Six Controlled Meteorological (CMET) balloons will be supplied by researchers from Smith College and the University of Massachusetts (http://www.science.smith.edu/cmet/main.html) and released from Longyearbyen during the spring 2007 campaign. These small and lightweight balloons (payload ~ 400 grams) can be commanded via the internet and satellite link to change altitudes, perform repeated soundings, or follow constant-potential temperature surfaces. Data from the balloons (position, altitude, winds, temperature, pressure, and humidity) will be available in real time. CMET balloons can remain airborne for several days.

The strategy for using the balloons is as follows: A starting research aircraft will profile the atmosphere above Longyearbyen to find a polluted layer. Its altitude will be reported to the ground in real time and two balloons will be launched into that layer immediately. One balloon will strictly follow this polluted air mass by staying at constant potential temperature (corrected for slow diabatic cooling). The other balloon will occasionally perform vertical soundings to explore the variability of the meteorological parameters and aerosol backscatter around this layer. The returning aircraft will visit the balloons to sample again the polluted layer “tagged” by the balloons. The aircraft will start again on the next day (and possibly on a third day) to repeat the measurements in the balloon’s vicinity. Through this Lagrangian experiment, information is obtained about important processes that otherwise cannot be observed directly. The measurement data taken repeatedly in the same volume of air will allow inferring changes in the aerosol size distribution and the chemical composition (e.g., ozone formation or destruction), thus yielding important constraints for the models used in WP 7. The meteorological conditions will be ideal for this experiment, as turbulence, hence mixing with surrounding air masses, is almost negligible in the Arctic in early spring.