Atmospheric Moisture Transport Associated with Precipitation in Present and Simulated Future Climates

Abstract

Abstract Precipitation and the atmospheric moisture budget are analyzed for 40-yr periods of recent and future climate simulated by the 10 CMIP6 models from which the vertically integrated moisture flux data are available. This allows new assessments of this important atmospheric transport, which can typically only be approximated. Seasonal climatological fields are compared with those from the ERA5 reanalysis. Using the four-season average M skill score for the globe, precipitation from the 10 models is similar in skill to that from a further 25 models. The scores for six moisture variables, including flux and its convergence, demonstrate global skill for each model. The 10-model average fields have better skill than any individual model. Changes are calculated for 2040–79 under the SSP5-8.5 forcing scenario. The focus is on the 10-model average scaled as a projection of change for a global warming of 2°C. The changes in precipitation, temperature, and pressure in each season are largely consistent with those from the larger ensemble. The changes in flux, convergence, water column, and winds at three levels are presented. The role of convergence in balancing precipitation changes over many land regions is evident. Flux, convergence, and precipitation are shown in detail for selected cases, including central North America, the South American monsoon, southern Africa in summer, southern South America in winter, Europe in summer, and both polar regions. Typically, flux is enhanced, but the associated convergence may shift. The production of the vertically integrated flux vector as a standard output from climate models is supported.