Surface soil moisture dry-down in a land-atmosphere hotspot observed by SMOS and AMSRE/2, and modelled by ORCHIDEE

RUSCICA, ROMINA; SALVIA, MARÍA MERCEDES; POLCHER, JAN; SÖRENSSON, ANNA; MARIA PILES; JOBBAGY, ESTEBAN; KARSZENBAUM HAYDEE

Canmore

Conferencia; 8TH GEWEX OPEN SCIENCE CONFERENCE: EXTREMES AND WATER ON THE EDGE; 2018

Regional Surface Soil Moisture (RSSM) spatio-temporal knowledge is essential for the theoretical understanding of water cycle processes but also for many practical applications such as weather forecasting, or climate extremes monitoring and prediction of floods, droughts, and heat waves. Nevertheless, some inconsistencies in soil moisture dynamics behavior are usually found in different studies regarding the chosen metric (absolute values, anomalies, indexes, etc.).A different framework for studying RSSM dynamics is presented. Soil moisture dry-downs during non-rainy days after precipitation events are studied on scales of the landscape. This is an essential knowledge to better understand how the surface will respond to changes in the characteristics of rainfall. The dry-down is critical for soil moisture stress of plants, surface Bowen ratio, surface warming and atmospheric response, being so an integrated concept.We proposed the study of the RSSM spatio-temporal dynamics over southeastern South America (SESA) through boxplots and maps of the e-folding time parameter of surface soil moisture dry-downs, making use of daily data from satellite products and a suitable land surface model at a 25km spatial resolution during the 2010-2014 period.The importance of the SESA region lies in the fact that: it has been recognized as a land- atmosphere interaction hotspot by different studies using climate models and more recently remote sensing products; it has the largest population density of the continent and is the most productive region in terms of agriculture, livestock and industry; it comprises the low and flat Pampas plains where (a) the availability of satellite data is high regarding simple topography and low vegetation density and (b) soil water horizontal contributions are low which is the most common approach in land surface models; the most severe subtropical storms of the globe are developed, which impact on but are also affected by soil moisture; and it is a subtropical region where the sampling frequency of the polar satellites is higher than in tropical ones.Two satellite products based on different band emissions (L and C-X) were chosen: a recent version of SMOS RSP (v.620) and a merged temporal product from AMSRE and AMSR2 due to the selected period. On the other hand, ORCHIDEE land surface model was selected since it provides a high vertical resolution of the soil surface, making it suitable for comparison with satellite products.Results are analyzed for each season and the complete period in terms of many different types of dry-down detections, two precipitation datasets (definition of a precipitation event), sensitivity to soil depth, soil and land cover characteristics, and sampling frequency. Preliminary results showed that the later seems to be the most important factor on the e-folding time and not the soil depth as other studies suggest.