Spatial and temporal characteristics of atmospheric water vapour content and its relationship with precipitation conversion in China during 1980-2016

Atmospheric precipitable water (PW) is the basis of precipitation (P) formation, and the spatial difference between them is one of the focus of water resources research. Based on daily P from 552 meteorological stations and four reanalysis datasets during 1980-2016, the spatial-temporal pattern of PW and precipitation conversion rate (PWCR) in China are investigated using the whole layer atmospheric PW calculation formula, univariate linear regression, and inverse distance weighting. Results showed that ERA-Interim reanalysis seems to match the magnitude and pattern of P over China with small regional differences. At daily scale, an increase (decrease) in P was connected with an increase (decrease) of PW in most regions, and the temporal change showed that PW was highest in summer and lowest in winter. Across China, the mean daily PW for CFSR, ERA-Interim, JRA 55, and NCEP-1 varied between 41.18-48.43 mm, 39.02-43.13 mm, 37.41-41.79 mm, and 43.06-48.33 mm, respectively in summer and between 11.67-13.79 mm, 10.21-11.87 mm, 9.96-11.83 mm, 11.92-13.73 mm in winter. The spatial pattern of PW showed increased moisture over the southwest, with a maximum positive trend of about 0.25 mm per day, particularly over the Tibet Plateau. Moreover, summer and autumn had the highest and lowest PWCR, respectively. During summer, PWCR for CFSR, ERA-Interim, JRA 55 and NCEP-1 ranged between 8.3-11.9%, 8.1-9.7%, 10.3-11.7% and 9.4-14.1%, while in autumn, 6.4-9.8%, 5.9-7.7%, 7.1-9.5%, and 8.1-12.3% were reported, respectively. Therefore, the potential of P arising from PW was great in summer. The PWCR had a declining trend from east to west and from south to north in space and the regional fluctuation was large, making the regional development potential of atmospheric water resources obvious. These results that lead to a better understanding of water vapour conversion over China will help to rationally develop and utilize atmospheric water resources.