Journal articles on the topic 'Southern Hemisphere'
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Xue, Jiaqing, Bingchao Wang, Yongkui Yu, Jianping Li, Cheng Sun, and Jiangyu Mao. "Multidecadal variation of northern hemisphere summer monsoon forced by the SST inter-hemispheric dipole." Environmental Research Letters 17, no. 4 (March 21, 2022): 044033. http://dx.doi.org/10.1088/1748-9326/ac5a65.
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Abstract The sea surface temperature inter-hemispheric dipole (SSTID) is an important variability mode of global SST anomalies, characterized by an anti-phase variation of SST between the two hemispheres. In this study, the decadal variation of the northern hemisphere summer monsoon (NHSM) is found to be strongly regulated by the SSTID, with positive (negative) phases of the SSTID corresponding to the strengthening (weakening) of NHSM. Both observation and SST-forced atmospheric model simulations suggest that the SSTID related thermal forcing modulates the NHSM by causing planetary-scale atmospheric circulation adjustments. Positive SSTID events lead to coherent increase (decrease) of surface air temperature over the entire northern (southern) hemisphere, increasing the inter-hemispheric thermal contrast (ITC). As sea level pressure changes are just opposite to air temperature, the increase of ITC enhances the inter-hemispheric pressure gradient (southern hemisphere minus northern hemisphere), leading to the strengthening of summer monsoonal circulation and the increase of monsoon rainfall in the northern hemisphere.
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Virtanen, I. O. I., I. I. Virtanen, A. A. Pevtsov, and K. Mursula. "Reconstructing solar magnetic fields from historical observations." Astronomy & Astrophysics 616 (August 2018): A134. http://dx.doi.org/10.1051/0004-6361/201732323.
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Aims. Sunspot activity is often hemispherically asymmetric, and during the Maunder minimum, activity was almost completely limited to one hemisphere. In this work, we use surface flux simulation to study how magnetic activity limited only to the southern hemisphere affects the long-term evolution of the photospheric magnetic field in both hemispheres. The key question is whether sunspot activity in one hemisphere is enough to reverse the polarity of polar fields in both hemispheres. Methods. We simulated the evolution of the photospheric magnetic field from 1978 to 2016 using the observed active regions of the southern hemisphere as input. We studied the flow of magnetic flux across the equator and its subsequent motion towards the northern pole. We also tested how the simulated magnetic field is changed when the activity of the southern hemisphere is reduced. Results. We find that activity in the southern hemisphere is enough to reverse the polarity of polar fields in both hemispheres by the cross-equatorial transport of magnetic flux. About 1% of the flux emerging in the southern hemisphere is transported across the equator, but only 0.1%–0.2% reaches high latitudes to reverse and regenerate a weak polar field in the northern hemisphere. The polarity reversals in the northern hemisphere are delayed compared to the southern hemisphere, leading to a quadrupole Sun lasting for several years.
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Chowdhury, Partha, Ravindra Belur, Luca Bertello, and Alexei A. Pevtsov. "Analysis of Solar Hemispheric Chromosphere Properties using the Kodaikanal Observatory Ca–K Index." Astrophysical Journal 925, no. 1 (January 1, 2022): 81. http://dx.doi.org/10.3847/1538-4357/ac3983.
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Abstract The Kodaikanal Observatory has provided long-term synoptic observations of chromospheric activities in the Ca ii K line (393.34 nm) since 1907. This article investigates temporal and periodic variations of the hemispheric Ca–K-index time series in the low-latitude zone (±40°), utilizing the recently digitized photographic plates of Ca–K images from the Kodaikanal Observatory for the period of 1907–1980. We find that the temporal evolution of the Ca–K index differs from one hemisphere to another, with the solar cycle peaking at different times in the opposite hemisphere, except for cycles 14, 15, and 21, when the phase difference between the two hemispheres was not significant. The monthly averaged data show a higher activity in the northern hemisphere during solar cycles 15, 16, 18, 19, and 20, and in the southern hemisphere during cycles 14, 17, and 21. We notice an exponentially decaying distribution for each hemisphere’s Ca–K index and the whole solar disk. We explored different midterm periodicities of the measured Ca–K index using the wavelet technique, including Rieger-type and quasi-biennial oscillations on different timescales present in the time series. We find a clear manifestation of the Waldmeier effect (stronger cycles rise faster than the weaker ones) in both the hemispheres separately and the whole disk in the data. Finally, we have found the presence of the Gnevyshev gap (time interval between two cycle maxmima) in both the hemispheric data during cycles 15 to 20. Possible interpretations of our findings are discussed with the help of existing theoretical models and observations.
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Lin 林, Jiaqi 家琪, Feng 锋. Wang 王, Linhua 林华 Deng 邓, Hui 辉. Deng 邓, Ying 盈. Mei 梅, and Xiaojuan 小娟 Zhang 张. "Evolutionary Relationship between Sunspot Groups and Soft X-Ray Flares over Solar Cycles 21–25." Astrophysical Journal 958, no. 1 (November 1, 2023): 1. http://dx.doi.org/10.3847/1538-4357/ad0469.
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Abstract Studying the interaction between solar flares and sunspot groups (SGs) is crucial for understanding and predicting solar activity. We examined the distribution, correlation, and flaring rates in the northern and southern hemispheres to reveal the relationship between different classes of soft X-ray (SXR) flares and different magnetic classifications of SGs. We discovered a significant north–south asymmetry in SXR flares and SG distribution over Solar Cycles (SC) 21–25. In the rising phase of SC24, the northern hemisphere’s activity is significantly excessive. In the declining phase of SC24, the southern hemisphere’s activity becomes significantly excessive. The total numbers of various SXR flares and SGs vary between the northern and southern hemispheres over the solar cycle. B-class flares are negatively correlated with all SGs at maximum but positively correlated at minimum. C-class flares correlate best with α and β SGs. M-class flares correlate best with β γ δ and β SGs. X-class flares correlate highest with β γ δ SGs. The flaring rate of each flare class is lowest for α SGs and highest for β γ δ SGs. The flaring rates are higher in the southern hemisphere than in the northern hemisphere. Our results demonstrate that solar flares originate from different sources of solar active regions; the high-energy flares tend to be caused by more complex magnetic fields.
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Awuor, Adero Ochieng, Paul Baki, Joseph Olwendo, and Pieter Kotze. "Storm-Time Behaviour of Meso-Scale Field-Aligned Currents: Case Study with Three Geomagnetic Storm Events." Journal of Astronomy and Space Sciences 36, no. 3 (September 2019): 133–47. http://dx.doi.org/10.5140/jass.2019.36.3.133.
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Challenging Minisatellite Payload (CHAMP) satellite magnetic data are used to investigate the latitudinal variation of the storm-time meso-scale field-aligned currents by defining a new metric called the FAC range. Three major geomagnetic storm events are considered. Alongside SymH, the possible contributions from solar wind dynamic pressure and interplanetary magnetic field (IMF) BZ are also investigated. The results show that the new metric predicts the latitudinal variation of FACs better than previous studies. As expected, the equatorward expansion and poleward retreat are observed during the storm main phase and recovery phase respectively. The equatorward shift is prominent on the northern duskside, at ~58° coinciding with the minimum SymH and dayside at ~59° compared to dawnside and nightside respectively. The latitudinal shift of FAC range is better correlated to IMF BZ in northern hemisphere dusk-dawn magnetic local time (MLT) sectors than in southern hemisphere. The FAC range latitudinal shifts responds better to dynamic pressure in the duskside northern hemisphere and dawnside southern hemisphere than in southern hemisphere dusk sector and northern hemisphere dawn sector respectively. FAC range exhibits a good correlation with dynamic pressure in the dayside (nightside) southern (northern) hemispheres depicting possible electrodynamic similarity at day-night MLT sectors in the opposite hemispheres.
