Eliane Gonçalves Larroza1, Eduardo Landulfo1

1Instituto de Pesquisas Energéticas e Nucleares - IPEN

 

Recently, cirrus clouds have been considered as having a significant impact on the terrestrial climatology because they influence the radiation budget of the atmosphere. However, the satellites as GOES (Geostationary Operational Environmental Satellites) or NOAA (National Oceanic and Atmospheric Administration) are limited to the cloud top and its reflectivity or brightness temperature, without determine accurately the optical depth or physical thickness. Other more recent sensors as MODIS (Moderate Resolution Imaging Spectrometer) are able to determine optical depths for aerosols and clouds, but especially if treating to cirrus, they are still not accurated. Then research programs as First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment - FIRE International Cirrus Experiment - HOIST, Experimental Cloud Lidar Pilot Study – ECLIPS and the Atmospheric Radiation Measurement - ARM Program have concentrated efforts in the research of cirrus, being based mainly on the observations of combined terrestrial remote sensing and airplanes instruments. Instruments as LIDAR (Light Detection and Ranging) are able to detect sub-visual cirrus cloud (temperatures around -50°C to -90°C and particles with 50µm size) in altitudes above 15km and estimate exactly their height, thickness and optical depth, contributing with information sufficiently accurated for satellites sensors and radiative transfer models. Following this context, the Center for Lasers and Applications (CLA) at Instituto de Pesquisas Energéticas e Nucleares (IPEN) has as objective determine such parameters and implement a cirrus cloud mask that could be used in the satellite images processing as well as in the qualitative improvement of the radiative parameters for numerical models of climate changes and weather forecast.