The Aeroclipper: A New Device to Explore Convective Systems and Cyclones

Abstract

Aeroclipper balloons, designed for taking measurements at the air-sea interface, can withstand extreme conditions encountered when they are drawn into tropical cyclones and then follow the eye trajectory. The Aeroclipper (Fig. 1) is a new balloon device designed to perform relatively long flights (of up to 30 days) in the surface layer (under 50 m) over remote ocean regions. Up to now, most long-lasting balloon measurements in the marine boundary layer have been made using superpressure balloons. These superpressure balloons have a constant volume and are thus supposed to fly at a level of constant density. Superpressure balloons in the boundary layer were first developed to probe local dynamical properties along Lagrangian trajectories. Early experiments used a manually operated radar to follow aluminized tetrahedral balloons (or tetroons) for a few hours (Angell and Pack 1960). These tetroons were found to be suitable Lagrangian tracers at a constant level. They were progressively improved (by adding, e.g., a radar transponder) and contributed to new results on turbulence, diffusion, and transport properties, in particular over urban areas (see Businger et al. 1996 for a review). Superpressure balloons of various shapes are still used in local field experiments. These balloons have a life expectancy of a few hours and require a local receiver system. In order to study large-scale flows in the marine boundary layer over remote regions, long-lasting balloons tracked by satellite are required. For the VASCO prototypes, there were two transmission gondolas, one dedicated to science telemetry (using either Argos for Aeroclippers 1,2,3, and 7, or Iridium for the others) and a security transmission gondola providing a redundancy of the position as well as software for automatic balloon separation in forbidden areas (around the island and continental regions). The length of the guide rope is 50 m between the ocean gondola and the security transmission gondola.

A Pressure-Based Analysis of the Historical Western North Pacific Tropical Cyclone Intensity Record

“…Furthermore, as more remote sensing methods for intensity estimation become available and operational procedures evolve further, there is a possibility that the intensity records will diverge even more. An international effort to provide ground truth via low-level AR or other platform [e.g., the Aeroclipper discussed in Duvel et al (2009)] for an adequate period of time to calibrate the agency intensity estimates could be fruitful. Large international efforts to observe TCs have been conducted in the WP before, but these campaigns typically collect more comprehensive datasets for a shorter period of time than would be optimal for calibrating intensity estimates.…”

The Role of the Western Arabian Sea Upwelling in Indian Monsoon Rainfall Variability

“…For example, the recent VASCO-Cirene program Duvel et al 2008) and associated field experiment in January-February 2007 evidenced a nice example of strong downwelling Rossby waves in the Seychelles-Chagos thermocline ridge, which likely played a role in the ϳ30% higher than normal rainfall over the Western Ghats observed during the following summer, 2007. For example, the recent VASCO-Cirene program Duvel et al 2008) and associated field experiment in January-February 2007 evidenced a nice example of strong downwelling Rossby waves in the Seychelles-Chagos thermocline ridge, which likely played a role in the ϳ30% higher than normal rainfall over the Western Ghats observed during the following summer, 2007.…”

Dynamical and Physical Processes Leading to Tropical Cyclone Intensification under Upper-Level Trough Forcing

“…Unlike Hurricane Claudette (2003) (Shelton and Molinari 2009), Dora was able to remain at hurricane strength despite the detrimental influence of dry air. Also, an Aeroclipper, a lowlevel balloonborne instrumented platform (Duvel et al 2008), measured the radius of maximum wind ( horizontal resolution; Montroty et al 2008). The domain extends from 08 to 328S and from 31.58 to 88.58E, which is much larger than the region displayed in Fig.…”