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Eigen, Jacob. "The Southern Hemisphere." Yale Review 108, no. 3 (2020): 55. http://dx.doi.org/10.1353/tyr.2020.0013.
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RAVEN, P. H. "Southern Hemisphere Biota." Science 191, no. 4226 (March 6, 2003): 460. http://dx.doi.org/10.1126/science.191.4226.460.
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Orchiston, Wayne. "Southern Hemisphere Observations." Highlights of Astronomy 12 (2002): 322–25. http://dx.doi.org/10.1017/s1539299600013654.
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AbstractBecause of insurmountable problems associated with absolute dating, the non-literate cultures of the Southern Hemisphere can contribute little to Applied Historical Astronomy, although Maori traditions document a possible supernova dating to the period 1000-1770AD. In contrast, the abundant nineteenth century solar, planetary, cometary and stellar observational data provided by Southern Hemisphere professional and amateur observatories can serve as an invaluable mine of information for present-day astronomers seeking to incorporate historical data in their investigations.
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Sykes, T. J. S., J. Y. Royer, A. T. S. Ramsay, and R. B. Kidd. "Southern hemisphere palaeobathymetry." Geological Society, London, Special Publications 131, no. 1 (1998): 1–42. http://dx.doi.org/10.1144/gsl.sp.1998.131.01.02.
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Eigen, Jacob. "The Southern Hemisphere." Yale Review 108, no. 3 (September 24, 2020): 55. http://dx.doi.org/10.1111/yrev.13660.
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Zuo, Meng, Tianjun Zhou, and Wenmin Man. "Hydroclimate Responses over Global Monsoon Regions Following Volcanic Eruptions at Different Latitudes." Journal of Climate 32, no. 14 (June 21, 2019): 4367–85. http://dx.doi.org/10.1175/jcli-d-18-0707.1.
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Abstract Understanding the influence of volcanic eruptions on the hydroclimate over global monsoon regions is of great scientific and social importance. However, the link between the latitude of volcanic eruptions and related hydroclimate changes over global monsoon regions in the last millennium remains inconclusive. Here we show divergent hydroclimate responses after different volcanic eruptions based on large sets of reconstructions, observations, and climate model simulation. Both the proxy and observations show that Northern Hemispheric (Southern Hemispheric) monsoon precipitation is weakened by northern (southern) and tropical eruptions but is enhanced by the southern (northern) eruptions. A similar relationship is found in coupled model simulations driven by volcanic forcing. The model evidence indicates that the dynamic processes related to changes in atmospheric circulation play a dominant role in precipitation responses. The dry conditions over the Northern Hemisphere (Southern Hemisphere) and global monsoon regions following northern (southern) and tropical eruptions are induced through weakened monsoon circulation. The wet conditions over Northern Hemispheric (Southern Hemispheric) monsoon regions after southern (northern) eruptions are caused by the enhanced cross-equator flow. We extend our model simulation analysis from mean state precipitation to extreme precipitation and find that the response of the extreme precipitation is consistent with that of the mean precipitation but is more sensitive over monsoon regions. The response of surface runoff and net primary production is stronger than that of precipitation over some submonsoon regions. Our results imply that it is imperative to consider the potential volcanic eruptions at different hemispheres in the design of near-term decadal climate prediction experiments.
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Gary, B. L. "Mesoscale temperature fluctuations in the Southern Hemisphere stratosphere." Atmospheric Chemistry and Physics Discussions 8, no. 3 (May 21, 2008): 9167–78. http://dx.doi.org/10.5194/acpd-8-9167-2008.
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Abstract. Isentrope surfaces in the Southern Hemisphere stratosphere reveal that air parcels undergo mesoscale temperature fluctuations that depend on latitude and season. The largest temperature fluctuations occur at high latitude winter, whereas the smallest fluctuations occur at high latitude summer. This is the same pattern found for the Northern Hemisphere stratosphere. However, the amplitude of the seasonal dependence in the Southern Hemisphere is only 37% of the Northern Hemisphere's seasonal amplitude.
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Gary, B. L. "Mesoscale temperature fluctuations in the Southern Hemisphere stratosphere." Atmospheric Chemistry and Physics 8, no. 16 (August 14, 2008): 4677–81. http://dx.doi.org/10.5194/acp-8-4677-2008.
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Abstract. Isentrope surfaces in the Southern Hemisphere stratosphere reveal that air parcels undergo mesoscale temperature fluctuations that depend on latitude and season. The largest temperature fluctuations occur at high latitude winter, whereas the smallest fluctuations occur at high latitude summer. This is the same pattern found for the Northern Hemisphere stratosphere. However, the amplitude of the seasonal dependence in the Southern Hemisphere is only 37% of the Northern Hemisphere's seasonal amplitude.
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Hogg, Alan G., Timothy J. Heaton, Quan Hua, Jonathan G. Palmer, Chris SM Turney, John Southon, Alex Bayliss, et al. "SHCal20 Southern Hemisphere Calibration, 0–55,000 Years cal BP." Radiocarbon 62, no. 4 (August 2020): 759–78. http://dx.doi.org/10.1017/rdc.2020.59.
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ABSTRACTEarly researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14C yrs older.
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Kettle, A. J., U. Kuhn, M. von Hobe, J. Kesselmeier, P. S. Liss, and M. O. Andreae. "Comparing forward and inverse models to estimate the seasonal variation of hemisphere-integrated fluxes of carbonyl sulfide." Atmospheric Chemistry and Physics 2, no. 5 (November 14, 2002): 343–61. http://dx.doi.org/10.5194/acp-2-343-2002.
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Abstract. A simple inverse model is proposed to deduce hemisphere-integrated COS flux based on published time series of total column COS. The global atmosphere is divided into two boxes representing the Northern and Southern Hemispheres, and the total column COS data from several stations are used to calculate hemispheric COS loadings. The integrated flux within each hemisphere is calculated as a linear combination of a steady-state solution and time-varying perturbation. The nature of the time-varying perturbation is deduced using two different approaches: an analytic solution based on a cosine function that was fitted to the original total column COS measurement time series and a Simplex optimization with no underlying assumption about the functional form of the total column time series. The results suggest that there is a steady-state COS flux from the Northern to the Southern Hemisphere. There is a seasonal variation superimposed on this flux that in the Southern Hemisphere has a maximum rate of COS input into the atmosphere around January and a maximum rate of COS removal from the atmosphere around August--September. In the Northern Hemisphere, the maximum rate of COS input into the atmosphere is around May--June, and the maximum rate of COS removal is either August or January, depending on which station in the Northern Hemisphere is considered. The results of the inverse model are compared with the outcome of a forward approach on the temporal and spatial variation of the dominant global sources and sinks published earlier. In general, the deduced hemisphere-integrated flux estimates showed good agreement with the database estimates, though it remains uncertain whether COS removal from the atmosphere in the Northern Hemisphere is dominated by plant and soil uptake in the boreal summer or by oceanic uptake in boreal winter.
