著者

Timothy J LANG Ana P BARROS

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.82, no.3, pp.829-844, 2004 (Released:2004-09-27)

参考文献数

28

被引用文献数

134 186

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Based on observations from a hydrometeorological network on the eastern slopes of the Annapurna Range, nearly all the annual precipitation at low elevations ( 3000 m MSL) can receive up to 40% of their annual precipitation as snowfall during the winter, with the highest altitude stations (∼4000 m MSL and above) having the most total winter precipitation (which can exceed 100 cm). Significant snowstorms are associated with terrain-locked low-pressure systems that form when an upper-level disturbance passes over the notch formed by the Himalayas and Hindu Kush mountains (the so-called Western Disturbances), causing upper-level SW flow over central Nepal and orographically forced precipitation. Based on these results, a 30-year (1973-2002) climatology of these notch depressions is developed and reveals that significant interannual variability in central Himalayan winter storms exists. Weak but statistically significant correlation between notch depressions and the Polar/Eurasia teleconnection pattern was found, suggesting that the strength of the circumpolar vortex may affect the number of depressions passing through the Himalayan region. A typical snow event (11 February 2000) was the subject of an observational and modeling case study. Local precipitation (snow and rain) and other meteorological observations, as well as satellite (Meteosat-5 and TRMM) and NCEP/NCAR Reanalysis data were used, along with a cloud-resolving model with realistic topography. This study shows that significant wintertime precipitation only occurs in the central Himalayas when the large-scale flow evolves to a favorable geometry with respect to the mountains.