珠江流域实际蒸散发的时空变化及影响要素分析

SPATIO-TEMPORAL VARIATION OF ACTUAL EVAPOTRANSPIRATION AND ITS IMPACT FACTORS IN THE PEARL RIVER BASIN, CHINA

采用基于互补相关理论的平流-干旱模型,根据60个气象站1961—2010年气象资料,计算并分析了珠江流域实际蒸散发(ETa)的时空变化特征,通过对实际蒸散发的辐射能量项、空气动力学项与主要气象要素的相关分析,对珠江流域实际蒸散发的时空变化进行了归因研究。结果表明:(1)珠江流域多年平均实际蒸散发量为665.6 mm/a。1961—2010年,珠江流域实际蒸散发量呈明显的下降趋势,下降幅度为-24.3 mm/(10a)。夏秋季节实际蒸散发的下降对年际尺度实际蒸散发的下降具有明显的贡献。(2)珠江流域东南沿海地区年实际蒸散发量较高(大于690 mm),该区年实际蒸散发量呈现显著的下降趋势。流域中部有一条呈东北-西南走向的条带状实际蒸散发低值区,年均实际蒸散发量在630 mm以下,但该区域的时间变化趋势不明显。(3)气温日较差和日照时数的下降以及大气压的增加使得辐射能量项的下降,是造成实际蒸散发下降的主要原因;平均气温、最高、最低气温的上升使空气动力学项呈现增加趋势,从而在一定程度上贡献于实际蒸散发的下降。春秋冬三季平均风速的下降引起空气动力学项的下降趋势或减缓其增加趋势,反过来在一定程度上减缓了实际蒸散发的下降趋势。

Spatio-temporal changes of actual evapotranspiration（ETa） in the Pearl River Basin from 1961 to 2010 are analyzed using daily data of 60 weather stations. The Advection-Aridity model is used to calculate ETa and the Mann–Kendall test（MK） is used to detect trends. The spatial variability of trends is displayed by interpolating ETa with the Inverse Distance Weighted interpolation method（IDW）. The Person correlation analysis method is used to attribute changes in ETa to changes in meteorological components and the radiation-energy/aerodynamics factors of ETa. The following are the major results of the research：（1） the average annual ETa in the Pearl River Basin is about 665.6 mm/a. It has significantly decreased from 1961—2010 at a rate of-24.3 mm/（10 a）. The negative trend of the ETa in summer and autumn is higher than in spring and winter.（2） ETa is higher in the southeast coastal area than in the northwest inland area of the Pearl River Basin. The negative trend of ETa is strongest in the northwest inland area and weakest in the coastal area. Trends of ETa are low in a band stretching from the northeast to the southwest in the central of the basin.（3） Negative trends of ETa in the Pearl River Basin can be attributed to decreasing radiation-energy and increasing aerodynamics. Declining diurnal temperature range and sunshine duration and increasing atmospheric pressure caused the decrease of the radiation-energy item. The increase of average/maximum/ minimum temperature in the basin contributed to the increase of the aerodynamics item in the ETa but not to the radiation-energy item. The same is valid for the average wind speed in spring, autumn and winter that slowed down the negative trend of the ETa.