The regional surface soil heat flux (G0) estimation is very important for the large-scale land surface process modeling. However, most of the regional G0 estimation methods are based on the empirical relationship between G0 and the net radiation flux. A physical model based on harmonic analysis was improved (referred to as “HM model”) and applied over the Heihe River Basin northwest China with multiple remote sensing data, e.g., FY-2C, AMSR-E, and MODIS, and soil map data. The sensitivity analysis of the model was studied as well. The results show that the improved model describes the variation of G0 well. Land surface temperature (LST) and thermal inertia (Γ) are the two key input variables to the HM model. Compared with in situG0, there are some differences, mainly due to the differences between remote-sensed LST and the in situ LST. The sensitivity analysis shows that the errors from −7 to −0.5 K in LST amplitude and from −300 to 300 J m−2 K−1 s−0.5 in Γ will cause about 20% errors, which are acceptable for G0 estimation.
An exceptional drought struck Henan province during the summer of 2014. It caused directly the financial loss reaching
to hundreds of billion Yuan (RMB), and brought the adverse influence for people’s life, agricultural production as well
as the ecosystem. The study in this paper characterized the Henan 2014 summer drought event through analyzing the
spatial distribution of drought severity using precipitation data from Tropical Rainfall Measuring Mission (TRMM)
sensor and Normalized difference vegetation index (NDVI) and land surface temperature (LST) products from Moderate
Resolution Imaging Spectroradiometer (MODIS) sensor. The trend analysis of the annual precipitation from 2003 to
2014 showed that the region over Henan province is becoming dry. Especially in the east of Henan province, the
decrease of precipitation is more obvious with the maximum change rate of ~48 mm/year. The rainfall in summer (from
June to August) of 2014 was the largest negtive anomaly in contrast with the same period of historical years, which was
43% lower than the average of the past ten years. Drought severity derived from Standardized Precipitation Index (SPI)
indicated that all areas of Henan province experienced drought in summer of 2014 with different severity levels. The
extreme drought, accounting for about 22.7 % of Henan total area, mainly occurred in Luohe, Xuchang, and
Pingdingshan regions, and partly in Nanyang, Zhengzhou, and Jiaozuo. This is consistent with the statistics from local
municipalities. The Normalized Drought Index Anomaly (NDAI), calculated from MODIS NDVI and LST products, can
capture the evolution of the Henan 2014 summer drought effectively. Drought severity classified by NDAI also agreed
well with the result from the SPI.
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