P3.14
The impact of differences between water vapor continuum models and measurements upon radiative transfer calculations
David Paynter, AOS, Princeton, NJ; and V. Ramaswamy
Recent measurements of the water vapour continuum have been combined to form an empirical continuum called the BPS continuum. This covers the 800-7500 cm-1 spectral region for the self continuum and most of the major absorbing areas between 290 and 7500 cm-1 for the foreign continuum. Longwave and shortwave line by line radiative transfer calculations have been performed for clearly-sky condition in three standard test atmospheres using line data from the HITRAN database. This has allowed the BPS continuum to be compared to the commonly used CKD and MT_CKD continuum models. Using experimental errors it has been possible to estimate the upper and lower limits of the continuum. In the longwave the outgoing and surface down-welling radiation calculated using all three continua agree within 0.5% in a MLS atmosphere. In the shortwave, even though the contribution of the continuum is smaller, it still accounts for up to 5% of shortwave water vapour absorption. Between 1000 and 17000 cm-1 there is a more significant disagreement between the three formulations, with CKD predicting a 2% greater value of water vapour shortwave absorption than the BPS continuum. The role of the continuum in a warming atmosphere has been investigated. The results suggest that in the longwave, even though the continuum is responsible for a great deal of cooling, the magnitude is insensitive to the continuum formulation used. In the shortwave the role of the continuum is less significant, but there is a greater variation between the different formulations.
Poster Session 3, Radiative Transfer Theory and Radiative Parameterizations
Wednesday, 30 June 2010, 5:30 PM-8:30 PM, Exhibit Hall
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