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Kettle, A. J., U. Kuhn, M. von Hobe, J. Kesselmeier, P. S. Liss, and M. O. Andreae. "Comparing forward and inverse models to estimate the seasonal variation of hemisphere-integrated fluxes of carbonyl sulfide." Atmospheric Chemistry and Physics Discussions 2, no. 3 (June 12, 2002): 577–621. http://dx.doi.org/10.5194/acpd-2-577-2002.
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Abstract. A simple inverse model is proposed to deduce hemisphere-integrated COS flux based on published time series of total column COS. The global atmosphere is divided into two boxes representing the Northern and Southern Hemispheres, and the total column COS data from several stations are used to deduce hemispheric COS loadings. The integrated flux within each hemisphere is calculated as a linear combination of a steady-state solution and time-varying perturbation. The nature of the time-varying perturbation is deduced using two different approaches: an analytic solution based on a cosine function that was fitted to the original total column COS measurement time series and a Simplex optimization with no underlying assumption about the functional form of the total column time series. The results suggest that there is a steady-state COS flux from the Northern to the Southern Hemisphere. There is a seasonal variation superimposed on this flux that in the Southern Hemisphere has a maximum rate of COS input into the atmosphere around January and a maximum rate of COS removal from the atmosphere around August--September. In the Northern Hemisphere, the maximum rate of COS input into the atmosphere is around May--June, and the maximum rate of COS removal is either August or January, depending on which station in the Northern Hemisphere is considered. The results of the inverse model are compared with the outcome of a forward approach on the temporal and spatial variation of the dominant global sources and sinks published earlier. In general, the deduced hemisphere-integrated flux estimates showed good agreement with the database estimates, though it remains uncertain whether COS removal from the atmosphere in the Northern Hemisphere is dominated by plant and soil uptake in the boreal summer or by oceanic uptake in boreal winter.
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Aparicio, A. J. P., V. M. S. Carrasco, M. C. Gallego, and J. M. Vaquero. "Hemispheric Sunspot Number from the Madrid Astronomical Observatory for the Period 1935–1986." Astrophysical Journal 931, no. 1 (May 1, 2022): 52. http://dx.doi.org/10.3847/1538-4357/ac5dc6.
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Abstract Long-term studies on hemispheric asymmetry can help to understand better the solar dynamo. We present the hemispheric sunspot number calculated from daily sunspot observations made at the Madrid Astronomical Observatory for the period 1935–1986 (corresponding approximately to Solar Cycles 17–21). From this data set, we also analyzed the asymmetry index and hemispheric phase shifts. We conclude that the northern hemisphere was predominant in Solar Cycles 17–20, whereas the southern hemisphere was predominant in Solar cycle 21. The strongest asymmetries are found in Solar Cycles 20 (with a relative difference between both hemispheres of 44%) and 19 (39%). A normalization of the Madrid hemispheric sunspot number was also made with respect to the sunspot number (Version 2). Our results agree with previous studies on hemispheric asymmetry around the mid-20th century and their secular trends.
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Hachmeister, Jonas, Oliver Schneising, Michael Buchwitz, John P. Burrows, Justus Notholt, and Matthias Buschmann. "Zonal variability of methane trends derived from satellite data." Atmospheric Chemistry and Physics 24, no. 1 (January 15, 2024): 577–95. http://dx.doi.org/10.5194/acp-24-577-2024.
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Abstract. The Tropospheric Monitoring Instrument (TROPOMI) on board the Sentinel-5 Precursor (S5P) satellite is part of the latest generation of trace gas monitoring satellites and provides a new level of spatio-temporal information with daily global coverage, which enables the calculation of daily globally averaged CH4 concentrations. To investigate changes in atmospheric methane, the background CH4 level (i.e. the CH4 concentration without seasonal and short-term variations) has to be determined. CH4 growth rates vary in a complex manner and high-latitude zonal averages may have gaps in the time series, and thus simple fitting methods do not produce reliable results. In this paper we present an approach based on fitting an ensemble of dynamic linear models (DLMs) to TROPOMI data, from which the best model is chosen with the help of cross-validation to prevent overfitting. This method is computationally fast and is not dependent on additional inputs, allowing for fast and continuous analysis of the most recent time series data. We present results of global annual methane increases (AMIs) for the first 4.5 years of S5P/TROPOMI data, which show good agreement with AMIs from other sources. Additionally, we investigated what information can be derived from zonal bands. Due to the fast meridional mixing within hemispheres, we use zonal growth rates instead of AMIs, since they provide a higher temporal resolution. Clear differences can be observed between Northern Hemisphere and Southern Hemisphere growth rates, especially during 2019 and 2022. The growth rates show similar patterns within the hemispheres and show no short-term variations during the years, indicating that air masses within a hemisphere are well-mixed during a year. Additionally, the growth rates derived from S5P/TROPOMI data are largely consistent with growth rates derived from Copernicus Atmospheric Monitoring Service (CAMS) global-inversion-optimized (CAMS/INV) data, which use surface observations. In 2019 a reduction in growth rates can be observed for the Southern Hemisphere, while growth rates in the Northern Hemisphere stay stable or increase. During 2020 a strong increase in Southern Hemisphere growth rates can be observed, which is in accordance with recently reported increases in Southern Hemisphere wetland emissions. In 2022 the reduction in the global AMI can be attributed to decreased growth rates in the Northern Hemisphere, while growth rates in the Southern Hemisphere remain high. Investigations of fluxes from CAMS/INV data support these observations and suggest that the Northern Hemisphere decrease is mainly due to the decrease in anthropogenic fluxes, while in the Southern Hemisphere, wetland fluxes continued to rise. While the continued increase in Southern Hemisphere wetland fluxes agrees with existing studies about the causes of observed methane trends, the difference between Northern Hemisphere and Southern Hemisphere methane increases in 2022 has not been discussed before and calls for further research.
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Naud, Catherine M., Derek J. Posselt, and Susan C. van den Heever. "Observational Analysis of Cloud and Precipitation in Midlatitude Cyclones: Northern versus Southern Hemisphere Warm Fronts." Journal of Climate 25, no. 14 (July 15, 2012): 5135–51. http://dx.doi.org/10.1175/jcli-d-11-00569.1.
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Abstract Extratropical cyclones are responsible for most of the precipitation and wind damage in the midlatitudes during the cold season, but there are still uncertainties on how they will change in a warming climate. A ubiquitous problem among general circulation models (GCMs) is a lack of cloudiness over the southern oceans that may be in part caused by a lack of clouds in cyclones. This study analyzes CloudSat, Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) observations for three austral and boreal cold seasons, and composites cloud frequency of occurrence and precipitation at the warm fronts for Northern and Southern Hemisphere oceanic cyclones. The authors find that cloud frequency of occurrence and precipitation rate are similar in the early stage of the cyclone life cycle in both the Northern and Southern Hemispheres. As cyclones evolve and reach their mature stage, cloudiness and precipitation at the warm front increase in the Northern Hemisphere but decrease in the Southern Hemisphere. This is partly caused by lower amounts of precipitable water being available to Southern Hemisphere cyclones, and smaller increases in wind speed as the cyclones evolve. Southern Hemisphere cloud occurrence at the warm front is found to be more sensitive to the amount of moisture in the warm sector than to wind speeds. This suggests that cloudiness in Southern Hemisphere storms may be more susceptible to changes in atmospheric water vapor content, and thus to changes in surface temperature than their Northern Hemisphere counterparts. These differences between Northern and Southern Hemisphere cyclones are statistically robust, indicating A-Train-based analyses as useful tools for the evaluation of GCMs in the next Intergovernmental Panel on Climate Change (IPCC) report.
