GIDS-1 CD-ROM Overview 1.0 General Description Within the overall scientific strategy of the World Climate Research Programme (WCRP) of the World Meteorological Organization (WMO), the Global Energy and Water-cycle Experiment (GEWEX) has been launched to study on the global scale the fast climate system mechanisms controlling radiation, clouds and rain, evaporation and fresh water storage. The GEWEX Continental-scale International Project (GCIP) initiative is the first major project under GEWEX. The first of the GCIP Initial Data Sets (GIDS-1) was compiled as a static systems test of the GCIP data management system. Descriptions of the objectives and configuration of the GCIP data management system, and of the GCIP project as a whole, are provided in the GCIP scientific and implementation plans (WMO, 1992; IGPO 1993, 1994a, b). The GCIP Static Data Systems Test made use of existing experimental and operational capabilities to produce a composite observational and model-output data set (GIDS-1) which was derived from new observation and assimilation schemes. GIDS-1 contains data from the west-central Mississippi River basin with data from 1 February 1992 to 30 April 1992. Data are primarily based on the STORM-Fronts Experiment Systems Test (STORM-FEST) which was conducted from 1 February to 15 March 1992 over the central United States augmented by additional hydrological, geographical and surface characterization data. STORM-FEST investigated the structure and evolution of fronts, embedded precipitation, and associated mesoscale phenomena in winter storms over a total of twenty Intensive Observation Periods (IOPs). To achieve the STORM-FEST objectives, data sets from the operational, enhanced operational, and research observational systems were collected. Refer to the STORM-FEST Operations Summary and Data Inventory Document (NOAA U.S. Weather Research Program Office, 1993), for further details regarding the experiment and data collection. GIDS-1 took advantage of the existing STORM-FEST special observational database. To complete the GIDS-1 data set, an additional six weeks of atmospheric and hydrological data from 15 March through 30 April 1992, was added from existing data centers. GIDS-1 provides a short-term data set suitable for: (a) Initial diagnostic studies to improve representation of sub-grid- scale processes; (b) Development of improved 4-Dimensional Data Assimilation (4DDA) methodology; and (c) Validation and analysis studies. In addition, GIDS-1: (d) Provides information on what is available now from existing data centers in terms of data quantity and quality; (e) Assists in identifying primary and supplemental data sources; (f) Helps to develop GCIP Project relationships with existing data centers; (g) Directly involves research scientists in developing the GCIP Data Management and Service System (DMSS); and (h) Provides information to assess the benefit of special versus operational data sets and therefore assist in identifying actions needed by GCIP to assure suitable EOP data sets. 2.0 GIDS-1 Objectives and Approach The purpose of compiling the GIDS-1 data set was to create a prototype data set that would be similar to future data sets collected during the GCIP Enhanced Observing Period (EOP). GIDS-1 provides GCIP researchers with access to both routine operational as well as high- resolution augmented research network data. To accomplish this objective prior to actual data collection during the EOP, data from the recent STORM-FEST Field Project was selected as a "nucleus" around which to build GIDS-1. STORM-FEST provided a data set that: (1) included atmospheric and hydrological data obtained in the center of the GCIP area; (2) occurred during a hydrologically important time of year (i.e., late winter/early spring); (3) included routine operational data as well as special research observing platforms combined for a six-week period; and (4) provided similar quality controlled surface and upper air composite data sets as required by GCIP. An additional six weeks of operational data was added to the STORM-FEST database to (1) increase the collection period of GIDS-1 into the spring snow melt/runoff in the Mississippi River basin; and (2) provide a direct comparison of six weeks of intensive observations to six weeks of routine observations for evaluating future GCIP observational enhancements. Additional hydrological data sets (i.e., stream flow) and surface characterization (i.e., vegetation) were included as required for GCIP objectives. Further information on all the datasets included in GIDS-1 can be found in IGPO 1994c. Note that this CD-ROM contains only a subset of the complete GIDS-1 dataset. 