Open AccessAtmospheric water vapor estimate by a differential absorption technique with the polarisation and directionality of the Earth reflectances (POLDER) instrument
Author(s) -
Bouffiès S.,
Bréon F. M.,
Tanré D.,
Dubuisson P.
Publication year - 1997
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/96jd03126
Subject(s) - water vapor , environmental science , radiative transfer , zenith , remote sensing , radiosonde , aerosol , atmospheric radiative transfer codes , atmospheric sciences , meteorology , optics , geology , physics
The polarization and directionality of the Earth reflectances (POLDER) instrument, to be launched in 1996 on the Japanese ADEOS (advanced Earth observing satellite) platform includes a channel which covers the 910 nm water vapor absorption band (near IR), as well as a channel centered at 865 nm. An estimate of the total atmospheric water vapor content can be derived from the ratio of the two reflectance measurements. In addition to the spectroscopic parameterization, the major uncertainties of this estimate result from (1) the surface reflectance spectral signature, (2) scattering by atmospheric aerosol, and (3) the water vapor vertical profile. A radiative transfer model has been developed in order to quantify these uncertainties. From radiative transfer simulations an uncertainty on the order of 10% is expected on the total water vapor amount. An airborne version of the POLDER instrument has been developed and flown over various targets. These targets include semiarid surfaces (Sahel), bog, coniferous and deciduous forest (Boreal forest), and the ocean in the glint direction. Water vapor measurements from radiosondes, concomitant with the POLDER measurements, are available for the method validation. Over water bodies with glint present, an overestimate is found, which is still not understood at present. For other surfaces the comparisons are, in general, in good agreement with the uncertainty analysis.