Recent intensification of extreme precipitation events in the La Plata Basin in Southern South America (1981–2018)

Abstract A sensitivity study of the impact of a groundwater scheme on hydrometeorological variables in coupled land–atmosphere simulations over southern South America is presented. It is found that shallow water tables in the groundwater scheme lead to reduced drainage and even upward capillary fluxes over parts of the central and southern La Plata basin. This leads to an increase in the simulated moisture in the root zone, which in turn produces an increase in evapotranspiration (ET) over the southern part of the domain, where ET is water limited. There is also a decrease in the near-surface temperature, in the range 0.5°–1.0°C. During the dry season, the increases in ET and relative humidity over the central La Plata coincide with an increase in precipitation downstream. Including groundwater leads to an increase in precipitation over parts of the central and southern La Plata basin during the early rainy season (October–December). The overall increase in ET and precipitation over the southern La Plata basin during the early rainy season is 13% and 10%, respectively. The additional precipitation comes from both an increase in the availability of atmospheric moisture when the groundwater scheme is used and its effect on the atmospheric instability. In the La Plata basin, including a representation of groundwater increases simulated precipitation and partially alleviates a warm and dry bias present in simulations without realistic subsurface hydrology.

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Extreme Precipitation Events in Southeastern South America and Large-Scale Convective Patterns in the South Atlantic Convergence Zone

Journal of Climate ◽

10.1175/1520-0442(2002)015<2377:epeiss>2.0.co;2 ◽

2002 ◽

Vol 15 (17) ◽

pp. 2377-2394 ◽

Cited By ~ 162

Author(s):

Leila M. V. Carvalho ◽

Charles Jones ◽

Brant Liebmann

Keyword(s):

South America ◽

Extreme Precipitation ◽

Large Scale ◽

South Atlantic Convergence Zone ◽

South Atlantic ◽

Convergence Zone ◽

The South ◽

Extreme Precipitation Events ◽

Precipitation Events

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Effects of a Groundwater Scheme on the Simulation of Soil Moisture and Evapotranspiration over Southern South America

Journal of Hydrometeorology ◽

10.1175/jhm-d-16-0051.1 ◽

2016 ◽

Vol 17 (11) ◽

pp. 2941-2957 ◽

Cited By ~ 11

Author(s):

J. Alejandro Martinez ◽

Francina Dominguez ◽

Gonzalo Miguez-Macho

Keyword(s):

South America ◽

Land Surface ◽

Climate Model ◽

Soil Column ◽

Water Storage ◽

Surface Model ◽

Southern South America ◽

La Plata ◽

Continental Scale ◽

La Plata Basin

Abstract The effects of groundwater dynamics on the representation of water storage and evapotranspiration (ET) over southern South America are studied from simulations with the Noah-MP land surface model. The model is run with three different configurations: one including the Miguez-Macho and Fan groundwater scheme, another with the Simple Groundwater Model (SIMGM), and the other with free drainage at the bottom of the soil column. The first objective is to assess the effects of the groundwater schemes using a grid size typical of regional climate model simulations at the continental scale (20 km). The phase and amplitude of the fluctuations in the terrestrial water storage over the southern Amazon are improved with one of the groundwater schemes. An increase in the moisture in the top 2 m of the soil is found in those regions where the water table is closer to the land surface, including the western and southern Amazon and the La Plata basin. This induces an increase in ET over the southern La Plata basin, where ET is water limited. There is also a seasonal increase in ET during the dry season over parts of the southern Amazon. The second objective is to assess the role of the horizontal resolution on the effects induced by the Miguez-Macho and Fan groundwater scheme using simulations with grid sizes of 5 and 20 km. Over the La Plata basin, the effect of groundwater on ET is amplified at the 5-km resolution. Notably, over parts of the Amazon, the groundwater scheme increases ET only at the higher 5-km resolution.

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