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.