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The Synthesizer is a vehicle for viewing, managing, and analyzing geographic information in the form of spatially distributed data (grids), vectors (digital line graphs), labels, and time-series point data. It contains common GIS components along with enhanced tools for working with time-series point data such as those collected at climate stations. The specific tools in the Synthesizer allow users to organize data into common workable formats, view and manipulate that data according to specific needs, and analyze the results of the manipulation.
This software package:
- Utilizes existing climate grids for large regional and global scale reconnaissance studies.
- Provides a localization capability for working with national meteorological agencies and other groups to utilize local data sets which can provide much more detailed and accurate grids of specific areas.
- Enables researchers who are not GIS experts to easily conduct sophisticated analyses using climate and other data.
- Combines climate information with other information such as maps of river basins, population densities, vegetative indices from remote sensing, and the like to substantially improve the level and quality of GIS analysis in agriculture, water resources, and many other fields.
Summary of tools available in the Synthesizer
1) Virtual world zooming. This allows the user to zoom in and move around climate regions as needed with simple mouse movements.
2) Polygon creation. The user can create polygons by either drawing with the mouse or by clipping them from digital line graph (DLG) data. Many DLGs are not polygons, but groups of points. Having completed polygons allows the user to clip regions using those polygons. The Synthesizer includes a DLG editor. Examples of DLGs that can be converted to polygons include the boundaries of river basins, agroclimatic regions and countries.
3) Polygon / point specific data extraction. This tool allows the user to retrieve selected data from a single cell or group of cells in a specific area (or polygon) from a grid or set of grids.
4) Conditional grid masking. This feature allows creation of a "mask" grid of areas meeting certain conditions. For example, the user can create a mask showing only those grid cells where the maximum air temperature is greater than 15° C and the total precipitation is greater than 1000 mm. These masks can then be used for clipping and summarizing data and in the grid equation editor.
5) Grid equation editor. This allows the user to create mathematical equations with grids as variables. Constants and functions are also available. A simple example would be (Tmax + Tmin) / 2 = Tmean. This would create a mean temperature grid from maximum and minimum temperature grids.
6) Evapotranspiration estimation. Evapotranspiration represents the demand and consumption of water by evaporation and transpiration. The equation editor includes an Ra function (latitude and time dependant solar radiation at the top of the earth's atmosphere) making it possible to compute evapotranspiration using the Hargreaves method or other methods depending upon the availability of required climate data.
7) Point data preparation. The user can manipulate time-series point data from climate stations and the like. For example, the user can calculate the average or total precipitation for a water year instead of a calendar year. The user could also calculate the extreme minimum temperatures for the period of record. This tool is extremely versatile and powerful.
8) Localized gridding. This is a set of gridding techniques (or links to external gridding packages such as Surferä) that allows the user to grid point data in a specific area.
9) CropWat link. This tool allows the user to select a group of grids and extract a specific point from those grids into a data file compatible with FAO's CropWat program. The user can then use this file in CropWat for analysis. The same facility for other crop models will be added later.
10) Specification checking tool. This tool takes a set of x, y, and parameter value points and extracts the cells at the x and y locations from a grid. This allows the user to compare a set of points with a grid to see how well the grid matches the points and how closely it meets selected criteria.
11) Import / Export Arc ASCII grids. Arc ASCII is the standard for exchanging spatially distributed data on a fixed distance or latitude/longitude grid in which each grid cell has a unique value for the parameter being mapped.
12) Other tools. Other tools in the Synthesizer include DLG, label and point plotting and color adjustment tools.
Available Data Products compatible with IWMI Synthesizer
A major benefit of the IWMI World Water and Climate Atlas is the growing library of data products either directly compatible, or easily converted, for use in the Synthesizer. Data products are accessible using the Synthesizer and available over the web at the IWMI site unless otherwise noted. We are in the process of developing additional data products for distribution on CD-ROM. Specific questions about individual data sets should be addressed directly to the originators of the products rather than to IWMI.
IWMI has located and made ready to use in Synthesizer the following externally produced grids. IWMI recognizes the propriety and vested interest of the producers of these data products and is in the process of obtaining permission to reformat and distribute these data.
