Penurunan nilai albedo dan suhu permukaan dari data Terra MODIS L1B untuk klasifikasi awan

Abstract

Clouds affect the energy balance in atmosphere through absorbtion, reflection and solar radiation process. These processes affect albedo values and the cloud surface temperature. The differences between albedo values and surface temperature can be the indicator in cloud classification and can be the separation between the cloud covered area and non-cloud covered area. Terra MODIS L1B data can be used for classifying between cloud and non-cloud using reflectant information at wavelength 0.62 μm to 0.67 μm, 0.459 μm to 0.479 μm, and 0.545 μm to 0.565 μm and the extraction of surface temperature using wavelenght 10.780 μm to 11.280 μm dan 11.770 μm to 12.270 μm. Yet, before the classification process, it is needed to look at the response of each wave lenght to the same object at the same location. Cloud‟s surface temperature can be derived from canal 31 and canal 32. The error values of both canal are 1.7 K on Januari 1st 2008, 3.3 K on March 26st 2008, 1.7 K on November 2st 2008, 5.6 K on April 6st 2008, and 12.8 K on September 24st 2008. Albedo value can be derived from band 1, band 3, band 4 since the values distribution pattern of all these canal are relatively in common. The results of the relation between reflectance bands and thermal bands show that the albedo approach method and surface temperature approach method can be used for clouds classification. The classification using albedo approach method is the based on the thickness of the clouds, while the surface temperature approach method is based on the height of clouds.