【作者】 樊红芳；

【导师】 张虎才；

【作者基本信息】 兰州大学 ， 自然地理， 2008， 博士

【摘要】 联合国政府间气候变化专门委员会在巴黎发表的气候变化评估报告说,气候变暖已经是“毫无争议”的事实,人为活动“很可能”是导致气候变暖的主要原因。研究表明,现在二氧化碳的增加和全球变暖的程度是最近上千万年所没有的,只有在新生代早期才有过类似的状况。因此,地球科学界正在将预测未来气候变化的研究重点一部分放到对地球过去气候变化的研究上,以此来更好地理解气候变化的原因、过程及其结果,从而为未来地球生态环境系统的可能预测提供相似型的科学依据。号称“世界屋脊”的青藏高原,幅员辽阔、地势高亢,其地约占我国陆地面积的1/4,平均海拔4500米以上,年轻的地质历史、独特的自然地理环境、复杂的生物区系组成,特别是高原隆起对其自然环境及周边气候的影响一直引起人们的深切关注和孜孜不倦的探求。为此,本文利用先进的数据处理软件及绘图软件,对所有的月平均地面气温和月平均大气降水数据进行精确的处理,以期分析在全球气候变暖的大背景下,青藏高原区在1936～1964年、1965～1977年和1978～2000年三个时间段的气候变化特点,了解青藏高原区不同海拔高度气温变化的异同以及气温变化与海拔高度、经纬度三者之间的关系,探悉青藏高原内部不同区域气温变化所存在的差异、大地形的存在对周边地区气候所产生的影响,与青藏高原邻区相比是否体现了高原在气候变化上的驱动机和放大器作用。本文通过研究得到以下主要结论:(1)在全球气候变暖的大背景下,青藏高原区与全球相比升温幅度较大,1965～1977年全球气温变化和缓,基本稳定,1978～2000年全球气温呈迅速上升趋势,青藏高原区在前一时间段气温上升幅度较大,青藏高原区在后一时间短上升幅度较小,高原区提前进入气温迅速上升时期,这一点可能验证了高原区作为气候变化放大器的学说(潘保田等,1996)。(2)青藏高原及其邻近地区23年来年平均气温呈整体上升趋势,且上升幅度与海拔高度有关,海拔高度小于2500m、2500～3000m、3000～3500m、3500～4000m、大于4000m不同高度范围内相应的春季气温年际增温率是0.033、0.035、0.036、0.040、0.046℃/a,冬季的是0.038、0.039、0.030、0.031、0.024℃/a,夏季是0.024、0.033、0.031、0.020、0.038℃/a,年平均是0.034、0.039、0.037、0.032、0.036℃/a,高海拔(2500m以上)地区上升幅度普遍大于低海拔(2500m以下)地区,但在海拔2500m以上的区域并不是随着高度的上升增温率一直呈增加趋势,而是呈降低的趋势;春季高原上随海拔高度上升变暖幅度加大;冬季高原上随海拔高度上升变暖幅度减小;同一高度范围内的气温变化冬季的增温幅度普遍大于夏季(海拔大于4000m高度范围例外);高原上1981年夏季气温异常偏高,1983年冬季气温异常偏低。(3)高原36年(1965～2000年)来总体情况是降水量在增加,但在不同季节,不同区域增加的幅度存在一定的差异。从季节上讲,春季和夏季呈明显增加的趋势,增幅分别为8.20mm和11.23mm。从区域上讲位于高原东北部青海区的降水明显减少,如大柴旦站春、夏、秋、冬降水量的变化值分别是3.76mm,-14.86mm,-1.09mm,0.67mm,春季和冬季是增加的,增加的幅度与夏季减少的值比起来显得太小了,所以年平均值还是减少的,具体数值为-11.52mm。呈明显增加趋势的区域是位居高原东南部的江河谷地,如贡山和波密增加的量分别是166.35mm,145.95mm。(4)兹格塘错区域的气候变化特征:(a)不考虑年际变化,兹格塘错1970,1977,1992,2001,2006五年间湖泊面积是逐渐增大的。(b)分析该区的气象数据可以看出,该区那曲、班戈、安多自1970到2000年年均温度有明显增高,增高幅度为0.45℃/10a、0.32℃/10a和0.16℃/10a,年均温度的增高主要是夏季温度的增高,冬季温度没有明显变化。三个站点的降水量也有增加,表现在夏季和冬季降水都有增加。气候变化会对湖泊面积的变化产生一定影响,可能的原因是夏季和冬季降水的增加以及蒸发能力的减弱导致了兹格塘错湖面面积的增大。(5)通过对1206个气象台站1961～1990年月平均气温数据的处理分析,得到三个关系式:T=-0.0041·H+16.91、T=-0.0020·H-0.3210·N+26.24、T=-0.0020·H-0.2692·N-0.0216·E+26.21(其中T代表年平均气温,H代表海拔高度,N代表纬度,E代表经度),能够通过0.01信度检验服从第一个关系式的有342个台站,台站分布主要位于高原东部,服从第二个关系式的有332个台站,台站分布主要位于高原东南部,服从第三个关系式的台站有251个,台站分布主要位于高原东北部,剩下281个台站相对前面三组台站来说位居高原的比较多,这可能与高原特殊的大地形有关,至于台站分布的具体原因,还有待于做进一步的分析研究。(6)位居青藏高原东部的长江流域地区在气温与海拔高度之间存在着这样的关系式:T=-0.0046·H+18.2725(其中T代表年平均气温,H代表海拔高度)更多还原

【Abstract】 IPCC (Intergovernmental Panel on climate change) at Paris presented a record stating that global warming trend has become clear and it has been widely accepted that human activities are the dominant factors. The latest studies show that the significant increase trends of the atmosphere carbon dioxide concentration and the temperature can only be observed in the climatic records of early Cenozoic. Therefore, amounts of interest s have been invoked in the driving forces of past climate changes and especially those of geologically abrupt warming events; the knowledge about the driving forces, processes and the influences of past climate change can help us better understand the current climatic changes. The Tibetan Plateau, with an average elevation of 4500 m, account for a quarter of China’s land. It is the highest plateau on the earth, and known as "the roof of the World". It attracts many scholars to explore tirelessly and concerned deeply because it’s young geological history, unique geography environment