Future climate projections focusing on precipitation and water resource trends over South America (SA) are investigated using two ensembles. One of them is composed of three global climate models ...(GCMs), and the other of eight regional climate models (RCMs) from the Coordinated Regional Climate Downscaling Experiment (CORDEX). The present (1970–2005) and the future (2006–2100) climate trends are analyzed for representative pathway scenarios 4.5 (RCP4.5) and 8.5 (RCP8.5). For the most pessimistic scenario (RCP8.5), trends in water resources are assessed considering the terrestrial branch of the hydrologic cycle by analyzing the precipitation minus evapotranspiration (P-ET). For the present climate, RCMs added value to the GCMs in simulating more realistic precipitation fields in several regions. GCMs and RCMs project, in general, the same precipitation change signal for the end of the 21st century over SA, which is stronger in RCP8.5 than in RCP4.5. For RCP8.5 in most regions, GCMs and RCMs ensembles have the same precipitation trend signal, but a great spread between the ensemble members, which is greater in austral summer than winter, can be noted. In winter a negative trend in rainfall in most members and regions predominates. At the end of the 21st century, relative changes in rainfall in RCP8.5 are in the range of +14% (over northeastern Brazil in summer) to − 36% (over the Andes Mountains in winter). In RCP8.5, the ensembles project an increase in air temperature with a similar magnitude, while in RCP4.5 the trends are weaker. For air temperature, there is small spread between members, and the positive trend is statistically significant for all ensemble members in the RCP8.5 scenario. In terms of water resources, on an annual scale, for RCP8.5 the RCM ensemble projects a larger area with wetter conditions in the future than GCMs. Regionally, it is expected a decrease in water availability in the Amazon basin and an increase over northeast Brazil and southeast SA during the summer. In other regions (northern Amazon, the Andes Mountains and Patagonia) the ensembles indicate drier conditions in the future winter, except in southern Amazon. It is expected that such information could be useful for devising adaptation and mitigation policies due to climate change over the SA.
Regional climate models have been used since 1989 in order to improve climate simulation in regions where mesoscale forcings modulate the regional climate. These models are driven by time‐dependent ...lateral boundary conditions from global climate models or reanalysis, and this process is called dynamical downscaling. Here, we review the evolution of regional climate modeling, as well as present the studies developed for South America.
Regional climate models have been used since 1989 in order to improve climate simulation in regions where the mesoscale forcings modulate the regional climate. These models are driven by time‐dependent lateral boundary conditions from global climate models or reanalysis, and this process is called dynamical downscaling. Here, we review the evolution of regional climate modeling as well as present the studies developed for South America.
We analyse an ensemble of statistically downscaled Global Climate Models (GCMs) to investigate future water availability in the Upper Indus Basin (UIB) of Pakistan for the time horizons when the ...global and/or regional warming levels cross Paris Agreement (PA) targets. The GCMs data is obtained from the 5th Phase of Coupled Model Inter-Comparison Project under two Representative Concentration Pathways (RCP4.5 and RCP8.5). Based on the five best performing GCMs, we note that global 1.5 °C and 2.0 °C warming thresholds are projected in 2026 and 2047 under RCP4.5 and 2022 and 3036 under RCP8.5 respectively while these thresholds are reached much earlier over Pakistan i.e. 2016 and 2030 under RCP4.5 and 2012 and 2025 under RCP8.5 respectively. Interestingly, the GCMs with the earliest emergence at the global scale are not necessarily the ones with the earliest emergence over Pakistan, highlighting spatial non-linearity in GCMs response. The emergence of 2.0 °C warming at global scale across 5 GCMs ranges from 2031 (CCSM4) to 2049 (NorESM) under RCP8.5. Precipitation generally exhibits a progressive increasing trend with stronger changes at higher warming or radiative forcing levels. Hydrological simulations representing the historical, 1.5 °C and 2.0 °C global and region warming time horizons indicate a robust but seasonally varying increase in the inflows. The highest inflows in the baseline and future are witnessed in July. However, the highest future increase in inflows is projected in October under RCP4.5 (37.99% and 65.11% at 1.5 °C and 2.0 °C) and in April under RCP8.5 (37% and 62.05% at 1.5 °C and 2.0 °C). These hydrological changes are driven by increases in the snow and glacial melt contribution, which are more pronounced at 2.0 °C warming level. These findings should help for effective water management in Pakistan over the coming decades.
