Characteristics and Changes in Air Temperature and Glacier's Response on the North Slope of Mt. Qomolangma (Mt. Everest)

Weather and climatic conditions over the Himalaya regions are of great interest to the scientific community at large. The objective of this study is to present spatial and temporal variations of air temperatures and relative humidity on the north slope of Mt. Qomolangma. Both hourly air temperatures and relative humidity were measured at seven automatic weather stations (AWS) from 5207 to 7028 m a.s.l. from May 2007 through September 2008. Long-term (1959-2007) air temperature and precipitation data were obtained from Dingri Meteorological Station. The preliminary results show that the elevational gradient of mean annual air temperature is non-linear, which decreases from 0.2 degrees C at an elevation of 5207 m to -4.4 degrees C at 5792 m, and -5.4 degrees C at 5955 m. The maxima are 14.6, 9.1, and 18.6 degrees C, and the minima are -24.2, -28.8, and -29.3 degrees C at the three elevations, respectively. The relative humidity does not change significantly with increasing elevation except over glacier ice, but the mixing ratio decreases due to the decrease in air temperature. The mean diurnal ranges of air temperature and relative humidity decrease with increasing elevation. The daily maximum air temperature occurs significantly later at the high-elevation site than that at the low elevation site because the air temperature at the high-elevation site is affected to a large extent by downward mixing of warm air near the ablation zone of the glacier during daytime. The air moisture content reflects the pronounced alternation of the wet and dry seasons, and the highest water vapor content is associated with the southwesterly Indian monsoon. The mean annual surface air temperature-elevation gradient is 0.72 +/- 0.01 degrees C (100 m)(-1), and also shows a pronounced seasonal signature. Mean annual air temperatures have increased by about 0.62 degrees C per decade over the last 49 years in this region; the greatest warming trend is observed in winter, the smallest in summer. Warmer conditions have been observed since the mid-1980s. Additional studies have shown a reduction in precipitation in the 1960s that resulted in a decrease in net snow accumulation. Therefore, accelerated retreat of the Rongbuk Glacier since the 1980s may be caused by rising air temperature and the decreased precipitation.