广宁县1971—2020年低温和霜冻变化特征

On the Variation Characteristics of Chilly Temperatures and Frosts of Guangning County from 1971 to 2020

利用广宁站(59271)1971—2020年逐日最低气温和最低裸地温度的气象资料,并采用数理统计、Mann-Kendall突变检验、滑动t检验和Morlet小波分析等方法对广宁县低温、霜冻日数变化特征进行分析。结果表明:广宁县年低温、霜冻日数平均为17.6和2.8 d,低温、霜冻日数每10年减少2.7和1.7 d,总体上低温期与霜冻期呈缩短趋势,其中近年来霜冻出现次数趋近于零。12月至次年2月是霜冻和低温天气集中出现期,其中12月出现最多低温日数,平均日数为6.9 d;最多霜冻日数出现于1月,平均日数为4.1 d。低温、霜冻存在多重时间周期尺度上的嵌套结构现象,其中低温突变年份为1972、1973、1978和1984年;霜冻突变年份为1972和1975年。

Using the daily meteorological data of minimum temperature for both the air and bare land surface at the Guangning station(site No.:59271)from 1971 to 2020 and with the methods of mathematical statistics,Mann⁃Kendall abruptness test,running t⁃test and Morlet wavelet analysis,this work analyzes the variation characteristics of the number of days with chilly temperatures and frosts in the county.The results are shown as follows.For the county of Guangning,the annual average numbers of days with chilly tempera⁃tures and frosts are 17.6 and 2.8 d respectively,and the number of days with chilly temperatures and frosts decrease by 2.7 and 1.7 d respectively every 10 years.The duration of chilly temperatures and frosts show a generally shrinking trend and frosts tend to disappear in recent years.Chilly temperatures and frosts mainly take place from December to the following February,with December having the most number of chilly⁃tem⁃perature days(6.9 d on average),and January having the most number of frosty days(4.1 d on average).Chilly temperatures and frosts are nested together on multiple time scales with the former experiencing abrupt changes in 1972,1973,1978 and 1984,and the latter in 1972 and 1975,respectively.