A Review of the Study on the Impact of Snow Cover in the Tibetan Plateau on Asian Monsoon

Impact of snow cover on climate in large scale is a major project in the earth sciences. Data analysis and numerical simulations show that the anomalies of snow cover area and the duration of snow accumulation on the Tibetan Plateau, an uplifted surface, are related to the strength, the beginning and the end of the Asian summer monsoon. If the snow cover area is large and the duration of the snow accumulation is long, then Asian monsoon occurs later and advances slowly. In such a year, Asian monsoon is weak. If the snow cover area is small and the duration of the snow accumulation is short, then Asian monsoon is strong and occurs early and advances quickly. It seemed easy to understand on the physical aspect that there exists correlationship between the snow cover on the plateau and the Asian summer monsoon precipitation, because snow cover is one of the important physical factors that affects the underlying surface condition and the air heat condition. It is well known that the monsoon relates to the heat conditions of the underlying surface. So it is certain that the snow cover anomaly would affect the summer monsoon activities. There are also some other opinions that are not accord with the above results. The study results reported by Li Peiji show that the variations of the Indian summer monsoon precipitation are not mainly caused by the anomalies of the snow cover on the plateau. The snow cover on the plateau in pre-winter does not have the so-called significant correlationship with the Indian summer monsoon precipitation in post-summer. Therefore, the relationship between the snow cover on the plateau and the strength of Asian summer monsoon and its corresponding precipitation belt is still an unresolved problem. It is necessary to cumulate quality snow cover data and to enhance the understanding of the monsoon and its corresponding precipitaiton belt.