Hydrological cycle, temperature, and land surface-atmosphere interaction in the La Plata Basin during summer: response to climate change

Abstract

The austral summer response (2071−2100 with respect to 1981−2010) in terms of precipitation, temperature, and evapotranspiration was analyzed over South America, with emphasis on the La Plata Basin (LPB), using an ensemble of regional climate models. Seasonal mean precipitation increased over the southern LPB, consistent with CMIP3 and CMIP5 ensembles. However, the region of wetting (in the sense of precipitation minus evapotranspiration) over the LPB shifts to the north and northwest, compared to the region of increased precipitation. The LPB is characterized as the South American region with the largest gradient in temperature change (maximum warming north of the LPB and lowest temperature rise near the Rio de la Plata). The interannual variability of evapotranspiration has a geographic distribution similar to that of temperature variability, with a maximum in northern Argentina, suggesting that the 2 variables are interrelated. In turn, in the current climate, the southern LPB is a transition zone in which the evapotranspiration regime depends on the availability of soil water. The model ensemble also points to a similar geographical distribution of limitation regimes (energy-vs. soil moisture-limited evapotranspiration) for present-day and future conditions over South America. In particular, the evapotranspiration regime is projected to continue to be soil moisture-limited over the LPB. Nevertheless, the coupling between land and temperature decreases in areas with increasing soil water availability. In the southern LPB, interannual variability in temperature and evapotranspiration tend to decrease, while rainfall variability exhibits the opposite behavior.KEY WORDS: Land−temperature coupling · Temperature variability · Evapotranspiration regimes · Ensemble of regional climate models · South America Resale or republication not permitted without written consent of the publisherContribution to

Analysis of Current and Future SPEI Droughts in the La Plata Basin Based on Results from the Regional Eta Climate Model

“…Moreover, they stated that these results were due to the cancelation of offsetting errors in the individual models. Menéndez et al [37] found that the ensemble seasonal (December, January and February, DJF) mean precipitation compared to the CPC-Unified Gauge-Based data [45] is underestimated in the southern LPB down to 3 mm/day and it is overestimated in the northern and eastern LPB up to 4 mm/day. Solman et al [38] found that although the results of the ensemble of the RCMs systematically improved the quality of the modelled climate compared to the single RCM model evaluated in the CLARIS-LPB project, they did not identify anyone producing systematically worse or better results for every variable over every region.…”

“…The most ambitious collaborative initiative for producing ensembles of RCM simulations over the La Plata Basin was performed within the CLARIS-LPB Project (a Europe-South America network for climate change assessment and impact studies [42,43]). A suite of seven coordinated RCM simulations over South America (with an approximate grid resolution of 50 km) driven by both the ERA-interim [44] reanalysis and a set of GCMs were evaluated [34,[36][37][38][39][40]42]. Carril et al [36] found relatively good agreement for the annual precipitation average cycle over the La Plata Basin by applying an ensemble of RCMs.…”

“…Concerning the future climate, several models showed, in general, a precipitation increase over the La Plata Basin region [29][30][31]33,34,37]. According to Menéndez et al [37], for the period 2071-2100, the seasonal mean precipitation (DJF) from the CLARIS LPB ensemble under the SRES A1B scenario is projected to increase between 20% and 40% over the southern LPB.…”

“…Under-and over-estimations by about 1 • C are observed in the north of the basin. However, Menéndez et al [37] found that the ensemble seasonal (DJF) temperature compared to the CRU data [60] is overestimated by 3 • C in the southern and western LPB and underestimated by 2.5 • C in the eastern LPB. In addition, they estimated the potential evapotranspiration (PET) for the current climate.…”

“…With regard to the modelling of the current climate and the evaluation of projections of the effects of climate change on the basin, several studies were conducted by assembling different emission scenarios (RCP 8.5, RCP 6.0, RCP 4.5, and RCP 2.6) with regional climate models (RCM, e.g., REGCM3, RegCM4, Eta, RCA, MM5, and REMO) driven by global climate models (GCM, e.g., HadGEM2, HadCM3, MIROC5, EC5OM, ECHAM5, GFDL, and MPI) (e.g., [3,11,13,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]). In order to assess a wide range of uncertainty sources, in recent years many studies have followed an ensemble modelling approach.…”