scholarly journals Comparison of 20th century and pre-industrial climate over South America in regional model simulations

2012 ◽  
Vol 8 (5) ◽  
pp. 1599-1620 ◽  
Author(s):  
S. Wagner ◽  
I. Fast ◽  
F. Kaspar
Keyword(s):  
South America ◽  
Greenhouse Gas ◽  
Atmospheric Circulation ◽  
20Th Century ◽  
Climate Model ◽  
Regional Climate ◽  
Regional Model ◽  
Andes Mountains ◽  
Southern South America ◽  
The Andes

Abstract. In this study, we assess how the anthropogenically induced increase in greenhouse gas concentrations affects the climate of central and southern South America. We utilise two regional climate simulations for present day (PD) and pre-industrial (PI) times. These simulations are compared to historical reconstructions in order to investigate the driving processes responsible for climatic changes between the different periods. The regional climate model is validated against observations for both re-analysis data and GCM-driven regional simulations for the second half of the 20th century. Model biases are also taken into account for the interpretation of the model results. The added value of the regional simulation over global-scale modelling relates to a better representation of hydrological processes that are particularly evident in the proximity of the Andes Mountains. Climatic differences between the simulated PD minus PI period agree qualitatively well with proxy-based temperature reconstructions, albeit the regional model overestimates the amplitude of the temperature increase. For precipitation the most important changes between the PD and PI simulation relate to a dipole pattern along the Andes Mountains with increased precipitation over the southern parts and reduced precipitation over the central parts. Here only a few regions show robust similarity with studies based on empirical evidence. However, from a dynamical point-of-view, atmospheric circulation changes related to an increase in high-latitude zonal wind speed simulated by the regional climate model are consistent with numerical modelling studies addressing changes in greenhouse gas concentrations. Our results indicate that besides the direct effect of greenhouse gas changes, large-scale changes in atmospheric circulation and sea surface temperatures also exert an influence on temperature and precipitation changes in southern South America. These combined changes in turn affect the relationship between climate and atmospheric circulation between PD and PI times and should be considered for the statistical reconstruction of climate indices calibrated within present-day climate data.

scholarly journals Climatic changes between 20th century and pre-industrial times over South America in regional model simulations

2011 ◽  
Vol 7 (5) ◽  
pp. 2981-3022 ◽  
Author(s):  
S. Wagner ◽  
I. Fast ◽  
F. Kaspar
Keyword(s):  
South America ◽  
20Th Century ◽  
Large Scale ◽  
Climate Model ◽  
Climatic Changes ◽  
Andes Mountains ◽  
Model Simulations ◽  
The Andes ◽  
Paraná Basin ◽  
Parana Basin

Abstract. Two simulations with a regional climate model are analyzed for climatic changes between the late 20th century and a pre-industrial period over central and southern South America. The model simulations have been forced with large-scale boundary data from the global simulation performed with a coupled atmosphere-ocean general circulation model. The regional simulations have been carried out on a 0.44° × 0.44° grid (approx. 50 km × 50 km horizontal resolution). The differences in the external forcings are related to a changed greenhouse gas content of the atmosphere, being higher in the present-day simulation. For validation purposes the climate model is analyzed using a five year long simulation between 1993 and 1997 forced with re-analysis data. The climate model reproduces the main climatic features reasonably well, especially when comparing model output co-located with observational station data. However, the comparison between observed and simulated climate is hampered by the sparse meteorological station network in South America. The present-day simulation is compared with the pre-industrial simulation for atmospheric fields of near-surface temperatures, precipitation, sea level pressure and zonal wind. Higher temperatures in the present-day simulation are evident over entire South America, mostly pronounced over the southern region of the Andes Mountains and the Parana basin. During southern winter the higher temperatures prevail over the entire continent, with largest differences over the central Andes Mountains and the Amazonian basin. Precipitation differences show a more heterogeneous pattern, especially over tropical regions. This might be explained by changes in convective processes acting on small scales. During southern summer wetter conditions are evident over the Amazonian and Parana basin in the present-day simulation. Precipitation increases are evident over Patagonia together with decreases to the north along the western slope of the Andes Mountains. During southern winter also a dipole pattern along the Andes Mountains with wetter conditions over the southern parts and drier conditions over the central parts is evident. An interesting feature relates to precipitation changes with changing sign within a few 10th of kilometers along the southern parts of the Andes mountain chain. This pattern can be explained by changes in large-scale circulation related to latitudinal changes of the extratropical southern hemispheric westerlies.

