Jayanta Kar

Measurement of low‐altitude CO over the Indian subcontinent by MOPITT

We show that the dayside MOPITT retrievals in the lower troposphere can provide useful information on surface sources of atmospheric CO over the Indian subcontinent. We find that MOPITT retrievals at 850 hPa show localized enhancements over the Indian subcontinent, which correlate with similar enhancements seen in the tropospheric NO2 columns from the SCIAMACHY instrument. In particular, high concentrations of CO over the Indo-Gangetic basin and some prominent cities are captured in the lower-tropospheric retrievals in spring. MOPITT averaging kernels (normalized to take into account the absorber amounts in the layers) indicate that the retrievals are sensitive to CO in the lower troposphere. In winter, MOPITT retrievals at 850 hPa can detect the strongest source areas over the eastern states of Bihar and West Bengal, thus confirming the so-called “Bihar pollution pool,” which was detected earlier in the aerosol measurements by the multiangle imaging spectroradiometer (MISR) aboard Terra. The pollution features are consistent with the spatial distribution of CO emissions in India, as reflected in the GEOS-Chem simulation of CO. Furthermore, these lower-tropospheric features in the simulation are still present after smoothing the modeled fields using the MOPITT averaging kernels and a priori profile, demonstrating that the retrievals do have sensitivity in the lower troposphere. This work indicates that although MOPITT retrievals are often most sensitive to CO in the middle and upper troposphere, they do provide information on lower-tropospheric CO in selected continental regions with strong thermal contrast and could be useful for pollution studies.

Initial comparison of ozone and NO2 profiles from ACE‐MAESTRO with balloon and satellite data

[1] Atmospheric retrievals of ozone and NO 2 by the Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) instrument which is part of the Atmospheric Chemistry Experiment (ACE) satellite aboard SCISAT are compared statistically with coincident measurements by ozonesondes, the Fourier Transform Spectrometer (ACE-FTS) also aboard SCISAT, the SAGE III and the POAM III instruments. The ozone mixing ratio profiles from MAESTRO and ozonesondes agree within about 5-10% from 16-30 km in the northern middle and high latitudes. Further, ACE-FTS and MAESTRO ozone profiles agree within ∼5-15% from 16-50 km. MAESTRO ozone profiles show a systematic bias which is opposite for sunrise (SR) and sunset (SS) events and was also seen in comparisons with SAGE III and POAM III ozone. MAESTRO SS ozone profiles mostly agree within 5-10% from 16-40 km with either SAGE III or POAM III SR or SS retrievals, but show a significant high bias from 40-55 km, reaching a maximum of ∼20-30%. MAESTRO SR ozone profiles show a low bias of ∼5-15% from 20-50 km, as compared to SAGE III and POAM III SR or SS measurements. The NO 2 profiles agree within about 10-15% between ACE-FTS and MAESTRO from 15-40 km for the SR and 22-35 km for the SS measurements. Further, MAESTRO NO 2 profiles agree with SAGE III NO 2 mostly within 10% from 25-40 km. MAESTRO NO 2 profiles agree with POAM III SR profiles within 5-10% from 25-42 km. However, compared to POAM III SS profiles, MAESTRO NO 2 profiles show a low bias between 20 and 25 km (∼30-50%), a high MAESTRO bias between 25 and 32 km (10-30%), and again a low bias above 33 km that increases with altitude to 50-60%.