陈迪桃1,2, 黄法融1,3, 李倩1,2, 李兰海1,3,4,51 中国科学院新疆生态与地理研究所荒漠与绿洲生态国家重点实验室,乌鲁木齐 8300112 中国科学院大学,北京 1000493 中国科学院伊犁河流域生态系统研究站,乌鲁木齐 8300114 中国科学院新疆资源环境科学大型仪器区域中心,乌鲁木齐 8300115 中国科学院中亚生态与环境研究中心,乌鲁木齐 830011
1 中国科学院新疆生态与地理研究所荒漠与绿洲生态国家重点实验室,乌鲁木齐 830011
2 中国科学院大学,北京 100049
3 中国科学院伊犁河流域生态系统研究站,乌鲁木齐 830011
4 中国科学院新疆资源环境科学大型仪器区域中心,乌鲁木齐 830011
5 中国科学院中亚生态与环境研究中心,乌鲁木齐 830011
CHEN Di-Tao1,2, HUANG Fa-Rong1,3, LI Qian1,2, LI Lan-Hai1,3,4,51 State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China2 University of Chinese Academy of Sciences, Beijing 100049, China3 Ili Station for Watershed Ecosystem Research, Chinese Academy of Sciences, Urumqi 830011, China4 Xinjiang Regional Center of Resources and Environmental Science Instrument, Chinese Academy of Sciences, Urumqi 830011, China5 Research Center for Ecology and Environment in Central Asia, Chinese Academy of Sciences, Urumqi 830011, China
1 State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
2 University of Chinese Academy of Sciences, Beijing 100049, China
3 Ili Station for Watershed Ecosystem Research, Chinese Academy of Sciences, Urumqi 830011, China
4 Xinjiang Regional Center of Resources and Environmental Science Instrument, Chinese Academy of Sciences, Urumqi 830011, China
5 Research Center for Ecology and Environment in Central Asia, Chinese Academy of Sciences, Urumqi 830011, China
作者简介 About authors
利用天山地区近50年(1966—2015年)逐日气象资料,采用Mann-Kendall趋势检验法研究了天山南北坡相对湿度(RH)的时空变化特征,分析了天山南北坡RH对平均气温、降水量、平均风速、参考蒸散量、日照时数的敏感性,并探讨了引起RH变化的主导因素。结果表明：(1)整个天山地区RH变化有略微上升的趋势但不显著,北坡RH总体呈下降趋势,南坡RH总体呈上升趋势。(2) RH空间分布呈自北向南递减趋势,南北坡全年及春季以下降趋势为主,而夏、秋、冬三季均以上升趋势为主,且南坡变化趋势的显著性高于北坡。(3) RH对风速、气温、日照时数及参考蒸散量均为负敏感,对降水量为正敏感。北坡RH对各气象因子的敏感程度依次为日照时数>参考蒸散量>风速>气温>降水量,南坡敏感程度依次为日照时数>风速>参考蒸散量>气温>降水量。空间分布上,仅降水量敏感系数高值区位于北坡伊犁河谷,其余要素敏感系数高值区均位于南坡。(4)参考蒸散量是影响天山地区RH变化的主导因子,整个天山地区参考蒸散发贡献率较高,日照时数贡献率高值区集中于北坡伊犁河谷,风速、降水量、气温贡献率高值区均集中于南坡克孜勒苏地区。关键词：天山南北坡;相对湿度(RH);差异;Mann-Kendall趋势检验法;敏感性分析
利用天山地区近50年(1966—2015年)逐日气象资料,采用Mann-Kendall趋势检验法研究了天山南北坡相对湿度(RH)的时空变化特征,分析了天山南北坡RH对平均气温、降水量、平均风速、参考蒸散量、日照时数的敏感性,并探讨了引起RH变化的主导因素。结果表明：(1)整个天山地区RH变化有略微上升的趋势但不显著,北坡RH总体呈下降趋势,南坡RH总体呈上升趋势。(2) RH空间分布呈自北向南递减趋势,南北坡全年及春季以下降趋势为主,而夏、秋、冬三季均以上升趋势为主,且南坡变化趋势的显著性高于北坡。(3) RH对风速、气温、日照时数及参考蒸散量均为负敏感,对降水量为正敏感。北坡RH对各气象因子的敏感程度依次为日照时数>参考蒸散量>风速>气温>降水量,南坡敏感程度依次为日照时数>风速>参考蒸散量>气温>降水量。空间分布上,仅降水量敏感系数高值区位于北坡伊犁河谷,其余要素敏感系数高值区均位于南坡。(4)参考蒸散量是影响天山地区RH变化的主导因子,整个天山地区参考蒸散发贡献率较高,日照时数贡献率高值区集中于北坡伊犁河谷,风速、降水量、气温贡献率高值区均集中于南坡克孜勒苏地区。
关键词：天山南北坡;相对湿度(RH);差异;Mann-Kendall趋势检验法;敏感性分析
Daily meteorological data during 1966-2015 were used to analyze the spatio-temporal distribution characteristics of relative humidity (RH) in the north and south slopes of the Tianshan Mountains by using Mann-Kendall trend test. In addition, sensitivity coefficient and relative contribution were calculated to assess the impact of temperature, precipitation, reference evapotranspiration, wind speed and sunshine duration on RH. The results revealed that RH in the north slope exhibited fluctuating downward trend, but in the south slope it showed the opposite trend. Furthermore, the RH showed a rising gradient from south to north slope. As for seasonal RH, an upward trend was found in summer, autumn and winter, but a downward trend was observed in spring in the entire Tianshan Mountains. Sensitivity analysis indicated that RH was negatively related to temperature, reference evapotranspiration, wind speed and sunshine duration, but positively related to precipitation. Moreover, RH was the most sensitive to sunshine duration, reference evapotranspiration