Aerosol retrievals from METEOSAT-8 - CM SAF
Aerosol retrievals from METEOSAT-8 - CM SAF Aerosol retrievals from METEOSAT-8 - CM SAF
SAF on Climate Monitoring Visiting Scientists Report Doc. No: 1.0 Issue : 1.0 Date : 4 October 2006 absorbing aerosols as one can see in Fig. 6 (For example, for a surface albedo of 0.4 and aerosol model with a single scattering albedo of 0.81, the TOA reflectance decreases with the AOT) The aerosol model is assumed to be continental and the accuracy of the retrieved AOT is ±0.13 when compared to AERONET data. A global analysis for one year of data suggests that the optimal composite time period is around 14 days and that a continental aerosol model is most of the time well adapted for the retrieval of an AOT. Almost no bias is found between GOES and AERONET AOT's when the surface reflectance reference is found after applying a residual aerosol correction using a background AOT of 0.02. Figure 5: Example of Aerosol Optical Thickness level 2 product over land and ocean retrieved from the GOES 8 instrument on 19 th of April 2005 over US East Coast. (University of Maryland at Baltimore County server : http://alg.umbc.edu/usaq/archives/000474.html) - 14 -
SAF on Climate Monitoring Visiting Scientists Report Doc. No: 1.0 Issue : 1.0 Date : 4 October 2006 Figure 6 : The reflection function as a function of aerosol optical thickness and surface reflectance for a Junge size distribution given by n(r) ∝r 4 , where λ = 0.61 µm and θ 0 = 40°. Panels (a) and (b) apply to θ = 60° and φ = 0° but for different single scattering albedo; (c) and (d) to nadir observations (θ = 0°) (adapted from Fraser and Kaufman 1985). 5.1.4 MSG/SEVIRI The MSG/SEVIRI sensor is unique and although it is not optimised for observation over land surfaces, because of the lack of a blue channel, this sensor has several advantages for aerosol retrievals over land. The time sampling of 15 minutes gives access to the diurnal cycle of the aerosol properties and allows the detection of rapid changes in the atmosphere. Moreover, it increases the chance of having cloud-free observations. The thermal IR channels allow the determination of a good cloud mask. The constant viewing geometry and target localisation allow an easy co registration of images. And finally, the variable solar angles allow some angular - 15 -
- Page 1 and 2: SAF on Climate Monitoring Visiting
- Page 3 and 4: SAF on Climate Monitoring Visiting
- Page 5 and 6: SAF on Climate Monitoring Visiting
- Page 7 and 8: SAF on Climate Monitoring Visiting
- Page 9 and 10: SAF on Climate Monitoring Visiting
- Page 11 and 12: SAF on Climate Monitoring Visiting
- Page 13: SAF on Climate Monitoring Visiting
- Page 17 and 18: SAF on Climate Monitoring Visiting
- Page 19 and 20: SAF on Climate Monitoring Visiting
- Page 21 and 22: SAF on Climate Monitoring Visiting
- Page 23 and 24: SAF on Climate Monitoring Visiting
- Page 25 and 26: SAF on Climate Monitoring Visiting
- Page 27 and 28: SAF on Climate Monitoring Visiting
- Page 29 and 30: SAF on Climate Monitoring Visiting
- Page 31 and 32: SAF on Climate Monitoring Visiting
- Page 33 and 34: SAF on Climate Monitoring Visiting
- Page 35 and 36: SAF on Climate Monitoring Visiting
- Page 37 and 38: SAF on Climate Monitoring Visiting
- Page 39 and 40: SAF on Climate Monitoring Visiting
- Page 41 and 42: SAF on Climate Monitoring Visiting
- Page 43 and 44: SAF on Climate Monitoring Visiting
- Page 45 and 46: SAF on Climate Monitoring Visiting
- Page 47 and 48: SAF on Climate Monitoring Visiting
- Page 49 and 50: SAF on Climate Monitoring Visiting
- Page 51: SAF on Climate Monitoring Visiting
<strong>SAF</strong> on Climate Monitoring Visiting Scientists Report Doc. No: 1.0<br />
Issue : 1.0<br />
Date : 4 October 2006<br />
Figure 6 : The reflection function as a function of aerosol optical thickness and surface<br />
reflectance for a Junge size distribution given by n(r) ∝r 4 , where λ = 0.61 µm and θ 0 = 40°.<br />
Panels (a) and (b) apply to θ = 60° and φ = 0° but for different single scattering albedo; (c) and<br />
(d) to nadir observations (θ = 0°) (adapted <strong>from</strong> Fraser and Kaufman 1985).<br />
5.1.4 MSG/SEVIRI<br />
The MSG/SEVIRI sensor is unique and although it is not optimised for observation over land<br />
surfaces, because of the lack of a blue channel, this sensor has several advantages for aerosol<br />
<strong>retrievals</strong> over land. The time sampling of 15 minutes gives access to the diurnal cycle of the<br />
aerosol properties and allows the detection of rapid changes in the atmosphere. Moreover, it<br />
increases the chance of having cloud-free observations. The thermal IR channels allow the<br />
determination of a good cloud mask. The constant viewing geometry and target localisation allow<br />
an easy co registration of images. And finally, the variable solar angles allow some angular<br />
- 15 -
Change language