Technical Note: Evaluation of the Skill in Monthly-to-Seasonal Soil Moisture Forecasting Based on SMAP Satellite Observations over the Southeast US

Abstract. Providing accurate soil moisture (SM) conditions is a critical step in model initialization in weather forecasting, agricultural planning, and water resources management. This study develops monthly to seasonal (M2S) top layer SM forecasts by forcing 1–3 month ahead precipitation forecasts with Noah3.2 Land Surface Model. The SM forecasts are developed over the Southeast US (SEUS) and the SM forecasting skill is evaluated in comparison with the remotely sensed SM observations collected by Soil Moisture Active Passive (SMAP) satellite. Our results indicate potential in developing real-time SM forecasts. The retrospective 18-months (April 2015–September 2016) comparison between SM forecasts and the SMAP observations shows statistically significant correlations of 0.62, 0.57, and 0.58 over 1–3 month lead times respectively. As a case study, the evaluation of the issued forecasts based on the drought indexes monitored during the 2007 historical drought over the SEUS also indicate promising skill in monthly SM forecasting to support agricultural planning and water management for such natural hazards.