A climatological study of evapotranspiration and moisture stress across the continental United States based on thermal remote sensing: 2. Surface moisture climatology

Abstract

Robust satellite‐derived moisture stress indices will be beneficial to operational drought monitoring, both in the United States and globally. Using thermal infrared imagery from the Geostationary Operational Environmental Satellites (GOES) and vegetation information from the Moderate Resolution Imaging Spectrometer (MODIS), a fully automated inverse model of Atmosphere‐Land Exchange (ALEXI) has been used to model daily evapotranspiration and surface moisture stress over a 10‐km resolution grid covering the continental United States. Examining monthly clear‐sky composites for April–October 2002–2004, the ALEXI evaporative stress index (ESI) shows good spatial and temporal correlation with the Palmer drought index but at considerably higher spatial resolution. The ESI also compares well to anomalies in monthly precipitation fields, demonstrating that surface moisture has an identifiable thermal signature that can be detected from space, even under dense vegetation cover. Simple empirical thermal drought indices like the vegetation health index do not account for important forcings on surface temperature, such as available energy and atmospheric conditions, and can therefore generate spurious drought detections under certain circumstances. Surface energy balance inherently incorporates these forcings, constraining ESI response in both energy‐ and water‐limited situations. The surface flux modeling techniques described here have demonstrated skill in identifying areas subject to soil moisture stress on the basis of the thermal land surface signature, without requiring information regarding antecedent rainfall. ALEXI therefore may have potential for operational drought monitoring in countries lacking well‐established precipitation measurement networks.

Thermal Remote Sensing of Drought and Evapotranspiration

“…The proposed HyspIRI mission could serve as a prototype for future space-based, remote sensing systems dedicated to addressing critical issues in global water resource management. [Anderson et al, 2007b] 4-year (2002-2005) …”

“…Figure 2 shows monthly anomalies in an Evaporative Stress Index (ESI), given by 1 -ET/ PET, where ET is the actual evapotranspiration determined by a surface energy balance model using TIR imagery from multiple satellites [Anderson et al, 2007b]. This thermal-based stress index shows good correspondence with standard drought metrics and with patterns of antecedent precipitation but at significantly higher spatial resolution due to limited reliance on ground observations.…”

Estimation of evapotranspiration of temperate grassland based on high-resolution thermal and visible range imagery from unmanned aerial systems

“…In this study, we applied the two-source energy balance (TSEB) model developed by Norman, Kustas, and Humes (1995). The basic idea of this and other two source EB models is to solve explicitly the problem of the ambiguity of the relationship between aerodynamic and radiometric temperature by separating surface temperature, radiative and turbulent fluxes, as well as resistances into a canopy and soil component (Shuttleworth and Wallace 1985; Norman, Kustas, and Humes 1995; Anderson et al 1997; Anderson et al 2007; Norman et al 2000). Due to the more detailed treatment of the radiative exchange and energy fluxes between the two components, the parameterization of these models is more complex and requires more input data.…”

Disaggregation of MODIS surface temperature over an agricultural area using a time series of Formosat-2 images

“…MODIS and GOES are routinely used to monitor drought and surface moisture deficit in relation with climatological forcing at the continental scale (e.g. Nishida et al, 2003;Anderson et al, 2007;Stisen et al, 2008). On the other hand, the temporal frequency of 90 m resolution Advanced Spaceborne Thermal Emission and Reflection Radiome-ter (ASTER) sensor is larger than 15 days.…”