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Voigt, Aiko, Bjorn Stevens, Jürgen Bader, and Thorsten Mauritsen. "The Observed Hemispheric Symmetry in Reflected Shortwave Irradiance." Journal of Climate 26, no. 2 (January 15, 2013): 468–77. http://dx.doi.org/10.1175/jcli-d-12-00132.1.
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Abstract While the concentration of landmasses and atmospheric aerosols on the Northern Hemisphere suggests that the Northern Hemisphere is brighter than the Southern Hemisphere, satellite measurements of top-of-atmosphere irradiances found that both hemispheres reflect nearly the same amount of shortwave irradiance. Here, the authors document that the most precise and accurate observation, the energy balanced and filled dataset of the Clouds and the Earth’s Radiant Energy System covering the period 2000–10, measures an absolute hemispheric difference in reflected shortwave irradiance of 0.1 W m−2. In contrast, the longwave irradiance of the two hemispheres differs by more than 1 W m−2, indicating that the observed climate system exhibits hemispheric symmetry in reflected shortwave irradiance but not in longwave irradiance. The authors devise a variety of methods to estimate the spatial degrees of freedom of the time-mean reflected shortwave irradiance. These are used to show that the hemispheric symmetry in reflected shortwave irradiance is a nontrivial property of the Earth system in the sense that most partitionings of Earth into two random halves do not exhibit hemispheric symmetry in reflected shortwave irradiance. Climate models generally do not reproduce the observed hemispheric symmetry, which the authors interpret as further evidence that the symmetry is nontrivial. While the authors cannot rule out that the observed hemispheric symmetry in reflected shortwave irradiance is accidental, their results motivate a search for mechanisms that minimize hemispheric differences in reflected shortwave irradiance and planetary albedo.
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Deng, L. H., Y. Fei, H. Deng, Y. Mei, and F. Wang. "Spatial distribution of quasi-biennial oscillations in high-latitude solar activity." Monthly Notices of the Royal Astronomical Society 494, no. 4 (May 6, 2020): 4930–38. http://dx.doi.org/10.1093/mnras/staa1061.
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ABSTRACT Quasi-biennial oscillations (QBOs) are considered to be a fundamental mode of solar magnetic activity at low latitudes (≤50°). However, the evolutionary aspect and the hemispheric distribution of solar QBOs at high latitudes (≥60°) are rarely studied. Here, we apply a relatively novel time-frequency analysis technique, called the synchrosqueezed wavelet transform, in order to extract the main components of the polar faculae in the Northern and Southern hemispheres for the time interval from 1951 August to 1998 December. We note the following. (i) Apart from the 22-yr Hale cycle, the 17-yr extended activity cycle and the 11-yr Schwabe cycle, QBOs have been estimated as a prominent time-scale of solar magnetic activity at high latitudes. (ii) The QBOs of the polar faculae are coherent in the two hemispheres, but the temporal (phase) and the spatial (amplitude) variations of solar QBOs occur unevenly on both hemispheres. (iii) For the 11-yr period mode, this begins in the Northern hemisphere three months earlier than in the Southern hemisphere. Moreover, the spatial and temporal distributions of the hemispheric QBOs differ from those of the 11-yr Schwabe cycle mode in the two hemispheres. Our findings could be helpful to improve our knowledge of the physical origin of the spatial distribution of solar QBOs at high latitudes, and could also provide more constraints on solar dynamo models introduced to characterize the different components of the solar magnetic activity cycle.
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Timmermann, Axel, Oliver Timm, Lowell Stott, and Laurie Menviel. "The Roles of CO2 and Orbital Forcing in Driving Southern Hemispheric Temperature Variations during the Last 21 000 Yr*." Journal of Climate 22, no. 7 (April 1, 2009): 1626–40. http://dx.doi.org/10.1175/2008jcli2161.1.
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Abstract Transient climate model simulations covering the last 21 000 yr reveal that orbitally driven insolation changes in the Southern Hemisphere, combined with a rise in atmospheric pCO2, were sufficient to jump-start the deglacial warming around Antarctica without direct Northern Hemispheric triggers. Analyses of sensitivity experiments forced with only one external forcing component (greenhouse gases, ice-sheet forcing, or orbital forcing) demonstrate that austral spring insolation changes triggered an early retreat of Southern Ocean sea ice starting around 19–18 ka BP. The associated sea ice–albedo feedback and the subsequent increase of atmospheric CO2 concentrations helped to further accelerate the deglacial warming in the Southern Hemisphere. Implications for the interpretation of Southern Hemispheric paleoproxy records are discussed.
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Burns, Stephen J. "Speleothem records of changes in tropical hydrology over the Holocene and possible implications for atmospheric methane." Holocene 21, no. 5 (March 21, 2011): 735–41. http://dx.doi.org/10.1177/0959683611400194.
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Recent speleothem records from the tropics of both hemispheres document a gradual decrease in the intensity of the monsoons in the Northern Hemisphere and increase in the Southern Hemisphere monsoons over the Holocene. These changes are a direct response of the monsoons to precession-driven insolation variability. With regard to atmospheric methane, this shift should result in a decrease in Northern Hemisphere tropical methane emissions and increase in Southern Hemisphere emissions. It is plausible that that overall tropical methane production experienced a minimum in the mid-Holocene because of decreased seasonality in rainfall at the margins of the tropics. Changes in tropical methane production alone might, therefore, explain many of the characteristics of Holocene methane concentrations and isotopic chemistry.
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Ozguc, Atila, Ali Kilcik, Volkan Sarp, Hülya Yeşilyaprak, and Rıza Pektaş. "Periodic Variation of Solar Flare Index for the Last Solar Cycle (Cycle 24)." Advances in Astronomy 2021 (August 23, 2021): 1–8. http://dx.doi.org/10.1155/2021/5391091.
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In this study, we used the flare index (FI) data taken from Kandilli Observatory for the period of 2009–2020. The data sets are analyzed in three categories as Northern Hemisphere, Southern Hemisphere, and total FI data sets. Total FI data set is obtained from the sum of Northern and Southern Hemispheric values. In this study, the periodic variations of abovementioned three categories FI data sets were investigated by using the MTM and Morlet wavelet analysis methods. The wavelet coherence (XWT) and cross wavelet (WTC) analysis methods were also performed between these data sets. As a result of our analysis, the following results were found: (1) long- and short-term periodicities ( 2048 ± 512 day and periodicities smaller than 62 days) exist in all data sets without any exception at least with 95 % confidence level; (2) all periodic variations were detected maximum during the solar cycle, while during the minima, no meaningful period is detected; (3) some periodicities have data preference that about 150 days Rieger period appears only in the whole data set and 682-, 204-, and 76.6-day periods appear only in the Northern Hemisphere data sets; (4) During the Solar Cycle 24, more flare activity is seen at the Southern Hemisphere, so the whole disk data periodicities are dominated by this hemisphere; (5) in general, there is a phase mixing between Northern and Southern Hemisphere FI data, except about 1024-day periodicity, and the best phase coherency is obtained between the Southern Hemisphere and total flare index data sets; (6) in case of the Northern and Southern Hemisphere FI data sets, there is no significant correlation between two continuous wavelet transforms, but the strongest correlation is obtained for the total FI and Southern Hemisphere data sets.