Size and Locomotion in Teratorns (Aves: Teratornithidae)

The Auk ◽  
1983 ◽  
Vol 100 (2) ◽  
pp. 390-403 ◽  
Author(s):  
Kenneth E. Campbell ◽  
Eduardo P. Tonni
Keyword(s):  
South America ◽  
New World ◽  
Pelvic Girdle ◽  
Andes Mountains ◽  
New Method ◽  
Southern South America ◽  
The Andes ◽  
Body Weights ◽  
Westerly Winds

Abstract The extinct family Teratornithidae contains the world's largest known flying birds. A new method of determining body weights of extinct birds, based on the size of their tibiotarsi, facilitates the estimation of the wing dimensions of these giant birds. An analysis of the bones of the teratorn wing shows that they closely resemble those of condors, suggesting that teratorns flew in a manner similar to these large New World vultures. The bones of the pelvic girdle and hindlimbs indicate that teratorns were probably agile on the ground, though better adapted for walking and stalking than running. We estimate that the largest teratorn, Argentavis magnificens, weighed 80 kg and had a wingspan of 6-8 m. It probably became airborne by spreading its huge wings into the strong, continuous, westerly winds that blew across southern South America before the elevation of the Andes Mountains and, once aloft, flew in the manner of condors.

Application of Scale-Selective Data Assimilation to Regional Climate Modeling and Prediction

2010 ◽  
Vol 138 (4) ◽  
pp. 1307-1318 ◽  
Author(s):  
Shiqiu Peng ◽  
Lian Xie ◽  
Bin Liu ◽  
Fredrick Semazzi
Keyword(s):  
Data Assimilation ◽  
Regional Climate Model ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Regional Model ◽  
Global Model ◽  
Small Scale ◽  
Pass Filter

Abstract A method referred to as scale-selective data assimilation (SSDA) is designed to inject the large-scale components of the atmospheric circulation from a global model into a regional model to improve regional climate simulations and predictions. The SSDA is implemented through the following procedure: 1) using a low-pass filter to extract the large-scale components of the atmospheric circulation from global analysis or model forecasts; 2) applying the filter to extract the regional-scale and the large-scale components of the atmospheric circulation from the regional model simulations or forecasts; 3) assimilating the large-scale circulation obtained from the global model into the corresponding component simulated by the regional model using the method of three-dimensional variational data assimilation (3DVAR) while maintaining the small-scale components from the regional model during the assimilation cycle; 4) combining the small-scale and the assimilated large-scale components as the adjusted forecasts by the regional climate model and allowing the two components to mutually adjust outside the data assimilation cycle. A case study of summer 2005 seasonal climate hindcasting for the regions of the Atlantic and the eastern United States indicates that the large-scale components from the Global Forecast System (GFS) analysis can be effectively assimilated into the regional model using the scale-selective data assimilation method devised in this study, resulting in an improvement in the overall results from the regional climate model.

scholarly journals 21st Century Macro-Imagineering: Lake Titicaca Hydropower Megaproject

2019 ◽  
Vol 4 (1) ◽  
pp. 12
Author(s):  
Alexander Bolonkin ◽  
Richard Brook Cathcart
Keyword(s):  
South America ◽  
Key Words ◽  
20Th Century ◽  
21St Century ◽  
Andes Mountains ◽  
Lake Titicaca ◽  
The Andes ◽  
The Pacific ◽  
Class 1 ◽  
The Pacific Ocean

