黄河流域日潜在蒸散量变化及气象敏感要素分析

潜在蒸散量反映了大气的蒸发能力,准确的估算和科学客观的分析其气象影响要素,是水资源优化配置的重要依据和基础。该文以国家气象局整编的黄河流域109个站点近52a(1961-2012年)逐日气象资料计算潜在蒸散量及其敏感系数,探明黄河流域上游、中游和下游日潜在蒸散量(potential evapotranspiration,ET0)对4种气象要素的敏感性时空变化特征。结果表明:从ET0日值来看,黄河流域上游变化趋势不明显,但其均值高于中游和下游,下游以-0.043 mm/10a的趋势显著(p0.05)递减;在年内变化上,上游、中游和下游太阳辐射和温度及太阳辐射敏感系数均呈单峰型曲线变化,风速敏感系数呈单谷型变化,而相对湿度、风速以及相对湿度和温度的敏感系数波动较大;年际变化上,上游、中游和下游太阳辐射、相对湿度和风速都显著下降,温度显著提升,ET0对太阳辐射量和温度的敏感性减弱,而对相对湿度和风速敏感性增强;相对湿度是上游、中游和下游ET0变化的最敏感的要素,而太阳辐射量是ET0年内和年际变化的主控气象要素;太阳辐射、相对湿度和温度3个气候变量的敏感系数都在研究区西南部形成高值区,表明ET0在黄河流域西南部对气候变化最敏感。该研究对于指导黄河流域不同区域农业种植结构的调整和生态工程科学布局,合理开发调配水土资源,促进农业和生态环境的良性发展,具有重要的科学意义。

Changes of daily potential evapotranspiration and analysis of its sensitivity coefficients to key climatic variables in Yellow River basin

Abstract: Potential evapotranspiration (ET0) is generally accepted to be an important element of the hydrological cycle, and changes in sensitivity coefficients of ET0 to climate variables are of great significance for agricultural water use planning, irrigation system design and management, especially under the condition when climate change may have important influence on water-shortage regions, such as Yellow River basin (YRB), where warmer and drier conditions might augment water demand by crop. However, little reports have focused on the related issues in the upper, middle, and lower regions of YRB. Therefore, this study aimed to investigate the variation of ET0 and its response to climate variables in the upper, middle, and lower regions of YRB. Based on data for 109 meteorological stations in and around YRB from the Chinese Meteorological Administration (CMA) in years of 1961-2012, ET0 was estimated using the Penman-Monteith equation recommended by Food and Agricultural Organization (FAO-56) and its sensitivity coefficient to climate variables (solar radiation, relative humidity, daily air temperature, and wind speed) was calculated. The results showed that the average daily ET0 value in upper region was higher than in the middle and lower region of YRB and a significantly decreasing trend of ET0 was detected with the magnitude of 0.043 mm per decade in lower region. The diurnal variation curve of solar radiation, air temperature and their sensitivity coefficients was in a single apex type in the upper, middle and lower regions of YRB, and that the sensitivity coefficients of wind speed changed following a single trough type curve. However, the curves fluctuated largely for relative humidity, wind speed along with sensitivity coefficient for relative humidity and air temperature. Furthermore, the maximum value of sensitivity coefficient for relative humidity was found in December, similarly for air temperature and solar radiation in July and August, respectively. A decreasing trend was observed for solar radiation, relative humidity, wind speed and sensitivity coefficient of solar radiation and air temperature. But, an increasing trend was detected for air temperature, sensitivity coefficient of relative humidity and wind speed in recent 52 years. Relative humidity is considered to be the most sensitive variable, while solar radiation is recognized as primarily controlling variable for ET0 in the whole year and recent 52 years. Moreover, the high value of sensitivity coefficients to solar radiation, relative humidity and air temperature was found in the southwest study area, while the high value of sensitivity coefficients to wind speed was in the north region. Therefore, the southwest region was recognized as the most sensitive region for response of ET0 to climate change. The findings from this research provide important information for crop planting adjustment, ecological engineering planning and water-soil resource management in YRB in an attempt to improving the healthy development of agriculture and ecological environment.