3.0 Directory Structure The GIDS-1 CD-ROM contains two precipitation composites, three surface composites, three hydrology datasets, one soil moisture dataset, high resolution and mandatory and significant upper air sounding datasets, NOAA 405 MHz Wind Profiler Demonstration Network (WPDN) data, and several different types of imagery. For each composite/dataset, the data, associated documentation, station information, etc. are all located in separate directories. This CD-ROM is divided into nine high-level directories (i.e., precip, sfc_met, hydro, soilmois, sounding, images, prof_405, stn_list, and docs). Several of these high-level directories are further divided into subdirectories, depending on the nature of the data contained within that directory. Each directory contains a distinct set of data. Different composites and datasets are located in separate directories. Directory names and data file names are never more than eight prefix characters followed by three suffix characters and are compatible with personal computer name limitations. File sizes vary according to the type of data contained in the dataset or composite. Detailed descriptions of the data, quality control processing, etc. for each dataset are located in the /docs directory of this CD-ROM. The user should review these documents for each dataset which is extracted from this CD-ROM. A brief description of the data contained in each high-level directory is given below. 3.1 /hydro This directory contains the GIDS-1 hydrology data from the United States Geological Survey (USGS) and the Tennessee Valley Authority (TVA). The USGS stream flow, TVA stream flow, and TVA dam discharge data are located in three separate subdirectories, each containing a single file. The three subdirectories are /usgsflow, /tvaflow, and /damdisch, respectively. Each file has been given a name which describes the data it contains (e.g., the TVA stream flow data file is named strmflow.tva). Refer to the appropriate documents in the /docs directory of this GIDS-1 CD-ROM for a detailed data description of these datasets. 3.2 /images This directory contains the GIDS-1 imagery data. There are four subdirectories under this high-level directory (i.e., /analyses, /goes7_ir, /nowrad, /vegindex). The files located in each subdirectory have names that indicate the date on which the imagery is valid. Refer to the imagery document in the /docs directory of this GIDS-1 CD-ROM for a detailed data description of these datasets. The /analyses directory contains scanned 500mb and surface imagery at 1200 UTC acquired from the NOAA National Meteorological Center (NMC) Climate Analysis Center (CAC) Daily Weather Map Series Publication. The 500mb imagery is located in the /cac500mb subdirectory under the /analyses subdirectory. These Graphics Interchange Format (GIF) data files have names of the form uaYYMMDD.gif where YY is the UTC year, MM is the UTC month, and DD is the UTC day (e.g., ua920202.gif for 2 February 1992 data). The surface imagery is located in the /cac_sfc subdirectory under the /analyses subdirectory, and the data files have names of the form saYYMMDD.gif where YY is the UTC year, MM is the UTC month, and DD is the UTC day (e.g., sa920202.gif for 2 February 1992 data).. The /goes7-ir directory contains GOES-7 infrared imagery (8 Km resolution). This directory contains GIF files for the complete GIDS-1 time period (1 February 1992 through 30 April 1992), nominally at 1200 UTC daily or closest available time. Each GIF file has a name of the form YYMMDDHH.GIF, where YY is the UTC year, MM is the UTC month, DD is the UTC day and HH is the UTC hour. An example for 24 February 1992 1200 hours would be 92022412.GIF. The /nowrad directory contains NOWRAD imagery (8 Km resolution). This directory contains GIF files for 2 February 1992 through 16 March 1992, nominally at 1200 UTC daily or the closest available time.. Each GIF file is named YYMMDDHH.gif, where YY is the UTC year, MM is the UTC month, DD is the UTC day and HH is the UTC hour. An example for 24 February 1992 1200 hours would be 92022412.gif. The /vegindex directory contains monthly AVHRR derived vegetation index imagery for February through June of 1992. Each GIF file is named pYYMM.gif where YY is the UTC year and MM is the UTC month that the image is valid. An example for April 1992 would be p9204.gif. 3.3 /precip This directory contains the GIDS-1 hourly and daily precipitation data. Refer to either the hourly or daily precipitation composite documents in the /docs directory of this GIDS-1 CD-ROM for a detailed data description. The daily precipitation composite in monthly files are located in the /precip/dlycomp subdirectory. The files in this area are named YYMM.pqc where YY is the UTC year and MM is the UTC month that the data are valid. An example for April 1992 would be 9204.pqc. The hourly precipitation composite in daily files are located in the /precip/hlycomp subdirectory. These files are named YYMMDD.pqc where YY is the UTC year, MM is the UTC month, and DD is the UTC day that the data are valid. For example, the file for 20 March 1992 would be named 920320.pqc. 3.4 /prof_405 This directory