<p class="-1"><strong><span lang="EN-US">Abstract: </span></strong><span lang="EN-US">Territorially shared by Peru and Bolivia, South America’s largest freshwater lake is navigable Lake Titicaca, situated on an highland endorheic river basin of the Andes Mountains. Currently, Lake Titicaca is mostly regulated by ever-changing Nature. But, since its closure during 2001 AD, a small anthropogenic dam (at elevation 3804 m), emplaced at the headwaters, the Rio Desaguadero is still the altiplano lake’s only flowing freshwater outlet. Intriguingly, from circa 1908 AD, Macro-Imagineers foresaw the creation of a second, completely artificial, flowing freshwater outlet for Lake Titicaca’s 935 km3 of valuable liquid freshwater accumulation. Such a lake-tapping hydropower megaproject could allow diverted freshwater to perhaps reach the Pacific Ocean. Here, we cursorily reappraise several similar 20th Century dam and pipeline macroproject proposals, with the educative goal, achieved by careful reconsideration, of exposing the basic megaproject proposal physics related to a potential major future South America hydropower installation. </span></p><p class="-1"><strong><span lang="EN-US"> </span></strong><strong><span lang="EN-US">Key words: </span></strong><span lang="EN-US">hydropower, Macro-Imagineering, Lake Titicaca.</span></p><p class="-1"><span lang="EN-US">=========================================================================== </span></p><p class="-1"><strong>Resumo: </strong>Territorialmente compartilhado pelo Peru e pela Bolívia, o maior lago de água doce da América do Sul, conhecido como Lago Titicaca, está situado em uma bacia endorrêica do altiplano da Cordilheira dos Andes. Atualmente, o Lago Titicaca ainda é regulado principalmente pela natureza local em constante mudança. Mas, após a construção de uma pequena barragem em 2001 d.C. (a uma altitude de 3804 m) situada nas cabeceiras, o rio Desaguadero permanece o único escoadouro natural do lago. Curiosamente, por volta de 1908 d.C., os macro-imaginadores previam a criação de uma segunda saída, completamente artificial, para os 935 km<sup>3</sup> da valiosa água doce líquida. Semelhante megaprojeto hidrelétrico poderia permitir que a água doce desviada alcançasse talvez o Oceano Pacífico. Aqui, reavaliamos várias propostas semelhantes de macroprojetos de barragens e dutos do século XX, com o objetivo educativo, guiado por uma cuidadosa avaliação, de expor a física básica da proposta para uma futura instalação hidrelétrica na América do Sul.</p><p class="-1"><strong>Palavras-chave: </strong>hidrelétrica, Macro-Imaginação, Lago Titicaca.</p>

scholarly journals Regional Climate Model–Simulated Timing and Character of Seasonal Rains in South America

2007 ◽  
Vol 135 (7) ◽  
pp. 2642-2657 ◽  
Author(s):  
Sara A. Rauscher ◽  
Anji Seth ◽  
Brant Liebmann ◽  
Jian-Hua Qian ◽  
Suzana J. Camargo
Keyword(s):  
South America ◽  
Regional Climate Model ◽  
Rainy Season ◽  
Climate Model ◽  
Regional Climate ◽  
Regional Model ◽  
Northeast Brazil ◽  
Monsoon Region ◽  
Enso Events ◽  
Dry Spells

Abstract The potential of an experimental nested prediction system to improve the simulation of subseasonal rainfall statistics including daily precipitation intensity, rainy season onset and withdrawal, and the frequency and duration of dry spells is evaluated by examining a four-member ensemble of regional climate model simulations performed for the period 1982–2002 over South America. The study employs the International Centre for Theoretical Physics (ICTP) regional climate model, version 3 (RegCM3), driven with the NCEP–NCAR reanalysis and the European Centre–Hamburg GCM, version 4.5. Statistics were examined for five regions: the northern Amazon, southern Amazon, the monsoon region, Northeast Brazil, and southeastern South America. RegCM3 and the GCM are able to replicate the distribution of daily rainfall intensity in most regions. The analysis of the rainy season timing shows the observed onset occurring first over the monsoon region and then spreading northward into the southern Amazon, in contrast to some previous studies. Correlations between the onset and withdrawal date and SSTs reveal a strong relationship between the withdrawal date in the monsoon region and SSTs in the equatorial Pacific, with above-average SSTs associated with late withdrawal. Over Northeast Brazil, the regional model errors are smaller than those shown by the GCM, and the strong interannual variability in the timing of the rainy season is better simulated by RegCM3. However, the regional model displays an early bias in onset and withdrawal over the southern Amazon and the monsoon regions. Both RegCM3 and the GCM tend to underestimate (overestimate) the frequency of shorter (longer) dry spells, although the differences in dry spell frequency during warm and cold ENSO events are well simulated. The results presented here show that there is potential for added value from the regional model in simulating subseasonal statistics; however, improvements in the physical parameterizations are needed for this tropical region.

