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

Abstract

Abstract. This study uses correlation analyses to explore relationships between the satellite-derived Evaporative Stress Index (ESI) – which depicts standardized anomalies in an actual to reference evapotranspiration (ET) fraction – 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 2 m 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.

Agricultural Drought Assessment in East Asia Using Satellite-Based Indices

“…Standardized ET fraction anomalies, expressed as pseudo z-scores normalized to a mean of 0 and a standard deviation of 1, are then computed at weekly intervals using data composited over 2, 4, and 8 week time periods. The mean and standard deviations for each week and compositing period are computed separately for each grid point using data from 2001-2015 [32]. The ESI images provided by the GOES represent a 7-day cycle and 5 km resolution world images, and provide composite images of 4-week data.…”

Monitoring Meteorological Drought in Southern China Using Remote Sensing Data

“…This indicator is used in daily business by the departments of the China Meteorological Administration, and it can assess monthly, seasonal, and annual drought events. The anomalies of soil moisture, vegetation, and temperature are also widely used in many studies [27][28][29][30][31][32][33][34], and they are collectively referred to as the Anomalies Percentage (AP).…”

Climatology and Variability of the Evaporative Stress Index and Its Suitability as a Tool to Monitor Australian Drought

“…Tools such as the evaporative stress index (ESI; Anderson et al 2011Anderson et al , 2013 and the standardized evaporative stress ratio (Christian et al 2019) can be used to represent the combined influence of multiple meteorological and land variables on land surface moisture conditions that are relevant for agricultural and ecological drought. These variables include precipitation, air temperature, humidity, net surface radiation, wind speed, and soil moisture.…”

“…These variables include precipitation, air temperature, humidity, net surface radiation, wind speed, and soil moisture. The ESI has been found to be useful for monitoring drought over the contiguous United States (Anderson et al 2007(Anderson et al , 2013, Brazil (Anderson et al 2016a), and the Czech Republic (Anderson et al 2016b). It is currently used as an input to the U.S. Drought Monitor (M. Svoboda 2019, personal communication).…”