陕西延安近50年极端气温变化及周期研究

Extreme temperature and its cycles in Yan'an of Shaanxi Province in recent 50 years

利用1962-2012年陕西省延安市每日气温资料,运用线性拟合及累积距平和Morlet复数小波等方法,对WMO发布的10种极端气温指数进行了计算和分析。结果表明,延安地区近50a来,极端最高气温、极端最低气温都有上升趋势,冰日、霜日、冷夜、冷日数量呈下降趋势,夏日、热夜、暖夜、暖日呈现波动上升。由20世纪60年代至今,各类极端天气现象的发生天数平均增加了6.61 d。极端最高气温、极端最低气温、夏日、热夜、冰日、暖夜都存在27a左右的周期,冰日、冷夜有5a左右或更短的周期。极端高温天数的增多会加大旱灾、森林和草原的防火压力,极端低温天数的减少易发生森林和草原的病虫灾害,应做好预防工作。

Using the daily air temperature data of Yan'an from 1962 to 2012,adopting the linear fitting,accumulative anomaly,Morlet complex wavelet method,we calculated and analyzed ten kinds of extreme air temperature indices released by WMO. Results show that the extreme maximum air temperature and extreme minimum air temperature in yan 'an region in recent 50 years have a rising trend,but the ice,frost,cold night,cold day' s numbers are on the decline,warm,hot summer night,warm night,warm day's numbers have fluctuating rise. Days of extreme weather phenomena have increased by an average of 6. 61 d since 1960 ' s. The extreme maximum temperature,minimum temperature,summer,hot night,ice day and warm night existed about 27 a cycle,ice day and cold night existed cycle of about 5a or less. Increase of extreme high temperature days will increase the drought and fire pressure of forest and grassland,decrease of extreme low temperature days is prone to forest and grassland pests and diseases. So,we should do good precaution work.