| Water vapor plays an important role in the atmosphere,not only as a major source of precipitation,but also as an important driver of the atmospheric water cycle.s one of the key parameters characterizing climate change,the phase change of water vapor causes a range of weather phenomena such as rain,snow and fog,and its drastic changes also play an important leading effect in the occurrence and development of extreme weather events.Water vapor is also a more important greenhouse gas than methane and CO2,and by virtue of its positive feedback effect with temperature,it determines the global warming trend and is an important contributor to the greenhouse effect.The Qinghai-Tibet Plateau is known as the "Roof of the World" and the "Third Pole of the Earth" due to its unique topography,and is also China’s climate initiation zone.Due to its high altitude,its surface can directly heat the middle and upper troposphere atmosphere,transporting water vapor to higher levels.In the context of global warming,the water vapor balance of the plateau is linked to the droughts and floods in its vicinity and in Asia as a whole,as surface evaporation and other effects on global warming processes become more important.The study of atmospheric precipitable water,the transport characteristics of water vapor and the relationship between water vapor,precipitation and temperature on the Tibetan Plateau is therefore of great importance to the analysis and understanding of climate change on the Tibetan Plateau and its surrounding areas.In this paper,the three meteorological elements of atmospheric precipitable water,surface temperature and precipitation in climate change are studied using EOF decomposition,SVD decomposition and correlation analysis.The spatial and temporal distribution of atmospheric precipitable water over the period 1979-2021 is analyzed,and the transport of water vapor and its relationship with temperature and precipitation in the Tibetan Plateau region is also explored.The main work and conclusions of this paper are as follows.(1)The accuracy of the water vapor product of the ERA5 reanalysis data set was assessed based on accurate sounding station water vapor data.The results show that the ECMWF provided ERA May mean atmospheric precipitable water with sounding station data of 0.9 mm MAE and 1.05 mm RMSE,and annual mean atmospheric precipitable water with MAE of 0.78 mm and RMSE of 0.63 mm.This indicates that the reanalysis information is of high accuracy and can be used to analyze changes in atmospheric precipitable water in the Tibetan Plateau region.(2)The analysis of atmospheric precipitation available on the Tibetan Plateau from 1979 to 2021 shows that the overall atmospheric precipitation available on the Tibetan Plateau is lower than that in the surrounding areas and is spatially unevenly distributed,decreasing in a southeast to northwest direction.Atmospheric precipitable water over the plateau has tended to increase over the last 43 years at a rate of about 0.2 mm/10 a.There are clear seasonal variations in atmospheric precipitation in the highlands,with the highest and fastest increasing atmospheric precipitation in summer and the lowest and slowest increasing atmospheric precipitation in winter.The results of the EOF analysis indicate a good convergence of atmospheric precipitable water in the Qinghai-Tibet Plateau region,with a consistent variation across the region.(3)The water vapor transport characteristics of the Tibetan Plateau were obtained by calculating NCEP reanalysis data providing specific humidity data,longitudinal and latitudinal wind data and elevation data,and the results indicate that water vapor flows into the plateau from the western and southern boundaries and out of the plateau from the eastern boundary.The entire plateau region is a zone of water vapor irradiation,with irradiation levels ranging from 0-3 mm/d.The results of the SVD analysis show that there is a close spatial coupling between atmospheric precipitable water,surface temperature and precipitation,and that when atmospheric precipitable water increases or decreases,surface temperature and precipitation increase or decrease simultaneously.(4)The correlation analysis of PWV and ZTD in the Qinghai-Tibet Plateau region for 2019-2021 shows that the correlation coefficient between the two exceeds 0.9 in most areas of the Qinghai-Tibet Plateau,and their scatter plots indicate a good linear relationship,which leads to the construction of a direct conversion coefficient grid model for PWV and ZTD in the Qinghai-Tibet Plateau region.The accuracy of the model was validated using the 2022 PWV data provided by the ERA5 reanalysis data and an RMS of 0.945 mm was obtained,indicating a good accuracy of the model. |