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McCormac, F. G., P. J. Reimer, A. G. Hogg, T. F. G. Higham, M. G. L. Baillie, J. Palmer, and M. Stuiver. "Calibration of the Radiocarbon Time Scale for the Southern Hemisphere: Ad 1850–950." Radiocarbon 44, no. 3 (2002): 641–51. http://dx.doi.org/10.1017/s0033822200032094.
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We have conducted a series of radiocarbon measurements on decadal samples of dendrochronologically dated wood from both hemispheres, spanning 1000 years (McCormac et al. 1998; Hogg et al. this issue). Using the data presented in Hogg et al., we show that during the period AD 950–1850 the 14C offset between the hemispheres is not constant, but varies periodically (∼130 yr periodicity) with amplitudes varying between 1 and 10% (i.e. 8–80 yr), with a consequent effect on the 14C calibration of material from the Southern Hemisphere. A large increase in the offset occurs between AD 1245 and 1355. In this paper, we present a Southern Hemisphere high-precision calibration data set (SHCal02) that comprises measurements from New Zealand, Chile, and South Africa. This data, and a new value of 41 ± 14 yr for correction of the IntCal98 data for the period outside the range given here, is proposed for use in calibrating Southern Hemisphere 14C dates.
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Garny, H., G. E. Bodeker, D. Smale, M. Dameris, and V. Grewe. "Drivers of hemispheric differences in return dates of mid-latitude stratospheric ozone to historical levels." Atmospheric Chemistry and Physics 13, no. 15 (August 1, 2013): 7279–300. http://dx.doi.org/10.5194/acp-13-7279-2013.
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Abstract. Chemistry-climate models (CCMs) project an earlier return of northern mid-latitude total column ozone to 1980 values compared to the southern mid-latitudes. The chemical and dynamical drivers of this hemispheric difference are investigated in this study. The hemispheric asymmetry in return dates is a robust result across different CCMs and is qualitatively independent of the method used to estimate return dates. However, the differences in dates of return to 1980 levels between the southern and northern mid-latitudes can vary between 0 and 30 yr across the range of CCM projections analyzed. Positive linear trends in ozone lead to an earlier return of ozone than expected from the return of Cly to 1980 levels. This forward shift is stronger in the Northern than in the Southern Hemisphere because (i) trends have a larger effect on return dates if the sensitivity of ozone to Cly is lower and (ii) the trends in the Northern Hemisphere are stronger than in the Southern Hemisphere. An attribution analysis performed with two CCMs shows that chemically-induced changes in ozone are the major driver of the earlier return of ozone to 1980 levels in northern mid-latitudes; therefore transport changes are of minor importance. This conclusion is supported by the fact that the spread in the simulated hemispheric difference in return dates across an ensemble of twelve models is only weakly related to the spread in the simulated hemispheric asymmetry of trends in the strength of the Brewer–Dobson circulation. The causes for chemically-induced asymmetric ozone trends relevant for the total column ozone return date differences are found to be (i) stronger increases in ozone production due to enhanced NOx concentrations in the Northern Hemisphere lowermost stratosphere and troposphere, (ii) stronger decreases in the destruction rates of ozone by the NOx cycle in the Northern Hemisphere lower stratosphere linked to effects of dynamics and temperature on NOx concentrations, and (iii) an increasing efficiency of heterogeneous ozone destruction by Cly in the Southern Hemisphere mid-latitudes as a~result of decreasing lower stratospheric temperatures.
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Martin, Jonathan E., and Taylor Norton. "Waviness of the Southern Hemisphere wintertime polar and subtropical jets." Weather and Climate Dynamics 4, no. 4 (October 20, 2023): 875–86. http://dx.doi.org/10.5194/wcd-4-875-2023.
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Abstract. The recently developed average latitudinal displacement (ALD) methodology is applied to assess the waviness of the austral-winter subtropical and polar jets using three different reanalysis data sets. As in the wintertime Northern Hemisphere, both jets in the Southern Hemisphere have become systematically wavier over the time series and the waviness of each jet evolves quite independently of the other during most cold seasons. Also, like its Northern Hemisphere equivalent, the Southern Hemisphere polar jet exhibits no trend in speed (though it is notably slower), while its poleward shift is statistically significant. In contrast to its Northern Hemisphere counterpart, the austral subtropical jet has undergone both a systematic increase in speed and a statistically significant poleward migration. Composite differences between the waviest and least wavy seasons for each species suggest that the Southern Hemisphere's lower-stratospheric polar vortex is negatively impacted by unusually wavy tropopause-level jets of either species. These results are considered in the context of trends in the Southern Annular Mode as well as the findings of other related studies.
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Baird, Mackenzie A., Sushanta C. Tripathy, and Kiran Jain. "Connection between Subsurface Layers and Surface Magnetic Activity over Multiple Solar Cycles Using GONG Observations." Astrophysical Journal 962, no. 2 (February 1, 2024): 194. http://dx.doi.org/10.3847/1538-4357/ad16db.
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Abstract We investigate the spatiotemporal evolution of high-degree acoustic-mode frequencies of the Sun and surface magnetic activity over the course of multiple solar cycles, to improve our understanding of the connection between the solar interior and atmosphere. We focus on high-degree p-modes due to their ability to characterize conditions in the shear layer just below the solar surface, and analyze 22 yr of oscillation frequencies obtained from the Global Oscillation Network Group. Considering 10.7 cm radio flux measurements, the sunspot number, and the local magnetic activity index as solar-activity proxies, we find strong correlation between the mode frequencies and each activity index. We further investigate the hemispheric asymmetry associated with oscillation frequencies and magnetic activity proxies, and find that both were dominant in the southern hemisphere during the descending phase of cycle 23, while in cycle 24 these quantities fluctuated between northern and southern hemispheres. Analyzing the frequencies at different latitudes with the progression of solar cycles, we observe that the variations at midlatitudes were dominant in the southern hemisphere during the maximum-activity period of cycle 24, but the values overlap as the cycle advances toward the minimum phase. The mode frequencies at the beginning of cycle 25 are found to be dominant in the southern hemisphere following the pattern of magnetic activity. The analysis provides added evidence that the variability in oscillation frequencies is caused by both strong and weak magnetic fields.
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Язев, Сергей, Sergey Yazev, Александр Мордвинов, Aleksandr Mordvinov, Антонина Дворкина-Самарская, and Antonina Dvorkina-Samarskaya. "Corona during the total solar eclipse on March 20, 2015, and 24 cycle development." Solar-Terrestrial Physics 2, no. 2 (August 10, 2016): 3–14. http://dx.doi.org/10.12737/20995.
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We analyzed the structure of coronal features, using data on the March 20, 2015 total solar eclipse. The Ludendorff index characterizing the flattening of the corona is 0.09. The solar corona structure in the Northern and Southern hemispheres corresponds to the maximum and post-maximum phases of solar activity, respectively. The asynchronous development of magnetic activity in the Sun’s Northern and Southern hemispheres caused a substantial asymmetry of coronal features observed at the reversal of polar magnetic fields in the current cycle. The polar ray structures in the Southern Hemisphere are associated with the polar coronal hole, while in the Northern Hemisphere a polar hole has not been formed yet. We examine the relation between large-scale magnetic fields and location of high coronal structures.
