What is running on my server every night?
From your profiler trace you should be able to see the Login and Host that the queries are coming from. I would then speak to your operations and/or development team to identify the application and function of the queries (or they should at least be able to point you in the direction of where you need to go/who you need to speak to).

Once you have that information you can see if the queries can be tuned in order to reduce the pressure on your disks.