藏北牧区牲畜掉膘期温度变化特征

 利用西藏那曲地区1971-2005年日平均气温≤-5℃的初终日、持续时间及期间的负积温、平均气温、最高气温、最低气温等资料，采用气候倾向率等方法分析了近35 a来藏北牧区牲畜掉膘期及期间温度要素的变化趋势和异常年份。结果表明：藏北各牧区牲畜掉膘期开始日均呈现推迟趋势，平均推迟2.1～4.9 d/10 a；终日变化不显著；掉膘期持续时间均呈现缩短趋势。掉膘期间各牧区平均气温呈升高趋势，≤-5℃的负积温为减少趋势。掉膘期持续时间年代际变化呈明显的下降趋势，20世纪90年代掉膘持续时间短，有利于牧业生产。

Temperature Changes in the Period of Livestock-Losing-Weight in Northern Tibet from 1971 to 2005

Using the data of the livestock-losing-weight period (defined as the daily mean temperature≤-5℃) including the starting date, ending date, and duration, and the data of the negative accumulated temperature, mean temperature, mean maximum and minimum temperatures in the period of livestock-losing-weight from 1971 to 2005 in Nakchu district of Tibet, the variation trends of various temperatures in this region were analyzed by climatic linear trend method. The main findings can be summarized as follows: in the past 35 years, the starting date postponed at an average rate of (2.1-4.9) d/10a in various pastoral areas in northern Tibet; the ending date showed no significant changes, and the duration displayed an obvious shortening tendency. In addition, during the period of the livestock-losing-weight in the 35 years, the mean temperature exhibited an increasing trend, and the negative accumulated temperature (≤-5℃) a decreasing trend in pastoral areas. In the 1990s, the period of livestock-losing-weight was shorter, and therefore there is advantage in husbandry production.