels, Je-Yuan Hsu, Chao Li, Huiwu Wang, Yang Yang, et al. "Tracking Air–Sea Exchange and Upper-Ocean Variability in the Indonesian–Australian Basin during the Onset of the 2018/19 Australian Summer Monsoon." Bulletin of the American Meteorological Society 101, no. 8 (August 1, 2020): E1397—E1412. http://dx.doi.org/10.1175/bams-d-19-0278.1.
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Abstract Sea surface temperatures (SSTs) north of Australia in the Indonesian–Australian Basin are significantly influenced by Madden–Julian oscillation (MJO), an eastward-moving atmospheric disturbance that traverses the globe in the tropics. The region also has large-amplitude diurnal SST variations, which may influence the air–sea heat and moisture fluxes, that provide feedback to the MJO evolution. During the 2018/19 austral summer, a field campaign aiming to better understand the influences of air–sea coupling on the MJO was conducted north of Australia in the Indonesian–Australian Basin. Surface meteorology from buoy observations and upper-ocean data from autonomous fast-profiling float observations were collected. Two MJO convective phases propagated eastward across the region in mid-December 2018 and late January 2019 and the second MJO was in conjunction with a tropical cyclone development. Observations showed that SST in the region was rather sensitive to the MJO forcing. Air–sea heat fluxes warmed the SST throughout the 2018/19 austral summer, punctuated by the MJO activities, with a 2°–3°C drop in SST during the two MJO events. Substantial diurnal SST variations during the suppressed phases of the MJOs were observed, and the near-surface thermal stratifications provided positive feedback for the peak diurnal SST amplitude, which may be a mechanism to influence the MJO evolution. Compared to traditionally vessel-based observation programs, we have relied on fast-profiling floats as the main vehicle in measuring the upper-ocean variability from diurnal to the MJO time scales, which may pave the way for using cost-effective technology in similar process studies.
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Burns, G. B., B. A. Tinsley, A. V. Frank-Kamenetsky, O. A. Troshichev, W. J. R. French, and A. R. Klekociuk. "Monthly Diurnal Global Atmospheric Circuit Estimates Derived from Vostok Electric Field Measurements Adjusted for Local Meteorological and Solar Wind Influences." Journal of the Atmospheric Sciences 69, no. 6 (June 1, 2012): 2061–82. http://dx.doi.org/10.1175/jas-d-11-0212.1.
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Abstract Local temperature, wind speed, pressure, and solar wind–imposed influences on the vertical electric field observed at Vostok, Antarctica, are evaluated by multivariate analysis. Local meteorology can influence electric field measurements via local conductivity. The results are used to improve monthly diurnal averages of the electric field attributable to changes in the global convective storm contribution to the ionosphere-to-earth potential difference. Statistically significant average influences are found for temperature (−0.47 ± 0.13% V m−1 °C−1) and wind speed [2.1 ± 0.5% V m−1 (m s−1)−1]. Both associations are seasonally variable. After adjusting the electric field values to uniform meteorological conditions typical of the Antarctic plateau winter (−70°C, 4.4 m s−1, and 623 hPa), the sensitivity of the electric field to the solar wind external generator influence is found to be 0.80 ± 0.07 V m−1 kV−1. This compares with the sensitivity of 0.82 V m−1 kV−1 to the convective meteorology generator that is inferred assuming an average ionosphere-to-ground potential difference of 240 kV taken with the annual mean electric field value of 198 V m−1. Monthly means of the Vostok electric field corrected for the influence of both local meteorology and the solar wind show equinoctial (March and September) and July local maxima. The July mean electric field is greater than the December value by approximately 8%, consistent with a Northern Hemisphere summer maximum. The solar wind–imposed potential variations in the overhead ionosphere are evaluated for three models that fit satellite measurements of ionospheric potential changes to solar wind data. Correlations with Vostok electric field variations peak with a 23-min interpolated delay relative to solar wind changes at the magnetopause.
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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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Jamali, Hizbullah, Stephen J. Livesley, Tracy Z. Dawes, Garry D. Cook, Lindsay B. Hutley, and Stefan K. Arndt. "Diurnal and seasonal variations in CH4 flux from termite mounds in tropical savannas of the Northern Territory, Australia." Agricultural and Forest Meteorology 151, no. 11 (November 2011): 1471–79. http://dx.doi.org/10.1016/j.agrformet.2010.06.009.
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Manson, A. H., C. Meek, M. Hagan, J. Koshyk, S. Franke, D. Fritts, C. Hall, et al. "Seasonal variations of the semi-diurnal and diurnal tides in the MLT: multi-year MF radar observations from 2–70° N, modelled tides (GSWM, CMAM)." Annales Geophysicae 20, no. 5 (May 31, 2002): 661–77. http://dx.doi.org/10.5194/angeo-20-661-2002.