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•The study assessed emergence of global and regional warming exceeding Paris Agreement targets.•PA warming targets are likely to exceed almost a decade earlier in Pakistan than at global scale.•1.5 °C warming is projected over Pakistan (Globe) by 2016 (2026) under RCP4.5.•2.0 °C warming is projected over Pakistan (Globe) by 2030 (2047) under RCP4.5.•Both precipitation and annual inflows are projected to increase within the PA warming targets.
Two 11‐year simulations were conducted to investigate the influence of two runoff schemes in the community land model version 4.5 (CLM45) on the Amazon surface energy balance and surface climate ...using a high‐resolution regional climate model (RegCM4‐CLM45). The default scheme is TOPMODEL (TOP), while the alternative is Variable Infiltration Capacity (VIC). In the two simulations, the vegetation status is prescribed (satellite phenology; SP). The first simulation was designated as SP‐TOP, while the second simulation was referred to as SP‐VIC, and both of them were evaluated using reanalysis products (e.g., ERA5) and micrometeorology data measurements. Results show that the SP‐VIC severely underestimates latent heat and overestimates sensible heat fluxes, more than SP‐TOP in comparison with the ERA5. This explains the large warm bias observed in the winter season. On the other hand, the SP‐VIC shows a slightly smaller dry bias than SP‐TOP against the Climate Research Unit (CRU) data. Our results show that SP‐VIC does not improve the quality of the simulation compared to SP‐TOP, which suggests the necessity of additional calibration of the VIC surface parameters using in situ observations of the Amazon and revising the VIC runoff scheme to perform new sensitivity experiments. The same needs to be done with SP‐TOP.
The runoff scheme has a strong influence on the surface climate of the Amazon as the SP‐VIC shows a higher warm bias than the SP‐TOP. In comparison with the micrometeorology data measurements, both simulations can reproduce the phase of the climatological seasonal cycle of the sensible, latent heat fluxes and Bowen ratio. However, they fail in reproducing the intensity of these variables.
There is research evidence that due to global warming, global precipitation and monsoon area have shown a shift which needs to be analyzed at regional scale. This study analyses future precipitation ...and monsoon spatial shift over Pakistan and Upper Indus Basin (UIB) based on latest Coordinated Regional Climate Downscaling Experiment - Coordinated Output for Regional Evaluations (CORDEX-CORE) high resolution projections (25 km) for the South Asian domain. Three global climate models from Coupled Model Intercomparison Project Phase 5 (CMIP5) (MIROC5, NorESM1-M and MPI-ESM-MR) provided the lateral boundary conditions for the Regional Climate Model (RegCM4) under Representative Concentration Pathways 2.6 (RCP2.6) and RCP8.5 scenarios. Results indicate that JJA precipitation over Upper Indus Basin (UIB which also includes North Pakistan) is projected to increase more under RCP8.5 and less under RCP2.6 while for Pakistan it shows slightly increase (decrease) in RCP2.6 (RCP8.5). The results also show a projected expansion in monsoon area in UIB and northward shift of MCR which corresponds with future precipitation changes in the area and hence indicate the penetration of monsoon system over UIB under higher warming scenario. The changes in monsoon precipitation and domain are related to the changes in wind circulation patterns at 850 hPa and 200 hPa atmospheric levels.
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•The monsoon precipitation (JJA) over Upper Indus Basin is projected to increase more (less) under RCP8.5 (RCP2.6).•For Pakistan it shows slightly increase (decrease) in RCP2.6 (RCP8.5).•The monsoon core region of Pakistan is projected to shift towards north and show expansion in UIB.•The precipitation changes are related to wind circulation patterns at 850 hPa and 200 hPa levels.
Oceanic heat sources disturb the atmosphere, which, to come back to its initial state, disperses waves. These waves affect the climate in remote regions, characterizing the teleconnection patterns. ...In this study, we describe eight teleconnection patterns that affect South America climate: the El Niño–Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO), the Tropical Atlantic Dipole (TAD), the South Atlantic Dipole (SAD), the Southern Annular Mode (SAM), the Madden–Julian Oscillation (MJO), and the Indian Ocean Dipole (IOD). Precipitation and winds at 850‐hPa anomalies, considering these teleconnection patterns in ENSO neutral periods, are also presented. Overall, southeastern South America and the north sector of the North and Northeast regions of Brazil are the most affected areas by the teleconnection patterns. In general, there is a precipitation dipole pattern between these regions during each teleconnection pattern.
