Satellite evidence for no change in terrestrial latent heat flux in the Three-River Headwaters region of China over the past three decades

Abstract

Terrestrial latent heat flux (LE) in the Three-River Headwaters region (TRHR) of China plays an essential role in quantifying the amount of water evaporation and carbon sink over the high altitude Tibetan Plateau (TP). Global warming is expected to accelerate terrestrial hydrological cycle and to increase evaporation. However, direct field observations are lacking in this region and the long-term variability in LE remains uncertain. In this study, we have revised a semi-empirical Penman LE algorithm based on ground eddy covariance (EC) observations from an alpine grass site and provided new satellitebased evidence to assess LE change in the TRHR during 1982-2010. Our results show that the average annual terrestrial LE in the TRHR is about 38.8 W/m 2 and there is no statistically significant change in annual LE from 1982 to 2010. We also found that during the same time period, terrestrial LE over the east region of the TRHR significantly decreased, on average, by 0.7 W/m 2 per decade, which was driven primarily by the surface incident solar radiation (R s ) limitation, offsetting the increased LE over the west region of the TRHR caused by the increased precipitation (P ) and soil moisture (SM ).

Long-Term Spatiotemporal Dynamics of Terrestrial Biophysical Variables in the Three-River Headwaters Region of China from Satellite and Meteorological Datasets

“…In the arid and semi-arid regions, the increased P promoted the water availability for ET, resulting in the increment of ET. The pattern of increasing ET was matched by an increasing P in the western part of the TRHR, which was also confirmed by Yao et al [29], who reported that P was the primary contributor to increasing ET during 1982-2010. However, in well-watered regions, climate (Ta, RH) and vegetation factors were considered to be related more to the ET dynamic.…”

“…Recently, several satellite-based models and approaches have been developed to estimate the spatiotemporal ET in the TRHR over the last few decades [28]. For instance, based on a revised semi-empirical algorithm, Yao et al [29] illustrated that there was no statistically significant trend in ET over the TRHR during the period 1982-2010. Xu et al [30] found that ET showed a slight decreasing trend at the rate of 3.3 mm/decade from 2000 through 2014 in the TRHR by using an enhanced surface energy balance system (SEBS) algorithm.…”