scholarly journals IMPACTS OF LAND COVER AND GREENHOUSE GAS (GHG) CONCENTRATION CHANGES ON THE HYDROLOGICAL CYCLE IN AMAZON BASIN: A REGIONAL CLIMATE MODEL STUDY

2015 ◽  
Vol 15 ◽  
Author(s):  
Vinícius Machado Rocha ◽  
Francis Wagner Silva Correia ◽  
Prakki Satyamurty ◽  
Saulo Ribeiro De Freitas ◽  
Demerval Soares Moreira ◽  
...  
Keyword(s):  
Land Cover ◽  
Regional Climate Model ◽  
Greenhouse Gas ◽  
Amazon Basin ◽  
Climate Model ◽  
Hydrological Cycle ◽  
Regional Climate ◽  
Model Study ◽  
Concentration Changes

scholarly journals Simulation of characteristic features of Asian summer monsoon using a regional climate model

MAUSAM ◽  
2021 ◽  
Vol 57 (2) ◽  
pp. 221-230
Author(s):  
O. P. SINGH ◽  
K. RUPA KUMAR ◽  
P. K. MISHRA ◽  
K. KRISHNA KUMAR ◽  
S. K. PATWARDHAN
Keyword(s):  
Greenhouse Gas ◽  
Climate Model ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Regional Climate ◽  
Lower Troposphere ◽  
Simulation Experiments ◽  
Gas Concentration ◽  
Asian Summer ◽  
Characteristic Features

