The role of shallow groundwater on land-atmosphere
interactions in southern South America

 

It has long been hypothesized that including a representation of groundwater into climate models will lead to improvements in their representation of surface hydrology and atmospheric processes. However, there have been very few studies analyzing the effect of groundwater on climate, and so far groundwater’s effect on precipitation has been inconclusive. In this work we use a newly developed representation of groundwater in the Noah-MP land surface model and its effect on surface hydrologic variables (soil moisture and evapotranspiration) and atmospheric variables (temperature, humidity and precipitation). Our geographical focus is the La Plata river basin in southern South America.

With groundwater, we find an increase of soil moisture in the root zone over those regions where the water table is closer to the surface, including parts of the western and southern Amazon, and of the central and southern La Plata.  ET increases in the central and southern La Plata, where it is water limited. During the early rainy season over the southern LPB, the groundwater scheme induces an increase in ET and precipitation of 13 and 10%, respectively.  Over the La Plata, the groundwater scheme tends to improve the warm and dry biases of the model, although the latter are larger than the modifications induced by the groundwater scheme.  We show that groundwater has a robust and significant impact on the hydroclimate of the La Plata region.

 

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