辽河三角洲湿地生长季蒸散量时空格局及影响因素

Temporal and spatial change characteristics of growing season evapotranspiration and its cause analysis in Liaohe River delta wetland, China

蒸散是湿地系统水分损失的重要途径之一,有效量化湿地蒸散量并对其时空格局进行研究具有重要意义。本文以Landsat数据和气象观测数据为基础,利用SEBAL模型估算辽河三角洲湿地1985—2017年共8期植被生长季的蒸散量,并分析其时空格局和影响因素。结果表明:(1)反演得到的蒸散量平均相对误差为9.01%,估测值与实测值相关系数为0.61,基本满足湿地蒸散研究需求;(2)研究区多年日蒸散量均值和相对变化率整体呈双峰态势,极小值出现在2005年,极大值出现在1989年和2014年;(3)日蒸散量具有水陆交界处最低、西部较低、中东部和南部高的趋势,具有显著的空间分异特征;(4)不同土地利用/覆被类型的蒸散量大小依次为:水体区>湿地植被区>非湿地植被区>非植被区(除水体外),多年不同土地利用/覆被类型的蒸散量变化也呈双峰态势,日总蒸散量变化与土地利用转型有关,土地利用/覆被是导致湿地蒸散时空分异的重要因素;(5)平均蒸散量与太阳辐射、气温、风速、相对湿度四个气象因子加权值显著相关,相关系数为0.69,两者年际波动趋势基本一致,蒸散量变化与气象条件变动联系密切。

Evapotranspiration(ET)is an important method of water loss in a wetland system.Accurately estimating wetland ET and analyzing its spatial and temporal patterns are crucial.The ET estimation of eight growing seasons in the Liaohe River Delta wetland during 1985—2017 was conducted using a Surface Energy Balance Algorithm for Land(SEBAL)model with Landsat and meteorological observation data.The temporal and spatial patterns and causes of growing season ET were analyzed.Results showed the following:(1)the average relative error of the regional ET estimated by the SEBAL algorithm was 9.01%,and the correlation coefficient between the measured and estimated values was 0.61,which indicated that the estimated values were reliable.(2)The distribution of the average and relative change rate of daily ET exhibited bimodal characteristics in the study area:the lowest trough happened in 2005,whereas the crests occurred in 1989 and 2014.(3)The area of land-water junction presented the lowest ET.The high values of ET appeared in the eastern,southern,and middle parts of the region,whereas a low ET happened in the western area.The daily ET displayed a highly heterogeneous spatial distribution.(4)The ET of different land use/cover types,in descending order,was water body,wetland vegetation,non-wetland vegetation,and non-vegetation(except the water area).The characteristic across different land use/cover types from 1985 to 2017 presented a bimodal trend.The total daily ET was related to landscape transformation.The land use/cover type was a significant factor of the temporal and spatial distribution of ET.(5)The daily values of ET were significantly correlated with the corresponding weighted values of solar radiation,air temperature,wind speed,and relative humidity.The correlation coefficient was 0.69,and their annual fluctuations were relatively similar.The ET was closely related to the meteorological factor change.