What type of satellite imagery is best to retrieve accurate AMVs?
This is a difficult question to answer since different methods, channels and satellites give different perspectives. It depends on what is required. If we look at some of the NWP SAF AMV monitoring plots, we can see that the visible imagery only supplies low-level winds, cloudy WV imagery mainly high-level winds, whereas the IR window channel around 11 μm provides winds at all levels. Medium-level winds suffer most from height-assignment difficulties. Once at low levels the visible imagery gives a clearer distinction between the warmer surface temperatures and the low-level tracers over the ocean than the IR imagery, but the height assignment can be problematic as a different channel is used in the height assignment (IR window) and tracking (VIS). If surface winds are required, scatterometers and microwave instruments provide information that AMVs cannot.
