南沙永暑海区日照时数的变化特征及影响因素

Characteristics of the Variation of Sunshine Duration in the Waters of Yongshu Reef,Nansha Islands and Their Governing Factors

根据南沙永暑礁1989年1月—2011年12月的日照观测资料,采用线性趋势及Morlet小波分析等方法,对南海永暑海区日照时数和影响因素进行分析。结果表明:海区日照时数呈显著减少的趋势,平均每年减少14.94 h,1997年是日照时数由较强期到偏弱期的转折年;影响年日照时数重要因素为总云量和降水量,年平均温度与风速对年日照时数影响不明显。年日照时数与降水、总云量均呈显著的负相关关系;而与风速、温度相关不显著。

With data of sunshine observations of Yongshu Reef,Nansha Islands from January 1989 to December 2011,we studied the characteristics of 23-year variation of sunshine duration in the waters of Yongshu Reef in the South China Sea using the methods of linear trend and Morlet wavelet and examined the factors governing the sunshine duration. The result is shown as follows. The sunshine duration tends to decrease significantly by an average rate of 14. 94 h per year and 1997 was the year that witnessed the shift from a period of relatively long duration to one of relatively short duration. Total cloudage and rainfall amount are important factors governing the duration of sunshine while the annual mean temperature and wind speed do not have much effect on it. The annual sunshine duration is negatively correlated with the precipitation and the total cloudage,by a coefficient of- 0. 567 and- 0. 705,respectively,all surpassing the 0. 01 confidence level in the t- test. It is negatively( and insignificantly) correlated with the temperature,by a coefficient of- 0. 047,but positively correlated with the wind speed,by a rate of 0. 191. The annual sunshine duration is multiply( and significantly) correlated with the temperature,rainfall amount,cloudage and wind speed by a coefficient of 0. 74.