1) Africa, monthly and annual summary climate grids for all of Africa. These grids consist of mean temperature and total precipitation. These grids contain sufficient climate information to estimate ETo. They are gridded at a 3-arc minute resolution. The Australian National University produced these.
2) World, monthly and annual summary climate grids. These grids consist of mean temperature and total precipitation. These grids contain sufficient climate information to estimate ETo. They are gridded at a 30-arc minute resolution. The current release has a very coarse data range (0-20mm, 21-50mm, etc.). FAO published these.
3) USA, monthly and annual summary climate grids. These grids consist of maximum, minimum and mean temperature, total precipitation, snowfall, etc. These grids contain sufficient climate information to estimate ETo. They are gridded at a 2.5-arc minute resolution. Oregon State University (PRISM) produced these.
4) Global monthly time-series climate grids. These grids consist of time-series monthly mean temperature and precipitation. They are gridded at a 3x5-arc degree resolution (very coarse). The USA National Climatic Data Center (NCDC) produced these.
5) Global monthly time-series climate grids. These grids consist of time-series temperature, precipitation and secondary variables from 1901-1996. These grids contain sufficient climate information to estimate ETo. They are gridded at a 30-arc minute resolution. The Climate Research Unit at the University of East Anglia produced these. A conversion program is available for download from the IWMI Synthesizer Data Products site for these products. Converted grids will be available for delivery on CD in January 1999.
1) Global Land Cover Characterization. Global / continental, summary and seasonal. These grids consist of indices for ecosystem, biosphere-atmosphere, vegetation, crops locations (irrigated and non-irrigated), seasonal vegetation and elevations. These are gridded at a 1-km resolution. A cooperative group including USGS and NASA produced these grids. (Due to the large size these are not available via the IWMI web site.
2) GTOPO30 Global elevation. This is gridded at a 30-arc second resolution. The USGS produced these grids. (Due to the large size this is not available via the IWMI web site).
3) HYDRO1K elevation / other. Hydrologically corrected elevation of North America, Africa, South America (coming soon), and other areas when provided by USGS. These include elevation, streamlines, slope, aspect, and watershed delineation. (Due to the large size these are not available via the IWMI web site).
4) Global, major river basins. This is gridded at a 30-arc minute resolution. The USGS produced this grid.
5) Global, population density. This is gridded at a 5-arc minute resolution. The Consortium for International Earth Science Information Network (CIESIN) produced this grid.
1) Global Daily Summary (daily 1977 - 1991). World, daily climate stations with maximum and minimum temperature and total precipitation. The USA National Climatic Data Center (NCDC) produced this product. (Due to the large size this is not available via the IWMI web site.)
2) Global Summary of the Day (daily 1994 - present). World, daily climate stations with maximum and minimum temperature and total precipitation. The USA National Climatic Data Center (NCDC) produces this product. (Due to the large size this is not available via the IWMI web site.)
3) FAO ClimWat - Summary FAO global data.
4) FAO - Monthly time-series organized by FAO. (At present, a link to source site for purchase on CD-ROM.)
5) Global Historical Climate Network (version 1 & 2, monthly 1870's to 1990's). World, monthly summary data from daily climate stations with maximum and minimum temperature and total precipitation. The USA National Climatic Data Center (NCDC) produces this product. (Due to the large size this is not available via the IWMI web site.)
6) USA COOP Daily Data (daily 1800's - present). USA, daily climate station data with numerous data elements such as maximum and minimum temperature, total precipitation, snowfall, snow depth, etc. USA National Climatic Data Center is the master archive of the data, while volunteer observers nationwide collect it. (Due to the large size this is not available via the IWMI web site.)
7) Other - Numerous monthly and daily data sets of temperature and precipitation data from around the world. Examples: Former Soviet Union (~250 stations with 50 years of daily data); China (200 stations, monthly); Indonesia / Malaysia (50 years of daily data); South America (monthly); Snotel data (USA, daily mountain regions 1985 -- present); etc. (These are yet to be converted to the Synthesizer format.)
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