Joint retrieval of surface reflectance and aerosol optical depth from MSG/SEVIRI observations with an optimal estimation approach: 2. Implementation and evaluation

Abstract

An original method, based on optimal estimation, was presented in a part one of this paper for the joint retrieval of the mean daily total column aerosol optical depth and the surface Bidirectional Reflectance Factor (BRF) from the daily accumulated Meteosat Second Generation–Spinning Enhanced Visible and Infrared Imager (MSG/SEVIRI) observations in the solar channels. The objective of this paper is to evaluate the benefits of the proposed approach and to document the limits of the algorithm assumptions in the context of its implementation in an operational ground segment. A twofold approach is followed. In a first step, by looking at the posterior correlation error matrix the capability of the so‐called Land Daily Aerosol (LDA) algorithm to decouple the surface‐atmosphere signal is analyzed. In particular, the impact of the prior information is investigated in detail. In a second step, the results of the algorithm are compared with independent data sets of aerosol optical depth and surface reflectance. In this phase, the accuracy of the algorithm is evaluated against ground observations from the AERONET network. LDA is shown to be in good agreement with these data, especially when the prior update mechanism is activated. Comparisons with the MODIS surface product showed that the bihemispherical reflectance derived from the LDA products is consistent with the equivalent MODIS white‐sky albedo. Aerosol spatial distributions are comparable in terms of geographical location and intensity, in particular for aerosol episodes with a limited daily variation.

Quantification of uncertainty in aerosol optical thickness retrieval arising from aerosol microphysical model and other sources, applied to Ozone Monitoring Instrument (OMI) measurements

“…This choice of an appropriate aerosol model plays a significant part in the retrieval of aerosols from satellites. An additional large source of uncertainty comes from the assumptions on surface albedo (Thomas et al, 2009;Govaerts et al, 2010;Wagner et al, 2010). This aspect will not be studied in the current paper.…”

“…Atmospheric aerosols have been monitored for years from several satellite instruments including the Ozone Monitoring Instrument (OMI) (Torres et al, 2007), the Moderate Resolution Imaging Spectroradiometer (MODIS) van Donkelaar et al, 2013), the Global Ozone Monitoring Experiment-2 (GOME-2), the Multi-angle Imaging SpectroRadiometer (MISR) , the (Advanced) Along-Track Scanning Radiometers ((A)ATSR) (Thomas et al, 2009;Sayer et al, 2010Sayer et al, , 2012, the Cloud-Aerosol Lidar and Infrared Path finder (CALIPSO), the Scanning Imaging Absorption spectroMeter for Atmospheric Chartography (SCIAMACHY), the Polarisation and Directionality of the Earth's Reflectances (POLDER) (Dubovik et al, 2011) and the Spinning Enhanced Visible and Infrared Imager (SE-VIRI) Wagner et al, 2010). The instruments vary in terms of spatial and spectral resolution, polarisation, and viewing geometry.…”

Reducing the Uncertainties in Direct Aerosol Radiative Forcing

“…Subsequently, two-channel retrievals were performed (Mishchenko et al 1999;Ignatov et al 2004), adding the 0.85 micrometer band, refining the assumed ocean surface reflectance model, and also retrieving the Angstrom exponent (ANG, related to the spectral slope of AOD), a quantity that can provide some indication of particle size. Similarly, AOD retrieval algorithms have been developed for imagers aboard geostationary satellites, such as NOAA's GOES series (Knapp 2002) and European Space Agency's Spinning Enhanced Visible and Infrared Imager (SEVIRI; Popp et al 2007;Wagner et al 2010), providing high-temporal-resolution products as frequently as every 15 or 30 min, making it possible to at least qualitatively map the development of aerosol plumes. Although broad spectral bands and poor radiometric calibration limit the quantitative application of these data, early results demonstrated the long-range, over-ocean transport of dust, smoke, and pollution particles from terrestrial sources (e.g., Husar et al 1997), highlighting the need to consider aerosol effects on the global energy budget.…”

Description and validation of an AOT product over land at the 0.6 μm channel of the SEVIRI sensor onboard MSG

“…Tech., 4, 2543Tech., 4, -2565Tech., 4, , 2011 www.atmos-meas-tech.net/4/2543/2011/ corrected from radiometric and geometric non-linearity, geolocated and calibrated (Muller, 2007). Recent investigations have used the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) sensor onboard MSG to retrieve AOT over land in the visible channel centred at 0.6 µm and noted VIS06 in the following (Popp et al, 2007;Guerrieri et al, 2007;Carrer et al, 2010;Wagner et al, 2010). All these studies showed the feasibility of retrieving the AOT at time-scales ranging from 15 min (Popp et al, 2007;Guerrieri et al, 2007) to daily means (Carrer et al, 2010;Govaerts et al, 2010;Wagner et al, 2010).…”