Rainfall influence on the microclimate of caves and the risk assessment of mural deterioration in Dunhuang Mogao Grottoes, China

The Dunhuang Mogao Grottoes are famous for the exquisite murals and statues. The changes in temperature and humidity caused by rainfall easily trigger the salt diseases of murals. In order to prevent the further deterioration of murals, the influence of rainfall on the thermal and moisture environment of caves was analyzed through the environmental monitoring test. The results show that the temperature of the caves is basically unchanged, and the humidity changes in three stages of rising, maintaining and falling. The relative humidity and duration of high humidity show as of semi-closed cave > closed cave, small cave > large cave. The optimal time node of environment control of cave is a atm =a cave , and the control condition is RH < 62%. The caves with small volume and large degree of connectivity to atmospheric environment are vulnerable objects. The disaster-deducing factor of mural deterioration is the accumulated rainfall in the next week, and the rainfall intensity is a reasonable parameter in risk monitoring and warning. The results have great significance for the risk prevention of mural deterioration and environment control of caves in Mogao grottoes.