The role of lateral boundary conditions in simulations of mineral aerosols by a regional climate model of Southwest Asia
- 123 Downloads
The importance of specifying realistic lateral boundary conditions in the regional modeling of mineral aerosols has not been examined previously. This study examines the impact of assigning values for mineral aerosol (dust) concentrations at the lateral boundaries of Regional Climate Model version 3 (RegCM3) and its aerosol model over Southwest Asia. Currently, the dust emission module of RegCM3 operates over the interior of the domain, allowing dust to be transported to the boundaries, but neglecting any dust emitted at these points or from outside the domain. To account for possible dust occurring at, or entering from the boundaries, mixing ratios of dust concentrations from a larger domain RegCM3 simulation are specified at the boundaries of a smaller domain over Southwest Asia. The lateral boundary conditions are monthly averaged concentration values (μg of dust per kg of dry air) resolved in the vertical for all four dust bin sizes within RegCM3’s aerosol model. RegCM3 simulations with the aerosol/dust model including lateral boundary conditions for dust are performed for a five year period and compared to model simulations without prescribed dust concentrations at the boundaries. Results indicate that specifying boundary conditions has a significant impact on dust loading across the entire domain over Southwest Asia. More specifically, a nearly 30% increase in aerosol optical depth occurs during the summer months from specifying realistic dust boundary conditions, bringing model results closer to observations such as MISR. In addition, smaller dust particles at the boundaries have a more important impact than large particles in affecting the dust loading within the interior of this domain. Moreover, increases in aerosol optical depth and dust concentrations within the interior domain are not entirely caused by inflow from the boundaries; results indicate that an increase in the gradient of concentration at the boundaries causes an increase of diffusion from the boundaries. Lastly, experiments performed using a climatology of dust concentrations yield similar results to those using actual monthly values. Therefore, using a climatology of dust mixing ratios is sufficient in implementing lateral boundary conditions for mineral aerosols. In short, this work concludes that realistic specification of lateral boundary conditions for mineral aerosols can be important in modeling the dust loading over arid regional climates such as Southwest Asia.
KeywordsMineral aerosols Regional climate modeling Southwest Asia Dust Boundary conditions
The authors are grateful to all members of the Eltahir group and M.I.T. Parsons Laboratory that contributed in some way to this work. This work has been funded through support by the Kuwait Foundation for the Advancement of Science.
- Abdou WA, Diner DA, Martonchik JV, Bruegge CJ, Kahn RA, Gaitley BJ, Crean KA, Remer LA, Holben B (2005) Comparison of coincident multiangle imaging spectroradiometer and moderate resolution imaging spectroradiometer aerosol optical depths over land and ocean scenes containing aerosol robotic network sites. J Geophys Res 110:D10S07CrossRefGoogle Scholar
- Dickinson R, Henderson-Sellers A, Kennedy P (1993) Biosphere atmosphere transfer scheme (BATS) version 1e as coupled to the NCAR Community Climate Model. Technical report, National Center for Atmospheric ResearchGoogle Scholar
- Giorgi F, Mearns L, Shields C, McDaniel L (1998) Regional nested model simulations of present day and 2xco2 climate over the Central Plains of the US. Clim Change 40:457–493Google Scholar
- Grell G, Dudhia JJ, Stauffer D (1994) A description of the fifth-generation Penn State/NCAR Mesoscale Model (MM5), Technical Note TN-398+IAGoogle Scholar
- Kahn RA, Nelson D, Garay M, Levy R, Bull M, Diner D, Martonchik J, Paradise S, Hansen E, Remer L (2009) Misr aerosol product attributes and statistical comparisons with modis. Geosci Remote Sens 47:4095–4114Google Scholar
- Kalnay E, Kanamitsu M, Kistler R, Collins W, Deaven D, Gandin L, Iredell M, Saha S, White G, Woollen J, Zhu Y, Leetmaa A, Reynolds B, Chelliah M, Ebisuzaki W, Higgins W, Janowiak J, Mo K, Ropelewski C, Wang J, Jenne R, Joseph D (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77:437–471CrossRefGoogle Scholar
- Kiehl J, Hack J, Bonan G, Boville B, Breigleb B, Williamson D, Rasch PJ (1996) Description of the ncar community climate model (ccm3). Technical Note TN-420+STR, National Center for Atmospheric ResearchGoogle Scholar
- Marcella MP, Eltahir EAB (2010) Effects of mineral aerosols on the summertime climate of southwest asia: Incorporating subgrid variability in a dust emission scheme. J Geophys Res D18203. doi: 10.1029/2010DOI14036
- Pal J, Giorgi F, Bi X, Elguindi N, Solmon F, Gao X, Francisco A, andd Zakey R, Winter J, Ashfaq M, Syed F, Bell J, Diffenbaugh N, Karmacharya J, Konare A, Martinez-Castro D, Porfirioda Rocha R, Sloan L, Steiner A (2007) Regional climate modeling for the developing world: the ICTP RegCNET and RegCM. Bull Am Meteorol Soc 88:1395–1409CrossRefGoogle Scholar