Assessment of seasonal soil moisture forecasts over Southern South America with emphasis on dry and wet events

5. SPENNEMANN P., RIVERA J.A., OSMAN M., SAULO C., PENALBA O. C. 2017.

Viena

Congreso; EGU General Assembly 2017; 2017

The importance of forecasting extreme wet and dry conditions from weeks to months in advance relies on the needto prevent considerable socio-economic losses, mainly in regions of large populations and where agriculture is akey value for the economies, like Southern South America (SSA). Therefore, to improve the understanding of theperformance and uncertainties of seasonal soil moisture and precipitation forecasts over SSA, this study aims to:1) perform a general assessment of the Climate Forecast System version-2 (CFSv2) soil moisture and precipitationforecasts; and 2) evaluate the CFSv2 ability to represent an extreme drought event merging observations withforecasted Standardized Precipitation Index (SPI) and the Standardized Soil Moisture Anomalies (SSMA) basedon GLDAS-2.0 simulations.Results show that both SPI and SSMA forecast skill are regionally and seasonally dependent. In general a fastdegradation of the forecasts skill is observed as the lead time increases with no significant metrics for forecastlead times longer than 2 months. Based on the assessment of the 2008-2009 extreme drought event it is evidentthat the CFSv2 forecasts have limitations regarding the identification of drought onset, duration, severity anddemise, considering both meteorological (SPI) and agricultural (SSMA) drought conditions. These results havesome implications upon the use of seasonal forecasts to assist agricultural practices in SSA, given that forecastskill is still too low to be useful for lead times longer than 2 months.