ENSO Signal on Subseasonal Precipitation Distribution and Soil Moisture Response in the Argentine Pampas

Abstract

Climate services provide information on El Niño-Southern Oscillation (ENSO) evolution and predicted seasonal precipitation, broadly used by decision makers from the agriculture sector. However, soil moisture participates in a more complex soil–atmosphere interaction at subseasonal scale. This work aims to identify the ENSO signal on subseasonal precipitation indices and to assess soil moisture response during austral spring–summer over the southern Argentine Pampas. From daily precipitation, 16 indices were analyzed, and the temperature vegetation dryness index (TVDI) was computed as representative of soil moisture availability. In general, the different precipitation indices presented coherence with wetter (drier) climate conditions under the El Niño (La Niña) phase. A strong signal was found for precipitation frequency in November and accumulation in December, whereas reversal and a weak signal was observed during January, crucial for summer crops. The analysis of soil–moisture interaction suggests that positive precipitation anomalies during El Niño can be reinforced by high soil moisture stored in previous months (e.g., during El Niño 2002–2003). The drying process increases in soils with low water retention capacity, producing a spatially heterogeneous impact (e.g., El Niño 2009–2010). The dry pattern expected for La Niña events was observed in 2007–2008, affecting regions with high water retention and productivity. In addition, long wet spells presented a stronger influence in these regions. Owing to the spatial and temporal heterogeneity observed at subseasonal scale, this study suggests the need for the joint analysis of atmospheric variables and soil moisture content for medium-term agricultural planning in the context of ENSO events in the southern Argentine Pampas.