| Abstract: |
Many applications of microwave radiometry make use of a forward model which relates brightness temperature to the quantities (such as an atmospheric profile) that will be estimated from the measured brightness temperatures. Therefore, characterization of forward-model accuracy is a part of retrieval error analysis, as discussed by Rodgers (1990). This paper examines correlated uncertainties in the spectroscopic parameters of models for atmospheric microwave absorption by water vapor (Turner et al, 2009) and oxygen (Tretyakov et al, 2005). The uncertainties can be correlated either by definition of the parameters (as for the water vapor continuum with line widths) or by the way in which they are measured (as for line mixing in the oxygen band). Spectroscopic parameter correlations affect the resulting uncertainty in calculated opacity and brightness temperature at any given frequency, as well as correlations between different frequencies. Uncertainty covariance matrices for the spectroscopic parameters with significant impact on the 20- to 60-GHz band (line intensities, broadening coefficients and their temperature dependence, line-mixing coefficients and their temperature dependence, water vapor continuum coefficients) are calculated, and the uncertainties are propagated to downwelling brightness temperatures and ground-based temperature profile and water vapor retrievals. This type of analysis can also be applied to other frequency ranges and to upwelling brightness temperatures.
References:
Rodgers, C.D. , "Characterization and error analysis of profiles retrieved from remote sounding measurements," J. Geophys. Res. v.95(D5), pp.5587-5595, 1990.
Tretyakov, M.Yu., M.A. Koshelev, V.V. Dorovskikh, D.S. Makarov, 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. Spectros., v.231, pp.1-14, 2005.
Turner, D.D, M.P. Cadeddu, U. Löhnert, S. Crewell, and A.M. Vogelmann, “Modification to the water vapor continuum in the microwave suggested by ground-based 150-GHz observations,” IEEE Trans. Geosci. Remote Sens. v.47(10), pp.3326-3337, 2009. |
