An improved satellite‐based approach for estimating vapor pressure deficit from MODIS data

Abstract

Vapor pressure deficit (VPD) is an important variable widely used in ecosystem and climate models. In this paper, an improved satellite-based approach to estimating VPD was presented that uses several remote sensing products coupled with field measured data. The proposed method exploits an optimized algorithm to derive near-surface actual vapor pressure (e a ) from Moderate Resolution Imaging Spectroradiometer (MODIS) data and upgrades Smith's (1966) methodology for estimating e a . The proposed new algorithm for calculating e a was evaluated against in situ measurements at 119 validation sites in China for 2 months in 2013. The mean absolute error (MAE) and root-mean-square error (RMSE) were less than 0.25 kPa and 0.33 kPa, respectively. The near-surface air temperature (T a ), which is an important input data for calculating VPD, was estimated from satellite-retrieved land surface temperature, and had an RMSE of less than 2.5 K. The estimated VPD values were validated with ground observation data from the Heihe River Basin for 5 months in 2012 and for all of China for August 2013. A coefficient of determination (R 2 ) of 0.912, MAE of 0.27 kPa, and RMSE value of 0.32 kPa were achieved for the 2012 test data, and corresponding values of 0.88, 0.278 kPa, and 0.367 kPa for the 2013 test data. These results are promising, especially considering the comparatively high spatial resolution (1 km) of the VPD map estimated from the satellite data. Potential applications include global evapotranspiration estimation, fire warning, and vegetation analysis.

Climate and soils together regulate photosynthetic carbon isotope discrimination within C3 plants worldwide

“…Daily temperature and humidity variation has important implications for the effective vapor pressure deficit during photosynthesis, one of many important effects that are not completely captured in currently available global maps. More precise maps of vapor pressure deficit would be very useful, and there has been recent progress on new methods for generating vapor pressure deficit maps (Zhang, Wu, Yan, Zhu, & Feng, ) from remote sensing products. The next generation of maps is likely to be much improved, and this question should be revisited at that point.…”

Remote sensing of plant-water relations: An overview and future perspectives

“…Besides assessing VPD with in-situ measured or extrapolated meteorological values, remote sensing techniques are increasingly used to provide spatial information of VPD and overcome the limited reliability of VPD estimates in regions with sparse meteorological observations (Hashimoto et al, 2008;Zhang et al, 2014). Given a reliable surface temperature estimate that facilitates the computation of the saturation pressure at this temperature, VPD would involve an estimate of the water vapour content of the near surface air.…”

Global Validation of MODIS Near‐Surface Air and Dew Point Temperatures

“…This finding implies that MODIS performance is marked by natural relative disparities rather than systematically biased or low‐quality observations. Dew point estimates generally fluctuated more in accuracy than T a measurements overall as well as between corresponding climate types, likely due to the difficulty of satellite‐based near‐surface humidity estimation (Zhang et al, ).…”