Spatio-Temporal Trends of Surface Energy Budget in Tibet from Satellite Remote Sensing Observations and Reanalysis Data

Usman Mazhar,Muhammad Bilal,Md Arfan Ali,Shuanggen Jin,Hasnain Farooq,Wentao Duan

doi:10.3390/rs13020256

Abstract

Being the highest and largest land mass of the earth, the Tibetan Plateau has a strong impact on the Asian climate especially on the Asian monsoon. With high downward solar radiation, the Tibetan Plateau is a climate sensitive region and the main water source for many rivers in South and East Asia. Although many studies have analyzed energy fluxes in the Tibetan Plateau, a long-term detailed spatio-temporal variability of all energy budget parameters is not clear for understanding the dynamics of the regional climate change. In this paper, satellite remote sensing and reanalysis data are used to quantify spatio-temporal trends of energy budget parameters, net radiation, latent heat flux, and sensible heat flux over the Tibetan Plateau from 2001 to 2019. The validity of both data sources is analyzed from in situ ground measurements of the FluxNet micrometeorological tower network, which verifies that both datasets are valid and reliable. It is found that the trend of net radiation shows a slight increase. The latent heat flux increases continuously, while the sensible heat flux decreases continuously throughout the study period over the Tibetan Plateau. Varying energy fluxes in the Tibetan plateau will affect the regional hydrological cycle. Satellite LE product observation is limited to certain land covers. Thus, for larger spatial areas, reanalysis data is a more appropriate choice. Normalized difference vegetation index proves a useful indicator to explain the latent heat flux trend. Despite the reduction of sensible heat, the atmospheric temperature increases continuously resulting in the warming of the Tibetan Plateau. The opposite trend of sensible heat flux and air temperature is an interesting and explainable phenomenon. It is also concluded that the surface evaporative cooling is not the indicator of atmospheric cooling/warming. In the future, more work shall be done to explain the mechanism which involves the complete heat cycle in the Tibetan Plateau.

Highlights

Linear Regression (LR) slope, Pearson’s correlation coefficient (r-value), mean bias error (MBE), and mean absolute error (MAE) were used to check the accuracy of satellite and ERA5 data
The spatio-temporal variations of surface energy budget (SEB) parameters, RN, latent heat flux (LE), and sensible heat flux (SH) are analyzed from 2001 to 2019 in the Tibetan Plateau (TP) using satellite data observed from Moderate Resolution Imaging Spectroradiometer (MODIS) and Clouds and Earth’s Radiant Energy System (CERES)
ERA5 LE is more accurate for monthly analysis, but for annual analysis satellite, LE product

Summary

Introduction

The Tibetan Plateau (TP) is one of the largest reservoirs of ice and is referred to as the third pole of the world [1]. Due to its vast area and exceptional height (>4000 m above mean sea level), it plays a major role in shaping the regional climate especially for the east and south Asian monsoon [2,3]. The warming rate of TP is 0.3 ◦ C per decade, which is more than any other part of the world. This affects permafrost and snow melting in TP.

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Conclusion