In addition to the aircraft missions that will characterize clouds and their surrounding environment on scales of 100-300 km, a large-scale sounding array (LSA) will be established to diagnose thermodynamic properties and air motions on a scale of 500-1000m and over a longer, uninterrupted time period. It will provide context for the airborne measurements relative to the diurnal cycle, transient disturbances (such as easterly waves), midlatitude intrusions, intraseasonal variability, and other modes of large-scale variability. The ships also provide a platform to enhance the characterization of the atmosphere and the macroscopic properties of clouds and precipitation as they will be additionally enable a broader coverage of surface based remote sensing.
It is planned for the LSA will be comprised of three to five stations: the Barbados Cloud Observatory and a network of research vessels (RVs) stationed in the trades upstream of Barbados (near 50 ºW). Applications for ship measurement time from Germany (Meteor and Maria S. Merian), The Netherlands (Pelagia) and the United States (RV Endeavor, or similar as part of the yearly NTAS buoy exchange) are being developed and or pending. Discussions about possible contributions from other countries, Barbados itself, or simply the rental of a cargo ship to serve as a sounding and surface station. The ships will ideally work on station, confined to an area that is small (100 km diameter) compared to the size of the overall array. This will allow for oceanographic investigations that are local in scope, or that will benefit from a network of research vessels. Here extensive sampling of the dynamics of an ocean eddy, and the nature of air-sea interactions both on and off an eddy is being proposed, as are investigations of air-sea gas exchange. Additional oceanographic research opportunities are being explored in the genera areas of ocean ecology, and mixing. One interesting aspect of Atlantic in this region is the evolution of freshwater eddies that are discharged from the Amazon and drift northward.
Rawinsondes will be launched from each station to collect simultaneous pro files of humidity, temperature, pressure and (thanks to GPS measurements) horizontal winds from the surface through the lower stratosphere. Large-scale divergence and vertical motion will then be diagnosed from these synchro-nized soundings. The accuracy of this divergence calculation increases with the number of stations; hence, earnest efforts to establish a five element array are underway. The LSA will operate over a four to twelve-week observing period depending on the availability of facilities and on funding. Soundings will be launched with a minimum frequency of 6 per day but perhaps as often as eight times daily.