青藏高原积雪异常的持续性研究

Persistence of the Snow Anomalies on the Qinghai-Tibetan Plateau

选取青海省和西藏自治区境内的 72个气象站 ,自建站至 1999年 12月逐日观测的积雪深度资料 ,规定凡观测到地面有 0 .5cm以上积雪深度的日子作为积雪日 ,分别统计了月、冬春、年的积雪日数 .通过对积雪日数的分析 ,确定出高原冬春积雪的异常年份 ,分析了这些异常年份高原积雪的持续特征 .结果表明 :高原冬春总体积雪的异常主要是由 11月至翌年 3月的积雪异常决定的 ,高原冬春的积雪异常和春末夏初的积雪异常是不相一致的 ;一般来讲 ,高原积雪负异常至少持续 4个月 ,大多数年份要持续 6个月以上 ;积雪正异常个别年份可持续 6个月 ,一般为 2～ 4个月 ,积雪的持续正异常一般到 3月份就结束了 ;高原冬春总体积雪的正负异常都很难持续到春末夏初 ,高原冬春异常多积雪的大规模消融期在 2月末到 3月初 .

By using the data of daily snow depth from the month of station built to December 1999 at 72 meteorological stations over the Qinghai- Tibetan Plateau, according to the rule that the snow cover day indicates the day which the snow depth ≥0.5 cm, the monthly, the winter-spring and the annual number of snow cover days are summarized. The anomalous winter-spring snow years are determined and the persistence characters of the snow anomaly on the Qinghai-Tibetan Plateau are analyzed. It is showed that the anomalies of the winter-spring snow cover are mainly decided by the snow anomalies from November to March, and arent in accordance with the ones in May and June. The negative anomalies can persist for 4 months at least in general and more than 6 months in most years, while the positive anomalies can last for 6 months in individual year and 2～4 months in general with ending in March in general. It was hardly happened that the positive or negative anomalies of the winter-spring snow persist to May and June. The main melting season of the snow in snowy winter-spring occurs from the later of February to the early of March. The snow of the winter- spring exists mainly on some high mountains. It is showed that there are four regions of the maximal value in the distribution map of the snow cover days observed by the stations. These regions are the northern slopes of the Himalaya Mountain, the region from the west of the South Qinghai Plateau to the North Tibetan Plateau, the East Plateau Pasturing Region from the eastern slopes of the Bayan Har Mountains to the southern slopes of the Anyêmaqên Mountain, the southern slopes of the Qilian Mountains in the northeastern Qinghai Province.