Variations of the Meteorological Elements at the Lanong Glacier in the Nyainqêntanglha Range

The diurnal and seasonal variations of air temperature,air pressure,relative humidity,wind speed and wind direction from September 1,2006 to August 31,2007 were analyzed,using the observation data from an automatic weather station at the Lanong Glacier of the Nyainq ntanglha Range.The diurnal temperatures rise rapidly while descend slowly.The mean annual temperature is-8.1 ℃.The minimum temperature(-18.2 ℃)occurs in December and the maximum one(0 3 ℃)occurs in July.The diurnal variation of relative humidity is characterized by a single peak and valley pattern.The mean annual relative humidity is 53 4%.The maximum relative humidity occurs in August and the minimum relative humidity occurs in January.However,diurnal variation of air pressure shows a pattern of double peaks and valleys.The mean annual air pressure is 497 1 hPa with a maximum(501 9 hPa)in September and a minimum(489 9 hPa)in February.The diurnal variation of wind speed fluctuates more dramatically in the winter and spring than that in the summer and autumn.The mean annual wind speed is 4 2 m·s-1 with a maximum(7 5 m·s-1)in January and a minimum(2 5 m·s-1)in August.The north and south winds prevail,which account for 75.2% of the year.