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Wendland, Wayne M., and Neil S. Mcdonald. "Southern Hemisphere Airstream Climatology." Monthly Weather Review 114, no. 1 (January 1986): 88–94. http://dx.doi.org/10.1175/1520-0493(1986)114<0088:shac>2.0.co;2.
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Reynolds, J. E., D. L. Jauncey, K. J. Johnston, J. L. Russell, G. Nicolson, G. L. White, C. de Vegt, and C. Ma. "Southern Hemisphere VLBI Astometry." International Astronomical Union Colloquium 127 (1991): 339. http://dx.doi.org/10.1017/s0252921100064150.
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Pittock, A. B., and M. J. Salinger. "Southern Hemisphere climate scenarios." Climatic Change 18, no. 2-3 (April 1991): 205–22. http://dx.doi.org/10.1007/bf00138998.
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Ellingsen, Simon, Mark Reid, Karl Menten, Lucas Hyland, Jayender Kumar, Gabor Oroz, Stuart Weston, Richard Dodson, and Maria Rioja. "Southern Hemisphere Maser Astrometry." Proceedings of the International Astronomical Union 18, S380 (December 2022): 457–60. http://dx.doi.org/10.1017/s1743921323002661.
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AbstractMany astrophysical phenomena can only be studied in detail for objects in our galaxy, the Milly Way, but we know much more about the structure of thousands of nearby galaxies than we do about our own Galaxy. Accurate distance measurements in the Milky Way underpin our ability to understand a wide range of astrophysical phenomena and this requires observations from both the northern and southern hemisphere. Our ability to measure accurate parallaxes to southern masers has been hampered a range of factors, in particular the absence of a dedicated, homogeneous VLBI array in the south. We have recently made significant advances in astrometric calibration techniques which allow us to achieve trigonometric parallax accuracies of around 10 micro-arcseconds (μas) for 6.7 GHz methanol masers with a hetrogeneous array of 4 antennas. We outline the details of this new “multiview” technique and present the first trigonometric parallax measurements that utilise this approach.
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Cai, Jinzhuo, Haiyuan Yang, Bolan Gan, Hong Wang, Zhaohui Chen, and Lixin Wu. "Evolution of Meridional Heat Transport by Subtropical Western Boundary Currents in a Warming Climate Predicted by High-Resolution Models." Journal of Climate 36, no. 22 (November 15, 2023): 8007–25. http://dx.doi.org/10.1175/jcli-d-23-0100.1.
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Abstract Subtropical western boundary currents (WBCs) are among the most energetic currents in the global circulation system and play an important role in the oceanic meridional heat transport (OHT). Based on nine high-resolution global coupled climate models, this study investigates the change of OHT by subtropical WBCs (WHT) under global warming. We found that WHT in both hemispheres depicts a weakening trend during 1950–2050, primarily caused by the transport change of WBCs. In the Northern Hemisphere, weakening of the Gulf Stream resulting from the slowing AMOC leads to the hemispheric WHT weakening. In the Southern Hemisphere, the WHT decrease is mainly induced by the sharp decline of Agulhas Current transport, associated with the change in wind field in the southern Indian Ocean and Indonesian Throughflow. Compared to the mean flow, the contribution of mesoscale eddies to OHT change is negligible along with WBCs but is important in their extension regions.
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Zhang, Yongqiang, Congcong Li, Francis H. S. Chiew, David A. Post, Xuanze Zhang, Ning Ma, Jing Tian, et al. "Southern Hemisphere dominates recent decline in global water availability." Science 382, no. 6670 (November 3, 2023): 579–84. http://dx.doi.org/10.1126/science.adh0716.
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Global land water underpins livelihoods, socioeconomic development, and ecosystems. It remains unclear how water availability has changed in recent decades. Using an ensemble of observations, we quantified global land water availability over the past two decades. We show that the Southern Hemisphere has dominated the declining trend in global water availability from 2001 to 2020. The significant decrease occurs mainly in South America, southwestern Africa, and northwestern Australia. In the Northern Hemisphere, the complex regional increasing and decreasing trends cancel each other, resulting in a negligible hemispheric trend. The variability and trend in water availability in the Southern Hemisphere are largely driven by precipitation associated with climate modes, particularly the El Niño-Southern Oscillation. This study highlights their dominant role in controlling global water availability.
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Butt, Nathalie. "Geographical bias constrains global knowledge of phenological change." Pacific Conservation Biology 25, no. 4 (2019): 345. http://dx.doi.org/10.1071/pc18073.
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Climate change is already driving shifts in phenology, the timing of life-history events such as flowering, fruiting, egg-laying, birth, and migration, and this is set to increase. Although climate change is happening, and will continue to happen, globally, most of our ecological knowledge around its potential impacts on phenology is derived from temperate areas and ecosystems in the Northern Hemisphere, and information from the Southern Hemisphere is greatly lacking. This would not be a problem if biomes, ecosystems, species assemblages and species were the same in the Northern and Southern Hemispheres, but as they, in fact, differ across many factors and scales, understanding gained from one hemisphere is not necessarily applicable to the other.
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Mayewski, P. A., and K. A. Maasch. "Recent warming inconsistent with natural association between temperature and atmospheric circulation over the last 2000 years." Climate of the Past Discussions 2, no. 3 (June 30, 2006): 327–55. http://dx.doi.org/10.5194/cpd-2-327-2006.
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Abstract. Comparison between proxies for atmospheric circulation and temperature reveals associations over the last few decades that are inconsistent with those of the past 2000 years. Notably, patterns of middle to high latitude atmospheric circulation in both hemispheres are still within the range of variability of the last 6–10 centuries while, as demonstrated by Mann and Jones (2003), Northern Hemisphere temperatures over recent decades are the highest of the last 2000 years. Further, recent temperature change precedes change in middle to high latitude atmospheric circulation unlike the two most notable changes in climate of the past 2000 years during which change in atmospheric circulation preceded or coincided with change in temperature. In addition, the most prominent change in Southern Hemisphere temperature and atmospheric circulation of the past 2000, and probably 9000 years, precedes change in temperature and atmospheric circulation in the Northern Hemisphere unlike the recent change in Northern Hemisphere temperature that leads. These findings provide new verification that recent rise in temperature is inconsistent with natural climate variability and is most likely related to anthropogenic activity in the form of enhanced greenhouse gases. From our investigation we conclude that the delayed warming over much of the Southern Hemisphere may be, in addition to other factors, a consequence of underpinning by natural climate variability. Further bipolar comparison of proxy records of atmospheric circulation demonstrates that change in atmospheric circulation in the Southern Hemisphere led by 400 years, the most abrupt change in Northern Hemisphere atmospheric circulation of the last 9000 years. This finding may be highly relevant to understanding a future when warming becomes more fully established in the Southern Hemisphere.
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Canales-Aguirre, Cristian B., Peter A. Ritchie, Sebastián Hernández, Victoria Herrera-Yañez, Sandra Ferrada Fuentes, Fernanda X. Oyarzún, Cristián E. Hernández, Ricardo Galleguillos, and Gloria Arratia. "Phylogenetic relationships, origin and historical biogeography of the genus Sprattus (Clupeiformes: Clupeidae)." PeerJ 9 (August 18, 2021): e11737. http://dx.doi.org/10.7717/peerj.11737.
