MARCH 2001: Tropospheric ozone maximum over the Middle East

Monthly mean ozone in July 1997 simulated by the GEOS-CHEM global 3-D model of tropospheric chemistry. Top panel: 400 hPa mixing ratios (ppbv). Bottom panel: tropospheric columns in Dobson units (1 DU = 2.69 x 10¹⁶ molecules cm^-2). Colored circles in the top panel show 400 hPa climatological monthly mean mixing ratios from ozonesonde data [ Logan, 1999] and monthly mean mixing ratios from commercial aircraft observations over Tel-Aviv (32 N, 35 E), Dubai (25 N, 55 E), and Teheran (36 N, 51 E) during 1995-2000 as part of the MOZAIC program. The GEOS-CHEM model predicts a summer ozone maximum in the middle troposphere over the Middle East (top panel). This maximum is also seen in the simulated tropospheric ozone column (bottom panel). The Middle East maximum in the model appears in May and disappears in September; mixing ratios in winter over the region are relatively low, both in the observations and in the model. This result is part of a study conducted by Qinbin Li, Daniel Jacob, Jennifer Logan, Isabelle Bey, Robert Yantosca, Hongyu Liu, Randall Martin, Arlene Fiore, Brendan Field, Bryan Duncan, and Valerie Thouret to understand the factors that lead to the summertime ozone maximum over the Middle East. A complete description of this work is given by Li et al., [2001].