开都河流域上下游过去50 a气温降水变化特征分析

利用开都河流域上下游4个气象台站（上游巴音布鲁克，下游焉耆、和静、和硕）1960-2009年的气温、降水资料，采用趋势分析与距平等统计方法，分析了近50 a来开都河流域的主要气象要素变化特征。研究发现：（1）1960-2009年开都河流域上下游年平均气温均呈明显上升趋势，增长强度分别为0.27 ℃/10 a和0.22 ℃/10 a。2000年后气温升高尤其显著，上游和下游的气温分别较50 a平均水平偏高0.97 ℃和0.69 ℃。该流域年最高温没有明显增加，而上下游年最低气温分别上升0.41 ℃/10 a和0.61 ℃/10 a，并与年平均气温有较好的相关性。通过对不同年代际各月气温的分析，发现该地区气温季节性特征在过去50 a发生了明显的变化。主要表现为冬季气温总体上升，夏季气温相对稳定，冬季与夏季温差逐渐减小，季节性呈变弱趋势。上游年代际间气温季节变化较下游更明显；（2）开都河流域降水主要集中在夏季，近50 a上下游降水量均呈增加趋势且上游达显著水平。上下游在降水分布及变化特征上有较大差异，上游年平均降水总量（273 mm）明显高于下游（77 mm），且上游降水量增加强度（9.13 mm/10 a）高于下游（5.34 mm/10 a）。降水量年代际之间有一定差异，降水波动主要是在夏季，上游降水量的波动性大于下游。

Temperature and precipitation along the Kaidu River over the past 50 years

There is evidence of significant climate changes over the past decades in northwest China. Studies are needed to characterize changes in climate variables over space and time. In this study, we collected daily data of air temperature and precipitation for the period of 1960-2009 along the Kaidu River which is located at the south of the Tianshan Mountains in Xinjiang, northwest China. Four meteorological stations were included, i.e., the Bayinbuluke Station at the upstream, and the Yanqi Station, Hejing Station, and Heshuo Station at the downstream. For the downstream, we used averaged values from the available three stations. The statistical analyses (e.g., trend analysis and anomaly) were applied to compare the temporal variability of temperature and precipitation between the upstream and downstream, focusing on seasonal, interannual and interdecadal variations. Our analyses indicated that there were significantly increasing trends in the annual mean temperature and the annual minimum temperature over the past 50 years. In general, there was a good correlation between the annual minimum temperature and mean temperature in this region. While annual mean temperature showed a similar increasing trend (i.e., 0.27 ℃/10 a at the upstream and 0.22 ℃/10 a at the downstream), the annual minimum temperature revealed a greater increasing trend at the downstream (0.61 ℃/10 a) than at the upstream (0.41 ℃/10 a). On average, the annual mean temperature over the most recent decade was 0.97 ℃ higher at the upstream and 0.69 ℃ higher at the downstream relative to those averaged over the past 50 years. Further analyses demonstrated that there were pronounced changes in temperature during the season of November – March at decadal time scale. In particular, the largest positive temperature anomalies in winter were found during the most recent decade at the upstream, and during the period of 1990-2009 at the downstream. Overall, there was a decreasing trend in the seasonality of temperature along the Kaidu River, despite of a considerable fluctuation at the upstream. Annual precipitation was higher at the upstream (273 mm) than at the downstream (77 mm), with majority during summer. There was an increasing trend in the annual precipitation, i.e., 9.13 mm/10 a (P< 0.05) at the upstream and 5.34 mm/10 a ([WTBX]P[WTBZ]= 0.07) at the downstream. In addition, there was a modest fluctuation in precipitation at seasonal to decadal time scales. The changes in temperature and precipitation over the past 50 years would have implications for the water cycle in this region.