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The genus Sprattus comprises five species of marine pelagic fishes distributed worldwide in antitropical, temperate waters. Their distribution suggests an ancient origin during a cold period of the earth’s history. In this study, we evaluated this hypothesis and corroborated the non-monophyly of the genus Sprattus, using a phylogenetic approach based on DNA sequences of five mitochondrial genome regions. Sprattus sprattus is more closely related to members of the genus Clupea than to other Sprattus species. We also investigated the historical biogeography of the genus, with the phylogenetic tree showing two well-supported clades corresponding to the species distribution in each hemisphere. Time-calibrated phylogenetic analyses showed that an ancient divergence between Northern and Southern Hemispheres occurred at 55.8 MYBP, followed by a diversification in the Oligocene epoch in the Northern Hemisphere clade (33.8 MYBP) and a more recent diversification in the Southern Hemisphere clade (34.2 MYBP). Historical biogeography analyses indicated that the most recent common ancestor (MRCA) likely inhabited the Atlantic Ocean in the Southern Hemisphere. These results suggest that the ancestral population of the MRCA diverged in two populations, one was dispersed to the Northern Hemisphere and the other across the Southern Hemisphere. Given that the Eocene was the warmest epoch since the Paleogene, the ancestral populations would have crossed the tropics through deeper cooler waters, as proposed by the isothermal submergence hypothesis. The non-monophyly confirmed for the genus Sprattus indicates that its systematics should be re-evaluated.
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Orchiston, Wayne. "Book Review: Southern Hemisphere Astronomy, under Capricorn: A History of Southern Hemisphere Astronomy." Journal for the History of Astronomy 21, no. 3 (August 1990): 304–6. http://dx.doi.org/10.1177/002182869002100311.
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Belenkaya, E. S., S. W. H. Cowley, V. V. Kalegaev, O. G. Barinov, and W. O. Barinova. "Magnetic interconnection of Saturn's polar regions: comparison of modelling results with Hubble Space Telescope UV auroral images." Annales Geophysicae 31, no. 8 (August 28, 2013): 1447–58. http://dx.doi.org/10.5194/angeo-31-1447-2013.
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Abstract. We consider the magnetic interconnection of Saturn's northern and southern polar regions controlled by the interplanetary magnetic field (IMF), studying in particular the more complex and interesting case of southward IMF, when the Kronian magnetospheric magnetic field structure is the most twisted. The simpler case of northward IMF is also discussed. Knowledge of the magnetospheric magnetic field structure is very significant, for example, for investigation of the electric fields and field-aligned currents in Saturn's environment, particularly those which cause the auroral emissions. Here we modify the paraboloid magnetospheric magnetic field model employed in previous related studies by including higher multipole terms in Saturn's internal magnetic field, required for more detailed considerations of inter-hemispheric conjugacy, together with inclusion of a spheroidal boundary at the ionospheric level. The model is employed to map Southern Hemisphere auroral regions observed by the Hubble Space Telescope (HST) in 2008 under known IMF conditions to both the equatorial plane and the northern ionosphere. It is shown that the brightest auroral features map typically to the equatorial region between the central ring current and the outer magnetosphere, and that auroral features should be largely symmetric between the two hemispheres, except for a small poleward displacement and latitudinal narrowing in the Northern Hemisphere compared with the Southern Hemisphere due to the quadrupole field asymmetry. The latter features are in agreement with the conjugate auroras observed under near-equinoctial conditions in early 2009, when IMF data are not available.
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Karpova, L. S., M. Yu Pelikh, M. Yu Eropkin, N. M. Popovtseva, T. P. Stolyarova, K. A. Stolyarov, A. A. Sominina, and O. I. Kiselev. "The Epidemiological Situation of Influenza in the World and Russia in the Season 2014 – 2015." Epidemiology and Vaccine Prevention 14, no. 4 (August 20, 2015): 8–17. http://dx.doi.org/10.31631/2073-3046-2015-14-4-8-17.
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Comparison of spatial-temporal spread of influenza in the Northern and southern hemispheres according to the WHO and the analysis of the epidemic of influenza in Russia in the 2014 – 2015 season, according to the research Institute of influenza on the incidence of influenza and ARI in 59 cities of Russia.It is shown that in the season 2014 – 2015 in the Northern hemisphere, the intensity of the epidemics was higher in North America and Europe than East Asia and North Africa. In the Southern hemisphere have experienced low influenza activity. In the etiology of epidemics in countries of both hemispheres was dominated by influenza A(H3N2) and influenza B. The proportion of influenza A(H1N1)pdm09 was less in the Southern hemisphere was higher than in Northern countries. The incidence of influenza A(H3N2) in the Northern hemisphere was predominantly linked to the new strain A/Switzerland/9715293/2013 (H3N2), differing from the vaccine. In Europe, the majority of circulating influenza B strains were related to the strain B/Phuket/3073/2013, did not match the vaccine.In Russia the intensity of the influenza epidemic in 2015, was more than the previous epidemic of 2014, the prevalence in the cities, the morbidity especially children 7 – 14 years of age and adult population, the incidence of hospitalization with a diagnosis of «influenza» and the number of deaths.
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Sierra, Carlos A. "Forecasting Atmospheric Radiocarbon Decline to Pre-Bomb Values." Radiocarbon 60, no. 4 (April 25, 2018): 1055–66. http://dx.doi.org/10.1017/rdc.2018.33.
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AbstractIn this manuscript, I present an estimation of the rate of decline in atmospheric radiocarbon and the amplitude of its seasonal cycle for the past four decades for the northern and southern hemispheres, and forecast the time required to reach pre-1950 levels (i.e. Δ14C<0‰). Using a set of 30 different exponential smoothing state-space models, the time series were decomposed into their error, trend, and seasonal components, choosing the model that best represented the observed data. According to the best model, the rate of change in Δ14C has decreased considerably since the 1970s and reached values below −5‰ per year since 2005. Overall, the time-series showed larger rates of radiocarbon decline in the northern than in the southern hemisphere, and relatively stable seasonal cycles for both hemispheres. A forecast of the exponential smoothing models predicts that radiocarbon values will reach pre-1950 levels by 2021 in the northern hemisphere with 20% probability, and by around 2035 in the southern hemisphere. However, at regional levels radiocarbon concentrations have already reached pre-1950 levels in several industrialized regions and cities around the world as a consequence of fossil-fuel emissions.
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Pishkalo, M. "Reversal of Sun’s polar magnetic field in solar cycle." Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, no. 58 (2018): 17–21. http://dx.doi.org/10.17721/btsnua.2018.58.17-21.
