Effects of Seasonal Rainfall Characteristics on the Hydrothermal State of Permafrost Active Layer in the Central Qinghai-Xizang （Tibet） Plateau

Abstract

Rainfall can cause significant changes in the hydrothermal state within the active layer of the permafrost regions， and the rainfall in the Qinghai-Xizang （Tibet） Plateau has obvious seasonal characteristics.In order to analyze the effects of seasonal rainfall characteristics on the hydrothermal state of permafrost active layer， the meteorological data and the changes of soil heat flux， water content， and temperature within the active layer were monitored in the Beiluhe area of the central Qinghai-Xizang （Tibet） Plateau.The results show that the Beiluhe area is mainly characterized by the light rain events， supplemented by the moderate rain events， and the light rain events accounted for about 90% of the rainfall events from March to November.In addition， the heavy rain events and sustained rain events occur in summer and autumn， respectively.Among them， the rainfall events in each season leads to an overall decrease in surface net radiation， and the impact of the heavy rain events on the net radiation in summer is more obvious.The sustained rain events in autumn lead to a trend of first increase and then decrease in net radiation， and the change trend of soil heat flux consistent with changes in net radiation.Rainfall changes the soil heat flux by affecting the surface net radiation， thus causing changes in the water field and temperature field within soil.Among them， the heavy and moderate rain events in summer can significantly increase shallow soil water content， while spring and autumn rainfall have little effect on soil water content.The effect of the light rain events on soil temperature in each season can be ignored， but the moderate rain， heavy rain and sustained rain events can significantly alleviate the warming trend of shallow soil， and the effect of the rainfall events on alleviating soil warming gradually weakened with the increase of depth.The research results have certain guiding significance for solving regional ecological environment problems and engineering building disease prevention and control problems in permafrost regions.

Keywords

• qinghai-xizang （tibet） plateau
• permafrost
• net radiation
• hydrothermal changes
• seasonal rainfall