Recent Aircraft Observations of High Aerosol Loadings in the Northern Hemisphere Pacific

Recent aerosol and trace gas measurements from the HIAPER Pole-to-Pole Observations (HIPPO) study provide insight into the role of synoptic-scale variability on the intercontinental transport of pollutants between Asia and North America. These observations offer relevant upstream context for the CalWater study region. Four HIPPO campaigns with the NSF/NCAR G-V aircraft have been completed over all four seasons and include over 500 vertical profiles from 0.30 to 14 km altitude between 85°N and 67°S latitude in the remote Pacific and Arctic regions. The aerosol observations in the northern hemisphere Pacific exhibit large variability between and also within each season. Very polluted conditions were encountered over a deep portion of the troposphere in large-scale plumes in the springtime north Pacific midlatitudes and subtropics from anthropogenic and biomass-burning sources in Asia. Observations of black carbon (BC) mass loadings across the intertropical convergence zone show large interhemispheric gradients in boreal spring. The northern hemisphere BC mass loadings account for over 90% of the pole-to-pole burden of BC mass in the remote Pacific during this time of year. The goal of this analysis, directly relevant to CalWater science objectives, is to identify and characterize the role of aerosol-induced precipitation in major precipitation events (e.g., landfalling atmospheric rivers) along the west coast of the US. Here we first present the HIPPO observations and then lay the groundwork for an analysis that examines these data in the context of the large-scale meteorological flow and satellite-derived precipitation patterns to address this potentially important impact of anthropogenic and biomass-burning aerosol.