Assessing the Roles of Terrestrial Stilling and Solar Dimming in Land Surface Drying/Wetting across China

Kai Duan,Tiesong Hu,Xianxun Wang,Yadong Mei,Jiali Guo

doi:10.3390/w12071996

Abstract

Decreases in wind speed (i.e., terrestrial stilling) and radiation (i.e., solar dimming) have been identified as important causes of aridity change both globally and regionally. To understand how their roles have varied across different natural and socioeconomic circumstances in China, this study presents a nationwide attribution analysis of land surface drying/wetting across the ten first-level river basins. The results suggest that consistent warming and reductions in relative humidity have significantly enhanced atmospheric evaporative demand and driven the land surface to become drier over the past six decades. However, the widespread terrestrial stilling and solar dimming have largely offset such trends by suppressing evaporation. While spatially varying changes in precipitation were the most influential driver of aridity change over half of the 713 used climate sites, decreasing wind speed and radiation were identified as the dominant cause of wetting at 15% and 13% of the sites, respectively. The impacts of terrestrial stilling and solar dimming were generally more prominent in the north (e.g., the Liao River, Songhuajiang, Hai River, and Huai River basins) and south (e.g., the Southeast, Pearl River, and Yangtze River basins) respectively, which could be associated with the weakening monsoon and intensified anthropogenic disturbances such as ecological restoration, urbanization, and air pollution. We conclude that more attention needs to be paid to the independent and combined climatological impacts of global- and regional-level human activities to develop proactive adaptation strategies of water and land management.

Highlights

There is evidence from both observation and simulation studies that climate change causes land surface drying in many regions across the world [1,2,3] which leads to depletion in water availability [4], larger irrigation water demand [5], more frequent wildfire [6], and land degradation and desertification [7]
The Northwest basin was the driest region with the lowest P (183 mm yr−1 ) and Aridity Index (AI) (0.17), where low relative humidity (Rh) (49%) and high Rs (16 MJ m−2 d−1 )
Significant increasing trends in P at the 5% significance level were found at 11% of the sites, mostly in the Northwest, while significant decreases (8% of the sites) occurred across the Southwest, Pearl, Yangtze, and Yellow River basins

Summary

Introduction

There is evidence from both observation and simulation studies that climate change causes land surface drying in many regions across the world [1,2,3] which leads to depletion in water availability [4], larger irrigation water demand [5], more frequent wildfire [6], and land degradation and desertification [7]. Water 2020, 12, 1996 maximum water exchange from the land to the atmosphere (i.e., atmospheric evaporative demand), which is determined by the status of ambient air and energy supplies. Many climate change studies only considered the effects of precipitation variability and rising temperature [15], i.e., modeling terrestrial water balance or evaluating dryness on the basis of temperature-based PET methods such as Thornthwaite [16] and Hamon [17]. These methods have been commonly used because they only require temperature data as input and are well validated for historical periods

Objectives

Methods

Results

Discussion

Conclusion