A cloud detection system using AVHRR HIRS/2 sensor data
Youichi Minowa,Mikio Takagi
Institute of industrial Science University of Tokyo, Japan
Abstract
We propose a cloud detection system using AVHRR (Advanced Very Resolution Radiometer) and HIRS/2 (High Resolution Infrared Radiation Sounder) data from NOAA (National Oceanic and atmosphere administration ) satellites . The purposes of this system is give guarantee the accuracy of the atmospheric correction method for AVHRR data using HIR /2 data there are three stages for cloud detection because two different sensors (AVHRR, HIRS/20 are used in our atmospheric correction method. On HIRS/2 stage gross cloud and channel deferential technique are On the AVHRR stage the gross cloud special coherence multi channel clouds detection technique are used final stage each HIRS/2 pixel uses results of the gross cloud and spatial coherence check of the AVHRR data which is covered with the HIRS/2 pixel to investigation the cloud contamination The relationship between the error of the atmospheric correction and the result of cloud detection in each stage is discussed.
Introduction
Remotely sensed data from meteorological satellite NOAA can provide very useful and important information in meteorology, oceanography and may other scientific fields because of its instantaneous and periodic observation of broad area of the earth. In our laboratory NOAA satellite data are received every day proceed and distributed to many other laboratories and institutes all over Japan The wide and simultaneous observation is one of the most important property of satellite sensor data especially for ocean observation ,it is useful to draw the temperature map. The distribution of the sea surface temperature (SST) observed by the satellite infrared sensors is contaminated by the atmosphere and cloud. In general remotely observed SST are cooler (about 2-6 K) than in situ data the causes are mainly emission absorption and scatter by the atmosphere and cloud. If there are some clouds which is not enough large or thick to cover the satellite sensors field of view the thermal radiance from the surface is partly blocked by them and observed SST's become cool. So in order to determine temperature on good accuracy it is necessary to remove clouds Mc lain et.al
(1) discussed about the cloud detection system and its performance for their multi channel correction method.
The NOAA satellites are on board some multi channel sensors (AVHRR, HRIS/2 and other the AVHRR sensor is used for observing the earth surface on high resolution and the HIRS/2 data. But the sounding the atmosphere vertical construction in the same time .So it is expected that the atmosphere effects in the AVHRR data can be compensated by using vertical information from HIRS/2 data. But the AVHRR and HIRS/2 have different resolution and it means that the clouds act different roles for observation accuracy in each field of view of AVHRR and HIRS/2. So it is necessary to remove the clouds on each sensor.
In this paper a cloud detection system for AVHRR and HIRS/2 data is proposed This method is applied to NOAA-10 image of northwest Pacific Ocean for 9 May 1987 (which received in our laboratory) and the results of those experiments show that the almost cloud pixels included in the satellite image can be removed.
