Atmospheric Chemistry and Physics Discussions
www.atmos-chem-phys-discuss.net
1680-7367
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7
1
2007
10.5194/acpd-7-911-2007
http://www.atmos-chem-phys-discuss.net/7/911/2007/
http://www.atmos-chem-phys-discuss.net/7/911/2007/acpd-7-911-2007.html
http://www.atmos-chem-phys-discuss.net/7/911/2007/acpd-7-911-2007.pdf
911
929
2007-01-18
Precision validation of MIPAS-Envisat products
C. Piccolo
piccolo@atm.ox.ac.uk
A. Dudhia
Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
This paper discusses the variation and validation of the precision,
or estimated random error, associated
with the ESA Level 2 products from the Michelson
Interferometer for Passive Atmospheric Sounding (MIPAS).
<br><br>
This quantity represents the propagation of the radiometric noise from
the spectra through the retrieval process into the
Level 2 profile values.
The noise itself
varies with time, steadily rising between decontamination events, but
the Level 2 precision has a greater variation due to the atmospheric
temperature which controls the total radiance received. Hence, for all
species, the precision varies latitudinally/seasonally with
temperature, with a small superimposed temporal structure determined by
the degree of ice contamination on the detectors.
<br><br>
The precision validation involves comparing two MIPAS retrievals at the
intersections of ascending/descending orbits. For 5 days per month of
full resolution MIPAS operation, the standard deviation of the
matching profile pairs is computed and compared with the precision
given in the MIPAS Level 2 data. Even taking into account the propagation of
the pressure-temperature retrieval errors into the VMR retrieval, the
standard deviation of the matching pairs is usually a factor 1–2
larger than the precision. This is thought to be due to effects such as
horizontal inhomogeneity of the atmosphere and instability of the retrieval.
ESA, SP-1229: ESA ENVISAT-MIPAS: an instrument for atmospheric chemistry and climate research, European Space Agency, ESTEC, Noordwijck, The Netherlands, 2000.
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