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Journal articles on the topic "Atmospheric circulation Central Australia"
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Taschetto, Andréa S., Reindert J. Haarsma, Alexander Sen Gupta, Caroline C. Ummenhofer, Khalia J. Hill, and Matthew H. England. "Australian Monsoon Variability Driven by a Gill–Matsuno-Type Response to Central West Pacific Warming." Journal of Climate 23, no. 18 (September 15, 2010): 4717–36. http://dx.doi.org/10.1175/2010jcli3474.1.
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Abstract The objective of this study is to investigate the mechanisms that cause the anomalous intensification of tropical Australian rainfall at the height of the monsoon during El Niño Modoki events. In such events, northwestern Australia tends to be wetter in January and February when the SST warming is displaced to the central west Pacific, the opposite response to that associated with a traditional El Niño. In addition, during the bounding months, that is, December and March, there is below-average rainfall induced by an anomalous Walker circulation. This behavior tends to narrow and intensify the annual rainfall cycle over northwestern Australia relative to the climatology, causing a delayed monsoonal onset and an earlier retreat over the region. Observational datasets and numerical experiments with a general circulation model are used to examine the atmospheric response to the central west Pacific SST warming. It is shown here that the increase of precipitation, particularly in February, is phased locked to the seasonal cycle when the intertropical convergence zone is displaced southward and the South Pacific convergence zone is strengthened. An interaction between the interannual SST variability associated with El Niño Modoki events and the evolution of the seasonal cycle intensifies deep convection in the central west Pacific, driving a Gill–Matsuno-type response to the diabatic heating. The westward-propagating disturbance associated with the Gill–Matsuno mechanism generates an anomalous cyclonic circulation over northwestern Australia, leading to convergence of moisture and increased precipitation. The Gill–Matsuno-type response overwhelms the subsidence of the anomalous Walker circulation associated with Modoki events over Australia during the peak of the monsoon.
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Ummenhofer, Caroline C., Alexander Sen Gupta, Andréa S. Taschetto, and Matthew H. England. "Modulation of Australian Precipitation by Meridional Gradients in East Indian Ocean Sea Surface Temperature." Journal of Climate 22, no. 21 (November 1, 2009): 5597–610. http://dx.doi.org/10.1175/2009jcli3021.1.
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Abstract This study explores the impact of meridional sea surface temperature (SST) gradients across the eastern Indian Ocean on interannual variations in Australian precipitation. Atmospheric general circulation model (AGCM) experiments are conducted in which the sign and magnitude of eastern Indian Ocean SST gradients are perturbed. This results in significant rainfall changes for western and southeastern Australia. A reduction (increase) in the meridional SST gradient drives a corresponding response in the atmospheric thickness gradients and results in anomalous dry (wet) conditions over Australia. During simulated wet years, this seems to be due to westerly anomalies in the thermal wind over Australia and anomalous onshore moisture advection, with a suggestion that the opposite occurs during dry conditions. Thus, an asymmetry is seen in the magnitude of the forced circulation and precipitation response between the dry and wet simulations. To assess the relative contribution of the SST anomalies making up the meridional gradient, the SST pattern is decomposed into its constituent “poles,” that is, the eastern tropical pole off the northwest shelf of Australia versus the southern pole in the central subtropical Indian Ocean. Overall, the simulated Australian rainfall response is linear with regard to the sign and magnitude of the eastern Indian Ocean SST gradient. The tropical eastern pole has a larger impact on the atmospheric circulation and Australian precipitation changes relative to the southern subtropical pole. However, there is clear evidence of the importance of the southern pole in enhancing the Australian rainfall response, when occurring in conjunction with but of opposite sign to the eastern tropical pole. The observed relationship between the meridional SST gradient in the eastern Indian Ocean and rainfall over western and southeastern Australia is also analyzed for the period 1970–2005. The observed relationship is found to be consistent with the AGCM results.
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Fan, Lingli, Jianjun Xu, and Liguo Han. "Impacts of Onset Time of El Niño Events on Summer Rainfall over Southeastern Australia during 1980–2017." Atmosphere 10, no. 3 (March 14, 2019): 139. http://dx.doi.org/10.3390/atmos10030139.
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El Niño–Southern Oscillation (ENSO) has large impacts on Australia’s rainfall. A composite analysis technique was utilized to distinguish the impact of onset time of El Niño on summer rainfall over southeastern Australia. Summer rainfall tended to be lower than normal in austral autumn El Niño events during December–January–February (DJF) and higher than normal in austral winter El Niño events, in 1980–2017. During autumn El Niño events, the Walker circulation and meridional cells served as a bridge, linking the warmer sea surface temperature (SST) in the eastern equatorial Pacific (EEP) and lower summer rainfall over southeastern Australia. This physical process can be described as follows: During DJF, a positive SST anomaly in the EEP was concurrent with anomalous downdraft over southeastern Australia via zonal anomalous Walker circulation, meridional anomalous cells along 170° E–170° W, and a Pacific South American (PSA) teleconnection wave train at 500 hPa. In addition, an anomalous convergence at 200 hPa depressed the convection. Meanwhile, an 850 hPa abnormal westerly was not conducive to transport marine water vapor into this area. These factors resulted in below-normal rainfall. During winter El Niño events, a positive SST anomaly in the central equatorial Pacific (CEP) and the changes in Walker circulation and meridional cells were weaker. The PSA teleconnection wave train shifted westward and northward, and there was a low-level anomalous ascent over southeastern Australia. At the western flank of the anomalous anticyclone, northerly transported water vapor from the ocean to southeastern Australia resulted in a sink of water vapor over this area. The development of low-level convective activity and the plentiful water vapor supply favored more rainfall over southeastern Australia. Onset time of El Niño may be a useful metric for improving the low predictive skill of southeastern Australian summer rainfall.
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Wilson, Aaron B., David H. Bromwich, Keith M. Hines, and Sheng-hung Wang. "El Niño Flavors and Their Simulated Impacts on Atmospheric Circulation in the High Southern Latitudes*." Journal of Climate 27, no. 23 (December 1, 2014): 8934–55. http://dx.doi.org/10.1175/jcli-d-14-00296.1.
