Increased winter precipitation over the North Pacific from 1984-1994 to 1995-2005 inferred from the Global Precipitation Climatology Project

An analysis of the results from the Global Precipitation Climatology Project (GPCP) reveals a trend of increased wintertime precipitation over the North Pacific from 1984 to 2005. The precipitation over the North Pacific increases by about 1.5 mm/year in winter during the period of 1984 to 2005. Statistic analyses are performed to validate the observed precipitation trend, showing the f-test and t-test significances of greater than 99%. A cloud-resolving weather research and forecast (CR-WRF) model with a two-moment bulk microphysical scheme is employed to consider the effects of an increasing Asian pollution outflow on wintertime precipitation over the North Pacific. The CR-WRF simulations demonstrate more precipitation with elevated polluted continental aerosols than that with typical maritime aerosols, reproducing the observed precipitation trend. The results suggest that the increasing Asian pollution outflow represents one of the most plausible explanations for the increased precipitation trend observed in winter over the North Pacific, likely with important climate implications.