Water vapor retrieval over ocean using near‐infrared radiometry

Abstract

[1] A methodology is presented and evaluated to retrieve vertically integrated water vapor content over the ocean in any viewing geometry from POLDER data. The methodology is based on differential absorption by water vapor in the near-infrared. Over the ocean, except in sun glint conditions, surface reflectance is small, and interaction between aerosol scattering and water vapor absorption is exploited to estimate total water vapor content. A sensitivity study performed with an accurate radiative transfer code (GAME) shows that a determination of total water vapor content is theoretically possible if the optical thickness and scale height of aerosols are known. An inaccuracy of 0.1 to 0.6 g cm À2 is expected, depending on water vapor content. The aerosol optical thickness d a at 865 nm is available from POLDER standard products. The aerosol scale height H a can be estimated from the surface pressure derived from POLDER oxygen channels at 763 and 765 nm. A retrieval scheme is devised using parameterizations calculated using GAME for water vapor and surface pressure. The inversion scheme is applied to 20 POLDER orbits with observed water vapor contents ranging from 0.2 to 6 g cm

Overview of the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Forcing on the Mediterranean Climate (ChArMEx/ADRIMED) summer 2013 campaign

“…The method of derivation is described in detail by García et al (2012). Briefly, the broadband fluxes were calculated using the GAME (Dubuisson et al, 2004; radiative transfer model that has been integrated into the operational AERONET inversion code. Sun-photometer stations used during the SOP-1a campaign over the western basin are listed in Table 2.…”

“…To this end, vertical profiles from the ATR-42 were combined with surface observations from the two (Ersa and Lampedusa) stations to calculate the SW DRF of different aerosol events (Nicolas et al, 2016;Meloni et al, 2016). Over the western basin and for the first period of the campaign (16 to 20 June), different calculations, with the GAME radiative transfer model (Dubuisson et al, 2004), of the downward and upward SW cloud-free irradiances have been performed by Nicolas et al (2016) for six vertical profiles over Granada, Minorca and Corsica. Briefly, the methodology is based on extinction, SSA and phase function vertical profiles (and their spectral dependence), obtained from observations and Mie calculations, and associated with atmospheric thermodynamic properties.…”

Shortwave radiative forcing and efficiency of key aerosol types using AERONET data

“…The use of correlated k-distribution allows accounting for interactions between gaseous absorption and multiple scattering with acceptably short computational time for providing broadband fluxes within AERONET operational procedure. The coefficients of the correlated k-distribution have been estimated from reference calculations using a line-by-line code (Dubuisson et al, 2004). Assessment of water vapor content is based on the instantaneous water vapor values retrieved by AERONET using absorption differential method at the 0.94 µm channel (Smirnov et al, 2004).…”

Comprehensive tool for calculation of radiative fluxes: illustration of shortwave aerosol radiative effect sensitivities to the details in aerosol and underlying surface characteristics

“…The coefficients of the correlated k distribution have been estimated from reference calculations using a lineby-line code (Dubuisson et al, 2004). Modeling of the surface reflectance is done either by BRDF model (using various models as described by Dubovik et al, 2011) or using Lambertian approximation.…”