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Abstract Two El Niño flavors have been defined based on whether warm sea surface temperature (SST) anomalies are located in the central or eastern tropical Pacific (CP or EP). This study further characterizes the impacts on atmospheric circulation in the high latitudes of the Southern Hemisphere associated with these types of El Niño events though a series of numerical simulations using the National Center for Atmospheric Research Community Atmosphere Model (CAM). Comparing results with the Interim ECMWF Re-Analysis (ERA-Interim), CAM simulates well the known changes to blocking over Australia and a southward shift in the subtropical jet stream across the eastern Pacific basin during CP events. More importantly for the high southern latitudes, CAM simulates a westward shift in upper-level divergence in the tropical Pacific, which causes the Pacific–South American stationary wave pattern to shift toward the west across the entire South Pacific. These changes to the Rossby wave source region impact the South Pacific convergence zone and jet streams and weaken the high-latitude blocking that is typically present in the Amundsen-Bellingshausen Seas during EP events. Anticyclonic flow becomes established farther west in the south central Pacific, modifying high-latitude heat and momentum fluxes across the South Pacific and South Atlantic associated with the ENSO–Antarctic dipole.
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LinHo, L. H., Xianglei Huang, and Ngar-Cheung Lau. "Winter-to-Spring Transition in East Asia: A Planetary-Scale Perspective of the South China Spring Rain Onset." Journal of Climate 21, no. 13 (July 1, 2008): 3081–96. http://dx.doi.org/10.1175/2007jcli1611.1.
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Abstract Analysis of observations from 1979 to 2002 shows that the seasonal transition from winter to spring in East Asia is marked with a distinctive event—the onset of the south China spring rain (SCSR). In late February, the reduced thermal contrast between ocean and land leads to weakening of the Asian winter monsoon as well as the Siberian high and the Aleutian low. Meanwhile, convection over Australia and the western Pacific Maritime Continent is suppressed on the passage of the dry phase of a Madden–Julian oscillation (MJO). In conjunction with the seasonal march of monsoon circulation in the Indonesian–Australian sector, this MJO passage weakens the local thermally direct cell in the East Asia–Australia sector. This development is further accompanied by a series of adjustments in both the tropics and midlatitudes. These changes include attenuation of the planetary stationary wave, considerable weakening of the westerly jet stream over much of the central Pacific adjacent to Japan, and reduction of baroclinicity near the East Asian trough. The influence of concurrent local processes in midlatitudes on the SCSR onset is also important. The weakened jet stream is associated with confinement of frontal activities to the coastal regions of East Asia as well as with rapid expansion of the subtropical Pacific high from the eastern Pacific to the western Pacific. A parallel analysis using output from an experiment with a GFDL-coupled GCM shows that the above sequence of circulation changes is well simulated in that model.
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Zhu, Zhiwei. "Breakdown of the Relationship between Australian Summer Rainfall and ENSO Caused by Tropical Indian Ocean SST Warming." Journal of Climate 31, no. 6 (March 2018): 2321–36. http://dx.doi.org/10.1175/jcli-d-17-0132.1.
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The relationship between El Niño–Southern Oscillation (ENSO) and Australian summer rainfall (ASR) during 1960–2015 experienced an interdecadal change around the mid-1980s. Before the mid-1980s, ASR was significantly correlated with tropical central Pacific (TCP) sea surface temperature (SST), whereas after that it was not. While El Niño was always independent from ASR, La Niña had a close relationship with ASR. However, this relationship was weakened after the mid-1980s. The Indian Ocean SST warming might contribute to the weakening relationship between La Niña and ASR. For La Niña events before the mid-1980s, the negative SSTA over TCP and the southern tropical Indian Ocean induced a large-scale lower-level cyclonic anomaly over Australia, leading to nearly uniform positive precipitation over Australia. In this manner, a significant relationship between ASR and La Niña was established. On the contrary, for the La Niña events after the mid-1980s, because of the Indian Ocean SST warming, the equatorial eastern Indian Ocean and Maritime Continent presented positive SSTAs and enhanced moisture, favoring enhanced rainfall anomalies over the equatorial Maritime Continent. This enhanced rainfall condensation heating induced a lower-level cyclonic anomaly to the west of Australia. The northerly anomalies at the eastern flank of this cyclonic anomaly counteracted the southerly anomalies at the western flank of the cyclonic anomaly over eastern Australia induced by the negative TCP SSTA, leading to insignificant circulation and rainfall anomalies over Australia. As such, being interfered with by the equatorial Maritime Continent heating, the relationship between ASR and La Niña was weakened.
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Li, Yuanlong, Weiqing Han, Lei Zhang, and Fan Wang. "Decadal SST Variability in the Southeast Indian Ocean and Its Impact on Regional Climate." Journal of Climate 32, no. 19 (August 26, 2019): 6299–318. http://dx.doi.org/10.1175/jcli-d-19-0180.1.
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Abstract The southeast Indian Ocean (SEIO) exhibits decadal variability in sea surface temperature (SST) with amplitudes of ~0.2–0.3 K and covaries with the central Pacific (r = −0.63 with Niño-4 index for 1975–2010). In this study, the generation mechanisms of decadal SST variability are explored using an ocean general circulation model (OGCM), and its impact on atmosphere is evaluated using an atmospheric general circulation model (AGCM). OGCM experiments reveal that Pacific forcing through the Indonesian Throughflow explains <20% of the total SST variability, and the contribution of local wind stress is also small. These wind-forced anomalies mainly occur near the Western Australian coast. The majority of SST variability is attributed to surface heat fluxes. The reduced upward turbulent heat flux (QT; latent plus sensible heat flux), owing to decreased wind speed and anomalous warm, moist air advection, is essential for the growth of warm SST anomalies (SSTAs). The warming causes reduction of low cloud cover that increases surface shortwave radiation (SWR) and further promotes the warming. However, the resultant high SST, along with the increased wind speed in the offshore area, enhances the upward QT and begins to cool the ocean. Warm SSTAs co-occur with cyclonic low-level wind anomalies in the SEIO and enhanced rainfall over Indonesia and northwest Australia. AGCM experiments suggest that although the tropical Pacific SST has strong effects on the SEIO region through atmospheric teleconnection, the cyclonic winds and increased rainfall are mainly caused by the SEIO warming through local air–sea interactions.
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Mayewski, Paul Andrew, Kirk A. Maasch, Yuping Yan, Shichang Kang, Eric A. Meyerson, Sharon B. Sneed, Susan D. Kaspari, et al. "Solar forcing of the polar atmosphere." Annals of Glaciology 41 (2005): 147–54. http://dx.doi.org/10.3189/172756405781813375.
