The operational Meteosat-7 is going soon to be replaced by Meteosat Second Generation or Meteosat-8, and means of exploiting the larger range of spectral information from MSG to improve the rainfall analyses are needed. Particular interest is focused on the near infrared band measurements that will be possible thanks to the 1.6µm and 3.9µm SEVIRI (Spinning Enhanced Visible and InfraRed Imager) channels. MSG data were not available at the time of this work therefore the investigation were carried out by considering SEVIRI-like measurements from the MODIS (Moderate Resolution Imaging Spectro-radiometer) on board the Terra polar-orbiting satellite. The relevance of those measurements rises from the following considerations: the 3.9µm scattered radiation is mainly determined by the cloud-top particles size, whereas the 1.6µm scattered radiation depends upon both the optical thickness and the cloud-top particles size. A parameter related to the mean distribution of clod-top particles size is the effective radius. This quantity is retrievable pending the availability of the optical cloud thickness. The latter can be obtained from visible measurements and for this reason the proper use of the 1.6µm channel is in combination with the visible channel. Previous work shown that the 3.9µm effective radius is correlated to the precipitation in case of deep convective cloud. On the other hand the investigations onto the correlation between 1.6µm effective radius and precipitation belong to a very new research area. This parameter is related to deeper cloud layer and thus in combination with the 3.9µm effective radius offers the possibility to estimate vertical variation of cloud droplet effective radius. In this work we investigate the correlation between VIS/1.6µm channels and the ground precipitation by a statistical approach.
On the sensitivity of modis visible/1.6 micron channels to radar-measured ground precipitation
PORCU', Federico;PRODI, Franco
2004
Abstract
The operational Meteosat-7 is going soon to be replaced by Meteosat Second Generation or Meteosat-8, and means of exploiting the larger range of spectral information from MSG to improve the rainfall analyses are needed. Particular interest is focused on the near infrared band measurements that will be possible thanks to the 1.6µm and 3.9µm SEVIRI (Spinning Enhanced Visible and InfraRed Imager) channels. MSG data were not available at the time of this work therefore the investigation were carried out by considering SEVIRI-like measurements from the MODIS (Moderate Resolution Imaging Spectro-radiometer) on board the Terra polar-orbiting satellite. The relevance of those measurements rises from the following considerations: the 3.9µm scattered radiation is mainly determined by the cloud-top particles size, whereas the 1.6µm scattered radiation depends upon both the optical thickness and the cloud-top particles size. A parameter related to the mean distribution of clod-top particles size is the effective radius. This quantity is retrievable pending the availability of the optical cloud thickness. The latter can be obtained from visible measurements and for this reason the proper use of the 1.6µm channel is in combination with the visible channel. Previous work shown that the 3.9µm effective radius is correlated to the precipitation in case of deep convective cloud. On the other hand the investigations onto the correlation between 1.6µm effective radius and precipitation belong to a very new research area. This parameter is related to deeper cloud layer and thus in combination with the 3.9µm effective radius offers the possibility to estimate vertical variation of cloud droplet effective radius. In this work we investigate the correlation between VIS/1.6µm channels and the ground precipitation by a statistical approach.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