In this study, we describe eight teleconnection patterns that affect South American climate: the El Niño–Southern Oscillation, the Pacific Decadal Oscillation, the Atlantic Multidecadal Oscillation, the Tropical Atlantic Dipole, the South Atlantic Dipole, the Southern Annular Mode, the Madden–Julian Oscillation, and the Indian Ocean Dipole. Considering these teleconnection patterns in ENSO neutral periods, precipitation and winds at 850‐hPa anomalies are also presented. Overall, southeastern South America and north of the North and Northeast regions of Brazil are the most affected areas by the teleconnection patterns. In general, a precipitation dipole pattern exits between these regions during each teleconnection pattern.
Since wind is an important source of renewable energy, it has attracted attention worldwide. Several studies have been developed in order to know favorable areas where wind farms can be implemented. ...Therefore, the purpose of this study is to project changes in wind intensity and in wind power density (PD), at 100 m high, over South America and adjacent oceans, by downscaling and ensemble techniques. Regional climate model version 4 (RegCM4) was nested in the output of three global climate models, considering the RCP8.5 scenario. RegCM4 ensemble in the present climate (1979–2005) was validated through comparisons with ERA-Interim reanalysis. The ensemble represents well the spatial pattern of the winds, but there are some differences in relation to the wind intensity registered by ERA-Interim, mainly in center-east Brazil and Patagonia. The comparison between the future climate (2020–2050 and 2070–2098) and the present one shows that there is an increase in wind intensity and PD on the north of SA, center-east Brazil (except in summer) and latitudes higher than 50°S. Such increase is more intense in the period 2070–2098.
Hurricane Catarina (2004) and subtropical storm Anita (2010) called attention to the development of subtropical cyclones (SCs) over the South Atlantic basin. Besides strong and organized storms, a ...large number of weaker, shallower cyclones with both extratropical and tropical characteristics form in the region, impacting the South American coast. The main focus of this study is to simulate a climatology of subtropical cyclones and their synoptic pattern over the South Atlantic, proposing a broader definition of these systems. In addition, a case study is presented to discuss the main characteristics of one weak SC. The Interim ECMWF Re-Analysis (ERA-Interim) and NCEP–NCAR reanalysis are used to construct the 33-yr (1979–2011) climatology, and a comparison between them is established. Both reanalyses show good agreement in the SCs’ intensity, geographical distribution, and seasonal variability, but the interannual variability is poorly correlated. Anomaly composites for austral summer show that subtropical cyclogenesis occurs under a dipole-blocking pattern in upper levels. Upward motion is enhanced by the vertical temperature gradient between a midtropospheric cold cutoff low/trough and the intense low-level warm air advection by the South Atlantic subtropical high. Turbulent fluxes in the cyclone region are not above average during cyclogenesis, but the subtropical high flow advects great amounts of moisture from distant regions to fuel the convective activity. Although most of the SCs develop during austral summer (December–February), it is in autumn (March–May) that the most “tropical” environment is found (stronger surface fluxes and weaker vertical wind shear), leading to the most intense episodes.
Cutoff lows (COLs) pressure systems climatology for the Southern Hemisphere (SH), between 10°S and 50°S, using the National Center for Environmental Prediction–National Center for Atmospheric ...Research (NCEP‐NCAR) and the ERA‐40 European Centre for Medium Range Weather Forecast (ECMWF) reanalyses are analyzed for the period 1979–1999. COLs were identified at three pressure levels (200, 300, and 500 hPa) using an objective method that considers the main physical characteristics of the conceptual model of COLs. Independently of the pressure level analyzed, the climatology from the ERA‐40 reanalysis has more COLs systems than the NCEP‐NCAR. However, both reanalyses present a large frequency of COLs at 300 hPa, followed by 500 and 200 hPa. The seasonality of COLs differs at each pressure level, but it is similar between the reanalyses. COLs are more frequent during summer, autumn, and winter at 200, 300, and 500 hPa, respectively. At these levels, they tend to occur around the continents, preferentially from southeastern Australia to New Zealand, the south of South America, and the south of Africa. To study the COLs at 200 and 300 hPa from a regional perspective, the SH was divided in three regions: Australia–New Zealand (60°E–130°W), South America (130°W–20°W), and southern Africa (20°W–60°E). The common COLs features in these sectors for both reanalyses are a short lifetime (∼80.0% and ∼70.0% of COLs at 200 and 300 hPa, respectively, persisting for up to 3 days), mobility (∼70.0% and ∼50% of COLs at 200 and 300 hPa, respectively, traveling distances of up to 1200 km), and an eastward propagation.
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