First estimates of global free-tropospheric NO2 abundances derived using a cloud-slicing technique applied to satellite observations from the Aura Ozone Monitoring Instrument (OMI)
Item
Title (Dublin Core)
First estimates of global free-tropospheric NO2 abundances derived using a cloud-slicing technique applied to satellite observations from the Aura Ozone Monitoring Instrument (OMI)
Description (Dublin Core)
We derive free-tropospheric NO<sub>2</sub> volume mixing ratios (VMRs) by applying a cloud-slicing technique to data from the Ozone Monitoring Instrument (OMI) on the Aura satellite. In the cloud-slicing approach, the slope of the above-cloud NO<sub>2</sub> column versus the cloud scene pressure is proportional to the NO<sub>2</sub> VMR. In this work, we use a sample of nearby OMI pixel data from a single orbit for the linear fit. The OMI data include cloud scene pressures from the rotational-Raman algorithm and above-cloud NO<sub>2</sub> vertical column density (VCD) (defined as the NO<sub>2</sub> column from the cloud scene pressure to the top of the atmosphere) from a differential optical absorption spectroscopy (DOAS) algorithm. We compare OMI-derived NO<sub>2</sub> VMRs with in situ aircraft profiles measured during the NASA Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign in 2006. The agreement is generally within the estimated uncertainties when appropriate data screening is applied. We then derive a global seasonal climatology of free-tropospheric NO<sub>2</sub> VMR in cloudy conditions. Enhanced NO<sub>2</sub> in the free troposphere commonly appears near polluted urban locations where NO<sub>2</sub> produced in the boundary layer may be transported vertically out of the boundary layer and then horizontally away from the source. Signatures of lightning NO<sub>2</sub> are also shown throughout low and middle latitude regions in summer months. A profile analysis of our cloud-slicing data indicates signatures of lightning-generated NO<sub>2</sub> in the upper troposphere. Comparison of the climatology with simulations from the global modeling initiative (GMI) for cloudy conditions (cloud optical depth > 10) shows similarities in the spatial patterns of continental pollution outflow. However, there are also some differences in the seasonal variation of free-tropospheric NO<sub>2</sub> VMRs near highly populated regions and in areas affected by lightning-generated NO<sub>x</sub>.
Creator (Dublin Core)
Choi, S.
Joiner, J.
Choi, Y.
Duncan, B. N.
Vasilkov, A.
Krotkov, N.
Bucsela, E.
Date (Dublin Core)
2018-09-27
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-14-10565-2014
https://acp.copernicus.org/articles/14/10565/2014/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
