湖南双季稻区5月低温特征及预警信号研究

Study on Characteristics and Warning Signals of Chilling in May in Double Cropping Rice Area of Hunan Province

利用湖南双季稻区66个气象站1961-2013年5月逐日气温资料,建立5月低温强度指数,对5月低温的时空分布和强度特征进行分析,并采用大气变量物理分解法探寻5月低温天气过程的前期信号.结果表明：5月低温在研究区具有南少北多的地域特点,根据影响范围主要可分为全省一致型、湘中以北型和湘北型3种空间分布形态.5月低温过程强度较大,80％达中度及以上程度,影响范围较广,50％的低温过程影响双季稻区70％以上的站点.研究期内15次5月低温过程中有14次分别在850hPa和300hPa图上出现温度扰动和位势高度扰动负值中心,因此,通过追踪850hPa层的温度扰动能提前5～10d预测5月低温的出现.温度扰动的移动路径主要有东路、西北路和西路3条,且以东路为主.移动路径为东路时,出现湘北型5月低温概率最大,为西北路时,一般出现湘中以北型5月低温.

Based on daily temperature data of May from 66 meteorological stations in double cropping rice area of Hunan province during 1961 -2013, the intensity index of c in May（IICM） was calculated, which was used to analyze the characteristics of temporal and spatial distribution and intensity of chilling in May. The method of physical decomposition of atmospheric variables was used to find possible precursors to indicate c process in May. The results showed that in the studied area the distribution of chilling in May was less in the south than that in the north and there were three main types： whole province, north-middle Hunan,north Hunan. The intensity index of eighty percent of chilling processes in May were moderate or above and fifty percent of c processes in May effected on seventy percent of stations in double cropping rice area. During the study, fourteen processes occupied the negative center of temperature transient anomalies on the 850hPa level and the negative on the 300hPa level, respectively. The negative center of temperature traced as precursors to indicate the occurrence of c process in track of temperature transient anomalies had three, such as west road moving track. The chilling processes in May were north Hunan type generally they were north-middle Hunan type when the moving track center of geopotential height transient anomalies transient anomalies on the 850hPa level could be May over 5 -10 days in advance. The moving , northwest road and east road which was primary mainly when the moving track was east road and was north-west road.