Abstract 114

Abstract ID: 114

Summer Heatwave Forecast skills in GEOS5-S2S version 2

Lead Author: Zhao Li
NASA-GSFC-GMAO, United States of America

Keywords: GEOS5-S2S2.0, summer heatwaves

Abstract: Summer heatwaves cause dangerous consequence to human society by threating public health, agriculture production, energy production and balance in earth ecosystem. Under climate changes such threats become more intensified through enhanced heatwave intensity and frequency. Due to the complex causing mechanisms and meteorological events time scale, prediction of heatwaves has been one of the major challenges in sub-seasonal to seasonal forecast. In this study, we diagnosed GEOS5-S2S2.0 hindcast from 1991 to 2022 to obtain a comprehensive understanding of heatwave forecast skills in the-state-of-art system. MERRA2 is used as a reference to evaluate the forecast skill. Heatwave is detected as maximum daily 2-meter temperature exceeds a 90th percentile during a 11-day window for more than 3 consecutive days. The total days under heatwave condition, occurrence of heatwave, maximum heatwave duration and heatwave magnitude index are calculated for both the model and MERRA2 at each grid cell as well as aggregating to obtain a regional value. Various skill scores such as hit-rate, false-alarm, brier skill score, ranked probability skill score and reliability diagram are calculated for regions like US, Europe and East Asia, etc. Spatial and temporal correlations for these regions and sub-regions are also computed for all the indices. Evaluating metrics are compared between GEOS5-S2S2.0 and MERRA2 for severe heatwaves only during the past 3 decades to evaluate the forecast skills for the most damaging events. In summary, GEOS5-S2S2.0 shows reliable skills in occurrence of severe heatwave events up to two weeks ahead. The forecast skill varies largely among events, metrics and sub-regions.

Andrea Molod (NASA-GSFC-GMAO)