Warm-season precipitation drivers in northeastern Argentina: Diurnal cycle of the atmospheric moisture balance and land-atmosphere coupling

Southeastern South America is influenced by moisture transport from lower latitudes, sustains intense convective storms and is a land-atmosphere coupling hotspot, but the interconnection between these processes is still not well understood. We present the warm-season diurnal cycle climatology of the atmospheric water balance components in the South American Low-Level Jet (SALLJ) exit region in northeastern Argentina during 1998-2012. Different precipitation-based types of events (clear-sky and rainy days) were explored together with processes tied to the land-atmosphere coupling at the daily scale. Our research was based on simulations with and without soil moisture-atmosphere coupling with the RCA4 regional climate model. A control simulation was compared with a sensitivity simulation where the soil moisture was prescribed with the daily climatological values from the control run. The ERA5 reanalysis and the satellite precipitation products TRMM-3B42 v7 and CMORPH v1.0 bias-corrected were used for comparative purposes. From the diurnal water balance analysis, we found that moisture flux convergence in the region is the main driver for nocturnal precipitation while local evapotranspiration feeds afternoon rain events. Rainy afternoons do not show differences between simulations, but rainy nights seem to be affected. Moreover, daily correlations between surface and boundary-layer variables showed that the local coupling is weaker during rainy days than during clear-sky days. Therefore, we suggest that changes in non-local drivers, such as the moisture flux through the SALLJ, are more relevant for rainy nights than the local coupling.