Retrieval of foreign-broadened water vapor continuum coefficients from emitted spectral radiance in the H2O rotational band from 240 to 590 cm(-1).

The paper presents a novel methodology to retrieve the foreign-broadened water vapor continuum absorption coefficients in the spectral range 240 to 590 cm(-1) and is the first estimation of the continuum coefficient at wave numbers smaller than 400 cm(-1) under atmospheric conditions. The derivation has been accomplished by processing a suitable set of atmospheric emitted spectral radiance observations obtained during the March 2007 Alps campaign of the ECOWAR project (Earth Cooling by WAter vapor Radiation). It is shown that, in the range 450 to 600 cm(-1), our findings are in good agreement with the widely used Mlawer, Tobin-Clough, Kneizys-Davies (MT CKD) continuum.

Breadboard of a Fourier-transform spectrometer for the radiation explorer in the far infrared atmospheric mission.

In preparation for a possible space mission, a breadboard version named REFIR-BB of the Radiation Explorer in the Far Infrared (REFIR) instrument has been built. The REFIR is a Fourier-transform spectrometer with a new optical layout operating in the spectral range 100-1100 cm(-1) with a resolution of 0.5 cm(-1), a 7-s acquisition time, and a signal-to-noise ratio of better than 100.

Radiances simulated in the presence of clouds by use of a fast radiative transfer model and a multiple-scattering scheme.

A fast-forward radiative transfer (RTF) model is presented that includes cloud-radiation interaction for any number of cloud layers. Layer cloud fraction and transmittance are treated separately and combined with that of gaseous transmittances. RTF is tested against a reference procedure that uses line-by-line gaseous transmittances and solves the radiative transfer equation by use of the adding-doubling method to handle multiple-scattering conditions properly.

Homomorphism between cloudy and clear spectral radiance in the 800-900-cm(-1) atmospheric window region.

The sensitivity of a new algorithm for cloud detection over a sea surface has been assessed on the basis of extensive simulations of clear and cloudy radiance spectra, including water and ice and low- and high-altitude clouds. The new algorithm makes use of autocorrelation and cross correlation between an observed spectrum and either a synthetic or a laboratory spectrum and can be used to determine quantitatively the degree of homogeneity of two spectra in the 800-900-cm(-1) region (11.11-12.

Simulation of uplooking and downlooking high-resolution radiance spectra with two different radiative transfer models.

Measurements of up-looking spectral radiances measured during the Convection and Moisture Experiment and down-looking spectral radiances measured at one of the Atmospheric Radiation Measurement sites are compared with simulations with use of two different line-by-line models. Simulations are performed in tightly controlled conditions to verify the behavior of the models. Spectra computed at higher samplings are used to study the spectral structure of the differences between simulations and measurements.