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AbstractWe present highly resolved, annually dated, calibrated proxies for atmospheric circulation from several Antarctic ice cores (ITASE (International Trans-Antarctic Scientific Expedition), Siple Dome, Law Dome) that reveal decadal-scale associations with a South Pole ice-core 10Be proxy for solar variability over the last 600 years and annual-scale associations with solar variability since AD 1720. We show that increased (decreased) solar irradiance is associated with increased (decreased) zonal wind strength near the edge of the Antarctic polar vortex. The association is particularly strong in the Indian and Pacific Oceans and as such may contribute to understanding climate forcing that controls drought in Australia and other Southern Hemisphere climate events. We also include evidence suggestive of solar forcing of atmospheric circulation near the edge of the Arctic polar vortex based on ice-core records from Mount Logan, Yukon Territory, Canada, and both central and south Greenland as enticement for future investigations. Our identification of solar forcing of the polar atmosphere and its impact on lower latitudes offers a mechanism for better understanding modern climate variability and potentially the initiation of abrupt climate-change events that operate on decadal and faster scales.
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Martin, David J. "Seasonal climate summary southern hemisphere (spring 2015): El Niño nears its peak." Journal of Southern Hemisphere Earth Systems Science 66, no. 3 (2016): 228. http://dx.doi.org/10.1071/es16017.
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Southern hemisphere circulation patterns and associated anomalies for the austral spring 2015 are reviewed, with an emphasis on Pacific climate indicators and Australian rainfall and temperature patterns. A strong El Niño persisted in the tropical Pacific Ocean with sea-surface temperature anomalies in excess of +2 °C in central and eastern parts, strongly negative outgoing longwave radiation near the Date Line, and the Southern Oscillation Index showing large negative departures. The positive Indian Ocean Dipole that had established in winter dissipated in late November, but was particularly influential on Australia's climate during the months of September and October.Australia’s spring rainfall was below average in the first two months, but improved later in the season: the northern half of Western Australia recorded above average November rainfall. Nevertheless, area-averaged rainfall in spring was below average for the country as a whole. For Australia, October was the warmest on record and had the highest mean temperature anomaly on record for any month since 1910. Spring temperatures were above average and Australia recorded its second-warmest spring on record, behind the record set in the previous year.
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Spinoni, Jonathan, Paulo Barbosa, Edoardo Bucchignani, John Cassano, Tereza Cavazos, Jens H. Christensen, Ole B. Christensen, et al. "Future Global Meteorological Drought Hot Spots: A Study Based on CORDEX Data." Journal of Climate 33, no. 9 (May 1, 2020): 3635–61. http://dx.doi.org/10.1175/jcli-d-19-0084.1.
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AbstractTwo questions motivated this study: 1) Will meteorological droughts become more frequent and severe during the twenty-first century? 2) Given the projected global temperature rise, to what extent does the inclusion of temperature (in addition to precipitation) in drought indicators play a role in future meteorological droughts? To answer, we analyzed the changes in drought frequency, severity, and historically undocumented extreme droughts over 1981–2100, using the standardized precipitation index (SPI; including precipitation only) and standardized precipitation-evapotranspiration index (SPEI; indirectly including temperature), and under two representative concentration pathways (RCP4.5 and RCP8.5). As input data, we employed 103 high-resolution (0.44°) simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX), based on a combination of 16 global circulation models (GCMs) and 20 regional circulation models (RCMs). This is the first study on global drought projections including RCMs based on such a large ensemble of RCMs. Based on precipitation only, ~15% of the global land is likely to experience more frequent and severe droughts during 2071–2100 versus 1981–2010 for both scenarios. This increase is larger (~47% under RCP4.5, ~49% under RCP8.5) when precipitation and temperature are used. Both SPI and SPEI project more frequent and severe droughts, especially under RCP8.5, over southern South America, the Mediterranean region, southern Africa, southeastern China, Japan, and southern Australia. A decrease in drought is projected for high latitudes in Northern Hemisphere and Southeast Asia. If temperature is included, drought characteristics are projected to increase over North America, Amazonia, central Europe and Asia, the Horn of Africa, India, and central Australia; if only precipitation is considered, they are found to decrease over those areas.
Dissertations / Theses on the topic "Atmospheric circulation Central Australia"
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Yetter, Joseph A. "The nature of the propagation of sea breeze fronts in Central California." Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA238635.
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Thesis (M.S. in Meteorology and Oceanography)--Naval Postgraduate School, September 1990.Thesis Advisor(s): Shaw, William J. Second Reader: Durkee, Philip A. "September 1990." Description based on title screen as viewed on December 15, 2009. DTIC Identifier(s): Fronts (Meteorology), Atmosphere Models, Wave Propagation, LASBEX (Land Sea Breeze Experiment), Meteorological Data, Circulation, Directional, Atmospheric Motion. Author(s) subject terms: LASBEX, Lidar, Sodar. Includes bibliographical references (p. 64-65). Also available in print.
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Coleman, Jill Susan Multon. "Atmospheric circulation types associated with cause-specific daily mortality in the central United States." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1123181126.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xvi, 264 p.; also includes graphics. Includes bibliographical references (p. 257-264). Available online via OhioLINK's ETD Center
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Coleman, Jill S. M. "Atmospheric circulation types associated with cause-specific daily mortality in the central United States." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1123181126.
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Surprenant, Jeremy Lee. "A Synoptic Climatology of Wildfires in the Midwestern United States." OpenSIUC, 2009. https://opensiuc.lib.siu.edu/theses/467.
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Predicting wildfire activity has been a major concern for fire weather forecasters and fire managers in recent decades. Identifying mid-tropospheric circulation patterns that are conducive to higher rates of spread has been widely employed as a predictive tool. This study classifies circulation patterns at the 500 mb level for 3865 fire days from 1970 through 2004 in the central hardwood region of the Midwestern United States. Several circulation patterns were identified that are associated with enhanced fire activity relative to other patterns. All patterns with elevated fire activity were associated with either flow from dry air source regions, or patterns that placed the region on the periphery of a high pressure system. Weather variables associated with each type of circulation pattern were also analyzed and were found to vary among patterns. Circulation patterns with greater fire activity were identified as being drier than patterns with lesser activity. The findings of this study provide crucial information to fire managers and forecasters, which can help them achieve their ultimate goal of minimizing loss of life and property.
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Karabanov, Oleksandr G. "Seasonal and spatial structure of the gravity waves and vertical winds over the central USA derived from the NOAA Profiler Network data." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-06262006-145120/.
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Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007.Dr. Paul Steffes, Committee Member ; Dr. Irina Sokolik, Committee Member ; Dr. Robert Black, Committee Member ; Dr. Robert G. Roper, Committee Chair ; Dr. Derek Cunnold, Committee Member.
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Aasa, Anto. "Changes in phenological time series in Estonia and central and eastern Europe 1951-1998 : relationships with air temperature and atmospheric circulation /." Tartu, Estonia : Tartu University Press, 2005. http://dspace.utlib.ee/dspace/bitstream/10062/847/5/aasa.pdf.
