The CSU graduate school considers students to be full time when they are registered for 9 or more credits. The department of Atmospheric Science however, requires that you register for 15 credits Fall and Spring semesters. In a students final semester at CSU it may be preferable for a student and their advisor to petition for a lower credit load.
The 15 semester hour requirement does not mean that you need to take 15 hours of classes! That would be miserable, and you would probably never graduate. What you need to do is top of registration by registering for ATS 699U-001 and adjust the number of credits so that you are at 15 total. ATS 699U-001 is tropospheric chemistry thesis credits under Emily Fischer. Look for this class when topping off registration.
Why do we register for 15 credits instead of 9?
1) The university facility fee goes up by $95 dollars and thus someone gets more money.
2) This increases the number of faculty credit hours for teaching credit purposes with the University. Basically, it is a more accurate acknowledgement (in terms of credits taken per student per faculty advisor) of the effort of students and faculty in regards to effort in the program.