Abstract. This study uses correlation analyses to explore relationships between the
satellite-derived Evaporative Stress Index (ESI) â which depicts
standardized anomalies in an actual to reference evapotranspiration (ET)
fraction â and various land and atmospheric variables that impact
ET. Correlations
between the ESI and forcing variable anomalies calculated over sub-seasonal
timescales were computed at weekly and monthly intervals during the growing
season. Overall, the results revealed that the ESI is most strongly
correlated to anomalies in soil moisture and 2âm dew point depression.
Correlations between the ESI and precipitation were also large across most of
the US; however, they were typically smaller than those associated with soil
moisture and vapor pressure deficit. In contrast, correlations were much
weaker for air temperature, wind speed, and radiation across most of the US,
with the exception of the south-central US where correlations were large for
all variables at some point during the growing season. Together, these
results indicate that changes in soil moisture and near-surface atmospheric
vapor pressure deficit are better predictors of the ESI than precipitation
and air temperature anomalies are by themselves. Large regional and seasonal
dependencies were also observed for each forcing variable. Each of the
regional and seasonal correlation patterns were similar for ESI anomalies
computed over 2-, 4-, and 8-week time periods; however, the maximum
correlations increased as the ESI anomalies were computed over longer time
periods and also shifted toward longer averaging periods for the forcing
variables.