Study on temperature and humidity environment of grotto 72 at the Mogao Grottoes in Dunhuang, China

This article presents research on destructive environmental mechanisms affecting the murals in the Mogao Grottoes, specifically Grotto 72, from a meteorological perspective. Analysis of outside monitoring data during 1999-2008 shows that condensation of moisture and/or salt deliquescence on the mural affects a high percentage of the internal grotto, whereas the interchange of moisture between the interior grotto and the surrounding air accounts for a relatively small effect. But high humidity was the threat to the mural, so the planting of the shelterbelts was a new threat to the mural due to irrigation of shelterbelts. The higher relative humidity (RH) produced by shelterbelts in front of the grottoes is only weakly related to local precipitation but is highly correlated with the times of water irrigation of those shelterbelts. The intra-seasonal variability of temperature and RH on the mural surface is relatively stable because temperature inversion frequently occurs in the internal grotto and is favourable for maintenance of stable air stratification that is beneficial to the preservation of the wall paintings. Using ridge regression estimation of the period data, coupling equations of the change of temperature and humidity on the mural surface, the internal grotto air and the external environment are obtained. The real-time dynamics of temperature and humidity are thus analysed and reported here, offering a scientific basis for establishing a long-term monitoring network in the Mogao Grottoes. Copyright (c) 2012 Royal Meteorological Society