念青唐古拉山脉西部水热过程及其环境响应研究
摘要：被称为“地球第三极”的青藏高原深刻影响着我国及东亚乃至北半球天气气候；同时作为众多冰川的集中地，青藏高原也是我国大江大河的发源地；低温干旱又使得高原生态环境十分脆弱。随着气候变暖，冰川加速退缩、极端气候重复出现、土地沙漠化等问题接踵而至；这些问题，都归结于水热的变化。然而由于高原环境恶劣，在一些典型区域鲜有系统的观测研究。念青唐古拉山脉西段是高原寒冷气候带和温暖气候带的分界线，区域内冰川、冻土、湿地和西藏第一大湖—纳木错湖共存，能水循环和交换过程复杂，生态系统多样，是进行各种研究的理想地点。本论文作为众多研究的一部分，利用自2005年来在该区域南北坡架设的自动气象站、雨量筒和临近国家气象站40多年数据结合遥感NDVI研究了该区域地面和土壤水热过程、水热特征的NDVI响应及变化，为促进对高原典型区域的水热特征、能水平衡和交换以及该区域草场变化的理解和研究都有一定的意义。
1 念青唐古拉山脉西部地面水热过程
利用6台自架气象站数据分析了该区域气温、相对湿度的季节和日变化特征并进行了简单对比，发现气温和相对湿度都主要受海拔控制，随海拔升高而减小。气温日变化升温剧烈而降温平缓，春季比其他季节剧烈；湖边的日变化幅度较其他区域大，非冰雪覆盖区域比冰雪表面区域大。纳木错湖在冷季对周边的气温影响更加明显，致使湖周气温年较差比其他区域大。除了气温和降水之外，下垫面情况（冰川、湖面、草甸）和坡向、风向也对相对湿度大小有较大影响，致使其局地性和季节性都比较明显。夏季风期间相对湿度日变化幅度保吉最大，非夏季风期间则是冰川垭口最大，南坡5,100 m处最小。
利用7个自计雨量筒数据分析了该区域夏季风降水的特征，研究表明，总体上该区域南北坡夏季风期间受同一降水过程的影响，但受到纳木错湖和地形的影响，南北坡降水量、振荡周期和日变化过程都存在差异。北面区域的纳木错流域降水比高原整体水平更加频繁，降水量呈现了从西南向东北增加的分布特征，但不同方向的日变化和昼夜雨分布也存在差异。
2 念青唐古拉山脉西部土壤水热过程
利用自架气象站和国家气象站观测的土壤温湿度数据的研究表明：念青唐古拉山脉西部冻土比青藏高原大部分地区冻结迟，融化早；土壤热量状况具有明显的海拔效应和微弱的纬度效应。同时可能受到积雪状况、植被和土壤含水量差异的影响，不同观测点的地温年较差、土壤内热量传输速度的时间分布和日变化过程都存在较大差异。土壤含水量受土壤温度、积雪状况、降水量、地表蒸发、土壤性质和地下水状况等的影响，在冻结期和融化期皆没有表现出随深度变化的趋势，在季节变化上，北坡在冻结期和融化期有较明显的突变现象，而在纳木错湖边由于土壤性质和难于形成积雪，没有显现突变现象。三个冻融周期内，北坡在经过冻结过程之后土壤中水分有损失，而在湖边的保吉几乎没有。对北坡土壤水热的进一步分析表明，未冻水和降水下渗对土壤水热特征的影响显著，积雪融水对土壤热特征有微弱影响。
3 念青唐古拉山脉西部水热过程的NDVI响应及气候变化
响应于水热过程，念青唐古拉山脉西部植被主要在每年的6-10月期间生长。不同时间尺度上，该区域植被的主要控制因子不一样。在年尺度上热量和水分对南部植被生长都有较大影响，而在北部区域受热量的影响更加严重。生长季，降水情况更为严重影响了植被的生长。月尺度上，南部区域降水比较多，热量是主要控制因子，而北部区域同时受到热量和水分状况的影响。
临近6个国家气象站近40多年的气候数据表明，念青唐古拉山脉西部气温升高显著，升温速率以冬季最快，其次是秋季；北部区域气温升高比南部区域剧烈。升温过程使得该区域冻土退化显著，地表0 cm地温、40 cm深度在1985年前后升温幅度分别达1.1 ℃和0.8 ℃，1963-2006年期间80 cm地温最大升高了3.4 ℃；最大冻结深度减小速度高于青藏高原的平均水平。升温过程也使得该区域域植被得到改善。但非季风期降水（雪）的显著增加，以及升温导致的积雪融化提前，有可能导致严重的春季洪水。
Abstract：As called “the Third Pole of the earth”, the Tibetan Plateau influences the climate of China, eastern Asia, even the north hemisphere greatly. It is slso the source for big rivers in China as a lot of glaciers exist there. The ecosystem is quite vulnerable due to the cold and arid environment. With climate warming, many problems such as glacier retreat, extreme climate and desertification occurred often, which caused by the changes in heat and water conditions. But few systematic researches had been conducted in some typical regions due to the formidable environment. The western Mts Nyainquentanglha is the dividing line of cold and warm climate on the plateau, where glacier, frozen soils, wetland and the Nam Tso lake, the biggest lake in Tibet, are, and is a ideal site for scientific studies. This study investigated on air and soil hydrothermal processes and its NDVI response, as well as the changes with climate warming, which may improve the understanding on energy and water balance and exchange and environmental evalution in the mountain areas of the plateau.
