渭河流域关中段潜在蒸发量时空变化特征

Spatial and Temporal Change of the Potential Evapotranspiration in Weihe River Basin: A Case Study in Guanzhong Area

根据渭河流域关中段11个主要代表气象站点1955~2012年逐日气象数据,以FAOPenman-Monteith公式得出潜在蒸发量,分析渭河流域关中段潜在蒸发量的时空变化特征。结果表明:1渭河流域关中段年平均潜在蒸发量在1 073.9~1 284.1 mm,流域内多年平均蒸发量随着海拔的降低逐渐增高。2夏季潜在蒸发量在327.6~547.2mm,占全年的34%~42%,变化趋势与全年潜在蒸发量变化趋势高度一致。3渭河关中段随气温上升,潜在蒸发量减少。4年均潜在蒸发量与日较差、平均气温、平均风速、日照时数呈正相关,与相对湿度和水汽压呈负相关。

Based on the daily data of 11 meteorological stations of Guanzhong area in Weihe River Basin in 1960-2006 and combined with the FAO Penman-Monteith model, spatial and temporal changes of potential evaporation were quantita-tively analyzed in this study, which mainly discussed the reason of the decreasing of potential evaporation. It was showed that potential evapotranspiration in Guanzhong area of Weihe River Basin decreased significantly with the increasing of mean tempera^re, which is mainly because mean wind speed and sunshine time decreased significantly. The main results are as follows： 1） The annual potential evapotrans- piration, gradually increased with the loss of the altitude, which range from 1 073.9 mm to 1 284.1 ram. 2） The potential evapotranspiration in spring range from 195.6 mm to 327 ram, accounted for about 19%-22% of the year, and the potential evapotranspiration in summer range from 327.6 mm to 547.2 mm, accounted for about 34%-42% of the year, which plays a leading role throughout the year. The potential evapotranspiration in au- tumn and winter is in 250.8-466.2 mm and 115.2-247.8 mm respectively, accounted for 24%-33% and 10%-18%. 3） The evaporation paradox actually existed in the study area, as the mean temperature increased, the potential evapotranspiration generally decreased. Linear trend rate of the potential evapotranspiration is -9.16 mm/10 a during 1955 to 2012, however, at the same time, linear trend rate of the mean temperature is 0.39℃/10 a. 4） Mean annual potential evapotranspiration and the diurnal range, mean temperature, mean wind speed and sunshine duration were positively correlated, and negatively correlated with relative humidity and water vapor pressure. The mean wind speed and sunshine time is the dominating factor leading to the decrease of potential evapotranspiration in the study area.