Abstract:
MODIS was launched aboard the Terra satellite on December 18, 1999
(10:30 am equator crossing time) as part of NASA's Earth Observing
System (EOS) mission. MODIS with its 2330 km viewing swath width
provides almost daily global coverage. It acquires data in 36 high
spectral
... resolution bands between 0.415 to 14.235 micron with spatial
resolutions of 250m(2 bands), 500m(5 bands), and 1000m (29
bands). MODIS sensor counts, calibrated radiances, geolocation
products and all derived geophysical atmospheric and ocean products
are archived at NASA Goddard DAAC and has been made available to
public since April 2000.
The level-2 MODIS cloud product consists of cloud optical and physical
parameters. These parameters are derived using remotely sensed
infrared, visible and near infrared solar reflected radiances. MODIS
infrared channel radiances are used to derive cloud top temperature,
cloud top height, effective emissivity, cloud phase (ice vs. water,
opaque vs. non-opaque), and cloud fraction under both daytime and
nighttime conditions. MODIS visible radiances are used to derive cloud
optical thickness and effective particle radius and cloud shadow
effects. Near infrared solar reflected radiance provides additional
information in the retrieval of cloud particle phase (ice vs. water,
clouds vs. snow). The shortname for this level-2 MODIS cloud product
is MOD06_L2 and the principal investigators for this product are MODIS
scientists Dr. Bo-Cai Gao ( gao@rsd.nrl.navy.mil) for cirrus cloud
detection; Dr. Paul Menzel ( paulm@ssec.wisc.edu) for cloud top
properties; and Dr. Michael King( king@climate.gsfc.nasa.gov) for
cloud optical properties .
The level-2 cloud product (MOD06_L2) consists of 46 gridded cloud
parameters. These parameters are produced at a spatial resolution of
either 1- km or 5-km (at nadir). Each MOD06_L2 product file covers a
five-minute time interval. This means that for 5-km resolution
parameters, the output grid is 270 pixels in width by 406 pixels in
length. Every tenth granule has an output grid size of 270 by 408
pixels. For 1-km resolution parameters, the output grid is 1354 pixels
in width by 2030 pixels in length and every tenth granule has an
output grid size of 1354 by 2040 pixels.
MOD06_L2 product files are stored in Hierarchical Data Format
(HDF-EOS). Forty four of the 46 gridded cloud parameters are stored as
Scientific Data Sets (SDS) within the file, the remaining two (band
number and statistics) are stored as Vdata(table
arrays). Approximately 288 files are produced daily. Nighttime files
are smaller than their daytime counterparts since only cloud top
properties are retrieved at night. Each daytime file is roughly 65.1
MB in size and each nighttime HDF file roughly 12.4 MB in size, and
the total data volume is approximately 12.3 GB/day.
MOD06_L2 Data Category & Parameters
Spatial & Temporal Resolution:
latitude,longitude
scan start time
Solar and Sensor Viewing Geometry:
solar zenith angle, solar azimuth angle
sensor zenith angle, sensor azimuth angle
Cloud Top Parameters (5km):
cloud top pressure from IR retriev(daytime,nighttime,all)
cloud top pressures from individual thermal band ratios
cloud height retrieval method, tropopause height
surface pressure
cloud top temperature (daytime,nighttime,all)
cloud effective emissivity (daytime,nighttime,all)
cloud fraction (daytime,nighttime,all)
cloud phase(daytime, nighttime, all)
Cloud Optical Properties (1km):
cloud optical thickness
cloud water path
effective particle radius
effective particle radius difference
Radiation Parameters:
spectral cloud forcing
cirrus reflectance
surface type (emissivity based)
Brightness Temperature
Brightness Temperature Difference
Quality Assurance Parameters:
Processing flag for 5 km resolution
cirrus reflectance flag for 1 km resolution
quality assurance flag for 1 & 5 km resolution
cloud mask for 1 & 5 km, radiance variance for thermal bands
statistics for parameters at 1km resolution
The MODIS Cloud Product will be used to investigate seasonal and
inter-annual changes in cirrus (semi-transparent) global cloud cover
and cloud phase with multispectral observations at high spatial (1
kilometer) resolution.
For more information about the MOD06_L2 product, visit the
MODIS-Atmosphere site at:
http://modis-atmos.gsfc.nasa.gov/MOD06_L2/
or
See the MODIS Science Team homepage for more data set
information at: http://modis.gsfc.nasa.gov/data/dataprod/ 
