Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 15, 6535-6548, 2015
https://doi.org/10.5194/acp-15-6535-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
15 Jun 2015
Impact of interannual variations in sources of insoluble aerosol species on orographic precipitation over California's central Sierra Nevada
J. M. Creamean1,2,*, A. P. Ault2,**, A. B. White1, P. J. Neiman1, F. M. Ralph3,***, P. Minnis4, and K. A. Prather2,3 1NOAA Earth System Research Laboratory, Physical Sciences Division, 325 Broadway St., Boulder, CO 80304, USA
2Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA
3Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA
4NASA Langley Research Center, 21 Langley Blvd., Hampton, VA 23681, USA
*now at: Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Box 216 UCB, Boulder, CO 80309, USA
**now at: Department of Environmental Health Sciences and Department of Chemistry, University of Michigan, 500 S State St., Ann Arbor, MI 48109, USA
***now at: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
Abstract. Aerosols that serve as cloud condensation nuclei (CCN) and ice nuclei (IN) have the potential to profoundly influence precipitation processes. Furthermore, changes in orographic precipitation have broad implications for reservoir storage and flood risks. As part of the CalWater field campaign (2009–2011), the variability and associated impacts of different aerosol sources on precipitation were investigated in the California Sierra Nevada using an aerosol time-of-flight mass spectrometer for precipitation chemistry, S-band profiling radar for precipitation classification, remote sensing measurements of cloud properties, and surface meteorological measurements. The composition of insoluble residues in precipitation samples collected at a surface site contained mostly local biomass burning and long-range-transported dust and biological particles (2009), local sources of biomass burning and pollution (2010), and long-range transport (2011). Although differences in the sources of insoluble residues were observed from year to year, the most consistent source of dust and biological residues were associated with storms consisting of deep convective cloud systems with significant quantities of precipitation initiated in the ice phase. Further, biological residues were dominant (up to 40%) during storms with relatively warm cloud temperatures (up to −15 °C), supporting the important role bioparticles can play as ice nucleating particles. On the other hand, lower percentages of residues from local biomass burning and pollution were observed over the three winter seasons (on average 31 and 9%, respectively). When precipitation quantities were relatively low, these insoluble residues most likely served as CCN, forming smaller more numerous cloud droplets at the base of shallow cloud systems, and resulting in less efficient riming processes. Ultimately, the goal is to use such observations to improve the mechanistic linkages between aerosol sources and precipitation processes to produce more accurate predictive weather forecast models and improve water resource management.

Citation: Creamean, J. M., Ault, A. P., White, A. B., Neiman, P. J., Ralph, F. M., Minnis, P., and Prather, K. A.: Impact of interannual variations in sources of insoluble aerosol species on orographic precipitation over California's central Sierra Nevada, Atmos. Chem. Phys., 15, 6535-6548, https://doi.org/10.5194/acp-15-6535-2015, 2015.
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Short summary
Aerosols impact how clouds and precipitation form. In the California Sierra Nevada, we found that the formation and resulting amount of rain and snow were impacted by mineral dust, bioparticles such as bacteria, and biomass burning and pollution particles during three winter seasons. Dust and bioparticles from distant sources impacted high-altitude clouds by forming ice, leading to more precipitation, whereas local biomass burning and pollution entered the base of clouds, leading to less rain.
Aerosols impact how clouds and precipitation form. In the California Sierra Nevada, we found...
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