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Wilson, Aaron Benjamin. "Using the NCAR CAM 4 to Confirm SAM’s Modulation of the ENSO Teleconnection to Antarctica and Assess Changes to this Interaction during Various ENSO Flavor Events." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376919626.
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Gonyo, Andrew William. "An 800-year multiple-proxy record of atmospheric circulation, climate change, and aquatic productivity from Kepler Lake, South-Central Alaska." 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1463971.
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Starheim, Colette Christiane Angela. "Regional scale tree-ring reconstructions of hydroclimate dynamics and Pacific salmon abundance in west central British Columbia." Thesis, 2011. http://hdl.handle.net/1828/3362.
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Long-duration records are necessary to understand and assess the long-term dynamics of natural systems. The purpose of this research was to use dendrochronologic modelling to construct proxy histories of hydroclimatic conditions and Pacific salmon abundance in west central British Columbia. A multi-species regional network of tree ring-width and ring-density measurements was established from new and archived tree-ring chronologies. These chronologies were then used in multivariate linear regression models to construct proxy records of nival river discharge, summer temperature, end-of-winter snow-water equivalent (SWE), the winter Pacific North America pattern (PNA) and Pacific salmon abundance.
All proxy hydroclimate records provide information back to 1660 AD. Reconstructions of July-August mean runoff for the Skeena and Atnarko rivers describe below average conditions during the early- to mid-1700s and parts of the early-, mid- and late-1900s. Models describe intervals of above average river discharge during the late-1600s, the early-1700s and 1800s, and parts of the early- and mid-1900s. Fluctuations in proxy reconstructions of July-August mean temperature for Wistaria and Tatlayoko Lake, May 1 SWE at Mount Cronin and Tatlayoko Lake and October-February PNA occurred in near synchrony with the shifts described in runoff records. Episodes of above average runoff were typically associated with periods of enhanced end-of-winter SWE, below average summer temperature and positive winter PNA.
A history of Pacific salmon abundance was reconstructed for four species of salmon (chinook, sockeye, chum and pink) that migrate to coastal watersheds of west central British Columbia. Proxy records vary in length and extend from 1400 AD, 1536 AD and 1638 AD to present. Salmon abundance reconstructions varied throughout the past six centuries and described significant collapse in population levels during the early-1400s, the late-1500s, the mid-1600s, the early-1700s, the early-1800s and parts of the 1900s.
Wavelet analyses of reconstructed hydroclimate and salmon population records revealed low- and high-frequency cycles in the data. Correlation analyses related reconstructions to atmospheric teleconnection indices describing variability in North Pacific sea surface temperatures and the Aleutian Low pressure centre. To a lesser degree, relationships were also established between reconstructions and the El Niño-Southern Oscillation. Results thus confirm the long-term influence of large-scale ocean and atmospheric circulation patterns on hydroclimate and Pacific salmon abundance in west central British Columbia.
The reconstructions introduced in this thesis provide insights about the long-term dynamics of the west central British Columbia environment. Several reconstructions presented in this thesis provide novel contributions to dendrohydroclimatic and paleoecologic research in Pacific North America. Proxy runoff records for the Skeena and Atnarko rivers are the first to be constructed for nival-regime basins in British Columbia. The models of Skeena River runoff and Mount Cronin SWE are additionally the first reconstructions of runoff and snowpack in Pacific North America based on a ring-density chronology, demonstrating the significant contribution that wood density measurements can make to dendrohydroclimate research. The models of Pacific salmon stocks are the first to utilize climate-sensitive tree-ring records to construct a history of regional salmon abundance and thus represent a significant advancement to paleoecological modelling.Graduate
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Pejchová, Plavcová Eva. "Vazby mezi atmosférickou cirkulací a rozděleními přízemní teploty vzduchu v klimatických modelech." Doctoral thesis, 2012. http://www.nusl.cz/ntk/nusl-305972.
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Title: Links between atmospheric circulation and surface air temperature distributions in climate models Abstract: This thesis comprises a collection of five papers dealing with validation of regional climate model (RCM) simulations over Central Europe. The first paper illustrates and discusses problems with observed data that are used for model validation and how the choice of reference dataset affects the outcomes in validating the RCMs' performances. The second paper evaluates daily temperatures, and it indicates that some temperature biases may be related to deficiencies in the simulations of large- scale atmospheric circulation. RCMs' ability to simulate atmospheric circulation and the observed links between circulation and surface air temperatures are examined in detail in the third paper. This article also compares performances of individual RCMs with respect to the driving data by analysing the results for the driving data themselves. The fourth paper focuses on biases in the diurnal temperature range within RCMs and their possible causes by examining links of the errors to the at- mospheric circulation and cloud amount. The last paper investigates the observed relationships between atmospheric circulation and daily precipitation amounts over three regions in the Czech Republic, as well as how these...
Books on the topic "Atmospheric circulation Central Australia"
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Steinrücke, Jürgen. Changes in the Northern-hemispheric zonal circulation in the Atlantic-European sector since 1881 and their relationship to precipitation frequencies in the Mediterranean and Central Europe. Bochum: Geographisches Institut der Ruhr-Universität, 1999.
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Behera, Swadhin, and Toshio Yamagata. Climate Dynamics of ENSO Modoki Phenomena. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.612.
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The El Niño Modoki/La Niña Modoki (ENSO Modoki) is a newly acknowledged face of ocean-atmosphere coupled variability in the tropical Pacific Ocean. The oceanic and atmospheric conditions associated with the El Niño Modoki are different from that of canonical El Niño, which is extensively studied for its dynamics and worldwide impacts. A typical El Niño event is marked by a warm anomaly of sea surface temperature (SST) in the equatorial eastern Pacific. Because of the associated changes in the surface winds and the weakening of coastal upwelling, the coasts of South America suffer from widespread fish mortality during the event. Quite opposite of this characteristic change in the ocean condition, cold SST anomalies prevail in the eastern equatorial Pacific during the El Niño Modoki events, but with the warm anomalies intensified in the central Pacific. The boreal winter condition of 2004 is a typical example of such an event, when a tripole pattern is noticed in the SST anomalies; warm central Pacific flanked by cold eastern and western regions. The SST anomalies are coupled to a double cell in anomalous Walker circulation with rising motion in the central parts and sinking motion on both sides of the basin. This is again a different feature compared to the well-known single-cell anomalous Walker circulation during El Niños. La Niña Modoki is the opposite phase of the El Niño Modoki, when a cold central Pacific is flanked by warm anomalies on both sides.The Modoki events are seen to peak in both boreal summer and winter and hence are not seasonally phase-locked to a single seasonal cycle like El Niño/La Niña events. Because of this distinction in the seasonality, the teleconnection arising from these events will vary between the seasons as teleconnection path will vary depending on the prevailing seasonal mean conditions in the atmosphere. Moreover, the Modoki El Niño/La Niña impacts over regions such as the western coast of the United States, the Far East including Japan, Australia, and southern Africa, etc., are opposite to those of the canonical El Niño/La Niña. For example, the western coasts of the United States suffer from severe droughts during El Niño Modoki, whereas those regions are quite wet during El Niño. The influences of Modoki events are also seen in tropical cyclogenesis, stratosphere warming of the Southern Hemisphere, ocean primary productivity, river discharges, sea level variations, etc. A remarkable feature associated with Modoki events is the decadal flattening of the equatorial thermocline and weakening of zonal thermal gradient. The associated ocean-atmosphere conditions have caused frequent and persistent developments of Modoki events in recent decades.