1 Ground surface hydrothermal processes in the western Nyainquentanglha
Based on meteorological data from six automatic weather stations, the seasonal and diurnal variations of air temperature (Ta), precipitation and relative humidity (RH) are investigated during 2005-2007, analysis shows that Ta and RH are controlled by altitude firstly. Ta rises quickly and drops slowly in a day. The amplitude of diurnal variation is largest in spring in the region near Nam Tso lake, so do at the place where no glacier is found than that of glacier. The effect of Nam Tso lake is quite evident and make the difference between Ta and ground surface temperature larger in cold season.The RH is also influenced by the ground surface condition, aspect, wind direction, which is different in different area and season.
The similar daily and diurnal precipitation variations demonstrated the southern and northern slopes of Nyainquentanglha are controlled by the same precipitation processes. Due to the vapor and disturbance from the lake and topography, differences exist in the precipitation amount, oscillation periods and diurnal variation processes. The frequency of precipitation near the lake is higher than other areas, the precipitation increases from southwest to northeast and the diurnal variations are different in different part of the lake.
2 Soil hydrothermal processes in the western Nyainquentanglha
Based on soil temperature and moisture data, the results show the soils freeze later and thaw earlier in the western Nyainquentanglha than that in other regions of Tibetan Plateau. The altitude effect of soil thermal condition is evident. The annual range, temporal distribution of the transfer rate of heat within soil
and diurnal variation are quite different at different measurement site due to the impact of snow cover, vegetation and soil moisture. The soil moisture is influenced by soil temperature, snowcover, precipitation, evaporation, soil characteristics and ground water, no evident trend exists in the amount and the soil depth. It shows evident an abrupt change during freezing and thawing periods and get lost after freezing in northern slope except for the place near the lake. A further study indicates the soil hydrothermal condition is influenced by unfrozen water and the infiltration of precipitation greatly and gets weak impact from the infiltration of snow meltwater.
3 The NDVI response to hydrothermal condition and climate change in the western Nyainquentanglha
The vegetation grows from June to October. The growth of vegetation is controlled by temperature and water together in southern slope and by temperature evidently in northern slope at a growth period, while it is inverse at monthly scale. It is relied by precipitation greatly during growth season.