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Abstract. In an earlier paper (Manson et al., 1999a) tidal data (1990–1997) from six Medium Frequency Radars (MFR) were compared with the Global Scale Wave Model (GSWM, original 1995 version). The radars are located between the equator and high northern latitudes: Christmas Island (2° N), Hawaii (22° N), Urbana (40° N), London (43° N), Saskatoon (52° N) and Tromsø (70° N). Common harmonic analysis was applied, to ensure consistency of amplitudes and phases in the 75–95 km height range. For the diurnal tide, seasonal agreements between observations and model were excellent while for the semi-diurnal tide the seasonal transitions between clear solstitial states were less well captured by the model. Here the data set is increased by the addition of two locations in the Pacific-North American sector: Yamagawa 31° N, and Wakkanai 45° N. The GSWM model has undergone two additional developments (1998, 2000) to include an improved gravity wave (GW) stress parameterization, background winds from UARS systems and monthly tidal forcing for better characterization of seasonal change. The other model, the Canadian Middle Atmosphere Model (CMAM) which is a General Circulation Model, provides internally generated forcing (due to ozone and water vapour) for the tides. The two GSWM versions show distinct differences, with the 2000 version being either closer to, or further away from, the observations than the original 1995 version. CMAM provides results dependent upon the GW parameterization scheme inserted, but one of the schemes provides very useful tides, especially for the semi-diurnal component.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)
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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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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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Singh, Jaydeep, Narendra Singh, Narendra Ojha, Amit Sharma, Andrea Pozzer, Nadimpally Kiran Kumar, Kunjukrishnapillai Rajeev, Sachin S. Gunthe, and V. Rao Kotamarthi. "Effects of spatial resolution on WRF v3.8.1 simulated meteorology over the central Himalaya." Geoscientific Model Development 14, no. 3 (March 15, 2021): 1427–43. http://dx.doi.org/10.5194/gmd-14-1427-2021.
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Abstract. The sensitive ecosystem of the central Himalayan (CH) region, which is experiencing enhanced stress from anthropogenic forcing, requires adequate atmospheric observations and an improved representation of the Himalaya in the models. However, the accuracy of atmospheric models remains limited in this region due to highly complex mountainous topography. This article delineates the effects of spatial resolution on the modeled meteorology and dynamics over the CH by utilizing the Weather Research and Forecasting (WRF) model extensively evaluated against the Ganges Valley Aerosol Experiment (GVAX) observations during the summer monsoon. The WRF simulation is performed over a domain (d01) encompassing northern India at 15 km × 15 km resolution and two nests (d02 at 5 km × 5 km and d03 at 1 km × 1 km) centered over the CH, with boundary conditions from the respective parent domains. WRF simulations reveal higher variability in meteorology, e.g., relative humidity (RH = 70.3 %–96.1 %) and wind speed (WS = 1.1–4.2 m s−1), compared to the ERA-Interim reanalysis (RH = 80.0 %–85.0 %, WS = 1.2–2.3 m s−1) over northern India owing to the higher resolution. WRF-simulated temporal evolution of meteorological variables is found to agree with balloon-borne measurements, with stronger correlations aloft (r = 0.44–0.92) than those in the lower troposphere (r = 0.18–0.48). The model overestimates temperature (warm bias by 2.8 ∘C) and underestimates RH (dry bias by 6.4 %) at the surface in d01. Model results show a significant improvement in d03 (P = 827.6 hPa, T = 19.8 ∘C, RH = 92.3 %), closer to the GVAX observations (P = 801.4 hPa, T = 19.5 ∘C, RH = 94.7 %). Interpolating the output from the coarser domains (d01, d02) to the altitude of the station reduces the biases in pressure and temperature; however, it suppresses the diurnal variations, highlighting the importance of well-resolved terrain (d03). Temporal variations in near-surface P, T, and RH are also reproduced by WRF in d03 to an extent (r>0.5). A sensitivity simulation incorporating the feedback from the nested domain demonstrates the improvement in simulated P, T, and RH over the CH. Our study shows that the WRF model setup at finer spatial resolution can significantly reduce the biases in simulated meteorology, and such an improved representation of the CH can be adopted through domain feedback into regional-scale simulations. Interestingly, WRF simulates a dominant easterly wind component at 1 km × 1 km resolution (d03), which is missing in the coarse simulations; however, the frequency of southeasterlies remains underestimated. The model simulation implementing a high-resolution (3 s) topography input (SRTM) improved the prediction of wind directions; nevertheless, further improvements are required to better reproduce the observed local-scale dynamics over the CH.
Book chapters on the topic "Meteorology Australia, Northern Diurnal variations"
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Whiteman, C. David. "Four Factors That Determine Climate." In Mountain Meteorology. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195132717.003.0007.
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Climate differs from one location to another because of differences in • latitude, the angular distance north or south from the equator • altitude, the height above sea level • continentality, the distance from the sea • exposure to regional circulations, including winds and ocean currents. The latitude of a given site determines the length of the day and the angle of incoming sunlight and therefore the amount of solar radiation received at that site. Seasonal and diurnal (day—night) variations in the amount of solar radiation received cause seasonal and diurnal variations in the weather. Near the equator, the days of the year are all about the same length, and the noon sun is nearly overhead year-round. Because day length and solar angle change little with the season, there is little seasonal variability in the weather. In the polar regions, on the other hand, the sun does not rise at all in the winter, and in the summer it never sets, although it remains low in the sky. Thus, polar weather has a high seasonal variability, but a low diurnal variability. In the midlatitudes, the climate is characterized by both seasonal and diurnal changes. Except at the equator, day length varies throughout the year. In the Northern Hemisphere, the longest day of the year is at the summer solstice (June 21), the shortest day of the year is at the winter solstice (December 21), and the day is 12 hours long on the vernal and autumnal equinoxes (March 20 and September 22). The altitude angle of the sun also varies throughout the year, with an increase of about 47° from winter to summer. The more direct summer sunlight produces more heating than the slanted rays of the winter sun. The latitude of a given site affects its climate not only because it determines the angle of solar radiation and the length of a day, but also because it determines the site’s exposure to latitudinal belts of surface high and low pressure that encircle the earth.
Conference papers on the topic "Meteorology Australia, Northern Diurnal variations"
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Duong, Ninh T., and Michael Wegener. "SensorVision validation: diurnal temperature variations in northern Australia." In AeroSense 2000, edited by Robert Lee Murrer, Jr. SPIE, 2000. http://dx.doi.org/10.1117/12.391702.
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