四川省潜在蒸散量变化及其气候影响因素分析

潜在蒸散(ET_0)是评价某一地区干旱程度的重要指标,在全球气候变暖趋势下,估计ET_0的变化对科学估算作物需水量,提高水分利用率具有重大意义。本文利用四川省1961-2014年151个气象站的气象资料,采用Penman-Monteith公式分3个区域(四川盆地、攀西地区和川西高原)计算ET_0,并对主要气象因子平均气温、相对湿度、日照时数、平均风速的相对变化率、敏感系数及其对ET_0贡献率的时空变化进行分析。结果表明:四川盆地和川西高原ET_0呈现微弱减少,而攀西地区则呈现一定的增加,其空间分布表现为:攀西地区和川西高原南部年ET_0为高值区,多在1000~1350mm,四川盆地的西南部年ET_0为低值区,多在651~900mm,从西南向东北呈现"高-低-高"趋势。各气象因子对ET_0的影响(对ET_0变化的贡献率)主要取决于敏感性和相对变化率两方面。3个区域ET_0对相对湿度的变化均表现最敏感,其敏感系数分别为-1.13、-1.40、-1.53。在主要气象因子中,在四川盆地和攀西地区,平均风速的多年相对变化率最大(-29.7%、-16.3%),川西高原则为平均温度(40.4%)。进一步分析得出,平均风速在四川盆地和川西高原对ET_0变化的贡献率最大,是主导影响因素,而在攀西地区则为相对湿度。

Potential Evapotranspiration Changes and its Effects of Meteorological Factors across Sichuan Province

Potential evapotranspiration(ET0) is an important metric in measuring drought conditions for an area. Examining ET0changes is critical for estimating crop water demand, and thus it is crucial for improving water use efficiency in the context of global warming. Based on daily meteorological data of 151 meteorological stations in Sichuan province from 1961 to 2014, the authors calculated ET0 with the Penman-Monteith formula for the three terrain regions of Sichuan: Sichuan basin, Panxi region and Western Sichuan Plateau, and also analyzed relative variation and sensitivity coefficients of the major meteorological factors (i.e., mean air temperature, relative humidity, radiation hours, and mean wind speed), and the spatiotemporal changes in their contribution to ET0changes. The results showed that ET0 in the Sichuan basin and the Western Sichuan Plateau presented a weak declining trend, as opposed to an increasing trend in Panxi region. In terms of spatial distribution, ET0 was high in the Panxi region and the Western Sichuan Plateau (1000-1350mm·y-1), and it was low in the southwestern Sichuan Plateau (651-900mm·y-1), with a decreasing and then increasing gradient of ET0 from the southwest to northeast. The effect of each meteorological factor on ET0(i.e., contribution of each meteorological factor to ET0change) was determined by their sensitivity to ET0 and relative variation. ET0 was most sensitive to relative humidity across the three regions, with sensitivity coefficients of-1.13,-1.40,-1.53, respectively. Among all the meteorological factors, the variable with the highest long-term relative variation was mean wind speed in Sichuan basin (-29.7%) and Panxi region (-16.3%), in contrast to mean air temperature in Western Sichuan Plateau (40.4%). Further analyses suggested that the dominant factor determining ET0 for Sichuan basin and Western Sichuan Plateau was mean wind speed, and that for Panxi region was relative humidity.