Climate warming is evident from 1963 to 2006 in the study region. The air temperature increase most quick in winter, then in autumn. Comparison, it is faster in northern slope than that in southern. As a result, the frozen soil degraded seriously, the ground temperature increased about 1.1 ℃at 0 cm depth and 0.8 ℃ at 40 cm depth respectively before and after 1985, it shown a maximum increase about 3.4 ℃ at 80 cm depth from 1963 to 2006. The decrease rate of the maximum freezing depth is higher than the average rate in the Tibetan Plateau. The evident increase of winter precipitation may result in spring flood. But the vegetation is better than before due to the climate warming
念青唐古拉山脉西部水热过程及其环境响应研究
摘要：被称为“地球第三极”的青藏高原深刻影响着我国及东亚乃至北半球天气气候；同时作为众多冰川的集中地，青藏高原也是我国大江大河的发源地；低温干旱又使得高原生态环境十分脆弱。随着气候变暖，冰川加速退缩、极端气候重复出现、土地沙漠化等问题接踵而至；这些问题，都归结于水热的变化。然而由于高原环境恶劣，在一些典型区域鲜有系统的观测研究。念青唐古拉山脉西段是高原寒冷气候带和温暖气候带的分界线，区域内冰川、冻土、湿地和西藏第一大湖—纳木错湖共存，能水循环和交换过程复杂，生态系统多样，是进行各种研究的理想地点。本论文作为众多研究的一部分，利用自2005年来在该区域南北坡架设的自动气象站、雨量筒和临近国家气象站40多年数据结合遥感NDVI研究了该区域地面和土壤水热过程、水热特征的NDVI响应及变化，为促进对高原典型区域的水热特征、能水平衡和交换以及该区域草场变化的理解和研究都有一定的意义。
1 念青唐古拉山脉西部地面水热过程
利用6台自架气象站数据分析了该区域气温、相对湿度的季节和日变化特征并进行了简单对比，发现气温和相对湿度都主要受海拔控制，随海拔升高而减小。气温日变化升温剧烈而降温平缓，春季比其他季节剧烈；湖边的日变化幅度较其他区域大，非冰雪覆盖区域比冰雪表面区域大。纳木错湖在冷季对周边的气温影响更加明显，致使湖周气温年较差比其他区域大。除了气温和降水之外，下垫面情况（冰川、湖面、草甸）和坡向、风向也对相对湿度大小有较大影响，致使其局地性和季节性都比较明显。夏季风期间相对湿度日变化幅度保吉最大，非夏季风期间则是冰川垭口最大，南坡5,100 m处最小。
利用7个自计雨量筒数据分析了该区域夏季风降水的特征，研究表明，总体上该区域南北坡夏季风期间受同一降水过程的影响，但受到纳木错湖和地形的影响，南北坡降水量、振荡周期和日变化过程都存在差异。北面区域的纳木错流域降水比高原整体水平更加频繁，降水量呈现了从西南向东北增加的分布特征，但不同方向的日变化和昼夜雨分布也存在差异。
2 念青唐古拉山脉西部土壤水热过程
利用自架气象站和国家气象站观测的土壤温湿度数据的研究表明：念青唐古拉山脉西部冻土比青藏高原大部分地区冻结迟，融化早；土壤热量状况具有明显的海拔效应和微弱的纬度效应。同时可能受到积雪状况、植被和土壤含水量差异的影响，不同观测点的地温年较差、土壤内热量传输速度的时间分布和日变化过程都存在较大差异。土壤含水量受土壤温度、积雪状况、降水量、地表蒸发、土壤性质和地下水状况等的影响，在冻结期和融化期皆没有表现出随深度变化的趋势，在季节变化上，北坡在冻结期和融化期有较明显的突变现象，而在纳木错湖边由于土壤性质和难于形成积雪，没有显现突变现象。三个冻融周期内，北坡在经过冻结过程之后土壤中水分有损失，而在湖边的保吉几乎没有。对北坡土壤水热的进一步分析表明，未冻水和降水下渗对土壤水热特征的影响显著，积雪融水对土壤热特征有微弱影响。
3 念青唐古拉山脉西部水热过程的NDVI响应及气候变化
响应于水热过程，念青唐古拉山脉西部植被主要在每年的6-10月期间生长。不同时间尺度上，该区域植被的主要控制因子不一样。在年尺度上热量和水分对南部植被生长都有较大影响，而在北部区域受热量的影响更加严重。生长季，降水情况更为严重影响了植被的生长。月尺度上，南部区域降水比较多，热量是主要控制因子，而北部区域同时受到热量和水分状况的影响。
临近6个国家气象站近40多年的气候数据表明，念青唐古拉山脉西部气温升高显著，升温速率以冬季最快，其次是秋季；北部区域气温升高比南部区域剧烈。升温过程使得该区域冻土退化显著，地表0 cm地温、40 cm深度在1985年前后升温幅度分别达1.1 ℃和0.8 ℃，1963-2006年期间80 cm地温最大升高了3.4 ℃；最大冻结深度减小速度高于青藏高原的平均水平。升温过程也使得该区域域植被得到改善。但非季风期降水（雪）的显著增加，以及升温导致的积雪融化提前，有可能导致严重的春季洪水。
Abstract：As called “the Third Pole of the earth”, the Tibetan Plateau influences the climate of China, eastern Asia, even the north hemisphere greatly. It is slso the source for big rivers in China as a lot of glaciers exist there. The ecosystem is quite vulnerable due to the cold and arid environment. With climate warming, many problems such as glacier retreat, extreme climate and desertification occurred often, which caused by the changes in heat and water conditions. But few systematic researches had been conducted in some typical regions due to the formidable environment. The western Mts Nyainquentanglha is the dividing line of cold and warm climate on the plateau, where glacier, frozen soils, wetland and the Nam Tso lake, the biggest lake in Tibet, are, and is a ideal site for scientific studies. This study investigated on air and soil hydrothermal processes and its NDVI response, as well as the changes with climate warming, which may improve the understanding on energy and water balance and exchange and environmental evalution in the mountain areas of the plateau.