and wind speed, but precipitation was most insensitive, whether in north or south slope. Spatially, the high value area of sensitivity coefficient of precipitation was located in the Ili Valley, while others were located in the south slope. Contribution analysis suggested that the impact of reference evapotranspiration on RH was much larger than other factors. The high contribution area of sunshine duration was distributed in the Ili Valley (north slope), but that of wind speed, precipitation and temperature in Kizilsu (south slope).Keywords：North and south slopes of the Tianshan Mountains;Relative humidity (RH);Differences;Mann-Kendall trend test;Sensitivity analysis
Daily meteorological data during 1966-2015 were used to analyze the spatio-temporal distribution characteristics of relative humidity (RH) in the north and south slopes of the Tianshan Mountains by using Mann-Kendall trend test. In addition, sensitivity coefficient and relative contribution were calculated to assess the impact of temperature, precipitation, reference evapotranspiration, wind speed and sunshine duration on RH. The results revealed that RH in the north slope exhibited fluctuating downward trend, but in the south slope it showed the opposite trend. Furthermore, the RH showed a rising gradient from south to north slope. As for seasonal RH, an upward trend was found in summer, autumn and winter, but a downward trend was observed in spring in the entire Tianshan Mountains. Sensitivity analysis indicated that RH was negatively related to temperature, reference evapotranspiration, wind speed and sunshine duration, but positively related to precipitation. Moreover, RH was the most sensitive to sunshine duration, reference evapotranspiration and wind speed, but precipitation was most insensitive, whether in north or south slope. Spatially, the high value area of sensitivity coefficient of precipitation was located in the Ili Valley, while others were located in the south slope. Contribution analysis suggested that the impact of reference evapotranspiration on RH was much larger than other factors. The high contribution area of sunshine duration was distributed in the Ili Valley (north slope), but that of wind speed, precipitation and temperature in Kizilsu (south slope).
Keywords：North and south slopes of the Tianshan Mountains;Relative humidity (RH);Differences;Mann-Kendall trend test;Sensitivity analysis
本文引用格式
图1天山南北坡气象站点分布图
Fig. 1Distribution of meteorological stations in the north and south slopes of the Tianshan Mountains
2.2.1 Mann-Kendall趋势检验法
2.2.2 相对贡献率
（1）
（2）
式中,y ̂为因变量标准化值;xi、bi分别为自变量标准化值及对应的回归系数;ηi为xi变化对y ̂变化的相对贡献率;其中i=1,2,…,k,k为自变量个数。
2.2.3 敏感性分析
（3）
式中,Fi为某一气象要素序列的第i个值;RHi为RH序列的第i个值;F和 RH分别为气象要素与RH的多年平均值;ε为该气象要素的敏感性系数,ε为正表明RH随着该气象要素的增加而增加,为负则表明RH随着气象要素的增加而减小,敏感系数的绝对值越大,敏感性越强。
3.1.1 RH空间分布特征
图2天山地区年平均相对湿度的空间分布
Fig. 2Spatial distribution of annual relative humidity in the north and south slopes of the Tianshan Mountains
天山南北坡RH具有明显的季节变化特征,北坡多年月平均RH从8月开始呈递增趋势,至12月达到最大值77%;12月至次年5月逐渐减小,5月达到最小值46%;5月至8月呈波动变化态势。南坡多年月平均RH从4月起逐渐增大,至12月达到最大值67%;12月至次年4月逐渐减小,4月达到最小值39%。从季节上看,整个天山地区RH值均在冬季最高,春、夏季节最低。
3.1.2 RH年际变化特征
图31966—2015年天山南北坡相对湿度年际变化趋势
Fig. 3Trends of annual relative humidity in the north and south slopes of the Tianshan Mountains during 1966-2015.
(a) North slope, (b) South slope, (c) the Tianshan Mountains
3.1.3 RH变化趋势的空间分布
图41966—2015年天山南北坡四季和年平均相对湿度变化趋势的空间分布
Fig. 4Spatial distribution of variation trend of relative humidity in the Tianshan Mountains during 1966-2015.
