Temporal And Spatial Distribution Characteristics Of Global Precipitable Water Based On Multiple Datasets

This research utilizes three datasets of IGRA radiosonde dataset,COSMIC satellite GPS RO retrievals and NCEP reanalysis dataset for the period of 2007 to 2016 to analyze distributions and trends of global precipitable water vapor.Also,station observations of precipitation in Fuzhou are analyzed for characteristic research.Here are the main conclusions.After comparing monthly average precipitable water of different stations in different latitudes and altitudes,the smaller differences among these three datasets in higher latitudes are found.And the differences are larger with stations in lower latitudes and higher altitudes.Also,the relationship between monthly zonal average precipitable water vapor retrieved from IGRA radiosonde observations and COSMIC retrievals is better than IGRA and NCEP's.The larger values of IGRA precipitable water in large value zone(>30mm)are found.The zonal average distribution of precipitable water from three datasets is studied as well as the zonal distribution of differences and bias.The results show linear change of the differences between IGRA and COSMIC in low latitude and largest bias of IGRA and smallest of NCEP.Based on the relationships and differences among three datasets,the distributions of global precipitable water are studied.The global map of seasonal precipitable water has three largest value zones in the tropical area and precipitable water decreases by the latitude till the polar areas.Also,these three maxima areas show shift motions in different seasons.The trends of precipitable water of IGRA and COSMIC have distinct differences over land and ocean areas.The precipitable water over land shows an overall increasing trend and over ocean in low latitude,the precipitable water has been descending for last ten years.Finally,the characteristics of precipitable water and precipitation of stations are further explored.Two elements do not show a significant relationship but the increase amount of annual precipitation and decrease of frequency in annual precipitation and trace precipitation.The precipitation conversion rate is also studied for the relationship between precipitation and precipitable water in Fuzhou station and Shenyang station.The rate is quite small,which means the transport of water vapor is the main source of precipitation.