After five different planes and roughly 35 hours of travel, I arrived on Gan on Sunday afternoon, just in time for the first all day rainstorm of the AMIE campaign. I was glad we got some rain to test out the performance of the various instruments, but sorry it made my flight into Gan a little less scenic.
After a much-needed night’s rest, I journeyed to the AMF2 airport site this morning (Monday) along with the AMF2 techs, Nate Hiers and Tom Flannery, and ARM radar engineer, Nitin Bharadwaj. My main roles during the campaign are to provide scientific guidance to the AMF2 technical crew, to analyze preliminary data to make sure the instruments are performing well, and to serve as a point of contact with the Maldivian Meteorological Service (MMS) staff and other local officials and with the other investigators in the broader DYNAMO field campaign. Today, I mainly focused on getting to know my way around the AMF2 site and the data system, but expect to have more interactions with the MMS and the DYNAMO crew in the upcoming weeks.
After an introduction to the local sonde launch crew and a brief visit with Ali Wafir and Ahmed Muslim of the MMS, we headed up to the AMF radar site near the wharf where the scanning ARM cloud radar (SACR) has been installed. A team from ProSensing installed the SACR last week, and Nitin has been busy checking on the performance of the radar, updating the radar software, and getting internet issues resolved. Today provided perfect cloud conditions for checking the sensitivity of the SACR—a beautiful thin altocumulus layer near 4 km (see photo). Nitin ran the radar through the set of scans specifically designed for AMIE and we eagerly started examining the data. This preliminary examination indicated that the SACR is performing very well.
Preliminary plots of the SACR data are shown here. The first plot shows a PPI (or planned position indicator) scan from the SACR Ka band. This scan is taken at a constant elevation angle, but with the radar scanning in azimuth angle and gives an overview of the surrounding cloud field. We only scan about 180 degrees in azimuth because of a line of tall trees behind the radar that would impact the scans. Although this scan gives a good overview of the cloud field, it is hard to tell the height of the clouds. So we also do a set of scans known as RHI (or range height indicator), in which we keep the radar at a constant azimuth angle but scan in elevation angle. An example of this type of scan (also with the Ka band) is shown in the second plot, where we see an altocumulus layer near 4 km. We typically do a set of 40 of these scans, moving over 3 degrees in azimuth angle with each scan to get a 3D view of the cloud field.
For the AMIE campaign, unlike some other field projects, we are more interested in statistics than in case studies of particular clouds. Therefore we are going to do the same set of scans (PPI, boundary layer RHI, and cross-wind RHI) over the whole campaign, which will allow us to build up a statistical view of the cloud field and how it changes as the MJO develops.
After a full first day on Gan, and some great cloud radar data, I am looking forward to what the next few weeks will bring.
Sally McFarlane
Co-Investigator, AMIE campaign