Search

Upper-air balloon soundings for weather predictions have been made since the beginning of the 20th century. New radiosonde instruments for in situ humidity-, radiation- and gas-profile measurements in the troposphere and the lower stratosphere, were introduced in recent years for atmospheric research and climate monitoring, but such instruments are often expensive and it is desired they be reused on multiple flights. Recovering instruments that freely descend with parachutes is time consuming, sometimes difficult and even dangerous. Here, we introduce the return glider radiosonde (RGR), which enables flying and retrieving valuable in situ upper-air instruments. The RGR is lifted with weather balloons similar to traditional radiosondes to a preset altitude, at which time a release mechanism cuts the tether string, and a built-in autopilot flies the glider autonomously back to the launch site or a desired preprogrammed location. Once the RGR reaches the landing coordinates it circles down and releases a parachute 100 m above ground for landing. The motivation for this project was to measure radiation profiles throughout the atmosphere with the same instrument multiple times and with a rapid turn-around time. The paper describes technical aspects of the return glider radiosonde and the built-in radiation instruments and shows test flights up to 24 km altitude that are analyzed in terms of flight performance and maximal distances covered. Several successive flights measuring radiation profiles demonstrate the reliability and the operational readiness of the RGR, allowing new ways for atmospheric in situ research and monitoring with payloads up to several kg depending on the specific size of the glider.

In situ upper-air measurements are often made with instruments attached to weather balloons launched at the surface and lifted into the stratosphere. Present-day balloon-borne sensors allow near-continuous measurements from the Earth's surface to about 35km (3–5hPa), where the balloons burst and their instrument payloads descend with parachutes. It has been demonstrated that ascending weather balloons can perturb the air measured by very sensitive humidity and temperature sensors trailing behind them, particularly in the upper troposphere and lower stratosphere (UTLS). The use of controlled balloon descent for such measurements has therefore been investigated and is described here. We distinguish between the single balloon technique that uses a simple automatic valve system to release helium from the balloon at a preset ambient pressure, and the double balloon technique that uses a carrier balloon to lift the payload and a parachute balloon to control the descent of instruments after the carrier balloon is released at preset altitude. The automatic valve technique has been used for several decades for water vapor soundings with frost point hygrometers, whereas the double balloon technique has recently been re-established and deployed to measure radiation and temperature profiles through the atmosphere. Double balloon soundings also strongly reduce pendulum motion of the payload, stabilizing radiation instruments during ascent. We present the flight characteristics of these two ballooning techniques and compare the quality of temperature and humidity measurements made during ascent and descent., Atmospheric Measurement Techniques, 9 (3), ISSN:1867-1381, ISSN:1867-8548