Calendar Event Details
AEROCENTER: Vandana Jha
Affiliation: Colorado State University
Event Date: Tuesday, September 1, 2015
Location: G133
Time: 11:00 AM
Potential impacts of dust and pollution aerosol on orographic precipitation in the Colorado River Basin
The Southwest United States has huge demands on water resources. The Colorado River Basin (CRB) covers the states of Colorado, Wyoming, Utah, Nevada, Arizona, New Mexico, and California as well as Mexico and serves 27 million people. Those in the CRB are potentially affected by anthropogenic aerosol pollution and dust acting as cloud-nucleating aerosol as well as impacting snowpack albedo. Painter et al., (2010) estimated that heavy dust loading in the San Juan Mountains of Colorado results in earlier peak runoff by 3 weeks, and increases evapotranspiration from earlier exposure of vegetation and soils, leading to decreases in annual runoff by more than 1.0 Billion Cubic Meters. The specific objectives of this research is to quantify the impacts of both dust and pollution aerosols on wintertime precipitation in the Colorado Mountains. The combined effects of dust serving as ice nuclei (IN), giant cloud condensation nuclei (GCCN), and cloud condensation nuclei (CCN) on precipitation, in combination of anthropogenic pollution aerosol and, in particular, on water resources in the CRB has been examined. This has been done for the entire winter season of 2005. We hypothesize that dust will enhance precipitation, while aerosol pollution will reduce water resources in the CRB via the “spill-over” effect. Since dust is more episodic and aerosol pollution is more pervasive throughout the winter season, we anticipate that the combined response to dust and aerosol pollution is a net reduction of water resources in the CRB. The question is by how much are those water resources affected. The Colorado State University (CSU) Regional Atmospheric Modeling System (RAMS) version 6.0 is used for this study. RAMS was modified to ingest GEOS-CHEM output data and periodically update aerosol fields. GEOS-CHEM is a chemical transport model which uses assimilated meteorological data from the NASA Goddard Earth Observation System (GEOS). The aerosol data comprise a sum of hydrophobic and hydrophilic black carbon and organic aerosol, hydrophilic SOAs, hydrocarbon oxidation and inorganic aerosols (nitrate, sulfate and ammonium). In addition, a RAMS-based dust source and transport model is used. In addition to the seasonal runs, sensitivity studies were also performed. The sensitivity studies are 5 different kinds. The base study has dust OFF with only the aerosol sources ON. The Case 2 has both the dust and aerosol pollution data ON. The Case 3 has the aerosol sources ON with dust multiplied by a factor of 3. Case 4 has the aerosol sources ON with dust multiplied by a factor of 10. Case 5 and Case 6 are the simulations where dust can act only as CCN and only as IN respectively. It was found that the precipitation increases when dust is increased 3 times. However, the response is non-monotonic when dust is increased 10 times and the response depends on the environmental conditions. Dust acting as CCN acts in opposition to dust acting as IN. In general, dust acting as IN tends to enhance precipitation in wintertime orographic clouds.