StratoSonde(TM) – Dropsondes from the Stratosphere
The StratoSonde system combines a low-cost, long endurance weather balloon with a micro-dropsonde dispensing system. This enables meteorological observations over remote areas of the globe by dispensing dropsondes from the Stratosphere.
The global weather observation system has large gaps, for example over the oceans and polar regions, where there are few regular in-situ observations. Such regions present uncertainty in the atmospheric state and introduce errors, limiting weather forecast model accuracy. Satellites partially fill this gap; they provide excellent horizontal coverage; and their poor vertical resolution can be enhanced with targeted micro-dropsonde data obtained using the StratoSonde High Altitude Balloon (HAB) system.
StratoSonde provides dropsonde observations over remote areas where forecast errors grow most rapidly. Operating as a sensor constellation, StratoSonde provides low-cost, wide area in-situ observations, and can respond dynamically to the needs of researchers or operational forecasters, gathering targeted observations “on demand” from specific areas.
How It Works: The environmentally safe StratoSonde uses a biodegradable latex weather balloon, and cardboard housing, fitted with a balloon vent and sand ballast system, to control float altitude. They select specific wind layers to drift towards targeted remote regions, with endurance up to 5-days. StratoSonde can be configured to carry up to 8 or 16 micro-dropsondes, which each weigh <25g. At the point of launch, each StratoSonde typically carries 2kg of ballast and has a total mass <4kg. This permits operation under ICAO regulations for ‘light’ category unmanned free balloons.
Data-Capture: Temp, Pressure, RH, wind speed and direction are transmitted at 1Hz over a UHF datalink to the HAB, which disseminates received data over SATCOM. Dropsondes dispensed from 70kft take approximately 20-minutes to reach sea-level and data is published in near-real-time on the StratoSonde data portal, after automatic quality checking.
The micro-dropsondes are stabilised by a ribbon drogue and descend at 10m/s (sea-level). In the stratosphere, the high descent speed places its thermodynamic sensors in a strong forced‑convection. This means dropsondes are not as affected by solar radiation, weak ventilation, pendulum motion, and balloon‑induced flow disturbance biases which can dominate observations from radiosonde and long endurance profiling balloons.
Use cases: By dispensing dropsondes from the lower stratosphere, the StratoSonde system offers cost effective and uniquely targeted full column observations. They deliver a breakthrough in Tropical Cyclone (TC) research since they can accurately observe the marine boundary layer even in remote regions, sample the full kinematic and thermodynamic variables at all levels, enabling accurate assessment of Potential Intensity (PI) and gather observations of the rarely observed TC outflow layer and tropical tropopause.
The system is equally effective in targeting observations at higher latitudes and polar regions, supporting research into Polar Lows and enhanced forecasting of atmospheric rivers and winter storms. Dropsonde observation data is intuitive and readily assimilated into numerical weather prediction (NWP) models, offering a disruptive and cost-effective method for improving forecast skill of extreme weather.
