Changes of summer cloud water content in China from ERA-Interim reanalysis

Cloud plays an important role in regulating radiation and energy exchange, and the hydrological cycle. In this study, the variability of summer vertical integral cloud water content (VCWC) (sum of cloud liquid water content and cloud ice water content) from ERA-Interim reanalysis is investigated over China from 1979 to 2016. We divide the country into regions dominated by monsoonal and non-monsoonal influences, and the Tibetan Plateau. Relationships between summer VCWC and surface mean temperature, precipitation and precipitable water (PW) are investigated by singular value decomposition. Summer VCWC decreases from southeast to northwest with the largest values in the southwestern China. Summer VCWC has increased in the non-monsoon and Tibetan Plateau sub-regions with rates of 1.04 and 3.39 g/m²/decade respectively, which corresponds to an increase of PW, precipitation and surface mean temperature. Summer VCWC has decreased by −2.71 g/m²/decade in the monsoon sub-region, related to decreased precipitation and PW as well as increased surface mean temperature. Temperature rises (decreases) will strengthen (weaken) the atmospheric circulation in favor of increased (decreased) summer VCWC in the non-monsoon/Tibetan Plateau sub-region, but weaken (strengthen) the climate systems in the monsoon sub-region. This explains the contrasting correlations between temperature and summer VCWC in the different regions, suggesting summer VCWC in China is moderated by atmospheric circulation through combined influences of surface mean temperature and PW.