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The connection of solar activity expressed by international sunspot (Wolf) numbers in the northern and southern hemispheres of the Sun in the current 24th cycle with the time of polar magnetic field reversal in the corresponding hemisphere is investigated. It was obtained that: – The change of the sign of the polar magnetic field at the southern pole occurs almost a year later than in the north. – The polar magnetic field reversals do not coincide with the maximum activity in each of the hemispheres. In the northern hemisphere, the activity maximum was observed almost one and a half years earlier than the first polar field reversal and two and a half years earlier than the third or final one. In the southern hemisphere, the activity maximum was observed almost a year earlier from the change of the field sign at the pole. – The maximum of the 24th cycle almost coincides with the time of the change of the sign of the magnetic field at the northern pole. – In each of the hemispheres, the change in the sign of a magnetic field in the polar zone above 55 degrees occurred almost two years earlier than the final polar field reversal. The second and third changes of the sign of the total field in the polar zone above 55 degrees occurred shortly after the corresponding polar field reversal. – In the northern hemisphere, the polar field reversals occur at the time of maximum values of the inclination of the heliospheric current sheet, and in the south – almost two years after the maximum inclination of the HCS. – Three-fold polar field reversal at the northern pole occurs at small values of polar magnetic field measured at the Wilcox Solar Observatory while single reversal at the southern pole occurs at sufficiently high value of the corresponding measured polar field.
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Kitagawa, H., Hitoshi Mukai, Yukihiro Nojiri, Yasuyuki Shibata, Toshiyuki Kobayashi, and Tomoko Nojiri. "Seasonal and Secular Variations of Atmospheric 14Co2 Over the Western Pacific Since 1994." Radiocarbon 46, no. 2 (2004): 901–10. http://dx.doi.org/10.1017/s0033822200035943.
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Air sample collections over the western Pacific have continued since 1992 as a part of Center for Global Environmental Research, National Institute for Environmental Studies (CGER-NIES) global environmental monitoring program. The air samples collected on the Japan-Australia transect made it possible to trace the seasonal and secular 14CO2 variations, as well as an increasing trend of greenhouse gases over the western Pacific. A subset of CO2 samples from latitudes of 10–15°N and 23–28°S were chosen for accelerator mass spectrometry (AMS) 14C analysis using a NIES-TERRA AMS with a 0.3–0.4% precision. These 14CO2 records in maritime air show seasonal variations superimposed on normal exponential decreasing trends with a time constant of about 16 yr. The Δ14C values in the Northern Hemisphere are lower those in the Southern Hemisphere by 3–4 during 1994–2002. The Northern Hemisphere record shows relatively high seasonality (2.3 ± 1.5) as compared with the Southern Hemisphere (1.3 ± 1.2). The maximum values of seasonal cycles appear in late autumn and early winter in the Northern and Southern Hemispheres, respectively. Oscillations of 1–10 yr over the western Pacific are found to correlate possibly with the El Niño/Southern Oscillation (ENSO) events.
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Young, Ian R., Ebru Kirezci, and Agustinus Ribal. "The Global Wind Resource Observed by Scatterometer." Remote Sensing 12, no. 18 (September 9, 2020): 2920. http://dx.doi.org/10.3390/rs12182920.
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A 27-year-long calibrated multi-mission scatterometer data set is used to determine the global basin-scale and near-coastal wind resource. In addition to mean and percentile values, the analysis also determines the global values of both 50- and 100-year return period wind speeds. The analysis clearly shows the seasonal variability of wind speeds and the differing response of the two hemispheres. The maximum wind speeds in each hemisphere are comparable but there is a much larger seasonal cycle in the northern hemisphere. As a result, the southern hemisphere has a more consistent year-round wind climate. Hence, coastal regions of southern Africa, southern Australia, New Zealand and southern South America appear particularly suited to coastal and offshore wind energy projects. The extreme value analysis shows that the highest extreme wind speeds occur in the North Atlantic Ocean with extreme wind regions concentrated along the western boundaries of the North Atlantic and North Pacific Oceans and the Indian Ocean sector of the Southern Ocean. The signature of tropical cyclones is clearly observed in each of the well-known tropical cyclone basins.
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BenZvi, S. "Observations of the anisotropy of cosmic rays at TeV–PeV." ASTRA Proceedings 1 (July 25, 2014): 33–37. http://dx.doi.org/10.5194/ap-1-33-2014.
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Abstract. During the past decade, multiple observatories have reported significant observations of the anisotropy of cosmic rays in the TeV energy band. The anisotropy has been observed at large scales and small scales in both the Northern and Southern Hemispheres. The source of the anisotropy is not well-understood, though both a galactic and a heliospheric origin have been suggested. We discuss recent observations of the shape and energy dependence of the anisotropy, with particular attention to measurements by the IceCube Neutrino Observatory in the Southern Hemisphere and the Milagro and High-Altitude Water Cherenkov (HAWC) observatories in the Northern Hemisphere.
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Janardhan, P., K. Fujiki, M. Ingale, S. K. Bisoi, and S. Ananthakrishnan. "Long term trends in solar photospheric fields and solar wind turbulence levels: Implications to the near-Earth space." Proceedings of the International Astronomical Union 13, S340 (February 2018): 121–24. http://dx.doi.org/10.1017/s1743921318001710.
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AbstractWe re-examined solar polar magnetic fields, using ground based synoptic photospheric magnetograms, during solar cycle 24. IThe signed polar magnetic fields showed an unusual hemispheric asymmetry in the polar field reversal process with a single unambigous reversal in the Southern hemisphere around late 2013 while the polar reversal in the Northern hemisphere started earlier around June 2012, but was completed only by the end of 2014. The examination of the unsigned polar magnetic fields in cycle 24 showed a continuing decline of fields in the Northern hemisphere whereas in the Southern hemisphere, it had partially recovered. However, the overall declining trend in solar polar fields, which began in the mid-1990’s, is still in progress. The continued decline seen in solar photospheric fields raises thequestion of whether we are heading towards a Grand or Maunder like solar minimum.
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Deutscher, N. M., V. Sherlock, S. E. Mikaloff Fletcher, D. W. T. Griffith, J. Notholt, R. Macatangay, B. J. Connor, et al. "Drivers of column-average CO<sub>2</sub> variability at Southern Hemispheric total carbon column observing network sites." Atmospheric Chemistry and Physics Discussions 13, no. 6 (June 3, 2013): 14331–76. http://dx.doi.org/10.5194/acpd-13-14331-2013.
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Abstract. We investigate factors that drive the variability in total column CO2 at the Total Carbon Column Observing Network sites in the Southern Hemisphere using CarbonTracker analysed fluxes tagged by process and by source region. We show that the terrestrial biosphere is the largest driver of variability in the Southern Hemisphere column CO2, however, it does not dominate in the same fashion as in the Northern Hemisphere. Local and hemispheric scale biomass burning can also play an important role, particularly at the tropical site, Darwin. The magnitude of seasonal variability in the column-average dry-air mole fraction of CO2, XCO2, is also much smaller in the Southern Hemisphere and comparable in magnitude to the annual increase. Comparison of measurements to the model simulations highlights that there is some discrepancy between the two timeseries, especially in the early part of the Darwin data record. We show that this mismatch is most likely due to erroneously estimated local fluxes in the Australian tropical region, which are associated with enhanced photosynthesis caused by early rainfall during the tropical monsoon season.
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Trenberth, Kevin F., and K. C. Mo. "Blocking in the Southern Hemisphere." Monthly Weather Review 113, no. 1 (January 1985): 3–21. http://dx.doi.org/10.1175/1520-0493(1985)113<0003:bitsh>2.0.co;2.
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Mo, Kingtse C., and Glenn H. White. "Teleconnections in the Southern Hemisphere." Monthly Weather Review 113, no. 1 (January 1985): 22–37. http://dx.doi.org/10.1175/1520-0493(1985)113<0022:titsh>2.0.co;2.
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