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Yang, Kun. Observed Regional Climate Change in Tibet over the Last Decades. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.587.
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The Tibetan Plateau (TP) is subjected to strong interactions among the atmosphere, hydrosphere, cryosphere, and biosphere. The Plateau exerts huge thermal forcing on the mid-troposphere over the mid-latitude of the Northern Hemisphere during spring and summer. This region also contains the headwaters of major rivers in Asia and provides a large portion of the water resources used for economic activities in adjacent regions. Since the beginning of the 1980s, the TP has undergone evident climate changes, with overall surface air warming and moistening, solar dimming, and decrease in wind speed. Surface warming, which depends on elevation and its horizontal pattern (warming in most of the TP but cooling in the westernmost TP), was consistent with glacial changes. Accompanying the warming was air moistening, with a sudden increase in precipitable water in 1998. Both triggered more deep clouds, which resulted in solar dimming. Surface wind speed declined from the 1970s and started to recover in 2002, as a result of atmospheric circulation adjustment caused by the differential surface warming between Asian high latitudes and low latitudes.The climate changes over the TP have changed energy and water cycles and has thus reshaped the local environment. Thermal forcing over the TP has weakened. The warming and decrease in wind speed lowered the Bowen ratio and has led to less surface sensible heating. Atmospheric radiative cooling has been enhanced, mainly through outgoing longwave emission from the warming planetary system and slightly enhanced solar radiation reflection. The trend in both energy terms has contributed to the weakening of thermal forcing over the Plateau. The water cycle has been significantly altered by the climate changes. The monsoon-impacted region (i.e., the southern and eastern regions of the TP) has received less precipitation, more evaporation, less soil moisture and less runoff, which has resulted in the general shrinkage of lakes and pools in this region, although glacier melt has increased. The region dominated by westerlies (i.e., central, northern and western regions of the TP) received more precipitation, more evaporation, more soil moisture and more runoff, which together with more glacier melt resulted in the general expansion of lakes in this region. The overall wetting in the TP is due to both the warmer and moister conditions at the surface, which increased convective available potential energy and may eventually depend on decadal variability of atmospheric circulations such as Atlantic Multi-decadal Oscillation and an intensified Siberian High. The drying process in the southern region is perhaps related to the expansion of Hadley circulation. All these processes have not been well understood.
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Kucharski, Fred, and Muhammad Adnan Abid. Interannual Variability of the Indian Monsoon and Its Link to ENSO. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.615.
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The interannual variability of Indian summer monsoon is probably one of the most intensively studied phenomena in the research area of climate variability. This is because even relatively small variations of about 10% to 20% from the mean rainfall may have dramatic consequences for regional agricultural production. Forecasting such variations months in advance could help agricultural planning substantially. Unfortunately, a perfect forecast of Indian monsoon variations, like any other regional climate variations, is impossible in a long-term prediction (that is, more than 2 weeks or so in advance). The reason is that part of the atmospheric variations influencing the monsoon have an inherent predictability limit of about 2 weeks. Therefore, such predictions will always be probabilistic, and only likelihoods of droughts, excessive rains, or normal conditions may be provided. However, even such probabilistic information may still be useful for agricultural planning. In research regarding interannual Indian monsoon rainfall variations, the main focus is therefore to identify the remaining predictable component and to estimate what fraction of the total variation this component accounts for. It turns out that slowly varying (with respect to atmospheric intrinsic variability) sea-surface temperatures (SSTs) provide the dominant part of the predictable component of Indian monsoon variability. Of the predictable part arising from SSTs, it is the El Niño Southern Oscillation (ENSO) that provides the main part. This is not to say that other forcings may be neglected. Other forcings that have been identified are, for example, SST patterns in the Indian Ocean, Atlantic Ocean, and parts of the Pacific Ocean different from the traditional ENSO region, and springtime snow depth in the Himalayas, as well as aerosols. These other forcings may interact constructively or destructively with the ENSO impact and thus enhance or reduce the ENSO-induced predictable signal. This may result in decade-long changes in the connection between ENSO and the Indian monsoon. The physical mechanism for the connection between ENSO and the Indian monsoon may be understood as large-scale adjustment of atmospheric heatings and circulations to the ENSO-induced SST variations. These adjustments modify the Walker circulation and connect the rising/sinking motion in the central-eastern Pacific during a warm/cold ENSO event with sinking/rising motion in the Indian region, leading to reduced/increased rainfall.
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Hameed, Saji N. The Indian Ocean Dipole. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.619.
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Discovered at the very end of the 20th century, the Indian Ocean Dipole (IOD) is a mode of natural climate variability that arises out of coupled ocean–atmosphere interaction in the Indian Ocean. It is associated with some of the largest changes of ocean–atmosphere state over the equatorial Indian Ocean on interannual time scales. IOD variability is prominent during the boreal summer and fall seasons, with its maximum intensity developing at the end of the boreal-fall season. Between the peaks of its negative and positive phases, IOD manifests a markedly zonal see-saw in anomalous sea surface temperature (SST) and rainfall—leading, in its positive phase, to a pronounced cooling of the eastern equatorial Indian Ocean, and a moderate warming of the western and central equatorial Indian Ocean; this is accompanied by deficit rainfall over the eastern Indian Ocean and surplus rainfall over the western Indian Ocean. Changes in midtropospheric heating accompanying the rainfall anomalies drive wind anomalies that anomalously lift the thermocline in the equatorial eastern Indian Ocean and anomalously deepen them in the central Indian Ocean. The thermocline anomalies further modulate coastal and open-ocean upwelling, thereby influencing biological productivity and fish catches across the Indian Ocean. The hydrometeorological anomalies that accompany IOD exacerbate forest fires in Indonesia and Australia and bring floods and infectious diseases to equatorial East Africa. The coupled ocean–atmosphere instability that is responsible for generating and sustaining IOD develops on a mean state that is strongly modulated by the seasonal cycle of the Austral-Asian monsoon; this setting gives the IOD its unique character and dynamics, including a strong phase-lock to the seasonal cycle. While IOD operates independently of the El Niño and Southern Oscillation (ENSO), the proximity between the Indian and Pacific Oceans, and the existence of oceanic and atmospheric pathways, facilitate mutual interactions between these tropical climate modes.
