中国植被类型区大气增温趋势及其不对称性研究

利用1962~2011年中国各植被类型区的452个站点的气温资料,分析了各植被类型区的年平均温度和极端温度随时间的变化趋势。结果表明：① 过去50 a间,中国各植被类型区年平均气温、年平均最高温、年平均最低温都显著升高,并且最低温增温速度快于最高温增温速度,呈温差减小的不对称增温趋势;同时,寒冷地区增温速度高于温暖地区的增温速度,其中寒温带森林的增温幅度超过亚热带森林的2倍。近30 a间,寒温带森林区和温带森林区增温速度减缓,其他各植被类型区增温速度加快,呈现出热带、亚热带地区增温速度高于温带、寒温带地区的空间特点;② 最高温增温速度在变快,最低温增加速度在变慢,多个植被类型区的最高温增温速度高于最低温增温速度,呈现出一种新的不对称增温趋势,即最高温与最低温间的温差在加大;③ 过去50 a和近30 a间,生长季和非生长季的温度变化多样,并分别对年平均温度产生了不同的影响,而生长季和非生长季温度的不同变化分别决定于其最高温和最低温的多样变化。

Rising Air Temperature and Its Asymmetry Under Different Vegetation Regions in China

The long-term trends of annual mean temperature (T_mean), mean maximum temperature (T_max) and minimum temperature (T_min) were analyzed across 453 weather stations from 1962-2011 across 8 vegetation regions according to China vegetation regionalization. During the past 50 years, T_mean, T_max and T_min increased significantly in all vegetation regions. In addition, the slope of temperature increase of T_min was greater than that of T_max. There was significant difference in slopes between T_max and T_min for all vegetation regions except for cold temperate forest, subtropical and tropical forests, showing asymmetric warming in temperature over time, i.e. the difference between T_max and T_min was gradually reduced. Over the recent 30 years, T_mean, T_max and T_min increased significantly for all vegetation regions except for T_max in temperate forest and T_min in temperate cold forest. The rate of temperature increase gradually increased for T_max, but decreased for T_min over the recent 30 years. The rate of temperature increase of T_max tended to be slower than that of T_min on alpine steppe, cold temperate forest and subtropical forest regions, but faster on the rest of vegetation regions. However, no significant difference was detected for the rate of temperature increase between T_max and T_min in any other vegetation regions. The temperature in growing season and non-growing season varied greatly and had different effects on T_mean during the past 50 years and recent 30 years. The changes of temperature in growing season and non-growing season were depended on changes of T_max and T_min. For growing season, T_mean, T_max and T_min increase significantly during the last 50 years for all vegetation regions except for warm forest region. In addition, the slope of temperature increase for T_min was greater than that of T_max, showing asymmetric warming with reduced difference between T_max and T_min. There was significant difference in rate of temperature increase between T_max and T_min on temperate forest, temperate steppe, temperate desert and warm forest regions, but no difference on alpine steppe, cold forest, subtropical and tropical forest regions. Over the recent 30 years, T_mean, T_max and T_min in growing season increased significantly for all vegetation regions. In general, the rate temperature increase accelerated for T_max but reduced for T_min. For non-growing season, T_mean, T_max and T_min increase greatly during the last 50 years for all vegetation regions, showing an asymmetric warming in temperature with reduced difference between T_max and T_min. There was significant difference in slope of temperature increase between T_max and T_min for most of vegetation regions except for cold temperate forest, subtropical and tropical forest regions. However, there were not significant differences in the rates of temperature increases for T_mean, T_max and T_min on some regions, such as cold temperate forest, temperate forest and temperate steppe region, in non-growing season during over the recent 30 years. For the rest of vegetation regions, T_mean, T_max and T_min increased significantly at a faster rate for T_max and a slower rate for T_min.