Abstract
Drought in the Mongolian Plateau (MP) has gradually intensified in recent decades. The energy and water cycles are key factors affecting drought. However, there are few quantitative studies on the mechanism of aridity change in this region. This study uses the ERA5, Moderate Resolution Imaging Spectroradiometer (MODIS) and Himawari 8 datasets and investigated the mechanism of drought change over the MP. The aridity index (the ratio of potential evaporation and total precipitation) is employed to detect drought changes. The results showed that the annual mean of aridity index increased by 0.73% per year (increased significantly since 1999) during the period 1979–2020. Moreover, the drought was most severe in the January to April of 2016–2020, mainly concentrated in the central and western parts of the MP. The potential evaporation increased (0.72% per year) and total precipitation decreased (0.16% per year) from 1979 to 2020. However, the surface temperature continued increasing from August to December in the period 2016–2020 (1.67% per year). This may result in an increase in potential evaporation and a decrease in volumetric soil water from August to December last year. The decrease of volumetric soil water resulted in the decrease of total cloud cover (0.25% per year) and total precipitation from January to April. The surface net radiation (increased by 0.42% per year) and the potential evaporation increased, which may aggravate the drought from January to April. The evaporation paradox is studied over the MP. The results show that the variation in evaporation is consistent with that of total precipitation, and the surface temperature will promote an increase in evaporation and potential evaporation. This study reveals that global warming, desertification and increased surface net radiation contribute to the increase in potential evaporation and reduced volumetric soil water, which together contribute to drought.
Highlights
Drought is a shortage of moisture in the climatic sense of the term, and its causes are closely related to the availability of key parameters of the energy and water cycle such as precipitation, evaporation, vegetation, surface radiation, water vapor and temperature, and their interactions [1,2,3,4]
This study uses total cloud cover, volumetric soil water layer 1, volumetric soil water layer 2, surface net radiation, surface temperature, total precipitation, potential evaporation, evaporation, total column water vapor from ERA5 data for the period 1979-2020, with a spatial resolution of 0.25◦ and a temporal resolution of months
We found that the peak and trough of total column water vapor were consistent with the difference between total precipitation and evaporation, but there was no obvious trend
Summary
Drought is a shortage of moisture in the climatic sense of the term, and its causes are closely related to the availability of key parameters of the energy and water cycle such as precipitation, evaporation, vegetation, surface radiation, water vapor and temperature, and their interactions [1,2,3,4]. The in-depth study of drought formation mechanism based on multiple dependent variables is important for environmental protection, desertification prevention and drought prediction. The Mongolian Plateau (MP) is an arid and semiarid region with large temperature variations and little precipitation. The annual mean temperature increased 0.96 ◦ C per year approximately from 1901 to 1998 over the MP [5]. The annual mean temperature increased 0.96 ◦ C per year approximately from 1901 to 1998 over the MP [5]. 4.0/).
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