Book chapters on the topic "Atmospheric circulation Central Australia"
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Glowczewski, Barbara. "Culture Cult: Ritual Circulation of Inalienable Knowledge and Appropriation of Cultural Knowledge (Central and NW Australia)." In Indigenising Anthropology with Guattari and Deleuze, 257–80. Edinburgh University Press, 2019. http://dx.doi.org/10.3366/edinburgh/9781474450300.003.0009.
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After recalling the international context of the contemporary claims to cultural property, Glowczewski discusses the concept of inalienability which, in central and north western Australia, surrounds the ritual circulation of sacred objects and the cults of which they are a part, including rituals of colonial resistance. Afterwards she examines the elaboration of a culture centre which involved in the 1990’s the representatives of a dozen Aboriginal languages and organisations based in the coastal town of Broome; this initiative reflected an attempt to control the representation given of their cultures and to claim the reappropriation of their objects (in Museums) and knowledge in a process of cultural repatriation and political affirmation. First published in 2002.
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"8 Culture Cult: Ritual Circulation of Inalienable Knowledge and Appropriation of Cultural Knowledge (Central and NW Australia)." In Indigenising Anthropology with Guattari and Deleuze, 257–80. Edinburgh University Press, 2019. http://dx.doi.org/10.1515/9781474450324-010.
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Bilimoria, Purushottama. "Totaram Sanadhya’s Experience of Racism in Early White Australia." In Indians and the Antipodes, 162–80. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199483624.003.0006.
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This chapter presents a fictionalized narrative of Totaram Sanadhya’s brief visit to Sydney in 1914. Pundit Sanadhya migrated to Fiji as an indentured labourer and spent twenty-one years on the Pacific Island. He became a nationalist and collaborated with C.F. Andrews in bringing down the indenture system. The story is based on the evidence provided in Sanadhya’s journal, published as My Twenty-One Years in the Fiji Islands (1991). As a work of fiction the narrative transcends temporal boundaries and refers to historical events that took place outside Sanadhya’s real time, such as Srinivasa Shastri’s visit to Australia and New Zealand in 1922–3 to inquire into race relations in these parts of the British Empire. This narrative embodies the process of circulation of people and ideas central to this book, with Sanadhya becoming an archetypal ex-indentured Indian from Fiji, visiting white Australia and encountering its racist bigotry.
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Essefi, Elhoucine. "Record of the Sedimentary Dynamics and Climatic Variability Within the Sedimentary Filling of Mchiguig Wetland During the Late Holocene." In Practice, Progress, and Proficiency in Sustainability, 252–66. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-9498-8.ch015.
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This work aimed to study the cyclicity of the geochemical chemical parameters and the carbonate percentages along a 59 cm core from the sebkha of Mchiguig, Central Tunisia. In fact, from the bottom upwards, six climatic phases were recorded including the Warming Present (Great Acceleration), the Late Little Ice Age (Anthropocene), the Early Little Ice Age, the Medieval Climatic Anomaly, the Dark Age, and the Roman Warm Period. In fact, the spectral analysis of the studied parameters visualized many cycles. Those cycles are related to sun activity, oceanographic, and atmospheric factors. Solar activity generated 500 yr cycles; however, the oceanographic circulation generated other cycles of 1500 yr and 700-800 yr. The 1500 yr cycle may be the result of the solar activity and NAO-like circulation.
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Purdon, James. "The Meaning of Monte Bello." In Cold War Legacies. Edinburgh University Press, 2016. http://dx.doi.org/10.3366/edinburgh/9781474409483.003.0005.
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On 3 October 1952, the first successful British nuclear test was conducted near the Monte Bello islands off the coast of Australia. The test was a media event as well as a military one, reported in The Times and documented in the Ministry of Supply’s film Operation Hurricane. The Monte Bello test marked a key success for Britain’s nuclear ambitions and a new phase in its relations with the Commonwealth of Nations. Australia -- with its vast uranium deposits and remote desert proving-grounds -- became central to the production and testing of British nuclear weapons. Meanwhile, the rhetoric of commodity circulation that had characterized the films of the Empire Marketing Board and the GPO provided a model for Operation Hurricane’s images of exported military hardware put to use in the former colony. This chapter traces these networks of exchange and their representation, showing how the Commonwealth’s iconography of nuclear defence revised the Empire’s iconography of free trade. It demonstrates how the supposedly remote and marginal spaces of the Australian continent came to serve British nuclear culture as a kind of geopolitical unconscious: a false terra nullius where, paradoxically, the strategic basis of the Commonwealth’s security could be created.
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Khatun, Samia. "To Hear." In Australianama, 169–86. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190922603.003.0008.
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Returning to the copy of Kasasol Ambia in Broken Hill, chapter 8 revisits the central question that underpins this book: Who brought the com- pendium of Bengali poetry to this inland Australian town? Focusing in upon the aural forms of knowledge transmission that this book was embedded in, I show that the forms of historical storytelling that the book reveals remain in circulation today in both contemporary South Asia and Australia. With the Kasasol Ambia pointing to another epistemic ground on which past South Asians situated historical storytelling, I demonstrate that we can use the text today to produce new forms of human ontology. This concluding chapter argues that at our current juncture of not only escalating state violence and racism, but also ecological crisis, historians and activists alike must challenge the epistemic arrogance of colonial-modern thought if we are to glimpse better futures.
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Stephens, Graeme. "Cirrus, Climate, and Global Change." In Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0024.
