Geoscience Reference
In-Depth Information
Spaceborne Datasets
The LITE data were recorded on board the Space Shuttle Discovery during the NASA
space shuttle mission STS-64 in September 1994. Over 11-day period of the mis-
sion, the LITE instrument accumulated 53 hr of data (i.e., 70 available orbits) with
a pulse repetition rate of 10 Hz, at ~240 km height, within a few degrees of nadir at
three wavelengths: 355, 532, and 1,064 nm. The vertical resolution is 15 m and the
horizontal sampling is 700 m along the footprint. Only the data at 532 nm are used in
this study because of its better SNR, which is close to nine in the planetary boundary
layer (PBL). The LITE database contains only Level 1 (calibrated and geolocated lidar
backscatter profiles) data that can be accessed at http://www-lite.larc.nasa.gov.
The GLAS instrument was on the satellite platform called ICESat (Ice, Cloud,
and land Elevation Satellite, http://icesat.gsfc.nasa.gov/). The ICESat was launched
on January 13, 2003, had an inclined orbit of about 94°, and an altitude of about 590
km at the equator. The vertical and the horizontal resolution of the collected data are
respectively 76.8 m and 175 m. Despite a pre-launch goal for the lidar of 3 years conti-
nuous operation, the GLAS Operation Center needed to reduce the energy and the time
period of the lidar activities because of a technical malfunction of the lidar (Abshire,
2005; Thome et al., 2004). In this study, we use data from laser 2A that was recorded
before a temperature anomaly occurred, and for the same season as when LITE was in
operation, that is between the September 25, 2003 and October 3, 2003. Raw data at
532 nm (named Level 1) and the Level 2 offi cial GLAS cloud product are used in this
study to assess the accuracy of our algorithm. The GLAS data are characterized by a
lower SNR than that of LITE, close to 1.5 in the PBL, due to the higher altitude of the
satellite and the lower energy emitted by the instrument. The GLAS database includes
Level 1 and Level 2 (derived products such as CTHs, optical depth, …) data (available
at http://nsidc.org/data/icesat.data.html).
The CALIOP instrument is on the CALIPSO satellite platform. The CALIPSO
satellite was inserted in the A-Train constellation (http://www-calipso.larc.nasa.gov/
about/atrain.php) behind Aqua on April 28, 2006. This satellite, which resulted from
a collaboration between NASA and CNES, began to collect data in June 2006. This
database is the fi rst to provide more than 1 year of spaceborne lidar ob-seasonal varia-
tions may be studied with a high vertical resolution. The mean altitude of the satellite
is 705 km, resulting in vertical and horizontal resolutions of 30 and 330 m, respec-
tively. The inclination of the satellite is about 98.2°, and thus covers the polar regions.
The technology of the GLAS and the CALIOP instrument are quasi-similar, but opera-
tional modes are different. The SNR values are similar to that of the GLAS instrument
(~2.1). The CALIOP Level 1 and Level 2 data can be accessed at http://eosweb.larc.
nasa.gov/PRODOCS/calipso/tablecalipso.html or at http://www.icare.univ-lille1.fr.
The ISCCP database (Schiffer and Rossow, 1983), collects analyzed infrared (11
μm) and visible (0.6 μm) radiances measured by the operational geostationary and
polar-orbiting weather satellites. The ISCCP products provide a detailed description
of the horizontal variations of cloud top pressure and optical thickness. The horizontal
resolution of the ISCCP-DX data, used in this work, is 30 × 30 km 2 (http://climserv.
lmd.polytechnique.fr). The ISCCP dataset is built from Meteosat (http://www.eumetsat.
 
Search WWH ::




Custom Search