A Smart Balloon Designed to Investigate Hurricane Inflow Energetics

A series of Smart Balloon experiments is planned during upcoming hurricane seasons. NOAA/UH Smart Balloons will be deployed as part of a Lagrangian experimental strategy to better characterize the evolution of the energy content of the marine boundary-layer inflow to hurricanes and its relationship with hurricane intensity changes. This effort will be accomplished in cooperation with reconnaissance missions currently planned by the NOAA Hurricane Research Division to investigate the energetics of landfalling hurricanes. The NOAA WP-3D aircraft will carry out an essentially Eulerian experiment with new high-resolution GPS dropwinsondes, turbulent flux sensors, and the Doppler radar. The Lagrangian component, represented by the smart balloons, will provide synergy that promises more than the sum of the experimental parts. The Smart Balloon, a fourth generation Lagrangian marker balloon developed at NOAA’s Air Resources Lab, Field Research Division in collaboration with the University of Hawaii, will collect meteorological and differential GPS position data and transmit these via satellite cellular telephone to the National Hurricane Center (NHC) and the WP-3D aircraft. The Smart Balloon has a large dynamic lift range (sea level to ~6 km), provided by a high strength spherical shell and a pump and release valve on an internal pressurized air bladder. This design allows the balloons to remain within prescribed altitude operating limits in the boundary layer despite precipitation loading and impacts of radiative heating/cooling on balloon lift. The instrument and transponder package will be contained within the outer shell of the balloon to protect them from environmental hazards. At the outset of each field experiment two smart balloons will be deployed from a coastal location within ~250 km of a passing hurricane. This strategy will allow the NOAA WP-3D aircraft to make a series of measurements in the vicinity of the balloons as they approach the hurricane eyewall. Balloon release sites and times will be chosen based on storm-track predictions from NCEP and forecasts of air-parcel trajectories made at the University of Hawaii. Sites along the affected US coast will serve as release points to investigate the evolution and impact of air streams of continental origin, while island sites (e.g., Puerto Rico) will serve as release points to investigate air streams with trajectories that remain over the open ocean. Balloon measured changes in equivalent potential energy in a Lagrangian framework reflect the integral of the surface fluxes and entrainment along the path traveled, provided the height of the mixed inflow layer is known along the path from complimentary aircraft or GPS dropwinsonde data. The data will be analyzed and used to validate 1-D boundary-layer model simulations, 2-D axis-symmetric hurricane model simulations, and NCAR/Penn State MM5 simulations of the investigated storms. Real time data, especially wind data, collected by the Smart Balloons and aircraft during the experiment will be made available to the NHC and NCEP in real time to aid in preparation of hurricane intensity forecasts, watches, and warnings prior to landfall.