1 Ground surface hydrothermal processes in the western Nyainquentanglha
Based on meteorological data from six automatic weather stations, the seasonal and diurnal variations of air temperature (Ta), precipitation and relative humidity (RH) are investigated during 2005-2007, analysis shows that Ta and RH are controlled by altitude firstly. Ta rises quickly and drops slowly in a day. The amplitude of diurnal variation is largest in spring in the region near Nam Tso lake, so do at the place where no glacier is found than that of glacier. The effect of Nam Tso lake is quite evident and make the difference between Ta and ground surface temperature larger in cold season.The RH is also influenced by the ground surface condition, aspect, wind direction, which is different in different area and season.
The similar daily and diurnal precipitation variations demonstrated the southern and northern slopes of Nyainquentanglha are controlled by the same precipitation processes. Due to the vapor and disturbance from the lake and topography, differences exist in the precipitation amount, oscillation periods and diurnal variation processes. The frequency of precipitation near the lake is higher than other areas, the precipitation increases from southwest to northeast and the diurnal variations are different in different part of the lake.
2 Soil hydrothermal processes in the western Nyainquentanglha
Based on soil temperature and moisture data, the results show the soils freeze later and thaw earlier in the western Nyainquentanglha than that in other regions of Tibetan Plateau. The altitude effect of soil thermal condition is evident. The annual range, temporal distribution of the transfer rate of heat within soil
and diurnal variation are quite different at different measurement site due to the impact of snow cover, vegetation and soil moisture. The soil moisture is influenced by soil temperature, snowcover, precipitation, evaporation, soil characteristics and ground water, no evident trend exists in the amount and the soil depth. It shows evident an abrupt change during freezing and thawing periods and get lost after freezing in northern slope except for the place near the lake. A further study indicates the soil hydrothermal condition is influenced by unfrozen water and the infiltration of precipitation greatly and gets weak impact from the infiltration of snow meltwater.
3 The NDVI response to hydrothermal condition and climate change in the western Nyainquentanglha
The vegetation grows from June to October. The growth of vegetation is controlled by temperature and water together in southern slope and by temperature evidently in northern slope at a growth period, while it is inverse at monthly scale. It is relied by precipitation greatly during growth season.
Climate warming is evident from 1963 to 2006 in the study region. The air temperature increase most quick in winter, then in autumn. Comparison, it is faster in northern slope than that in southern. As a result, the frozen soil degraded seriously, the ground temperature increased about 1.1 ℃at 0 cm depth and 0.8 ℃ at 40 cm depth respectively before and after 1985, it shown a maximum increase about 3.4 ℃ at 80 cm depth from 1963 to 2006. The decrease rate of the maximum freezing depth is higher than the average rate in the Tibetan Plateau. The evident increase of winter precipitation may result in spring flood. But the vegetation is better than before due to the climate warming