and complex biogeographic realm, especially about the plateau uplift and the climate vary. In order to investigate the temperature changes at different altitudes on Tibet Plateau area and the relationship of temperature vary with elevation height, latitude and longitude; the different temperature vary in different Tibetan Plateau area; Tibetan Plateau influence to the surrounding area, we applied advanced data analysis and graphic software to deal with the average month ground temperature and precipitation data in the three period: 1936 to 1964,1965 to 1977,1978 to 2000.The chief results obtained in this study as follow:(1) Under conditions of global climatic changing warming, the area in Tibetan plateau, comparing to the global climate, in which the temperature rising is more tantivy. From 1965 to 1977,the global climatic changed little and stabilization. Then it became uplifted fast in 1978 to 2000, besides, the trend of the air temperature ascending extent is larger in the former than the latter time in Tibetan plateau. The climatic changing warming is earlier than other places, which might prove the theory that Tibetan plateau is a amplifier of global climatic changing(Pan Baotian et al,1995,1996)(2) The temperature and elevation in Yangtze River valley of which is located in the eastern of Tibetan Plateau have the relationship of T=-0.0046×H+18.2725 (T represents average temperature, H represents elevation); (3) Three relationships were obtained by processing temperature data collected from 1206 observatories, they are: T= -0.0041×H+16.91, T= -0.0020×H-0.3210×N+26.24, T= - 0.0020×H-0.2692×N-0.0216×E+26.21 (T represents average temperature, H represents elevation, N represents latitude, E represents longitude). There are 342 observatories could pass the 0.01confidence testing of the first relationship, which mainly located in the eastern of the Tibetan Plateau; there are 332 observatories could pass the 0.01confidence testing of the second relationship, which mainly located in the southeast of the Tibetan Plateau; there are 251 observatories could pass the 0.01confidence testing of the third relationship, which mainly located in the northeast of the Tibetan Plateau. The other 281 observatories chiefly situated on the Tibetan Plateau. This phenomenon probably link to the plateau topography, but the cause need further investigation.(4) The average temperature was increasing from past 23 years in the Tibetan Plateau and surrounding area and the extent is linked to the elevation. The annual spring temperature increase rate in the elevation of less than 2500m, 2500m to 3000m, 3000m to 3500m, 3500m to 4000m, more than 4000m are 0.033, 0.035, 0.036, 0.040, 0.046℃/a, respectively; and in winter are 0.038、0.039、0.030、0.031、0.024℃/a, respectively; and summer are 0.024、0.033、0.031、0.020、0.038℃/a, annual average values are 0.034、0.039、0.037、0.032、0.036℃/a. In general, the change amplitude of temperature above 2500m of the plateau is more than the elevation below 2500m. However, the change amplitude of temperature shows decreasing trend above 2500m. The rate of warming trend increase accompany with the elevation rising in spring, whereas the rate of warming decreases accompany with the elevation rising in winter. The rate of warming trend of winter is greater than summer in the same elevation (the elevation of above 4000 m is exception); summer temperature in 1981 is abnormally high and winter temperature in 1983 is abnormally low.