Lkkj & bl 'kks/k&i= esa HkweaMyh; tyok;q ifjorZu ds ifj.kkeLo:i 'krkCnh ds e/; ¼2041&60½ ds nkSjku ,f’k;kbZ xzh"edkyhu ekulwu ds fof’k"V y{k.kksa dk iwokZuqeku djus ds mÌs’; ls vuqdj.k iz;ksxksa ds ifj.kke izLrqr fd, x, gSaA blds fy, gSMys tyok;q iwokZuqeku vkSj vuqla/kku dsUnz] ;w- ds- dk {ks=h; tyok;q ekWMy gSM vkj- ,e- 2 dk mi;ksx fd;k x;k gSA ,f’k;kbZ {ks= ds fy, 20 o"kksZa dh vof/k ds nks vuqdj.k iz;ksx fd, x, gSa uker% igyk] 1990 Lrjksa ds vuq:i xzhu gkml xSl lkanz.k dh fu/kkZfjr ek=k] ftls dUVªksy ¼lh- Vh- ,y-½ iz;ksx dgk x;k gS vkSj nwljk 1990 ls ysdj 2041&60 rd ds fy, xzhu gkml xSl lkanz.k ds okf"kZd feJ.k esa 1 izfr’kr dh o`f) lesr ftls vkxs xzhu gkml xSl ¼th- ,p- th-½ iz;ksx dgk x;k gSA xzhu gkml xSl lkanz.k esa okf"kZd feJ.k esa 1 izfr’kr dh o`f) tyok;q ifjorZu ds var% ljdkjh iSuy vkbZ- ih- lh- lh- }kjk rS;kj dh xbZ ;kstuk ls yh xbZ gSA bu iz;ksxksa ls 'krkCnh ds e/; ds nkSjku ,f’k;kbZ xzh"edkyhu ekulwu esa ik, tkus okys fof’k"V y{k.kksa esa gksus okys dqN ifjorZuksa dk irk pyk gS ftudk c<+s gq, ekuotfur mRltZdksa ds dkj.k gksuk LokHkkfor gSA lewph ekulwu _rq ds nkSjku Hkkjrh; {ks= ij fuEu {kksHk eaMy ¼850 gSDVkikLdy½ esa ekulwu nzks.kh ¼,e- Vh- ½ dk mRrj dh vksj lkekU; :i ls c<+uk lcls vf/kd egRoiw.kZ ifjorZu izrhr gksrk gSA vuqdj.k ifj.kkeksa ls ekulwu _rq ds nkSjku vjc lkxj esa leqnz Lrj nkc ¼,l- ,y- ih-½ esa yxHkx 1&2 gS- ik- dh o`f) dk irk pyk gS ftlds ifj.kkeLo:i fuEu {kksHk eaMy esa vlkekU; izfrpØokr gksrs gSaA bldk vFkZ ;g gqvk fd fuEu Lrjh; tsV ¼,y- ,y- ts-½ vkSj vjc lkxj esa ekulwu dh /kkjk det+ksj iM+ tkrh gSA ;g ekWMy m".krj leqnz lrg dh fLFkfr;ksa esa fgan egklkxj ds mRrj esa ekulwuh pØokrh; fo{kksHkksa dh vko`fr esa deh dks vuqdfjr djrk gS tks gky gh ds n’kdksa esa ekulwu ds vonkcksa dh vko`fr esa deh dh izo`fr;ksa ds vuq:i ikbZ xbZ gSA bu iz;ksxksa ls ;g irk pyrk gS fd ikfdLrku vkSj mlds lehiorhZ mRrjh if’peh Hkkjr ds Åij Å"ek fuEunkc rhoz gks ldrk gS vkSj ekulwu _rq           ds nkSjku FkksM+k iwoZ dh vksj c<+ ldrh gSA ;g ekWMy] Hkkjrh; leqnz ds nf{k.kh Hkkxksa esa 8° & 10° m- ds chp 100 gS- ik- ¼Vh- bZ- ts- dksj dk Lrj½ ij fo’ks"kdj ekulwu ds iwokZ)Z ds nkSjku m".kdfVca/kh; iwokZfHkeq[kh tsV¼Vh- bZ- ts-½ dks izHkkfor djrk gSA The paper presents the results of simulation experiments aimed at predicting the characteristic features of Asian Summer Monsoon during the middle of the century (2041-60) resulting from global climate change. The model used is HadRM2 regional climate model of the Hadley Centre for Climate Prediction and Research, UK. Two simulation experiments of 20 years length have been performed for the Asian domain, namely, one with a fixed amount of greenhouse gas concentration corresponding to 1990 levels called the 'control' (CTL) experiment and the other with the annual compound increase of 1 % in the greenhouse gas concentration for 2041-60 from 1990 onwards called the 'greenhouse gas' (GHG) experiment. The annual compound increment of 1 %, in the greenhouse gas concentration has been adopted from the projection given by the Intergovernmental Panel for Climate Change (IPCC). The experiments have brought out some of the changes in the characteristic features of mid-century Asian summer monsoons that are expected to occur due to increased anthropogenic emissions. The most significant change seems to be a general northward shift of the monsoon trough (MT) in the lower troposphere (850 hPa) throughout the monsoon season over the Indian region. The simulation results have shown an increase of about 1-2 hPa in the sea level pressure (SLP) over the Arabian Sea during the monsoon resulting in an anomalous anticyclone over there in the lower troposphere. This would mean the weakening of Low Level Jet (LLJ) and the Arabian sea branch of the monsoon current. The model has simulated a decrease in the frequency of the monsoonal cyclonic disturbances over the north Indian Ocean under the warmer sea surface conditions which conforms to the observed decreasing trends in the frequency of monsoon depressions in recent decades. The experiments have shown that the Heat Low over Pakistan and adjoining northwest India, may intensify and shift slightly eastward during the monsoon. The model has simulated the strengthening of Tropical Easterly Jet (TEJ) at          100 hPa (the location of TEJ core ) over the southern parts of Indian sea between 8° - 10° N, especially during the first half of the monsoon season.

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