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

A series of balloons, designed at NOAA Air Resources Laboratory Field Research Division, was released from shipboard to provide Lagrangian air-mass tracking information during three recent atmospheric chemistry field experiments. The position of the balloons was monitored via an onboard GPS receiver and transmitted via radio to a research aircraft operating in the vicinity of the balloons. In total, seven successful Lagrangian experiments have been carried out, two experiments during each of the ASTEX/MAGE (1992) and ACE1 (1995) field programs and three during the ACE2 (1997) field program. The ASTEX tetroon is a simple constant-level balloon made of Mylar with a tetrahedral shape to facilitate construction. The advantage of the 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. Control of balloon lift was added to the ACE1 tetroons, by the action of a pump and release valve on an internal pressurized ballast bladder. This design, referred to as a smart-balloon design, allows the tetroon buoyancy to automatically adjust when the tetroon travels vertically outside a range of pressures set prior to release. The ACE1 tetroon was deployed in the vicinity of Tasmania, Australia, and transmitted GPS location, barometric pressure, air temperature, relative humidity, and status data. These data provide balloon location, meteorological information on the air parcel and data to help understand the operation of the smart balloons. The ACE1 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. Significant design improvements were incorporated into the second-generation smart balloon, deployed during ACE-2 held between the coast of Portugal and the Canary Islands. 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 ACE1 tetroon, the ACE2 balloon provides balloon temperature, balloon superpressure, and solar radiation data. The ACE2 balloon proved very successful in maintaining altitude despite condensation loading and radiational effects. The dynamic range afforded by the high strength spherical shell used in the ACE2 design, allows the balloons to remain within desired altitude operating limits despite the impacts of condensation, light precipitation, and radiative cooling. The balloon’s dynamic range combined with in situ data the enables the balloon transponder to be programmed to remain at a constant altitude, to follow an isobaric or isentropic surface, or to perform soundings. The addition of satellite telephone communication to these capabilities and the economical cost of the design make the smart balloon an attractive platform for a range of future applications in the atmosphere.