Response Of Main Hydrological And Ecological Elements Of Lhasa River Basin To Climate Change

The Lhasa River Basin is located in the central-south part of the Qinghai-Tibet Plateau,and its special geographical location makes the area highly sensitive to climate change.A large number of observation data indicate that the Qinghai-Tibet Plateau is one of the most significant and sensitive regions in response to global climate change,so it is an important region to study climate change.Since the 1980s,with the acceleration of industrialization and the increasingly fierce climate change,the global climate has become warmer overall,the Qinghai-Tibet Plateau has become more warming,and obvious changes have taken place in the water resources cycle,glaciers,frozen soil,and ecosystems on the Qinghai-Tibet Plateau.The abnormal changes in the climate will also increase the degradation of vegetation.In-depth study of climate change in the region is helpful to clarify the impact of climate change on the hydro-ecological environment,so as to avoid risks for sustainable development.This article takes the Lhasa River Basin as an example,based on the measured meteorological data and remote sensing data of ground stations,using mathematical statistics,spatial interpolation,model simulation and other methods to analyze the characteristics of climate elements changes,evolution laws and climate change caused by the ecological environment.The main conclusions reached are as follows:1.The law of climate change in the Lhasa River Basin is as follows:interannual temperature,precipitation,rainfall erosion,and water vapor pressure show an increasing trend,while wind speed and sunshine hours show a decreasing trend.The distribution of rainfall during the day is characterized by less daytime and more nighttime.The spatial distribution of air temperature shows a pattern of high in the west and low in the east;the spatial distribution of precipitation and water vapor pressure is basically the same,all showing the characteristics of increasing from northeast to southwest.The wind speed shows the spatial distribution pattern of high east and low west,high south and low north.In the future,the temperature in the central region of the river basin will have an upward trend,while the temperature in the east and west will have a downward trend.There is a continuous increase in precipitation,and the basin will be in a relatively humid state.2.In the context of climate change,each climate element is affected by natural factors to varying degrees.The increase in rainfall is mainly caused by the increase in rainfall intensity and days of rainfall.The change of water vapor pressure is mainly controlled by precipitation,which shows a positive correlation with air temperature,ET₀,relative humidity,and precipitation;it shows a negative correlation with wind speed and sunshine hours.Air temperature is the main controlling factor for wind speed changes.Sunshine hours are mainly affected by precipitation,wind speed,relative humidity,and maximum temperature.3.Climate change affects various elements of the hydrological cycle.The ET₀ in the Lhasa River Basin as a whole showed a downward trend,and the spatial distribution showed a pattern of high in the middle and low on the sides.The rising temperature indicates that there is a"evaporation paradox"phenomenon in the watershed,and ET₀ may continue to decrease in the future.The wet and dry index showed a downward trend as a whole,and the spatial distribution was basically consistent with the precipitation distribution,both decreasing from west to east.The increase in moderate-intensity rainfall caused the rainfall erosion of the watershed to increase,and the conditions of surface runoff have changed.Due to the comprehensive influence of various climatic factors,the climate of the river basin tends to be humidified.4.The interannual variation of NPP in the Lhasa River Basin showed a decreasing trend overall.Its spatial distribution is consistent with the distribution of vegetation coverage and has spatial differentiation,which is closely related to the distribution of local hydrothermal conditions.In the Lhasa River Basin,62.75%of the regional NPP degraded to be affected by climate change,and 36.25%of the regional NPP increased due to human activities.The precipitation in the basin is relatively small due to the climate type.Although the increase in temperature is beneficial to photosynthesis,the uneven distribution of precipitation leads to a certain degree of drought,which causes a certain degree of vegetation degradation.In recent years,with the promulgation of national policies and the enhancement of people's awareness of ecological and environmental protection,vegetation has been restored in areas where human activities are occurring.