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CR 59:207-228 (2014)  -  DOI:

Climatological simulations of ozone and atmospheric aerosols in the Greater Cairo region

A. L. Steiner1,*, A. B. Tawfik1,6, A. Shalaby2, A. S. Zakey2, M. M. Abdel-Wahab3, Z. Salah2, F. Solmon4, S. Sillman1, R. A. Zaveri5

1Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109-2143, USA
2Egyptian Meteorological Authority, PO Box 11784, Cairo, Egypt
3Department of Meteorology, Cairo University, PO Box 12613, Cairo, Egypt
4Earth System Physics Group, International Centre for Theoretical Physics, 34151Trieste, Italy
5Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
6Present address: Center for Ocean-Land-Atmosphere Studies, Calverton, Maryland 20705-3106, USA
*Corresponding author:

ABSTRACT: An integrated chemistry–climate model (RegCM4-CHEM) simulates present-day climate, ozone and tropospheric aerosols over Egypt with a focus on northern Africa and the Greater Cairo (GC) region. The densely populated GC region is known for its severe air quality issues driven by high levels of anthropogenic pollution in conjunction with natural sources such as dust, and agricultural burning events. We find that current global emission inventories underestimate key pollutants such as nitrogen oxides and anthropogenic aerosol species. In the GC region, average ground-based observations of the daily July maximum nitrogen dioxide (NO2) are 40 to 60 parts per billion by volume (ppbv) and are about 10 ppbv higher than modeled estimates, likely due to model grid cell resolution, improper boundary layer representation, and poor emissions inventories. Observed July daily maximum ozone concentrations range from 30 ppbv (winter) to 90 ppbv (summer). The model reproduces the seasonal cycle fairly well, but modeled July ozone is underestimated by approximately 10 ppbv and exhibits little interannual variability. For aerosols, springtime dust events dominate the seasonal aerosol cycle. The chemistry–climate model captures the springtime peak aerosol optical depth (AOD) of 0.7 to 1 but is slightly greater than satellite-derived AOD. Observed AOD decreases in the summer and increases again in the fall due to agricultural burning events in the Nile Delta; however, the model underestimates this observed AOD peak in fall, as standard emissions inventories underestimate the extent of this burning and the resulting aerosol emissions. Our comparison of modeled gas and particulate phase atmospheric chemistry in the GC region indicates that improved emissions inventories of mobile sources and other anthropogenic activities, specifically NOx and organic aerosols, are needed to improve air quality simulations in this region.

KEY WORDS: Ozone · Mediterranean · Urban · Air quality

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Cite this article as: Steiner AL, Tawfik AB, Shalaby A, Zakey AS and others (2014) Climatological simulations of ozone and atmospheric aerosols in the Greater Cairo region. Clim Res 59:207-228.

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