Evolution in Design of a Smart Balloon
for Lagrangian Air Mass Tracking

ASTEX- was held in the Azores Islands to study the evolution of clean air emanating fron the north Atlantic. The ASTEX tetroon is a simple constant-level balloon made of Mylar (trademark) with a tetrahedral shape to facilitate construction (Fig. 1) (Businger et al. 1996). The advantage of these tetroons is their small size, ease of deployment, and low cost. Only GPS position data are available in this design. The disadvantage of the ASTEX tetroon is the lack of ability to compensate for the impact of precipitation loading and radiation on the buoyancy of the tetroons (Fig. 2a and Fig 2b).

ACE-1 - The ACE-1 design of Lagrangian marker tetroon includes control of balloon lift by the action of a pump and release valve on an internal pressurized ballast bladder (Fig. 3) (Johnson, Carter, and Businger 1998, Businger et al. 1998). This design, referred to as a smart tetroon design, allows the tetroon buoyancy to automatically adjust when the tetroon travels vertically outside a range of pressures set prior to release. The ACE-1 deployment in the vicinity of Tasmania, Australia, was the first for the smart tetroon design (Fig. 4a and Fig 4b). The ACE-1 tetroons provided GPS location, barometric pressure, air temperature, relative humidity, and tetroon status data transmitted via a transponder to a receiver aboard the NCAR C130 research aircraft flying in the vicinity of the tetroons to study the evolution of clean air. These data provide tetroon location, meteorological information on the air parcel and data to help understand the operation of the smart balloons. The ACE-1 tetroon design proved to have insufficient dynamic lift range to overcome the combined impact of water loading and radiational cooling at night, causing the tetroons to descend near the surface until after sunrise (Fig. 4a).

ACE-2 - Significant design improvements were incorporated into the second-generation smart balloon (Fig. 5), deployed during ACE-2 field program held between the coast of Portugal and the Canary Islands to study the evolution of polluted air emanating from Europe (Fig. 6a) (Johnson, Carter, and Businger 1998). These improvements include (i) a stronger outer shell to significantly increase dynamic lift range, (ii) two-way communication with the balloon to allow interactive control of the balloon operating parameters by an observer, and (iii) a spherical design to reduce exposure to precipitation. In addition to the variables transmitted by the ACE-1 tetroon, the ACE-2 balloon provides balloon temperature, balloon superpressure, and solar radiation data.

The success of the ACE-2 balloon in maintaining altitude despite condensation loading and radiational effects is noteworthy (Fig. 6b). The stronger balloon shell provides an order of magnitude increase in dynamic lift range over the ACE-1 design. The altitude control works during night and day even when the wetness sensor shows condensation on the surface of the balloon.
 
 

* The Atlantic Stratocumulus Transition Experiment/Marine Aerosol Gas Exchange (ASTEX/MAGE) field project, and the first and second Aerosol Characterization Experiments (ACE-1, ACE-2).

REFERENCES

• Businger, S., S.R. Chiswell, W.C. Ulmer, and R. Johnson, 1996: Balloons as a Lagrangian Measurement Platform for Atmospheric Research, Journal of Geophysical Research, 101, 4363-4376
• Johnson, R., R. Carter, and S. Businger, 1998: Evolution of Smart Balloon Design for Lagrangian Air Mass Tracking, GPS World. In press.
• Businger, S., R. Johnson, J. Katzfey, S. Siems, and Q. Wang, 1998: Smart Tetroons for Lagrangian Air Mass Tracking During ACE-1. Journal of Geophysical Research. In review.