Abstract
The Meteosat Second Generation (MSG) geostationary platform equipped with the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instrument provides observations of the Earth every 15 min since 2004. Based on those measurements, we present a new method called North African Sandstorm Survey (NASCube) to: (i) generate day/night remote sensing images in order to detect sandstorms over the Sahara and Saudi Arabia; and (ii) estimate day and night aerosol optical depth (AOD). This paper presents a method to create true color day and night images from the SEVIRI instrument level 1.5 products and the complete operational data processing system to detect sandstorms and quantify the AOD over the desert areas of North Africa and Saudi Arabia. The designed retrieval algorithms are essentially based on the use of artificial neural networks (ANN), which seems to be well suited to this issue. Our methods are validated against two different datasets, namely the Deep Blue NASA moderate-resolution imaging spectroradiometer (MODIS) product and AErosol RObotic NETwork (AERONET) acquisitions located in desert areas. It is shown that NASCube products deliver better estimations for high AOD (>0.2) over land areas than Deep Blue products. The open-public web platform will help researchers to identify, quantify and retrieve the impact of sandstorms over desert regions.
Highlights
Aerosols have an impact on the total radiative forcing [1] by scattering the shortwave solar radiation, absorbing long wave terrestrial radiation [2] and by modifying indirectly cloud properties [3,4,5,6].Mineral dust is one of the major aerosol types affecting our environment as it has one of the deepest boundary layers on the planet during the summer months [7]
We create a sandstorm colorinfrared anomaly using the well-known dust to be very helpful in dust storms detections over desert areas, because mineral dust aerosols have a composite [51,52] based on three infrared bands, 8.7, 10.8, and 12.0 μm
There are two types of instruments that provide aerosol optical depth (AOD) values; the in-situ instruments as those implemented by the AErosol RObotic NETwork (AERONET) network with, a very good accuracy and hundreds of measurements per day and the satellites retrievals as Deep Blue using the moderate-resolution imaging spectroradiometer (MODIS) experiment with large scenes
Summary
This has proven to be very high variable transmission and emission between 8 and 12 μm [53] This sole RGB product helpful in dust storms detections over desert areas, because mineral dust aerosols have a high variable is not sufficient to discriminate sandstorms from clouds or background thermal anomalies. The ANNs were trained with an iterative empirical process, which involves the selection of Empirically, andofafter several trials and errors, wastochosen to divide eight periods several millions pixels in representative cloudy it areas build the trainingthe set,year theninto a subsequent of approximately days and to mask, separate night of cases over imperfections ocean (2) andby land (2). A rolling cloudfree average background of the PTB within a period of 10 days (REF_PTB) is computed as a reference for each of 96 time slots at the pixel level, using our new cloud mask.
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