Using measurements from the vertical beams of a 915 MHz and a 1299 MHz wind profiler, as well as in-situ crystal observations at the DRI Storm Peak Laboratory (SPL), the relationships of the Mossiman riming index and crystal fall speed are examined. Information about the ice crystal habit and size distribution is available from in situ measurements at SPL. Issues such as the effects of vertical air motion and air density on the riming index are discussed.