Abstract
Wind speed and variability are the most critical climatic factors affecting sand/dust storms, which have not been sufficiently studied in the middle reaches of the Yarlung Tsangpo River (MYR). In this study, wind speed variability was investigated using the moving average over shifting horizon method (MASH), combined with the modified Mann–Kendall test and Sen’s slope based on data from the Tsetang, Lhasa, and Nyêmo meteorological stations during 1960–2015. The results indicated that annual wind speeds for the MYR wide valley regions declined significantly at decadal rates of − 0.216 m/s and underwent three stages from 1960 to 2015: an increasing trend from 1960 to 1975 (0.44 m/s per decade), a weakening until 2006 (− 0.46 m/s per decade), and a remarkable subsequent recovery (1.05 m/s per decade). Different variability trends were observed for the three stations: wind speed decreased significantly during all months at the Tsetang and Nyêmo stations, particularly in the spring, while for Lhasa, a non-significant wind speed increase was detected in summer, and the highest decline occurred in winter. The MASH method resulted in the effective visualization of different patterns, making seasonal process analysis and trend detection easier. In addition, the possible main causes for wind speed change were also discussed. The wind speed change in the study region was strongly associated with the large-scale atmospheric patterns, and the surface pressure gradient variability between the mid and low latitudes may have been a primary driving force. Positive/negative phases of the Pacific Decadal Oscillation (PDO) corresponded well with wind speed decreases/increases and were regarded as an indicator of wind speed variations. The effects of human activities associated with surface roughness change in the MYR were minor compared with the climatic changes.
Highlights
Wind speed and variability are the most critical climatic factors affecting sand/dust storms, which have not been sufficiently studied in the middle reaches of the Yarlung Tsangpo River (MYR)
Decreasing wind speeds were observed in all months, this image clearly shows that the largest changes in wind speed occurred during the gale period from March to April
Wind speed and variability are the most critical climatic factors affecting sand dust/storms, which has not been well-studied in the wide valley of the MYR
Summary
Wind speed and variability are the most critical climatic factors affecting sand/dust storms, which have not been sufficiently studied in the middle reaches of the Yarlung Tsangpo River (MYR). In the Tibetan Plateau, wind speed decreases have varied across different regions and time periods, ranging from − 0.06 to − 0.30 m/s per decade from 1960 to 2 00924,26–28 These previous studies mainly focused on global or national decadal wind speed variability but failed to include the most recent changes or to consider such changes in the MYR Basin, especially in the wide parts of the valley that have been severely affected by SDSs. In addition, meteorological variables, such as wind speed and temperature, are generally characterized by seasonal and inter-annual variability, making trend analysis at finer time scales more difficult (e.g., weekly or daily)[29,30]. The MASH method was supplemented by trend analysis using the Mann–Kendall method, Sen’s method and linear regression
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