Journal Article
Atmospheric Chemistry and Physics, vol. 22, iss. 10, pp. 6749-6771, 2022
Authors
Yun Lin, Jiwen Fan, Pengfei Li, Lai-yung Ruby Leung, Paul J. DeMott, Lexie Goldberger, Jennifer Comstock, Ying Liu, Jong-Hoon Jeong, Jason Tomlinson
Abstract
Abstract. A large fraction of annual precipitation over the western United States
comes from wintertime orographic clouds associated with atmospheric rivers
(ARs). Transported African and Asian dust and marine aerosols from the
Pacific Ocean may act as ice-nucleating particles (INPs) to affect cloud and
precipitation properties over the region. Here we explored the effects of
INPs from marine aerosols on orographic mixed-phase clouds and precipitation
at different AR stages for an AR event observed during the 2015 ACAPEX field
campaign under low dust (<0.02 cm−3) conditions. Simulations
were conducted using the chemistry version of the Weather Research and
Forecasting Model coupled with the spectral-bin microphysics at 1 km grid
spacing, with ice nucleation connected with dust and marine aerosols. By
comparing against airborne and ground-based observations, accounting for
marine INP effects improves the simulation of AR-precipitation. The marine
INPs enhance the formation of ice and snow, leading to less shallow warm
clouds but more mixed-phase and deep clouds, as well as to a large spillover
effect of precipitation after AR landfall. The responses of cloud and
precipitation to marine INPs vary with the AR stages, with more significant
effects before AR landfall and post-AR than after AR landfall, mainly
because the moisture and temperature conditions change with the AR
evolution. This work suggests weather and climate models need to consider
the impacts of marine INPs since their contribution is notable under low
dust conditions despite the much lower relative ice nucleation efficiency of
marine INPs.
