Low‐frequency snow changes over the Tibetan Plateau

Abstract

Snow change over the Tibetan Plateau may exert a large influence on climate variability in the surrounding regions. However, the characteristics of snow changes at different time scales and the factors for these changes are still not clear. The present study documents linear trends in snow cover and snow water equivalent over the Tibetan Plateau and their relationship to surface air temperature changes during 1979-2006 based on satellite data. The long-term snow variations display a remarkable regional difference and an obvious seasonal dependence. A significant decreasing trend is observed in the western part for snow cover and snow water equivalent in summer and fall and in the southern part for snow cover in all the four seasons. A significant increasing trend is identified in the central-eastern part for snow cover in fall, winter, and spring and in the eastern and far western parts for snow water equivalent in winter and spring. The relationship between snow and surface air temperature changes features regional disparity. The temperature increase is accompanied by snow cover decrease in the southern and western parts, but by snow cover and snow water equivalent increase in the central-eastern part. The reasons for the snow changes vary with the season. The increase in snowmelt following the temperature increase may be the reason for the snow cover decrease in the western and southern parts in summer. The snowfall change induced by vertical motion change appears to be a factor for the snow water equivalent increase in the far western part and the snow cover decrease in the southern part in winter. The increase in snowfall induced by the increase in atmospheric moisture following the temperature increase and the enhanced upward motion may contribute to the snow increase in the eastern part in winter.

Influence of Western Tibetan Plateau Summer Snow Cover on East Asian Summer Rainfall

“…The original weekly snow cover data cover the period from October 1966 to December 2016 with a 25 km spatial resolution. The weekly snow cover data were converted to monthly mean with regular 1° × 1° longitude‐latitude grids for the present analysis (Z. Wang et al, ). The global snow water equivalent data were derived from Scanning Multichannel Microwave Radiometer (1978–1987), and selected Special Sensor Microwave or Imagers (1987–2007) (Armstrong et al, ) with a 25 km spatial resolution, and also were converted to regular 1° × 1° longitude‐latitude grids.…”

“…The area‐mean JJA snow cover in the south region displays a relatively large fluctuation in the 1980s and around 2000 (Figure b). After the middle 2000s, the interannual variations of JJA snow cover are very small in the south region (Figure b), which may be related to the declining trend of JJA snow cover there (Z. Wang et al, ). The correlation coefficient between the two time series is about 0.19 for the period 1979–2015, which is below the 90% confidence level.…”

“…Snow variability affects surface energy budget and the hydrology cycle (Barnett et al, ; Cohen & Rind, ; Yasunari et al, ). The Tibetan Plateau has a large snow cover area in the cold seasons (Pu et al, ; Z. Wang et al, ). Numerous studies have demonstrated impacts of the cold season Tibetan Plateau snow change on Indian and East Asian climate (e.g., Chen & Wu, ; Dey & Kumar, ; Ding et al, ; Fasullo, ; Hahn & Shukla, ; Kripalani et al, ; Ose, ; Si & Ding, ; C. Wang et al, ; Wu & Kirtman, ; Wu et al, ; Xiao & Duan, ; Zhang et al, ; Zhao et al, ; Zuo et al, ; Zhu et al, ).…”

“…Numerous studies have demonstrated impacts of the cold season Tibetan Plateau snow change on Indian and East Asian climate (e.g., Chen & Wu, ; Dey & Kumar, ; Ding et al, ; Fasullo, ; Hahn & Shukla, ; Kripalani et al, ; Ose, ; Si & Ding, ; C. Wang et al, ; Wu & Kirtman, ; Wu et al, ; Xiao & Duan, ; Zhang et al, ; Zhao et al, ; Zuo et al, ; Zhu et al, ). However, due to the lack of station observations at the high‐elevation region (You et al, ) and the small snow cover area in summer (Z. Wang et al, ), few studies have been conducted on the summer snow variations over the Tibetan Plateau and their impacts on the climate variability.…”

“…Snow anomalies in a specific season may also related to the snow mass in the preceding season due to the persistence of snow anomalies (Liu, Wu, Zhang, & Nan, ; Z. Wang et al, ; Wu & Kirtman, ; Wu et al, ). For example, Liu, Wu, Zhang, and Nan () showed that the summer snow anomalies over the Tibetan Plateau may already exist in preceding May, which provides a precursory signal for summer rainfall anomalies.…”