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 will work for a period of time)
  • 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 .
  • 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. Also, web browsers are dropping support for the FTP protocol. One can take any of our links starting with "ftp://ftp2" and change that part to "https://downloads" and your browser will like the new URL. The FTP protocol is faster, however. So, command-line FTP clients, if available, offer a speed advantage.

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.

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.