 |
| Titel |
A comparison of OEM CO retrievals from the IASI and MOPITT instruments |
| VerfasserIn |
S. M. Illingworth, J. J. Remedios, H. Boesch, S.-P. Ho, D. P. Edwards, P. I. Palmer, S. Gonzi |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 4, no. 5 ; Nr. 4, no. 5 (2011-05-02), S.775-793 |
| Datensatznummer |
250001973
|
| Publikation (Nr.) |
 copernicus.org/amt-4-775-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
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. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|