Exploring seasonal and regional relationships between the Evaporative Stress Index and surface weather and soil moisture anomalies across the United States

摘要

This study uses correlation analyses to explore relationships between thesatellite-derived Evaporative Stress Index (ESI) – which depictsstandardized anomalies in an actual to reference evapotranspiration (ET)fraction – and various land and atmospheric variables that impactET. Correlationsbetween the ESI and forcing variable anomalies calculated over sub-seasonaltimescales were computed at weekly and monthly intervals during the growingseason. Overall, the results revealed that the ESI is most stronglycorrelated to anomalies in soil moisture and 2 m dew point depression.Correlations between the ESI and precipitation were also large across most ofthe US; however, they were typically smaller than those associated with soilmoisture and vapor pressure deficit. In contrast, correlations were muchweaker for air temperature, wind speed, and radiation across most of the US,with the exception of the south-central US where correlations were large forall variables at some point during the growing season. Together, theseresults indicate that changes in soil moisture and near-surface atmosphericvapor pressure deficit are better predictors of the ESI than precipitationand air temperature anomalies are by themselves. Large regional and seasonaldependencies were also observed for each forcing variable. Each of theregional and seasonal correlation patterns were similar for ESI anomaliescomputed over 2-, 4-, and 8-week time periods; however, the maximumcorrelations increased as the ESI anomalies were computed over longer timeperiods and also shifted toward longer averaging periods for the forcingvariables.