Amount and temperature effects responsible for precipitation isotope variation in the southern slope of Himalayas

作     者：Tek Bahadur Chhetri TanDong Yao LiDe Tian XinPing Zhang 

作者机构：Institute of Tibetan Plateau Research Chinese Academy of Sciences University of Chinese Academy of Sciences Central Dept. of Hydrology and Meteorology Tribhuvan University College of Resources and Environmental Sciences Hunan Normal University 

出 版 物：《Research in Cold and Arid Regions》 (寒旱区科学（英文版）)

年 卷 期：2013年第5卷第2期

页      面：165-176页

核心收录：

学科分类：07[理学] 070601[理学-气象学] 0706[理学-大气科学] 

基　　金：supported by the Ph.D.program of Institute of Tibetan Plateau Research ITPCAS 

主　　题：amount effect temperature effect precipitation meteoric water line 

摘      要：Seasonal variation of stable isotopes in precipitation of Kathmandu Valley on the southem slope of Himalaya was carried out to understand the controlling mechanism of amount and temperature effect on the basis of one year stable isotope data from 2010 to 2011. Highly depleted isotope values in major rainy period are obtained just after the onset of precipitation in summer, which ac- counts for ＂amount effect＂ due to saturation isotopic compositions in high moisture condition, whereas, the higher values in winter are indicative to regional vapors （temperature effect） recycling of various sources. An abrupt depletion of isotope values in mid- June, indicates the onset date of monsoon precipitation, by the replacement of winter air mass with southem monsoon. Thus, pre- cipitation isotopes are a tool revealing the onset date of summer monsoon and temporal features of variability, in local and regional monsoons precipitations. A comparison of long term monthly values of 5180, temperature, and precipitation with GNIP 6180 data shows the temporal variations of stable isotopes are mostly controlled by amount and temperature effects. During summer mon- soon, the amount effects are stronger for high values of precipitation （R=0.7） and altitude effect appears for low moisture in late rainy season, thus from December to June （winter to pre-monsoon） the controlling features of isotopes remains under the temper- ature effect. A temporal rate of temperature effect is derived as 0.04%0 per year which indicates a dry signal of atmospheric condition and a temperature relation 5180=（0.371±0.08）T＋（0.156±0.05） is obtained from this analysis. The meteoric water lines of Kathmandu before and after monsoon onset of 2011, are found as 5D=（4.36±0.3）5180＋（15.66±1.2） and 5D=（6.91±0.2）S180-（7.92±2.26） from lab samples result, and 5D=9.25180＋11.725 and 5D=8.535180＋16.65 from GNIP data, which lacks the consistency both for slopes and intercepts values for the study period. The mean lapse rate val