This is a step-by-step walkthrough explaining how to download NARCCAP data from the Earth System Grid data portal. To download NARCCAP data:

1. Go to the Earth System Grid homepage, http://www.earthsystemgrid.org/.
2. From the "Home" tab, click the NARCCAP logo or link in the middle of the page.
3. NARCCAP data is organized by model and driver. The top-level catalog page for NARCCAP shows a grid with RCM along the vertical axis and driver (GCM or NCEP reanalysis) along the horizontal axis. Click the "data" link of the RCM/driver combination you're interested in.
4. At the next level, data files are organized by variable into tables (groups). See the data tables page to find which table contains the variable you are interested in. For example, if you want surface temperature data, you want variable tas from Table 2. Note that primary impacts-assessment variables are all in Table 2. Click the appopriate link.
5. Click the "Download File" link.
6. The wget script and DML script options on the next page are for downloading all files in that table. Most users will want only a subset of the available variables, so click the "Download individual files" button down at the bottom.
7. The page will list individual datafiles. To download a file, click the "download" link in the rightmost column.
8. If you want to download multiple files using wget, select the files using the checkboxes (you may find the subselection panel to the left helpful), then click the "Download ALL Selected File(s)" button at the top of the page. Then click the download icon next to "WGet Script Download" to download a wget script. If you don't have wget, click the "DML Script Download" icon to get a script for downloading data using DataMover-Lite, a Java-based program you can launch from your browser.

Note: Most MacOS and linux systems have wget installed. You can download and install wget on a windows machine. DML should work on any system with Java installed, which is most of them. N.B. that the download authentication in the scripts will only last for about a day, so you can't re-use the script to download the data again at a later date.

The datafile names look like this: VarName_ModelName_DriverName_Time.nc.

• VarName is the IPCC/CF-convention Variable Name as listed in the data tables
• ModelName is the 4-character RCM identifier
• DriverName is "NCEP" or the name of the driving GCM
• Time is the starting time of the file, in the form YearMonthDayUTCtime.

So, for example, tas_RCM3_ncep_1981010103.nc contains data for variable tas from the RegCM3 regional model driven with NCEP boundary conditions starting at 03 UTC on January 1st, 1981 and ending at 00 UTC on January 1st, 1985.

3-D data (from Table 5) is separated into levels. The pressure height of the level in hPa is indicated in the filename between the driver and the time:
ta_RCM3_ncep_p750_1981010103.nc contains data at the 750 hPa pressure height.

Note that you very likely do not want to download the first file in each dataset. See the Time Periods Covered page for information about the spin-up period and why you probably don't want to use data from it.