contains the GIDS-1 405 MHz Wind Profiler data. Note that this data has been compressed using the `gzip' utility. The user must `gunzip' each file after extraction from the CD-ROM. Each `zipped' file is compressed by approximately 85%, and the user must allow approximately seven (7) times the compressed file size for the decompressed file. The files in this subdirectory are names XXXMMw60.gz, where XXX is the three letter identifier for the reporting station and MM is the UTC month that the data are valid. An example for station BLM for March would be BLM03w60.gz. Note that when the files are decompressed, the `gz' suffix is dropped. Refer to the wind profiler documentation in the /docs directory of this GIDS-1 CD-ROM for a detailed data description. 3.5 /sfc_met This directory contains the GIDS-1 daily and hourly surface meteorological data. The /sfc_met directory contains three subdirectories. The National Climatic Data Center (NCDC) Summary of the Day Co-operative data is located in the /dly_coop subdirectory. The NCDC Surface Aviation Observation (SAO) Hourly Composite in daily files are located in the /hlycomp subdirectory. The NCDC SAO "Specials" dataset in daily files are located in the /sao_spec subdirectory. In each subdirectory, the data files are named YYMMDD.xxx where YY is the year, MM is the month and DD is the day that the data are valid. The 'xxx' suffix is set to 'dqc' for the NCDC Summary of the Day Co-operative data and to 'qcf' for the NCDC SAO data. An example of the file name for the NCDC SAO data for 5 February 1992 would be 920205.qcf. Refer to the appropriate composite and dataset documentation in the /docs directory of this GIDS-1 CD-ROM for a detailed data description. 3.6 /soilmois This directory contains the GIDS-1 soil moisture data. There is a single file (soilmois.ill) containing only the state of Illinois soil moisture data in the /soilmois area. For a complete data description, refer to the soil moisture document in the /docs directory of this GIDS-1 CD-ROM. 3.7 /sounding This directory contains the GIDS-1 upper air sounding data. The high resolution sounding data is located in the /high_res subdirectory. The NCDC mandatory and significant sounding data is located in the /mand_sig subdirectory. Each of these subdirectories is further divided into another layer of directories that contain the sounding data for a particular date. The directories are names MMDD where MM is the UTC month and DD is the UTC day that the sounding data is valid. The subdirectory containing 15 February data is named /0215. Within the dated directories are dated files. The files are named MMDDHH.XXX where MM is the UTC month, DD is the UTC day, and HH is the UTC hour. The suffix for a particular file indicates the station where the data was collected. The file containing 00 hour 15 February data for Denver, Colorado is named 011500.DEN. For a complete data description, refer to the sounding documentation in the /docs directory of this GIDS-1 CD-ROM. 3.8 /stn_list This directory contains the station information for the data on this GIDS-1 CD-ROM. General station metadata such as network, station latitude, longitude, elevation, occurrence, station identifier and station name are listed in the station information file. Two files containing identical information, one sorted by station identifier (stn_list.IDN) and the other sorted by station name (stn_list.NAM), have been provided. 3.9 /docs This directory contains all of the GIDS-1 documentation. This directory contains detailed and general descriptions, formats, sample data, quality control processing, data remarks, and references for each composite/dataset on this CD-ROM. 4.0 References IGPO (International GEWEX Project Office), 1993: Implementation Plan for the GEWEX Continental-Scale International Project (GCIP) - Volume I - Data Collection and Operational Model Upgrade. IGPO Publication Series No. 6, IGPO, Washington, D.C. IGPO (International GEWEX Project Office), 1994a: Implementation Plan for the GEWEX Continental-Scale International Project (GCIP) - Volume II - Research Plan. IGPO Publication Series No. 7, IGPO, Washington, D.C. IGPO (International GEWEX Project Office), 1994b: Implementation Plan for the GEWEX Continental-Scale International Project (GCIP) - Volume III - Strategic Plan for Data Management. IGPO Publication Series No. 8, IGPO, Washington, D.C. IGPO (International GEWEX Project Office), 1994c: Tactical Data Management Plan for the first of the GCIP Initial Data Sets (GIDS-1). Currently in publication. Interim copies available from OFPS. USWRP (United States Weather Research Program, 1993: STORM-FEST Operations Summary and Data Inventory. USWRP Office/UCAR Office of Field Project Support, Boulder, Colorado. WMO (World Meteorological Organization), 1992: Scientific Plan for GEWEX Continental-Scale International Project (GCIP). WCRP-67, WMO/TD No. 461, WMO, Geneva, Switzerland.