University of Washington professor Bob Houze takes pictures of clouds at the SPol site.If you observe the typical AMIE/DYNAMO scientist during a day in the Maldives, you’ll find that they are rarely seen without a few key pieces of equipment—a laptop, a USB drive for sharing data, a notebook and pen for jotting notes, and a camera. The camera might seem more like a tourist accessory than a scientific tool, but if you check out those memory cards you’ll find that the vast majority of them are filled with more pictures of clouds than of people! While one tropical cloud may look like another to most people, to the AMIE/DYNAMO scientists, they are all unique signatures of the weather conditions on a given day.
One of the interesting things that I have observed during AMIE is that the cloud field is often quite complicated. It is rare to see only a single type of cloud in the sky; usually there are a variety of different cloud types, often at different heights. Cloud field looking south from the AMF2 site.This picture is a good example—you can see some low-level puffy cumulus in the background of the picture. In the foreground, in front of the cumulus from our perspective, are some thin laminar layers that are likely mid-level altocumulus, and then the rest of the sky is filled with wispy cirrus (high ice clouds).
Picture looking directly up at the sky from the AMF2 site, while standing next to the Ka-band ARM Zenith Radar (KAZR).There are a couple of reasons for the complicated cloud structure at Gan. One is that there is often wind shear (winds moving in different directions at different heights), while the low convective cloud field might be moving in one direction, the mid-level or high-level outflow might move in a different direction. Another cause is that the atmospheric column at Gan is often much wetter than you find at the mid-latitudes, so clouds may remain around longer after they’ve stopped actively developing rather than evaporating as quickly as they would in a drier environment.
This plot is from the Ka-band ARM Zenith Radar (KAZR) on October 23. Note that time in the radar plot is in GMT while the camera date stamp is in Gan local time, so the camera image corresponds to the radar profile at 05:35 GMT.Besides being pretty, these cloud pictures are useful for helping us understand the data that we are obtaining from all of our cloud-measuring instruments. Understanding the meaning of a radar reflectivity measurement is a lot easier when you can directly relate it to a visual cloud image. I often go out and snap a picture of the sky directly above the KAZR vertically pointing radar, such as this picture of the high-level ice cloud and then examine the radar display (below) to see what the clouds would look like if my eyes could see millimeter-wavelength radiation like the KAZR can.
