Satellite Sensors

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Revision as of 14:32, 15 April 2011

Common Database

The evaluation of passive imager cloud properties retrievals is part of the CREW. Hereto, a Common Database of cloud retrievals from different algorithms is build, which needs to be filled with cloud retrievals of the data providers. Below you will find relevant information for uploading your cloud retrievals to the common database. Note: The selected Golden Days are similar to those selected for CREW-2. Thus, providers that already provided their data for CREW-2, and that do not want to update their datasets or add new ones, do not need to upload their datasets again.

DATASET SPECIFICATIONS
We have selected five Golden Days that are listed in Table 1. During several hours of the selected Golden Days the A-Train satellites where aligned with AVHRR on-board NOAA-18. Our evaluation study will focus on these hours. However, we encourage the participants that are providing datasets from SEVIRI and MODIS to upload these datasets for the full day (24 hrs). The study area is restricted to the SEVIRI full disk. The following data are desired for the Common Database:

• SEVIRI 15 minutes data of the MSG disk preferably covering the golden days entirely (24hr)
• MODIS swath data covering the MSG disk preferably covering the golden days entirely (24hr)
• AVHRR swath data covering the MSG disk during the hours where NOAA-18 was aligned with the A-Train satellites
• Other instruments (MERIS/POLDER/..)

You can upload your data to the Common Database through the FTP site of ICARE, which is assessable for CREW members after registration, see Data_Access for more details.

Table 1: Golden Days that have been selected for the (inter)comparison

Table 2: Cloud Parameters that have been selected for the (inter)comparison

Passive Imagers

MSG/SEVIRI
SEVIRI is a 50 cm-diameter aperture, line-by-line scanning radiometer, which provides image data in four Visible and Near-InfraRed (VNIR) channels and eight InfraRed (IR) channels. A key feature of this imaging instrument (Fig. 1) is its continuous imaging of the Earth in 12 spectral channels with a baseline repeat cycle of 15 min. The imaging sampling distance is 3 km at the sub-satellite point for standard channels, and down to 1 km for the High Resolution Visible (HRV) channel. (from www.esa.int)
Data access for the CREW periods here: ./crew/observations/SEVIRI

MODIS
MODIS (Moderate-resolution Imaging Spectroradiometer) is a payload scientific instrument launched into Earth orbit by NASA in 1999 on board the Terra (EOS AM) Satellite, and in 2002 on board the Aqua (EOS PM) satellite. The instruments capture data in 36 spectral bands ranging in wavelength from 0.4 µm to 14.4 µm and at varying spatial resolutions (2 bands at 250 m, 5 bands at 500 m and 29 bands at 1 km). Together the instruments image the entire Earth every 1 to 2 days. (from Wikipedia)
Data access for the CREW periods here: ./crew/observations/MODIS

AVHRR
AVHRR instruments measure the reflectance of the Earth in 5 relatively wide (by today's standards) spectral bands. The first two are centered around the red (0.6 micrometer, 0.5 THz) and near-infrared (0.9 micrometer, 0.3 THz) regions, the third one is located around 3.5 micrometer, and the last two sample the thermal radiation emitted by the planet, around 11 and 12 micrometers, respectively. (from Wikipedia).
Data access for the CREW periods here: ./crew/observations/AVHRR

A-TRAIN Reference instruments

CALIOP
The Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) is the primary instrument on the CALIPSO satellite, which was launched in 2005. CALIOP provides profiles of total backscatter at two wavelengths, from which aerosol and cloud profiles will be derived. The instrument also measures the linear depolarization of the backscattered return, allowing discrimination of cloud phase and the identification of the presence of non-spherical aerosols.
Data access for the CREW periods here: ./crew/observations/CALIOP

CPR
./crew/observations/CPR

AMSR
./crew/observations/AMSR

Synthetic datasets

Simulated satellites scenes can be used to validate retrieval algorithms with a 'know truth'.
Data access for the CREW periods here: ./crew/observations/SYNTHETIC