Abstract:

Based on the observation data of 46 meteorological stations in Qinghai during 1961-2015, the spatial-temporal characteristics and influence factors of total cloud cover were analyzed by using the empirical orthogonal function (EOF) and Mann-Kendall test. The results show that the maximum total cloud cover was 64%, the minimum was 48%, and the average was 57% in Qinghai. The total cloud cover showed a decreasing trend with the average rate of -0.006% a-1, and the maximum was -0.187% a-1, which passed the significant level of 0.05. The abrupt change of the total cloud cover occurred in 1979. From EOF analysis of total cloud cover anomaly, the variance contribution rate of the first pattern reached 49.97%, which presented the consistency change feature of total cloud cover in Qinghai, while the second pattern showed an opposite change of total cloud cover for the northern and southern parts of Qinghai, and the third pattern corresponded well with the complex landforms of Qinghai Province, which was influenced by the large mountains. The correlation coefficients were calculated between time coefficients of the first three patterns from EOF of total cloud cover anomaly and meteorological factors. The time coefficient of the first pattern was negatively correlated with temperature and sunshine hours, but positively correlated with relative humidity, precipitation and evaporation. The time coefficient of the second pattern was closely and negatively related to temperature, and positively related to humidity, sunshine hours and evaporation.

Key words:  total cloud cover, distribution characteristics, climate indices, meteorological factors

摘要：

利用青海省46个地面观测站1961—2015年云量观测资料，采用经验正交函数（EOF）分解、Mann-Kendall检验等方法，分析青海省总云量的时空变化特征及影响因子。结果表明：青海省总云量多年平均最大值为6.4成，最小值为4.8成，平均值为5.7成；总云量总体呈减少趋势，线性倾向系数为-0.006成·a-1，云量线性倾向系数减少最大值为-0.018 7成·a-1，通过0.05显著性水平；1979年为总云量变化突变年。总云量距平场EOF展开第1模态方差贡献率为 49.97%，为主要模态，反映了全省总云量一致型变化特征；第2模态显示了总云量南北变化相反的特征；第3模态与青海省复杂的地貌对应较好，是受高大山脉影响的一种分布模态。分析总云量距平场展开前3模态相应时间系数与气象要素的相关，发现第1模态相应时间系数（PC1）与温度、日照时数呈负相关，与湿度、降水量、蒸发量呈正相关；第2模态相应时间系数(PC2)与温度呈显著负相关，与湿度、日照时数、蒸发量呈正相关。

关键词:
总云量, 分布特征, 气侯指数, 气象要素