Sciences in Cold and Arid Regions ›› 2018, Vol. 10 ›› Issue (6): 493–501.doi: 10.3724/SP.J.1226.2018.00493

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  • 收稿日期:2018-09-06 接受日期:2018-11-06 出版日期:2018-12-01 发布日期:2018-12-29

Local meteorology in a northern Himalayan valley near Mount Everest and its response to seasonal transitions

FangLin Sun1,2,*(),YaoMing Ma2,3,4,ZeYong Hu1,2   

  1. 1 Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China
    2 China University of Chinese Academy of Sciences, Beijing 100049, China
    3 Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
    4 CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China
  • Received:2018-09-06 Accepted:2018-11-06 Online:2018-12-01 Published:2018-12-29
  • Contact: FangLin Sun E-mail:flsun@lzb.ac.cn
  • Supported by:
    This research was funded by the National Natural Science Foundation of China (41661144043, 41005010, 41475010), the Strategic Priority Research Program (A) of the Chinese Academy of Sciences (Grant XDA20060101), and R & D Special Fund for Public Welfare Industry (meteorology), No. GYHY201406001. The authors thank the staff of QOMS, who provided lots of help in the field observation for this research or in data access.

Abstract:

An automatic weather station (AWS) has been installed at the Qomolangma Station of the China Academy of Sciences (QOMS) since 2005, in a northern Himalayan valley near Mount Everest, with an altitude of 4,270 m a.s.l.. Nine years of meteorological records (2006–2014) from the automatic weather station (AWS) were analyzed in this study, aiming to understand the response of local weather to the seasonal transition on the northern slopes of Mount Everest, with consideration of the movement of the subtropical jet (STJ) and the onset of the Indian Summer Monsoon (ISM). We found: (1) Both the synoptic circulation and the orography have a profound influence on the local weather, especially the local circulation. (2) Southwesterly (SW) and southeasterly (SE) winds prevail alternately at QOMS in the afternoon through the year. The SW wind was driven by the STJ during the non-monsoon months, while the SE was induced by the trans-Himalayan flow through the Arun Valley, a major valley to the east of Mount Everest, under a background of weak westerly winds aloft. (3) The response of air temperature (T) and specific humidity (q) to the monsoon onset is not as marked as that of the nearsurface winds. The q increases gradually and reaches a maximum in July when the rainy period begins. (4) The alternation between the SW wind at QOMS and the afternoon SE wind in the pre-monsoon season signals the northward shift of the STJ and imminent monsoon onset. The average interval between these two events is 14 days.

Key words: mountain meteorology, monsoon onset, Trans-Himalayan flow, orography influence

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Year 2006 2007 2008 2009 2010 2011 2012 2013 2014
Availability (%) 99.6 99.7 89.9 98 80.6 99.1 98.8 89.9 95.9

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Item Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.
U200 Mean 52.9 50.3 41.2 30.9 24.7 13.6 0.8 ?1.1 11.3 30.3 44.5 53.4
ISMIDX Mean ?6.1 ?6.2 ?5.9 ?4.7 ?1.6 5.4 8.2 6.7 5.3 ?0.67 ?3.6 ?5.3
Max 10.53 9.63 13.88 16.73 19.93 21.72 23.10 21.42 20.33 17.71 14.32 14.03
T Mean ?3.72 ?3.28 ?0.37 3.27 6.37 9.86 12.04 9.98 9.50 3.79 ?0.55 ?2.71
Min ?17.89 ?17.40 ?13.37 ?9.02 ?4.29 0.70 4.32 2.99 ?0.33 ?8.82 ?12.56 ?16.84
SP Max 1.88 2.71 2.99 3.88 6.23 8.87 10.03 9.80 8.53 6.24 3.09 2.13
Mean 0.81 1.16 1.62 2.56 3.95 5.89 8.62 7.58 6.89 3.64 1.64 1.03
Wind Max 12.14 10.46 9.29 7.19 6.00 5.74 5.16 4.77 4.87 6.01 9.01 10.27
Mean 5.34 5.60 5.10 4.67 4.03 4.04 4.04 3.25 3.74 3.89 4.22 5.20
DSR Mean 200.4 237.8 270.3 329.4 318.6 315.0 282.6 267.3 269.7 257.2 214.3 190.0

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2006 2007 2008 2009 2010 2011 2012 2013 2014
SW wind's end May 4 May 30 May 4 May 9 Jun. 3 Apr. 29 May 21 May 12 May 26
Monsoon onset May 22 Jun. 1 Jun. 2 May 20 Jun. 6 May 27 Jun. 4 May 30 Jun. 7
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