Cloudsat Project

CloudSat Project
A NASA Earth System Science Pathfinder Mission
Cloudsat MODIS-AUX Auxiliary Data
Process Description and Interface Control Document
Algorithm Version: 3.0
Date: July 30, 2004
Questions concerning the document and proposed changes shall be addressed to
Philip Partain
970-491-7835 partain@cira.colostate.edu
Cooperative Institute for Research in the Atmosphere
ColoradoState University
Fort Collins, CO 80523
Contents
Contents....................................................................................................................3
1. Introduction..................................................................................................5
1.1Overview......................................................................................................5
1.2 Applicable Documents.................................................................................5
2. Brief Description of the Generic-AUX Process…………….......................5
3. Generic-AUX Algorithm Inputs .................................................................6
3.1 1B-CPR ……….…………………………………………………………..6
3.2AN-MODIS…….……...................................................................……......7
4. Data Product Output Specifications……………………………………….7
5. Operator Instructions……………………………………………………..21
6. Acronym List..............................................................................................22
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1. Introduction
1.1. Overview
The MODIS-AUX data set is an intermediate product that contains a subset of ancillary MODIS radiance and cloud mask datathat overlaps and surrounds each CloudSat cloud profiling radar (CPR) footprint. Input data are obtained from the 1B-CPR and AN-MODIS products, and the MODIS-AUX data are used as input to the 2B-GEOPROF, 2B-CLDCLASS, 2B-TAU, and 2B-FLXHR algorithms in the CloudSat data processing system. The MODIS-AUX product is created by the Generic-AUX Subset-to-Reference algorithm. This document describes theinterfaces between the input data sets and the Generic-AUX algorithm, the format of the MODIS-AUX product, and quality assessment instructions for the Data Processing Center (DPC) operator. Details of the operation of the data sub-setting performed by the Generic-AUX algorithm can be found in the CORE Data Manipulation Routines document (see below).
1.2. Applicable Documents
• Level 1B CPRProcess Description and Interface Control Document (v2.7),
11JUN04.
• Cloudsat AN-MODIS Ancillary Data Interface Control Document (draft),
15APR02.
• atbd_mod01.pdf: Draft of the MODIS Level 1B Algorithm Theoretical Basis
Document Version 2.0 (ATBMOD-01).
• atbd_mod06.pdf: Discriminating Clear-Sky From Cloud With MODIS
Algorithm Theoretical Basis Document (MOD35).
• Cloudsat Data ProcessingCenter System Description and Data Processing Plan,
29MAY01.
• The CORE Data Manipulation Routines – Process Description, 1JUN04.
• Cloudsat L3 Ground System-Science Data Processing, 22APR01.
• End-to-End Information System (EEIS), 19APR01.
2. Brief Description of the Generic-AUX Process
The Generic-AUX subset-to-reference algorithm uses two datasets: an independent dataset and a referencedataset. To produce the MODIS-AUX product, AN-MODIS is the independent dataset containing the radiances, cloud mask, geolocation, etc. data that will be sub-set around each CloudSat ray. The geolocation data from the 1B-CPR product comprise the reference dataset. Operating one CloudSat ray at a time, the subset-to-reference algorithm uses the reference and independent geolocation data to find theclosest AN-MODIS pixel to the CloudSat ray, then stores a 3-pixel across-track by 5-pixel along-track grid of each AN-MODIS parameter of interest in a 15-element vector associated with that ray. If the CloudSat geolocation for a particular ray is missing or the
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closest valid AN-MODIS pixel is more than 0.71 km from the CloudSat ray, the resulting MODIS geolocation data and the associated...