黑河中游夏季昼夜水汽同位素特征及水汽来源分析

基于2012年6～8月的实测水汽同位素数据及相关气象数据,对黑河中游夏季昼夜的同位素基本特征、水汽来源方向及潜在蒸发源地进行了研究。结果表明:空气水汽线斜率白天大于夜晚和水汽过量氘值白天大于夜晚,综合说明白天局地蒸发较夜晚强烈;夏季受西风水汽影响显著。其中,6月主要受西风水汽和北冰洋水汽影响,7、8月主要受西风水汽和东南方向水汽影响,且8月受东南方向水汽影响最为明显;水汽运移路径上下垫面地形和气压带移动会影响水汽后向轨迹高度,西北方向上水汽输送通道较顺畅,风速较大,有利于水汽的输送;水汽蒸发源地主要集中在研究区周围及以东、以北部,其次是西北部。绿洲是主要的水汽蒸发源地,其次是城市和河流,白天较夜晚局地蒸发强烈且面积大。

Isotopic characteristics of water vapor and itssources during day and night along the Heihe River in summer

In this study,we analyzed the basic characteristics ofwater vapor isotopes in the middle reaches of the Heihe River,GansuProvince,China mainly based on water vapor d data. We used PSCF and CWT analysis for the 2012 summer monthsin the studied area.We identified potential steam source locations during theday and night,and connected this with backward trajectory clustering,maximumwind speed and direction analysis,atmospheric precipitation data,and vapor fluxdivergence.Our results showed that the slope of the moisture line in thedaytime was greater than that at night,with elevated d values during the day.This suggests that local evaporation isstronger during the day than at night.The values of D and ¹⁸O in thewater vapor increased every month,and were significantly elevated during theday due to the urban heat island effect.The water vapor source was complex,andthe d value of the water vapordecreased throughout the summer.In June,high values reflected relatively humidconditions in the western Pacific,which were significantly affected by arcticand westerly water vapor.In July and August,the arctic vapor was steadilyreplaced by southeast water vapor.Surface topography and the movement of thepressure zone on the path of water vapor transport both affected the height ofthe backward trajectory of the water vapor.The water vapor transportationchannel in the northwest direction was smooth with high wind speeds,whichencourages water vapor transportation.In response to the movement of thepressure belt,the backward trajectory height of water vapor in August washigher than that in June and July.The origins of the water evaporation weremainly concentrated to the east and north of the study area,with lessercontributions from the northwest.Oases were the main source of waterevaporation,followed by cities and rivers,with local evaporation being strongerduring the day than at night.Indeed,most of the observed features werestrengthened by warm daytime temperatures.