Responses of China's summer monsoon climate to snow anomaly over the Tibetan Plateau

Abstract

The climatological features of the winter snow depth over the Tibetan Plateau and the summer precipitation in China are diagnosed using datasets obtained from 78 snow observation stations and 160 rainfall stations during 1957 to 1998. The climatic effects of the snow anomaly over the Tibetan Plateau on the regional summer monsoon climate in China are diagnosed and numerically simulated by use of a regional climate model (RegCM2). The singular value decomposition technique is adopted to diagnose the relationships between the previous winter and spring plateau snow depth anomalies and the spring and summer regional precipitation in China. It is found that the snow depth anomaly, especially in winter, is one of the factors influencing precipitation in China; however, it is perhaps not the only one, and even not the most important one. Nevertheless, it is proved that the winter snow anomaly over the Tibetan Plateau is relatively more important than that in spring for the regional precipitation in China. Results of numerical simulations show that the snow anomaly over the plateau has effects that are evident on China's summer monsoon climate. The increase of both snow cover and snow depth can delay the onset and weaken the intensity of the summer monsoon obviously, resulting in a decrease in precipitation in southern China and an increase in the Yangtze and Huaihe River basins. The influence of the winter snow depth is more substantial than that of both the winter snow cover and the spring snow depth. The mechanism of how the plateau snow anomaly influences the regional monsoon climate is briefly analysed. It is found that snow anomalies over the Tibetan Plateau change the soil moisture and the surface temperature through the snowmelt process at first, and subsequently alter heat, moisture and radiation fluxes from the surface to the atmosphere. Abnormal circulation conditions induced by changes of surface fluxes may affect the underlying surface properties in turn. Such a long-term interaction between the wetland and the atmosphere is the key process resulting in later climatic changes.

Inter‐decadal variation of the summer precipitation in China and its association with decreasing Asian summer monsoon Part II: Possible causes

“…A similar correlative field in spring is also found, but for the first SVD, which accounts for 40.46% of the total squared variance and has a correlation coefficient of 0.96 (Figure 8(c), (d)). Similar results have been also indicated by some previous investigators (NCC, 1998;Chen and Wu, 2000;Qian et al, 2003;Zhang et al, 2004;Peng et al, 2005). National Climate Center (NCC, 1998) of China has further found that for winter and spring of more snow over the TP, the large-scale 500 hPa height pattern of '+ − +' meridional correlation mode prevails over East Asia in summer, which is characterized by significant positive correlation at high latitudes (in general, frequent development of blocking situation), negative correlation at mid-latitudes (low pressure disturbances frequently develop over the middle and lower basins of the Yangtze River) and significant positive correlation at lower latitudes (stronger subtropical high over the West Pacific with farther southern position than normal, i.e.…”

“…This implies that other external forcing factors can also exert an important effect on the inter-decadal variability of the summer precipitation in China. Among them, a special importance of the inter-decadal change in snow in the preceding winter and spring over the Tibetan Plateau (TP) has been stressed by numerous investigators in order to elucidate the interdecadal weakening of the Asian summer monsoon and variability of the summer precipitation in China (Li, 2002;Ding and Sun, 2003;Liu et al, 2003;Qian et al, 2003;Wu and Qian, 2003;Zhang et al, 2003Zhang et al, , 2004a. In contrast to the decreasing trend of the Eurasian winter and spring snow cover, especially from the mid-1970s, the winter and spring snow cover, snow depth and number of snow days over the TP have had an increasing trend during the last 45 years, with a significant increase occurring in the late 1970s.…”

Sensitivity studies on the impacts of Tibetan Plateau snowpack pollution on the Asian hydrological cycle and monsoon climate

“…Meanwhile, many studies based on modeling and observational data analysis have found a remarkable relationship between the winter or spring snow over the TP and rainfall over the mid-and lower-reaches of the Yangtze River Basin (YRB) in eastern China and South China in the subsequent summer (e.g. Wu and Qian, 2003;Qian et al, 2003;Zhang et al, 2004), primarily through two important effects of snow cover -influence on surface albedo and soil moisture (Barnett et al, 1989;Yasunari et al, 1991). Observational evidence indicates that the surface temperatures on the TP have increased by about 1.8 • C over the past 50 years (Wang et al, 2008).…”

“…First, through absorption and scattering, aerosols reduce downwelling insolation at the surface (dimming) (e.g., Ogren and Charlson, 1983;Qian et al, 2006), thus decreasing absorbed solar energy by snowpack. Second, absorbing particles (e.g.…”

Assessment of Simulations of Snow Depth in the Qinghai-Tibetan Plateau Using CMIP5 Multi-Models

“…At the end of the 19th century, Blanford (1884) first revealed that the winter-spring snow in the Himalayas had a negative correlation with the succeeding summer monsoon rainfall over India. Thereafter, many researchers have proved using data analysis and numerical simulation that the Qinghai-Tibetan Plateau snow plays significant roles in climatic variations in Asia (Guo and Wang, 1986;Wei et al, 1998;Chen and Song, 2000;Qian et al, 2003;Zhang et al, 2012). The snow anomalies over the Qinghai-Tibetan Plateau change the soil moisture and the surface temperature through the snowmelt process at first, and subsequently alter heat, moisture, and radiation fluxes from the surface to the atmosphere.…”