Maria Cadeddu, Jim Liljegren

1
Assessment of microwave line parameters for
oxygen Comparisons between models and
atmospheric measurements
Maria Cadeddu, Jim Liljegren Argonne National
Laboratory, 9700 S. C ass Avenue, Argonne, IL
60439, USA  Vivienne Payne, Karen Cady-Pereira,
Jean-Luc Moncet, Shepard. A. Clough Atmospheric
and Environmental Research Inc., 131 Hartwell
Ave., Lexington, MA, 02421-3626,
USA vpayne_at_aer.com
Introduction Improved spectroscopic parameters
for oxygen have recently been published for the
60 GHz band. These parameters are an update of
the MPM92 line parameters widely used in the
remote sensing community. They include updated
line widths, temperature dependence of the widths
and line-coupling coefficients. The 60 GHz
region is widely used for retrievals of
atmospheric temperature profiles. Accurate
spectroscopic parameters are crucial for accurate
retrievals of atmospheric temperature and
composition. Here we compare calculated
brightness temperatures from a monochromatic
radiative transfer model, MonoRTM, with
measurements from a twelve-channel ground-based
microwave radiometer (MWRP), situated at the
Atmospheric Radiation Measurement (ARM) site on
the North Slope of Alaska (NSA).

• Summary
• New microwave oxygen parameters from Tretyakov
  et al (2005) improve agreement between
  measurement and model.
• New parameters also result in improved
  ground-based temperature retrievals
• Measurement/model comparisons suggest that
  HITRAN microwave oxygen parameters should be
  updated.
• Oxygen parameters from Tretyakov et al (2005)
  show good agreement with atmospheric measurements
• Model/measurement agreement can be improved by
  increasing the temperature dependence of the line
  width used by Tretyakov et al (2005)

• Oxygen spectrum
• Group of lines around 0 GHz
  Horizontal/vertical lines show
• Group of lines around 60 GHz frequencies
  of instrument
• Single line at 118 GHz channels
• Line mixing effects are important

Line parameters Line
intensities Line widths
Mixing coefficients
Known within 2
Temperature
dependence of
widths H04 0.71
T05 0.8
Measurement/model comparisons Measurements
MWRP Ground-based microwave radiometer Used to
retrieve profiles of temperature, PWV and LWP 7
channels in the 60GHz band (3 are
opaque) Situated at ARM site at North Slope of
Alaska (NSA) 2 years of data Model MonoRTM
Microwave radiative transfer model Use sonde
profiles to calculate simulated Tb
Tb comparisons for 4 non-opaque channels
Effect on temperature retrievals Dotted
prior. Solid T05. Dashed H04.

• Retrievals of semi-empirical corrections to line
  parameters
• Retrieve scaling factors for
• Line width
• Temperature dependence of width
• Line mixing coefficients
• Maximum likelihood retrieval
• 2 cases
• H04 as prior information
• T05 as prior information
• H04 parameters as prior
• retrieval moves towards T05
• T05 parameters as prior
• retrieval moves little

References Boukabara, S.A., S.A. Clough and R.
N. Hoffman, MonoRTM a monochromatic radiative
transfer model for microwave and laser
calculation. In Programs and Abstracts
Specialist Meeting on Microwave Remote Sensing,
158, November 2001 Caddedu, M.P, V.H. Payne,
S.A. Clough, K. Cady-Pereira and J. Liljegren,
Efffect of the oxygen line parameter modelling
on temperature and humidity retrievals from
ground-based microwave radiometers, submitted to
Transactions in Geoscience and Remote Sensing,
June 2006 Hoke, M.L., S.A. Clough, W.J. Lafferty
and B.W. Olsen, Line coupling in oxygen and
carbon dioxide. In J. Lenoble and J.F Geleyn,
editors, IRS 88 Current Problems in Atmospheric
Radiation, 368-371. A. Deepak Hampton, VA,
1989. H.J. Liebe, P.W. Rosenkranz and G.A.
Hufford, J. Quant. Spectrosc. Radiat. Transfer
48, 629-643 (1992) Tretyakov, M.Yu., M.A.
Koshelev, V.V. Dorovskikh, D.S. Marakov and P.W.
Rosenkranz, 60 GHz oxygen band precise
broadening and central frequencies of
fine-structure lines, absolute absorption profile
at atmospheric pressure, and revision of mixing
coefficients, J. Molec. Spec. 231, 1-14 (2005)
Temperature dependence of widths H04_ret
0.82 T05_ret 0.83