湖南省近60年雨凇的气候特征

采用湖南97个地面气象站点气象观测资料、运用经验正交函数、旋转经验正交函数、一元线性回归、Mann-Kendall、小波分析等方法分析了湖南雨凇的时空分布特征及变化趋势,并与高山站的变化趋势进行了比较.结果表明:湖南雨凇发生在11月至翌年3月,空间分布特征呈现为南多北少、东多西少、迎风坡多、背风坡少、“三心二带”、高低交错.湖南雨凇日数空间分布既有全区一致性,也存在着南北反向变化的差异,空间分布大致可分为湖南南部、北部及中部、西北部3个异常区.湖南年雨凇日数和南岳高山站年雨凇日数呈现出的周期变化相同,即均存在2a、4a、9a和24 a左右的准周期,2a和4a周期尺度雨凇日数多和少转换频繁,9a周期尺度在1970年代末以前振荡明显,在24 a准周期尺度上经历了1960年代初期、1970年代中期、1990年代初期、2000年代中期4个转折年份.在过去60年全省年雨凇日数呈显著减少趋势,南岳高山站年雨凇日数趋势变化不明显,但存在明显的年际和年代际变化.

Climatological Features of the Glaze in Hunan Province in Recent 60 Years

Using observational data from 97 meteorological ground stations in Hunan Province, the temporal and spatial characteristics and the variation trend of the glaze of Hunan Province were analyzed by EOF (Empirical Orthogonal Function), REOF (Rotated Empirical Orthogonal Function), linear regression, Mann-Kendall mutation, and wavelet analysis and the variation trend was compared with the mountain station data. The results indicate that the glaze occurred mostly between November and March of the following year; the spatial distribution of glaze days showed a higher incidence in the South and East and to windward, and a lower incidence in the North and West and to leeward. There were two high value centers and three low value centers distributed among the high and low value regions. The spatial distribution of the number of glaze days showed characteristics of regional consistency and a discrepancy in the reverse variation between the south and north, which can be classified into three anomaly areas: South and North Hunan, Central and Northwest Hunan, and Northeast Hunan. The yearly glaze days in both Hunan and Nanyue station present the same periodic change of 2, 4, 9, and 24 years. The glaze days converse more or less frequently between period of 2 and 4 years. There is a clear oscillation pattern of 9-year glaze day before the late 1970s. The 24-year glaze day exists during the four transition years in the early 1960s, mid-1970s, early 1990, and mid-2000. There is a significant decreasing trend in the number of glaze days in Hunan over the past 60 years, while the variation tendency in Nanyue station is not obvious although significant inter-annual and inter-decadal variations exist in Nanyue station.