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Impact of non‐LTE processes on middle atmospheric water vapor retrievals from simulated measurements of 6.8 μm Earth limb emission
Author(s) -
Mertens Christopher J.,
Mlynczak Martin G.,
LopezPuertas Manuel,
Remsberg Ellis E.
Publication year - 2002
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2001gl014590
Subject(s) - atmosphere (unit) , satellite , environmental science , water vapor , mixing ratio , remote sensing , atmospheric sciences , channel (broadcasting) , meteorology , geology , physics , astronomy , telecommunications , computer science
We present an efficient and accurate algorithm for the retrieval of water vapor (H 2 O) volume mixing ratio (vmr) in the middle atmosphere from satellite measurements of 6.8 μm Earth limb emission, which rigorously includes non‐local thermodynamic equilibrium (non‐LTE) processes. A number of retrieval studies have been conducted with this algorithm leading to three major conclusions about the retrieval of H 2 O in the middle atmosphere: (1) satellite measurements of 6.3 μm limb emission must be made to high altitudes (85–90 km), where the few optically thick H 2 O absorption lines become optically thin, in order to prevent large errors in retrieved stratospheric and mesospheric H 2 O vmr; (2) the impact of non‐LTE on nighttime H 2 O retrievals is greater than previously thought; (3) the enhancements in the daytime H 2 O channel radiances of the NIMBUS 7 LIMS experiment may be entirely due to non‐LTE emission from the H 2 O 6.3 μm bands.