Data Resources: How to FTP data from PSL

All of the data which we make available to the public can be obtained via anonymous ftp.

These are the general steps for obtaining PSL data by FTP:

  • Connect to (previously which wil continue to work for a while)
  • login as anonymous
  • Enter your email address as your password. Please take the time to send us your correct email address. We will use that address to notify you of important additions or changes to our data offerings.
  • All data sets available this way are in subdirectories of the directory /Datasets .
  • Your FTP client must be able to use "passive" mode. You may have to switch clients. The default Windows ftp client uses only Active, for example
  • The vast majority of the data that are available through this server are stored as netCDF files. If necessary, refer to our documentation about netCDF and information on display/analysis software that reads our netCDF files.

Or, if you'd like you can use your browser to ftp directly. However, many users report better results using a command-line FTP client, such as the free "ncftp" (, than with using a web browser for FTP transfers. In particular, "ncftp" can automatically adapt to firewall changes at any point along the communications path.

Common anonymous FTP Problems and Their Solutions

These are configuration problems at your local site; they are not solvable at our end of things.

Unable to login using a Web browser:

Our FTP server sends detailed error messages for each of these problems. Unfortunately, web browsers often don't show these messages to users. Command line FTP clients are usually better about showing all error messages.

By default, most web browsers use a fake e-mail address as the password for anonymous FTP access. Our FTP server requests, but does not require, a real e-mail address to be used, so that we can try to contact you if there is a problem with, or update to, any data you may retrieve. If you use a fake e-mail address, the FTP server may warn you about it, referring to this document, but the server will let you in anyway.

If you are using Netscape version 3.x, then select, under the "Options" heading, the choice "Mail & News Preferences". Within that pop-up window, select the "Identity" option, and fill in your real e-mail address in the blank labeled "Email Address:", and press the OK button at the bottom of that popup window. Then, from the same "Options" category, select "Network Preferences", and, from that pop-up window, select "Protocols". On that form, check the final item, "Send Email Address as Anonymous FTP Password". If you are using a 4.x version, the procedure is similar, as the next paragraph details.

For Netscape 4.x, first select the "Preferences" item at the bottom of the "Edit" menu. On that pop-up, select "Mail & Newsgroups", and under that, select "Identity". There you will find a blank to enter your E-mail address. Then, select the "Advanced" category from the list on the left. The last item in the top box, "Send email address as anonymous FTP password", should be checked. Then, press the "OK" button at the lower left.

If you are using Internet Explorer (IE) 5.x after connecting to the anonymous ftp site, select "Login as..." from the file menu, check the "Login Anonymously" box and give a valid e-mail in the password box. For other versions try explicitly specifying the login name of anonymous in the FTP URL, like this: Then, when the browser pops up and queries for username and password, then the username should be "anonymous", and the password should be entered as your e-mail address.

Connection refused because of an invalid reverse name look-up.

This is generally a problem requiring a system administrator to solve at your site.

When your machine connects to our machine via FTP we choose to initiate a process called a reverse name look-up. That is to say we ask domain name service to translate your IP address back into a fully qualified domain name. This is a process that many sites are using as an added security feature. In this way we can verify that you are who you say you are. Now of course, we know that you're not trying to do anything sneaky, but this is something that we require of everyone that connects to us.

At your site, your computer managers maintain two lists of domain names. One is the forward name and the other is the reverse. Often, only the forward name is kept up-to-date. That's the one that is used when you say you want to connect to your machine and give its name. The forward name translates back to the IP address. But, there is also a table that keeps track of the reverse name, the one that answers the question what name belongs to this IP address.

Hopefully your system manager will understand from this message what's being asked and can correct the problem with a couple minutes of work. Another solution might be to try your FTP from a different machine.