Skip to main content

Research Repository

Advanced Search

A comparison of OEM CO retrievals from the IASI and MOPITT instruments

Illingworth, Samuel Michael; Remedios, John J.; Boesch, H.; Ho, S.-P.; Edwards, D.P.; Palmer, P.I.; Gonzi, S.

Authors

John J. Remedios

H. Boesch

S.-P. Ho

D.P. Edwards

P.I. Palmer

S. Gonzi



Abstract

Observations of atmospheric carbon monoxide (CO) can only be made on continental and global scales by remote sensing instruments situated in space. One such instrument is the Infrared Atmospheric Sounding Interferometer (IASI), producing spectrally resolved, top-of-atmosphere radiance measurements from which CO vertical layers and total columns can be retrieved. This paper presents a technique for intercomparisons of satellite data with low vertical resolution. The example in the paper also generates the first intercomparison between an IASI CO data set, in this case that produced by the University of Leicester IASI Retrieval Scheme (ULIRS), and the V3 and V4 operationally retrieved CO products from the Measurements Of Pollution In The Troposphere (MOPITT) instrument. The comparison is performed for a localised region of Africa, primarily for an ocean day-time configuration, in order to develop the technique for instrument intercomparison in a region with well defined a priori.

By comparing both the standard data and a special version of MOPITT data retrieved using the ULIRS a priori for CO, it is shown that standard intercomparisons of CO are strongly affected by the differing a priori data of the retrievals, and by the differing sensitivities of the two instruments. In particular, the differing a priori profiles for MOPITT V3 and V4 data result in systematic retrieved profile changes as expected. An application of averaging kernels is used to derive a difference quantity which is much less affected by smoothing error, and hence more sensitive to systematic error. These conclusions are confirmed by simulations with model profiles for the same region. This technique is used to show that for the data that has been processed the systematic bias between MOPITT V4 and ULIRS IASI data, at MOPITT vertical resolution, is less than 7 % for the comparison data set, and on average appears to be less than 4 %. The results of this study indicate that intercomparisons of satellite data sets with low vertical resolution should ideally be performed with: retrievals using a common a priori appropriate to the geographic region studied; the application of averaging kernels to compute difference quantities with reduced a priori influence; and a comparison with simulated differences using model profiles for the target gas in the region.

Journal Article Type Article
Acceptance Date Apr 21, 2011
Online Publication Date May 2, 2011
Publication Date 2011
Deposit Date Feb 15, 2021
Publicly Available Date Feb 16, 2021
Journal Atmospheric measurement techniques
Print ISSN 1867-1381
Publisher European Geosciences Union
Peer Reviewed Peer Reviewed
Volume 4
Pages 775-793
DOI https://doi.org/10.5194/amt-4-775-2011
Public URL http://researchrepository.napier.ac.uk/Output/2736561

Files





You might also like



Downloadable Citations