(a) spring, (b) summer, (c) autumn, (d) winter, (e) annual scale
南坡春季RH以下降趋势为主,仅库车站呈显著上升;夏、秋、冬三季RH均以上升趋势为主,3个季节RH呈显著上升的站点共有15个,呈显著下降的站点有9个;全年RH以显著上升趋势占主导,7个站点表现为显著上升,3个站点表现为显著下降。此外,乌恰与库尔勒年尺度和季节尺度RH变化均不显著。结果表明,南坡呈显著变化趋势的站点明显多于北坡,这可能是受南坡复杂自然条件的影响。
3.2.1 RH对气象因子的敏感性分析
Table 1Seasonal sensitivity coefficient of meteorological variables in the Tianshan Mountains
注：表中数字分别对应为“北坡/南坡”的敏感系数。
通过对比敏感系数的绝对值可知,北坡RH变化对各气象因子的敏感程度由高到低依次为日照时数、参考蒸散量、平均风速、平均气温及降水量。不同季节RH变化对气象因子的敏感性略有差异。春、秋、冬三季RH变化均对日照时数最为敏感,夏季对平均气温最为敏感。
就天山南坡而言,RH变化对日照时数的敏感程度最高,其次是风速、参考蒸散量与气温,对降水量的敏感程度最低。对于不同季节而言,春、夏季RH对参考蒸散量最为敏感,秋、冬季则对日照时数最为敏感。
图5天山南北坡各气象因子敏感系数空间分布
Fig. 5Spatial distribution of sensitivity coefficients for (a) reference evapotranspiration, (b) precipitation, (c) sunshine duration, (d) average temperature and (e) average wind speed in the Tianshan Mountains
3.2.2 RH变化的主导因子
自然条件下,气象因子与RH之间既相互联系又相互制约,相对贡献率可定量分析各气象因子对RH的影响,RH变化的主导因子即相对贡献率最大的气象因子。分析表明,北坡参考蒸散量为RH变化的主导因子,贡献率达46.30%,与敏感性分析结果相似;其次是日照时数(21.60%)、平均气温(16.05%)、降水量(15.48%)、平均风速(0.58%),可见受复杂地形及其他因素的影响,风速的变化对北坡RH的作用并不大。对于南坡,贡献率最大的仍为参考蒸散量,达32.16%;其次为平均风速(28.09%)、降水量(22.20%)、日照时数(12.13%)、平均气温(5.42%)。相对于北坡而言,南坡地形更为开阔平坦,风速的增加会导致水汽大范围扩散,并且由于水汽输送量明显少于北坡,所以降水量对南坡RH变化的贡献率明显较大。
Table 2Seasonal relative contributions by meteorological variables to relative humidity change in the Tianshan Mountains
注：表中数字分别对应为“北坡/南坡”的相对贡献率。
图6天山南北坡各气象因子相对贡献率空间分布
Fig. 6Spatial distribution of relative contributions for (a) reference evapotranspiration, (b) precipitation, (c) sunshine duration, (d) average temperature, and (e) average wind speed in the Tianshan Mountains
利用天山南北坡26个气象站1966—2015年的逐日气象资料,对该地区RH的时空变化特征进行了分析,并探讨了引起RH变化的主要影响因子。主要结论如下。
(1)近50年来天山地区年RH变化趋势不显著。天山北坡多年平均RH为60%,呈下降趋势;南坡多年平均RH为52%,呈上升趋势。
(2)天山地区RH空间分布整体呈现自北向南递减趋势,即北坡RH高于南坡;南北坡全年及春季RH均以下降趋势为主,夏、秋、冬三季则以上升趋势为主,由于南坡自然条件复杂,北坡RH变化趋势的显著性明显低于南坡。
(3)天山地区RH对风速、气温、日照时数和参考蒸散量均为负敏感,对降水量为正敏感。北坡年RH对各气象因子的敏感程度依次为日照时数>参考蒸散量>风速>气温>降水量;春、秋、冬三季RH变化对日照时数最为敏感,夏季对气温最为敏感。南坡RH对各气象因子的敏感程度依次为日照时数>风速>参考蒸散量>气温>降水量;春、夏季RH对参考蒸散量敏感程度最高,秋、冬季则对日照时数敏感程度最高。空间分布上,仅降水量敏感系数高值区位于北坡伊犁河谷,其余要素敏感系数高值区均位于南坡。
(4)参考蒸散量是影响天山地区年尺度和季节尺度RH变化的主导因子。除参考蒸散外,北坡春、夏、冬三季气温对RH的贡献率最大,秋季则是日照时数;南坡春、夏两季气温对RH贡献率最大,秋季为风速,冬季为降水量。空间分布上,日照时数贡献率高值区集中于北坡伊犁河谷地区,风速、降水量、气温贡献率高值区均集中于南坡克孜勒苏地区。