ESRI's ArcGIS suite is a collection of programs used for producing maps within a geographic information systems (GIS) environment. Data, in the form of shapefiles containing spatial coordinates, are loaded into an ArcMap document to quickly produce custom maps. Mapping weather phenomena is done using data that collected and made available by the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS). This article will describe how to create a map of precipitation as an example. However, many types of weather-related data are available from the NWS GIS portal.
- Skill level:
Things you need
- ArcMap 9.2 or 9.3
Click on the link labelled "Shapefile" on the National Weather Service GIS Data Portal (see References).
Locate the "Past Weather" heading and click on "Precipitation Record."
The browser will point to a page entitled "National Weather Service -- Climate Prediction Center." Click on the link located in the left-hand menu labelled "CPC GIS Data."
Locate the heading "Data in Support of the US Drought Monitoring" and click on the "Precipitation" link. The links to most recent data will appear as ordinal dates in the format YYYYMMDD (Y = year, M = month, and D = day). Click on the most recent link. Download the ZIP file to your desktop and decompress the file using an unzipping program.
Open ArcMap and begin with a new, blank map. Add any background data you wish such as state or county boundaries downloaded from the U.S. National Atlas website raw data shapefiles (see References). Project your data using the appropriate projection for the spatial scale in which you are working (see "Tips" below).
Click the "Add Data" button and navigate to the precipitation folder you downloaded and add the file named p.full.1stday_month_20100708.shp (the date for your file may be different than the example here).
Double-click on the shapefile's label and select the "Symbology" tab in the dialogue window. Select a colour scheme appropriate for the number of classes you intend to display, as well as one that is appropriate for the weather phenomena you are mapping (blue or green are good choices for rain events). Close the dialogue window once you select a colour scheme and class levels.
Add the necessary maps elements such as title, legend and scale bar.
Save your work with the file extension .mxd (ArcMap document).
Tips and warnings
- To produce a map of any of the weather events for which data is available, simply follow the steps above using whatever shapefile you deem appropriate.
- Make sure you are using a projection appropriate for the area you intend to map. For maps of the conterminous U.S., the best projections to use are either the Albers equal area conic or Lambert conformal conic, depending on where the states you are mapping are located. If you are mapping an area the size of a few states, use the universal transverse Mercator (UTM) system. If you are mapping data for only one state, use the state plane coordinate system for that state.
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