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基于洞庭湖流域内长沙市2010年1月至2012年12月降水事件、GNIP(Global Network for Isotopes in Precipitation)长沙站1988~1992年月降水同位素资料及ENSO(厄尔尼诺/拉尼娜和南方涛动)的2个常用指标(南方涛动指数SOI和Nino3区海面温度SST),分析了流域降水同位素与ENSO关系。结果表明:洞庭湖流域降水中δ~(18)O与降水量、气温在日、月尺度上均呈负相关且只有月度上与降水量的负相关不显著。洞庭湖流域降水中δ~(18)O与ENSO的SST指标则呈显著正相关。ENSO对洞庭湖流域降水同位素的影响机制可能如下:春季,La Nina年源自西太平洋的东南风强盛,其转向为西南风的区域达到印度洋,而El Nino年,东南风转向为西南风的发生区域位于印度洋以东,前者有利于挟带印度洋远源水汽向中国东部区域输送,进而造成降水同位素的贫化;夏季,La Nina年印度洋水汽输送在中国南海转为经向继而向北延伸,而El Nino年,源自印度洋的水汽沿纬向穿过南海,在东海转向往北延伸,后者有利于挟带西太平洋的近源水汽输送到中国东部季风区,进而引起降水同位素的富集。
Based on the precipitation events in Changsha from January 2010 to December 2012 in the Dongting Lake basin, the monthly precipitation isotope data of Changsha (GNIP) from 1988 to 1992 and ENSO (El Niño / La Niña and Southern Oscillation) Two commonly used indicators (SOI of the Southern Oscillation Index and SST of the Nino3 region), the relationship between precipitation isotopes and ENSO was analyzed. The results show that the δ 18 O in the precipitation of Dongting Lake basin is negatively correlated with the precipitation and temperature on the daily and monthly scales, and only the monthly negative correlation with the precipitation is insignificant. There was a significant positive correlation between δ 18 O in precipitation and the ENSO SST in Dongting Lake basin. The mechanism by which ENSO affects precipitation isotopes in the Dongting Lake basin may be as follows: In spring, La Nina was characterized by a strong southeast wind from the western Pacific, a southwest wind turning to the Indian Ocean in El Nino, and a southeasterly wind turning The former is located east of the Indian Ocean. The former is conducive to the transport of distant water vapor in the Indian Ocean to the eastern part of China, resulting in the depletion of precipitation isotopes. In summer, the Indian Ocean moisture transport in La Nina is converted to meridian and then northward in the South China Sea In El Nino year, water vapor from the Indian Ocean passes through the South China Sea in the latitudinal direction and extends northward in the East China Sea. The latter facilitates the transport of near-source water vapor carrying the western Pacific to the monsoon region in eastern China, leading to the enrichment of precipitation isotopes.