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半干旱地区降露水和蒸发特征研究

Research of Dew and Evaporation Characteristics of Semi-arid Area

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【Author in Chinese】 问晓梅

【Supervisor】 张强

【Author's Information】 中国气象科学研究院, 气象学, 2009, 硕士

【Abstract in Chinese】 本文利用中国气象局兰州干旱气象研究所定西干旱气象与生态环境试验基地野外观测场的大型蒸渗计、梯度塔、开路涡度协方差系统、辐射表和水分含量反射表等仪器观测的2004年6月~2005年5月一年的降露水、蒸发量、潜热通量、辐射等资料。研究了半干旱区陆面降露水和土壤蒸发的日变化、季节变化和年变化,并且初步分析了降露水和土壤蒸发的影响因子。通过对实验数据进行统计处理和对半干旱区降露水量与相应气象因子之间相互关系进行分析,取得如下认识:1.半干旱区降露水凝结是一个极其复杂的物理过程。多种气象因子共同影响降露水量,在所有因子中近地表的空气湿度与气温是影响降露水凝结的基本因素,而其它因子则通过修饰这两个因子而起作用。降露水日变化很明显,主要出现在夜间22时~次日上午09时,随着季节的变化,降露水量最大值出现时间逐渐推迟,秋季出现降露水的时间段最长,夏季和冬季次之,春季最短。晴天出现降露水量要远远高于阴天的,降水后一天出现的降露水量最高。降露水主要集中在9~12月份,2月份和6月份降露水量最少。秋季总的降露水量要远远高于其他季节的,可以达到3.59mm,夏季最少。2.土壤吸附水主要出现在傍晚18时~次日07时,冬季最大,秋季次之,夏季最小;全年的土壤吸附量为61.40mm,主要集中在10月~次年1月份;其主要影响因子是土壤含水量以及土壤性质。3.陆面水分分量中降水、降露水、土壤吸附水、雾水均是引起蒸渗计重量增加的因素,其出现时间不同,而且降水、土壤吸附水量远远大于降露水量、雾水量;降水对陆面水分的贡献最大,土壤吸附水次之,雾水最小。雾主要发生在秋季,在其它季节较少发生,而且主要发生在降露水发生后一天,并且多出现在阴天。雾的量较小,只有0.61mm。4.土壤蒸发的形成及蒸发强度受太阳辐射、气温、湿度、风速和气压等气象因素的影响,同时也受土壤含水量的大小和分布的影响。土壤蒸发的日变化很明显,主要出现在上午10~下午17时,主要集中在4月~次年的10月份;夏季的蒸发量和蒸发频率最大,春季次之,冬季最小,全年的土壤蒸发量可达571.7mm。蒸发皿蒸发量的季节变化特征明显,主要出现在春季和夏季,冬季的蒸发量较少,全年的蒸发皿蒸发量大约为1251.1mm;其年变化特征曲线呈开口向上的抛物线形式,在12月和1月出现最低值,4月份蒸发量最大。即蒸发量在5月~12月是单调递减的,在1月~4月是单调递增的。蒸发皿蒸发量主要受气温、地温、风速、相对湿度等气象因子的影响,与土壤含水量的关系不明显。土壤蒸发量与蒸发皿蒸发量的比值∏在9月和5月最大,11月~次年的3月最小;夏秋季最大,冬季最少。温度梯度、相对湿度、风速等是影响∏值的重要气象因子。

【Abstract】 The observed data in this paper were based on the large lymister during June 2004 to May 2005. The daily variation, seasonal variation and year variation of dewfall and the soil evaporation in semi-arid were studied, the impact factor of dewfall and soil evaporation was analyzed. Following understanding were obtained by statistic disposal on experimentation data,by analysising on the interrelation between dewfall amount in semi-arid and corresponding meteorological factors.1.Dewfall in semi-arid is an extreme complicated physical procedure. Many kinds of meteorological factors influence dewfall amount. Among all these factors, the surface air humidity and temperature were the basic factors which impact the dewfall. While other factors Play a role by decorating two factors. The diurnal variation was obvious which mainly appeared in P.M.22 to A.M.09, while there was nearly no dewfall in any other time. The maximum amount of dewfall change with seasons, which delay with time. The time segment in which dewfall appeared in autumn was longest, the summer and the winter took the second place , and the spring was the shortest. The total dewfall amount in autumn was much more than other seasons, which reached 3.59mm, while spring and winter took the second place, summer was the minimum. Dewfall mainly concentrated in September to December, while February and June was the minimum. The dewfall amount in clear day was much more than that in overcast. The dewfall amount after rainfall was much more than in which the day before and the following two days. 2. Soil adsorption mainly occured in P.M.18 to A.M.7. The soil adsorption amount in winter was the largest, while the autumn took the second place and the summer was the minimum. The total soil adsorption amount in a year was 61.40mm, which mainly concertrated in October and Feburary. The primary factors which affected the soil adsorption were soil water content and the soil property.3. The occurred time of Rainfall,dewfall, soil adsorption and fog-water were different, the amount of rainfall and soil adsorption were much more than the dewfall and fog. The rainfall made the greatest contribution to the land surface moisture, the soil adsorption took the second place and the fog was the minimum. Fog mainly occurred in autumn, and it rarely occurred in other seasons. While the fog mainly occurred the day after the dewfall, and always occurred in overcast. The amount of fog was tiny, only reached 0.61mm.4. The formation of soil evaporation and evaporation intensity were affected by those factors such as direct solar radiation、temperature、humidity、wind speed、pressure and so on. While the amount and distribution of soil water content affected the evaporation too. The daily variation of soil evaporation change obviously, which mainly appear in A.M.10 to P.M.5. While the soil evaporation in other time was much less. The amount and frequency of evaporation in summer was largest, spring took the second place, winter was the minimum. The total evaporation amount in that year reached 571.7mm. The distribution of soil evaporation mainly occurred in April to next October. The evaporation in evaporator changed obviously with seasons, and the evaporation mainly occurred in spring and summer, winter was the minimum. The total amount of the year reached 1251.1mm. Character curve of evaporator was parabola, with up direction. The minimum amount occurred in December and January, the evaporation in April was the maximum. The character cure was monotone decreasing in May to December, while in February to April was monotone increasing. The evaporation was affected by the factors such as temperature、ground temperature、wind speed、relative humidity and so on,while the soil water content didn’t show a clear relationship.

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