| Hydrogen and oxygen isotopic information in precipitation is the most direct and powerful indicator for the study of water gas mass circulation process. Since 1961, the International Atomic Energy Agency (IAEA) and the World Meteorological Organization (WMO) co-founded the global isotope monitoring network (GNIP), monitoring organization the hydrogen and oxygen isotope composition of the global rain. Hydrogen and oxygen stable isotopes as a powerful diagnostic tool, many domestic and foreign scholars on the basis of δD,δ18O value and deuterium excess extracted values in the information of multi scale water circulation of many problems in the process of in-depth discussion, and the accumulation of a large number of theoretical basis, application of hydrogen and oxygen isotopes in hydrology of technology the main natural precipitation isotope distribution, variation of isotopic water evaporation process, the significance of this study is not only for the synoptic scale down on water stable isotope to add new data, also has great significance for the study of the general circulation model for atmospheric monsoon region, provide data support and theoretical basis for stable isotope climate environment information contained in the ancient water restoration and interpretation.This paper selects Beibei District of Chongqing (29°39’10"N ～30°3’53"N,106°18 ’14"E～106°56’53"E) as the study area which belongs to subtropical monsoon climate, which is located in the Yangtze River basin. The Yangtze River is the longest River in China covering a large area. The geographical position superior, the lower reaches of the Yangtze River area, abundant rainfall, rich in resources, is not only the main origin China industry agriculture, but also is the area of the high speed development of economy. Affected by the East Asian summer monsoon, the Yangtze River Valley in summer occurs often persistent heavy rain, under the influence of the West Pacific subtropical high pressure from the bay of Bengal, South China Sea and the tropical western Pacific warm humid monsoon air often and from the cold air from the north of the Yangtze River Basin confluence, causing long river, downstream area is likely to occur in the 6-7 month of persistent heavy rainfall; and the Sichuan Basin, the upper reaches of the Yangtze River in the summer often appear torrential rain, triggering floods. Study on the causes of flood disasters in the Yangtze River Basin and persistent rainstorm showed that the variation of East Asia monsoon climate system flood disasters in the Yangtze River Basin and continuous rain in the inter-annual and inter-decadal change is with the atmosphere ocean land surface coupling is related closely. Based on the natural geographical conditions of Beibei area, combined with the method of simulation to track environmental stable isotope and the systematic analysis on the features of hydrogen and oxygen isotopes and water vapor source of temporal and spatial distribution, to provide basis for the study of the Yangtze River Basin and even Asian monsoon water cycle mechanism. Based on the monitoring data and meteorological elements at School of Geographic Sciences, Southwest University, Chongqing, which were collected from 75 times of precipitation from October 2014 to September 2014, combined with meteorological observation data and the δD and δ18O data measured by LGR (Los Gatos Research) Liquid-Water Isotope Analyzer device, the LMWL of Chongqing is formulated as δD= 8.71δ18O+18.19, r=0.97 (p<0.01). The influence of short-time weather factors account for the larger slope and intercept value. The characteristics of the hydrogen isotope and oxygen isotope and their relationships with temperature and precipitation were analyzed in order to reveal the moisture sources based on the statistics. The statistics shows that the relationships of hydrogen isotope and oxygen isotope with the both are not obvious. With further study, the co-existence of summer monsoon and winter monsoon during the transition span and complicate isotope composition in precipitation really matter. The study area during the study period of the precipitation samples δD and δ18O value according to formula of deuterium excess values were more than 10 per thousand show that water vapor source evaporation rate, the dry season most samples with d values greater than the rainy season, probably indicating due to different types of the monsoon and different water vapor source. Some scholars through in-depth study of deuterium excess values were also found, d value is often used as indicator of atmospheric water vapor source and source region of moisture and moisture evaporates isotopic disequilibrium fractionation index, relative humidity in precipitation D value depends primarily on the formation of the water vapor source, namely when the water vapor source of the atmospheric relative humidity is high, low D value, and with the decrease of water vapor source of the atmospheric relative humidity, precipitation will increase the value of D in the. According to the precipitation time order of all the samples were numbered, divided into the rainy season and dry season samples, using the calculation formula of the respective D values during the dry season.The model of HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) is developed by USA National Oceanic and Atmospheric Administration (NOAA) Air Resources Laboratory and the Australian Bureau of Meteorology in the past 20 years, a joint research and development with a Lagrange mixture calculation model to calculate and analysis the professional model of atmospheric pollutants transport, and diffusion path. Finally, the use of American Center for environmental prediction (NCEP) and the National Center for Atmospheric Research (NCAR) jointly launched the global reanalysis monthly meteorological data entering into the HYSPLIT software with selection backward trajectory simulation model to track and validate the area precipitation water vapor transport path, select the 850hPa level, discusses the impact of water vapor transport of delta D and delta 180 variations in precipitation. Results show that warm and humid rainy season is mainly influenced by the mass of vapor from the ocean the impact of summer monsoon, the dry season are mainly affected by the westerly transport of water vapor source influence, mainly from the northern arid and semi arid area. The simulation result further verified due to the different types of software to the seasonal variation of monsoon influence graph consistency and D value for different types of the monsoon and different water vapor source. |
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