Multi‐sensor satellite remote sensing of dust aerosols over North Africa during GERBILS

Abstract

In this paper we provide an overview of various satellite products over the Sahara Desert that were available during the GERBILS field campaign. Our results indicate that all mid-visible satellite aerosol optical depth (AOD) products match well with AERONET retrievals. For low AOD (AOD < 1), the satellite AODs compare well with aircraft AOD values but they tend to underestimate at high AOD values. We then assessed the satellite products in 0.5 × 0.5 degree grids for the entire study region (10-30 • N and 20 • W-10 • E). If we use a multi-angle imaging spectroradiometer (MISR) as a benchmark for AOD retrievals over bright targets, the estimated AOD derived from the ozone-monitoring instrument aerosol index-MISR relationship performs best when compared with MISR for the entire study region. Although differences exist among satellite products, the advancement in satellite retrieval techniques now provide AOD retrievals over bright targets such as deserts, which are useful for numerical modeling simulation comparisons and other studies. Furthermore, the in situ information from aircraft and the ground continue to provide valuable information for validating satellite products and for assessing their strengths and weaknesses.

Motivation, rationale and key results from the GERBILS Saharan dust measurement campaign

“…MISR is considered a particularly good sensor for making remote sensing retrievals owing to the multi-angle capabilities (Khan et al, 2005), but the narrow swath width makes validation of model fields during short-duration field campaigns such as GERBILS problematic. However, Christopher et al (2011) show correlations between MISR and the other retrievals which agree to within 25%. Taken together, the correlation between broad-swath satellite retrievals and AERONET and broad-swath retrievals and the narrow-swath MISR instrument is encouraging as the broad-swath products can then be used with reasonable confidence to validate models over larger spatial and temporal scales .…”

“…Good agreement in remotely sensed AODs from MODIS, MISR and OMI with aircraft measurements was also shown except when the AOD measured by the aircraft was particularly high. Christopher et al (2011) extend the analysis of satellite data from a single case study to the entire GERBILS period. In addition to polar orbiting satellite data, Christopher et al (2011) show the utility of the geostationary SEVIRI data at tracking large-scale dust events as the data are available at 15 minute temporal resolution.…”

“…Christopher et al (2011) extend the analysis of satellite data from a single case study to the entire GERBILS period. In addition to polar orbiting satellite data, Christopher et al (2011) show the utility of the geostationary SEVIRI data at tracking large-scale dust events as the data are available at 15 minute temporal resolution. AODs over land from MODIS Deep Blue (Hsu et al, 2006), estimated from correlation between OMI and MISR , the standard OMI product (Torres et al, 2007), and the SEVIRI sensor (Brindley and Russell, 2008), all show good agreement with those from AERONET sites.…”

Optical properties of Saharan dust aerosol and contribution from the coarse mode as measured during the Fennec 2011 aircraft campaign

“…Surface albedo is spectrally constant across solar wavelengths at 0.33 to represent a desert surface (e.g. Christopher et al 2011 Figure 5 shows the mean and range of size distributions measured during horizontal legs within dust layers during Fennec, using data from the PCASP, CDP and CIP, in terms of number distribution (Fig. 5a) and volume distribution (Fig.…”

Spatio-temporal variability of dust aerosols over the Sistan region in Iran based on satellite observations

“…Rosenfeld et al, 2001;Gautam et al, 2009a;Prasad et al, 2009;Anton et al, 2011;Christopher et al, 2011;Valenzuela et al, 2012).…”