Abstract
Abstract. We derive annual and seasonal global climatologies of tropospheric NO2 profiles from OMI cloudy observations for the year 2006 using the cloud-slicing method on six pressure levels centered at about 280, 380, 500, 620, 720 and 820 hPa. A comparison between OMI and the TM4 model tropospheric NO2 profiles reveals striking overall similarities, which confer great confidence to the cloud-slicing approach to provide details that pertain to annual as well as seasonal means, along with localized discrepancies that seem to probe into particular model processes. Anomalies detected at the lowest levels can be traced to deficiencies in the model surface emission inventory, at mid-tropospheric levels to convective transport and horizontal advective diffusion, and at the upper tropospheric levels to model lightning NOx production and the placement of deeply transported NO2 plumes such as from the Asian summer monsoon. The vertical information contained in the OMI cloud-sliced NO2 profiles provides a global observational constraint that can be used to evaluate chemistry transport models (CTMs) and guide the development of key parameterization schemes.
Highlights
Global maps of tropospheric NO2 vertical column densities (VCDs) derived from satellite UV–vis nadir sounders such as OMI, GOME and SCIAMACHY have contributed to the development of a variety of applications
Clouds affect the redistribution of trace gases via convection and interaction with chemistry, which are essential elements in chemistry transport models (CTMs)
A similar set of annual mean NO2 VCDs above cloud has been extracted from the TM4 model using identical cloud sampling for comparison
Summary
Global maps of tropospheric NO2 vertical column densities (VCDs) derived from satellite UV–vis nadir sounders such as OMI, GOME and SCIAMACHY have contributed to the development of a variety of applications. The utilization of cloudy data from satellite IR and UV– vis nadir sounders provides access to a large repository of observations with potential to reveal information about trace gas concentrations at different altitudes and to constrain the parameterizations of a number of cloud-related processes. The presence of convective clouds transports pollutants vertically and removes soluble species (like HNO3) by precipitation, and modulates photolysis rates by altering the actinic fluxes above and below the Published by Copernicus Publications on behalf of the European Geosciences Union
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