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Understanding the climate of Earth and the way climate varies in time requires a quantitative understanding of the way water cycles back and forth between the atmosphere and at the Earth's surface. The exchanges of water between the surface and atmosphere establish the hydrological cycle, and it is the influence of this cycle on the energy budget of Earth that is central not only to understanding present climate but also to the prediction of climate change. Processes relating to the smallest of the reservoirs of water—namely, the atmospheric branch of the hydrological cycle—play an especially critical role in climate change. Water in vapor phase is the critical greenhouse gas (e.g., Chahine 1992) providing much studied feedbacks on climate forcing (Lindzen 1990; Rind et al. 1991; Stephens and Greenwald 1991; Inamdar and Ramanathan 1998; Hall and Manabe 1999). Water in the form of condensed, precipitation-sized particles is an important source of energy fueling circulation systems and is the fundamental supply of fresh water to life on Earth. Liquid water cloud droplets significantly modulate the radiative budget of the planet (e.g., Wielicki et al. 1995). Water that exists as ice particles suspended in the atmosphere is perhaps the smallest of the water reservoirs of the atmosphere, yet these ice crystals when distributed as part of large-scale cirrus clouds exert a disproportionate influence on the energy and water budgets of the planet. This chapter briefly speculates on the important ways cirrus clouds affect the Earth's climate. The topics discussed are central to what is referred to as the cloud-climate problem, which might be schematically represented in terms of the coupled processes represented in figure 20.1. The two most critical scientific questions associated with the cloud-climate problem are also stated in figure 20.1. Answers to these questions require a clearer understanding of how the large-scale circulation of the atmosphere governs cloud formation and evolution, how these clouds heat and moisten the atmosphere, and how this heating and moistening effect in turn feeds back to influence the dynamical and thermodynamical properties of the atmosphere.
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Harding, Andrew, and Jean Palutikof. "The Climate System." In The Physical Geography of the Mediterranean. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780199268030.003.0013.
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The Mediterranean region has a highly distinctive climate due to its position between 30 and 45°N to the west of the Euro-Asian landmass. With respect to the global atmospheric system, it lies between subtropical high pressure systems to the south, and westerly wind belts to the north. In winter, as these systems move equatorward, the Mediterranean basin lies under the influence of, and is exposed to, the westerly wind belt, and the weather is wet and mild. In the summer, as shown in Figure 3.1, the Mediterranean lies under subtropical high pressure systems, and conditions are hot and dry, with an absolute drought that may persist for more than two or three months in drier regions. Climates such as this are relatively rare, and the Mediterranean shares its winter wet/summer dry conditions with locations as distant as central Chile, the southern tip of Cape Province in South Africa, southwest Australia in the Southern Hemisphere, and central California in the Northern Hemisphere. All have in common their mid-latitude position, between subtropical high pressure systems and westerly wind belts. They all lie on the westerly side of continents so that, in winter, when the westerly wind belts dominate over their locations, they are exposed to rain-bearing winds. In the Köppen classification (Köppen 1936), these climates are known as Mediterranean (Type Cs, which is subdivided in turn into maritime Csb and continental Csa). The influence of the Mediterranean Sea means that the Mediterranean-type climate of the region extends much further into the continental landmass than elsewhere, and is not restricted to a narrow ocean-facing strip. Nevertheless, within the Mediterranean region climate is modified by position and topographic influences can be important. The proximity of the western Mediterranean to the Atlantic Ocean gives its climate a maritime flavour, with higher rainfall and milder temperatures throughout the year. The eastern Mediterranean lies closer to the truly continental influences of central Europe and Asia. Its climate is drier, and temperatures are hotter in summer and colder in winter than in the west. Annual rainfall is typically around 750 mm in Rome, but only around 400 mm in Athens.
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Young, Kenneth R., and Paul E. Berry. "Flora and Vegetation." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0013.
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South America’s shape, size, and geographic position, now and in the past, have acted to influence the development of diverse coverings of land surfaces with plants of different sizes, adaptations, and origins. Underlying geologic structures have been exposed to weathering regimes, thereby resulting in a multiplicity of landforms, soil types, and ecological zones. The most notable large-scale features are the Andes, which curl along the western margin of the continent, and the broad swath of the Amazon lowlands in the equatorial zone. However, there are also extensive, more ancient mountain systems in the Brazilian Shield of east-central Brazil and the Guiana Shield in northern South America. The interplay of environmental factors has given rise to a panoply of vegetation types, from coastal mangroves to interior swamplands, savannas, and other grasslands, deserts, shrublands, and a wide array of dry to moist and lowland to highland forest types. The narrower southern half of South America is also complex vegetationally because of the compression of more vegetation types into a smaller area and the diverse climatic regimes associated with subtropical and temperate middle latitudes. Alexander von Humboldt began to outline the major features of the physical geography of South America in his extensive writings that followed his travels in the early nineteenth century (von Humboldt, 1815–1832). For example, he first documented the profound influences of contemporary and historical geologic processes such as earthquakes and volcanoes, how vegetation in mountainous areas changes as elevation influences the distributions of plant species, and the effect of sea surface temperatures on atmospheric circulation and uplift and their impacts on precipitation and air temperatures (Botting, 1973; Faak and Biermann, 1986). His initial insights, in combination with modern observations (Hueck and Seibert, 1972; Cabrera and Willink, 1973; Davis et al., 1997; Lentz, 2000), still serve to frame our synthesis of the major vegetation formations of South America. In this chapter, we relate vegetation formations to spatial gradients of soil moisture and elevation in the context of broad climatic and topographic patterns.
Conference papers on the topic "Atmospheric circulation Central Australia"
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Guedes, Pedro. "Healing Modern Architecture’s Break with the Past: Musings around Brazilian Fenestration." In The 38th Annual Conference of the Society of Architectural Historians Australia and New Zealand. online: SAHANZ, 2022. http://dx.doi.org/10.55939/a3990prwvx.
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This paper focuses on the role of Brazilian architects in emancipating Modern Architecture from overly limiting orthodoxies. In particular, this study follows direct, if weak influences across the Pacific to Australia and stronger ones across the South Atlantic to Southern Africa, where Brazilian ideas found fertile ground without being filtered through Northern Hemisphere mediations. Official delegations of architects from Australia and South Africa went to Brazil seeking inspiration and transferable ideas achieved mixed success. Central to the theme of this essay is a recently discovered and unpublished manuscript. It is the work of Barrie Biermann who, upon graduation from the University of Cape Town sailed across to Brazil in 1946 to gain first-hand knowledge of the architecture that had achieved worldwide renown through the 1943 Brazil Builds exhibition at the Museum of Modern Art in New York (MoMA). Biermann’s close observations and discussions with several of Brazil’s leading architects helped him develop a fresh narrative that placed recent developments in a continuum linked to Portuguese colonial architecture that had taken lessons from the ‘East’. Published in a very abridged form in a professional journal in 1950, it lost much of the charm of the original, which, in addition to imaginative theoretical speculation, is enriched by evocative, atmospheric sketches, water colours and photographs. This study shows that South-South connections were quite independent and predated the influence of ‘scientific’ manuals of ‘how-to build in the tropics’ that proliferated from metropolitan centres in the mid-1950s, preparing for decolonization but perhaps also motivated by ambitions of engendering other forms of dependence. Brazilian ideas and examples of built work played an important role in bringing vitality to some of the architectures of Africa. They also engaged with crucial issues of identity and the production of buildings celebrating values beyond the utilitarian.
