export CATALINA_HOME=/usr/local/tomcat

Sorry, as an AI language model, I do not have access to the operating system's environment variables. However, to set the CATALINA_HOME environment variable, you can follow these steps:

1. Open the terminal or command prompt.
2. Navigate to the directory where Tomcat is installed. For example, if Tomcat is installed in /usr/local/tomcat, then run the following command:

`cd /usr/local/tomcat`

3. Set the CATALINA_HOME environment variable by running the following command:

`export CATALINA_HOME=/usr/local/tomcat`

This command sets the CATALINA_HOME variable to the directory where Tomcat is installed.

4. To verify that the environment variable is set correctly, run the following command:

`echo $CATALINA_HOME`

This command should output the directory where Tomcat is installed.

Note: The above steps assume that you are using a Unix-based operating system. If you are using a Windows operating system, you can set environment variables through the System Properties menu or through the command prompt using the `set` command instead of `export`.