(5) Generally speaking the precipitation is increasing in recent 36 years, but the increasing extent exists some differences in different seasons, different regions. The precipitation increased obviously and the amplitudes are 8.20mm and 11.23m. However the precipitation is decreasing distinctly in the northeast of the Tibetan Plateau, such as the Dachaidan observatories which the precipitation varies are 3.76mm, -14.86mm, -1.09mm, 0.67mm in spring, summer, autumn and winter, respectively. Although the precipitations in spring and winter had increased, the total annual values also decreased and the amount is -11.52mm. The precipitation of the rivers and valleys in the southeast of the plateau exhibited distinctly increasing trend, such as Gong Mountain and Bomi Mountain which are 166.35mm and 145.95mm respectively. We tentatively identify the June to September as the flood season and its distribution characteristics are precipitation increased in the eastern Qinghai region and reduce in the south, whereas the precipitation in the south of Tibetan Plateau, southeast and North Tibet Plateau increased obviously. Since the 1980, the flood season increased obviously in the Tibetan especially in the Yarlungzangbo River, whereas precipitation significantly reduced in the eastern part of Qinghai Rivers particularly in the source area of the river. Another characteristic of the plateau precipitation is the inverse change trend in the North and South from which basically along with the Tanggula Mountain. According to this boundary, Tibetan Plateau could be divided into two regions—west area (Tibetan area) and north area (Qinghai area). In Qinghai area, the precipitation in 1970 is more than in 1980 and the turning point is 1990. Tibetan area displayed unique variation in winter and spring. In the late 1970s to the 1990s the precipitation became more. Actually, flood season precipitation represents the annual rainfall changes. Precipitation in Qinghai and Tibetan Plateau in flood season has inverse relationship but this relationship is not strong just because the difference between the two mutations and rainfall in Qinghai area is lag than Tibetan area.(6) Climate variation characteristics of Zigetongco region are described as follow: (a) the lake area of Zigetangco is increasing gradually from 1970,1977,1992, 2001, 2006 years if the annual change of the lake area is not considered, (b) the annual temperature of the Nagqu, Bangor and Anduo areas increased significantly since 1970 to 2000 years, the temperature change extent are 0.45℃/ 10 a, 0.32℃/ 10 a and 0.16℃/10a, respectively. The average annual temperature is higher in summer but did not change significantly in winter. The precipitation in summer and winter of the three observatories has also increased obviously.Climate changes probably have certain impacts on the Lake area variation. The lake area of the Zigetangco expanded gradually these years and it might be due to the precipitation increased and evaporation decreased in summer and winter.更多还原