Introduction

The MAPSS database has been established to provide a means of intercomparison and cross-validation of MODIS Atmosphere products with those of other sensors and instruments (ground based, airborne, or spaceborne) obtained at different locations around the globe. Currently, only the Level 2 Aerosol (MOD04) and Water Vapor (MOD05) products are represented, b ut other Atmosphere products may be included in the future.


Download Data Files (Separated by Parameter/Location/Year)

Disclaimer

This database currently contains the Beta release of MAPSS data. The data is provided in good faith, without express or implied warranty. Note that the AERONET (Aerosol Robotic Network) data were automatically cloud cleared but may not have final calibration applied. These data are not Quality Assured.

Description

The database comprises statistics of spatial subsets of some scientific data sets (SDS) from the above referenced MODIS products. Certain ground locations including (but not limited to) the AERONET Sunphotometer measurement sites have been identified as f ocal points for these spatial statistics. The process of generating the statistics involves identifying these locations on the MODIS products, extracting the values of the pixel corresponding to each point as well as surrounding pixels falling within a ra dius of 25 Km. This subset array of pixels for each location is then used to compute the following statistics:

1. Value of the central pixel
2. Mean of the subset
3. Standard deviation of the subset
4. Slope of a plane fitted to the subset
5. Azimuth (direction) of the slope
6. Multiple Correlation Coefficient

These statistical parameters have been calculated for most of the MOD04 and MOD05 products on a regular basis. There are however some data gaps resulting from non-retrieval of such data from MODIS images due to some unfavorable factors such as cloud cover in the reflective wavebands. Similar statistics are included for AERONET data, except that in this case, the subset is temporal (30 minutes on either side of corresponding MODIS overpass) rather than spatial, there is no direction of slope, and Linear (n ot Multiple) correlation coefficient is obtainable. It is possible to query this database and extract desired parameters for any number of locations and time period (beginning from February 2000) by filling out a form through this web interface.

Data Retrieval

To extract data, click the Retrieve Data button. In the query form, data representing the above listed statistics (1 - 6) are prefixed by: "pval_", "mean_", "sdev_", "slop_", "slaz_", and "mcoc_" (or "lcoc_" for AERONET data), respectively, followe d by a short acronym to designate the product. If numbers or number ranges are included in these acronyms, they represent wavelength in nanometers. If the acronym ends with a "-l", this indicates that the product covers only land surfaces, but if it ends with a "-o" the product covers only ocean (sea) surfaces, otherwise, it can potentially cover any type of surface. The instrument (MODIS or AERONET) product group and scientific dataset from which each parameter originates are indicated in rectangular bra ckets.

Data availability

Only data acquired starting from 20 August 2000 have been released at this time. Note also that due to data processing and transfer constraints, the time lag between the date of MODIS data acquisition and the date it appears in this web site is currently estimated to be between 1 and 2 weeks.


Database Curator: Charles Ichoku (ichoku@climate.gsfc.nasa.gov)
Authorized by: Dr. Yoram Kaufman (kaufman@climate.gsfc.nasa.gov)