An Intercomparison of Radiation Codes for Retrieving Upper-Tropospheric Humidity in the 6.3-μm Band: A Report from the First GVaP Workshop

© Get Permissions Rent on DeepDyve
Restricted access

An intercomparison of radiation codes used in retrieving upper-tropospheric humidity (UTH) from observations in the ν2 (6.3 μm) water vapor absorption band was performed. This intercomparison is one part of a coordinated effort within the Global Energy and Water Cycle Experiment Water Vapor Project to assess our ability to monitor the distribution and variations of upper-tropospheric moisture from spaceborne sensors. A total of 23 different codes, ranging from detailed line-by-line (LBL) models, to coarser-resolution narrowband (NB) models, to highly parameterized single-band (SB) models participated in the study. Forward calculations were performed using a carefully selected set of temperature and moisture profiles chosen to be representative of a wide range of atmospheric conditions. The LBL model calculations exhibited the greatest consistency with each other, typically agreeing to within 0.5 K in terms of the equivalent blackbody brightness temperature (Tb). The majority of NB and SB models agreed to within ±1 K of the LBL models, although a few older models exhibited systematic Tb biases in excess of 2 K. A discussion of the discrepancies between various models, their association with differences in model physics (e.g., continuum absorption), and their implications for UTH retrieval and radiance assimilation is presented.

aNOAA/GFDL, Princeton, New Jersey.

bEUMETSAT, Darmstadt, Germany.

cECMWF, Reading, United Kingdom.

dNOAA/CDC, Boulder, Colorado.

eUniversity of Maryland at College Park, College Park, Maryland.

fColorado State University, Fort Collins, Colorado.

gAES, Dorval, Quebec, Canada.

hNASA/MSFC, Huntsville, Alabama.

iNOAA/NESDIS, Washington, D.C.

jCIRA/CSU, Fort Collins, Colorado.

kMeteorological Office, Bracknell, United Kingdom.

lUniversity of Washington, Seattle, Washington.

mCNRS/LMD, Palaiseau, France.

nSeoul National University, Seoul, South Korea.

oUniversity of Maryland–Baltimore County, Baltimore, Maryland.

pUniversity of Wisconsin—Madison, Madison, Wisconsin.

Corresponding author address: Dr. Brian J. Soden, Princeton University, Forrestal Campus, U.S. Route 1, P.O. Box 308, Princeton, NJ 08542-0308. E-mail: bjs@gfdl.gov

An intercomparison of radiation codes used in retrieving upper-tropospheric humidity (UTH) from observations in the ν2 (6.3 μm) water vapor absorption band was performed. This intercomparison is one part of a coordinated effort within the Global Energy and Water Cycle Experiment Water Vapor Project to assess our ability to monitor the distribution and variations of upper-tropospheric moisture from spaceborne sensors. A total of 23 different codes, ranging from detailed line-by-line (LBL) models, to coarser-resolution narrowband (NB) models, to highly parameterized single-band (SB) models participated in the study. Forward calculations were performed using a carefully selected set of temperature and moisture profiles chosen to be representative of a wide range of atmospheric conditions. The LBL model calculations exhibited the greatest consistency with each other, typically agreeing to within 0.5 K in terms of the equivalent blackbody brightness temperature (Tb). The majority of NB and SB models agreed to within ±1 K of the LBL models, although a few older models exhibited systematic Tb biases in excess of 2 K. A discussion of the discrepancies between various models, their association with differences in model physics (e.g., continuum absorption), and their implications for UTH retrieval and radiance assimilation is presented.

aNOAA/GFDL, Princeton, New Jersey.

bEUMETSAT, Darmstadt, Germany.

cECMWF, Reading, United Kingdom.

dNOAA/CDC, Boulder, Colorado.

eUniversity of Maryland at College Park, College Park, Maryland.

fColorado State University, Fort Collins, Colorado.

gAES, Dorval, Quebec, Canada.

hNASA/MSFC, Huntsville, Alabama.

iNOAA/NESDIS, Washington, D.C.

jCIRA/CSU, Fort Collins, Colorado.

kMeteorological Office, Bracknell, United Kingdom.

lUniversity of Washington, Seattle, Washington.

mCNRS/LMD, Palaiseau, France.

nSeoul National University, Seoul, South Korea.

oUniversity of Maryland–Baltimore County, Baltimore, Maryland.

pUniversity of Wisconsin—Madison, Madison, Wisconsin.

Corresponding author address: Dr. Brian J. Soden, Princeton University, Forrestal Campus, U.S. Route 1, P.O. Box 308, Princeton, NJ 08542-0308. E-mail: bjs@gfdl.gov
Save