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

SALVIA, M.; PILES M; R. C. RUSCICA; SÖRENSSON, ANNA A.; KARSZENBAUM, H.; R. C. RUSCICA; SÖRENSSON, ANNA A.; KARSZENBAUM, H.; POLCHER J; JOBBAGY E; POLCHER J; JOBBAGY E; SALVIA, M.; PILES M

Canmore

Conferencia; 8th Gewex Open Science Conference: Extremes and water on the edge; 2018

GEWEX (http://www.gewex.org/)

AbstractKnowledge of spatio-temporal dynamics of Regional Surface Soil Moisture (RSSM) is essential for theoretical understanding of water cycle processes but also for many practical applications such as weather forecasting, climate extremes monitoring and prediction of floods, droughts, and heat waves. Here, 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 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 SESA region has been recognized as a land-atmosphere interaction hotspot by different studies using climate models and more recently remote sensing products. The region has the largest population density of the continent and is the most productive region in terms of agriculture, livestock and industry. SESA is also suitable for studying dry-downs with satellite and land surface model data since it comprises the low and flat Pampas plains where (a) the most severe subtropical storms of the globe are developed in the region, which impact on but are also affected by soil moisture (b) the availability of satellite data is high because of simple topography, low vegetation density and higher sampling frequency of polar orbiting satellites than in tropical regions and (c) soil water vertical transport, which is simulated by LSMs, dominates over horizontal transport.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 product from AMSRE and AMSR2. ORCHIDEE land surface model was employed 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, sensitivity to soil depth, soil and land cover characteristics, and sampling frequency. Preliminary results showed that sampling frequency seems to be the most important factor on the e-folding time and not soil depth as other studies suggested.