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 ( firstname.lastname@example.org) for cirrus cloud detection; Dr. Paul Menzel ( email@example.com) for cloud top properties; and Dr. Michael King( firstname.lastname@example.org) 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)
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.
Near real-time (NRT) data are available from MODAPS for certain Aqua and Terra MODIS L0, L1, L2, L2G, and L3 products. Whereas the standard MODIS forward processing acquires 2-hour L0 files for Aqua and Terra from EDOS within 7-8 hours of real time, LANCE-MODIS acquires session-based L0 files from EDOS and the end of the session is available within 10-30 minutes after real time.
The 'version 004' or 'collection 004' product is better than 'version 003' and earlier versions. The quality of this version 004 product is ... established as 'Provisional' . It is based on a better calibration algorithm but the product is not fully validated yet. Product images look reasonable when compared to other spaceborne instruments or comparable data in limited situations. Scientific use should be performed with caution with careful reference to QA statements provided with each product.For the latest information please see: http://modis-atmos.gsfc.nasa.gov/products_calendar_overview.html.
Available to public to gain familiarity with the data format and parameters.
This Data set (version 004/collection 004) is of 'Provisional' Quality. Even though, it is based on better calibration algorithm but ... is not fully validated yet. This data is still not appropriate for use in scientific publications. Before using it in any publication please contact science team representative for the known problems and updates.
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