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Babanin, Alexander V. "Wave-Induced Turbulence, Linking Metocean and Large Scales." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18373.
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Abstract Until recently, large-scale models did not explicitly take account of ocean surface waves which are a process of much smaller scales. However, it is rapidly becoming clear that many large-scale geophysical processes are essentially coupled with the surface waves, and those include ocean circulation, weather, Tropical Cyclones and polar sea ice in both Hemispheres, climate and other phenomena in the atmosphere, at air/sea, sea/ice and sea/land interface, and many issues of the upper-ocean mixing below the surface. Besides, the wind-wave climate itself experiences large-scale trends and fluctuations, and can serve as an indicator for changes in the weather climate. In the presentation, we will discuss wave influences at scales from turbulence to climate, on the atmospheric and oceanic sides. At the atmospheric side of the interface, the air-sea coupling is usually described by means of the drag coefficient Cd, which is parameterised in terms of the wind speed, but the scatter of experimental data with respect to such dependences is very significant and has not improved noticeably over some 40 years. It is argued that the scatter is due to multiple mechanisms which contribute into the sea drag, many of them are due to surface waves and cannot be accounted for unless the waves are explicitly known. The Cd concept invokes the assumption of constant-flux layer, which is also employed for vertical profiling of the wind measured at some elevation near the ocean surface. The surface waves, however, modify the balance of turbulent stresses very near the surface, and therefore such extrapolations can introduce significant biases. This is particularly essential for buoy measurements in extreme conditions, when the anemometer mast is within the Wave Boundary Layer (WBL) or even below the wave crests. In this presentation, field data and a WBL model are used to investigate such biases. It is shown that near the surface the turbulent fluxes are less than those obtained by extrapolation using the logarithmic-layer assumption, and the mean wind speeds very near the surface, based on Lake George field observations, are up to 5% larger. The dynamics is then simulated by means of a WBL model coupled with nonlinear waves, which revealed further details of complex behaviours at wind-wave boundary layer. Furthermore, we analyse the structure of WBL for strong winds (U10 > 20 m/s) based on field observations. We used vertical distribution of wind speed and momentum flux measured in Topical Cyclone Olwyn (April 2015) in the North-West shelf of Australia. A well-established layer of constant stress is observed. The values obtained for u⁎ from the logarithmic profile law against u⁎ from turbulence measurements (eddy correlation method) differ significantly as wind speed increases. Among wave-induced influences at the ocean side, the ocean mixing is most important. Until recently, turbulence produced by the orbital motion of surface waves was not accounted for, and this fact limits performance of the models for the upper-ocean circulation and ultimately large-scale air-sea interactions. While the role of breaking waves in producing turbulence is well appreciated, such turbulence is only injected under the interface at the vertical scale of wave height. The wave-orbital turbulence is depth-distributed at the scale of wavelength (∼10 times the wave height) and thus can mix through the ocean thermocline in the spring-summer seasons. Such mixing then produces feedback to the large-scale processes, from weather to climate. In order to account for the wave-turbulence effects, large-scale air-sea interaction models need to be coupled with wave models. Theory and practical applications for the wave-induced turbulence will be reviewed in the presentation. These include viscous and instability theories of wave turbulence, direct numerical simulations and laboratory experiments, field and remote sensing observations and validations, and finally implementations in ocean, Tropical Cyclone, ocean and ice models. As a specific example of a wave-coupled environment, the wave climate in the Arctic as observed by altimeters will be presented. This is an important topic for the Arctic Seas, which are opening from ice in summer time. Challenges, however, are many as their Metocean environment is more complicated and, in addition to winds and waves, requires knowledge and understanding of ice material properties and its trends. On one hand, no traditional statistical approach is possible since in the past for most of the Arctic Ocean there was limited wave activity. Extrapolations of the current trends into the future are not feasible, because ice cover and wind patterns in the Arctic are changing. On the other hand, information on the mean and extreme wave properties is of great importance for oceanographic, meteorological, climate, naval and maritime applications in the Arctic Seas.
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Whitaker, Dwight L., Robert Simsiman, Emily S. Chang, Samuel Whitehead, and Hesam Sarvghad-Moghaddam. "Numerical Modeling of Spores Dispersal of Sphagnum Moss Using ANSYS FLUENT." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69417.
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The common peat moss, Sphagnum, is able to explosively disperse its spores by producing a vortex ring from a pressurized sporophyte to carry a cloud of spores to heights over 15 cm where the turbulent boundary layer can lift and carry them indefinitely. While vortex ring production is fairly common in the animal kingdom (e.g. squid, jellyfish, and the human heart), this is the first report of vortex rings generated by a plant. In other cases of biologically created vortex rings, it has been observed that vortices are produced with a maximum formation number of L/D = 4, where L is the length of the piston stroke and D is the diameter of the outlet. At this optimal formation number, the circulation and thus impulse of the vortex ring is maximized just as the ring is pinched off. In the current study, we modeled this dispersal phenomenon for the first time using ANSYS FLUENT 17.2. The spore capsule at the time of burst was approximated as a cylinder with a thin cylindrical cap attached to it. They were then placed inside a very large domain representing the air in which the expulsion was modeled. Due to the symmetry of our model about the central axis, we performed a 2D axisymmetric simulation. Also, due the complexity of the fluid domain as a result of the capsule-cap interface, as well as the need for a dynamic mesh for simulating the motion of the cap, first a mesh study was performed to generate an efficient mesh in order to make simulations computationally cost-effective. The domain was discretized using triangular elements and the mesh was refined at the capsule-cap interface to accurately capture the ring vortices formed by the expulsed cap. The dispersal was modeled using a transient simulation by setting a pressure difference between inside of the capsule and the surrounding atmospheric air. Pressure and vorticity contours were recorded at different time instances. Our simulation results were interpreted and compared to high-speed video data of sporophyte expulsions to deduce the pressure within the capsule upon dispersal, as well as the formation number of resulting vortex rings. Vorticity contours predicted by our model were in agreement with the experimental results. We hypothesized that the vortex rings from Sphagnum are sub-optimal since a slower vortex bubble would carry spores more effectively than a faster one.