近50年青藏高原气候变化及其对农牧业的影响

Climate Change over the Qinghai-Tibet Plateau and Its Impacts on Local Agriculture and Animal Husbandry in the Last 50 Years

本文主要讨论了青藏高原最近50年的气温、降水以及其它气候因子变化及对农牧业的影响。青藏高原气温呈上升趋势,平均最低气温的升高趋势大于平均最高气温的升高趋势。青藏高原降水量呈东南向西北地区逐渐递减的分布规律,降水量大都集中在夏季,主要降水量分布在东南部及雅鲁藏布江河谷农区及藏东农林区等,而整个青藏高原的西北部的大部分地区降水量极其匮乏,降水量与高原的草场类型分布有很好的对应。近几十年来,高原东部和西南部都以增温、增湿为特点有利于牧草生产,而柴达木盆地西侧以及祁连山地区略有变干趋势对牧草生产不利。多年冻土呈现区域性退化状态,高原湿地也呈现退化趋势,气候变化对当地农牧业影响显著,冬季气温升高延长了小麦生长期,对小麦的生长有利,但同时病虫害越冬基数也增加,对农作物不利;荒漠化及气候不稳定因素的增加、异常天气增多等将导致对农牧业生产极为不利的影响。

Annual average trends of average temperature, minimum temperature, maximum temperature, and precipitation on a daily timescale from 47 stations across Qinghai and Tibet during the period 1961-2010 were analyzed using the least square method. Impacts on local agriculture and animal husbandry caused by changes in temperature, precipitation, and other climatic factors were discussed. In general, the Qinghai-Tibetan plateau showed an increasing trend in temperatures, with the magnitude of increase in average daily minimum temperature greater than that of average daily maximum temperature. In addition, annual average temperature increased during the past five decades. There was a small increase of 0.3℃/10a in southeast Tibet. Northern Tibet, and southern and northern Qinghai showed a （0.3~0.4）℃/10a increasing trend. A increasing rate of （0.5~0.9）℃/10a occurred in Lhasa and Nagqu in central Tibet, and Golmud and Mangya in northwestern Qinghai. There was an increasing trend of （0.4~0.5）℃/10a at Banma and other observational stations across southeast Qinghai. The amount of precipitation in the Tibetan Plateau gradually declined from southeast to northwest, mainly concentrated in the south-eastern Tibetan Plateau, Brahmaputra valley agricultural areas, and forestry areas in eastern Tibet. Southeast and northwest Qinghai showed an increase in precipitation of less than 5 mm/10a. Northern Tibet and southern and northern Qinghai ranged （5~10）mm/10a. Over central Tibet and north-central of Qinghai, precipitation mainly increased at rates of （10~20）mm/10a. Individual sites over the southeastern Tibetan Plateau showed increasing trends in precipitation larger than 20 mm/10a. However, most parts of the northwest of the entire Tibetan Plateau did not have rainfall, with the rainfall being in accordance with the distribution of pastures in the plateau. Climate warming would lead to increases in evapotranspiration from agriculture and ecological systems. Changes in spatial and temporal distributions of precipitation would change effective utilization of vegetation, thereby affecting agricultural and ecological purposes. The permafrost was reducing regionally as well as plateau wetlands. Increased winter temperatures, on the one hand, would accelerate the growth rate of winter wheat. On the other hand, rising temperatures would lead to increased demand for agricultural water use. Degrading capacity to adapt to climate change due to desertification of pastures, degradation of wetland permafrost, increases in unstable climatic factors, and abnormal weather would lead to significant adverse effects to agriculture and animal husbandry over the study regions.