2017 Academic High Altitude Conference

Using Thermocouple, Thermistor, and Digital Sensors to Characterize the Thermal Wake Below Ascending Weather Balloons

In this paper we present additional results from our on-going research effort to characterize the thermal wake that trails below ascending latex weather balloons on flights into the stratosphere; a wake which interferes with the ability of temperature sensors in payload boxes hanging from the balloon (and hence enveloped by the wake) to correctly measure the ambient temperature of the atmosphere through which the balloon is ascending. A “wake boom” is used to measure temperature variations up to 1.5 m horizontally from varying distances directly below the neck of the balloon. Results to date agree with the literature that especially above the tropopause the thermal wake is warmer than the ambient air during daytime ascents, due to solar radiation warming the balloon skin, but colder than ambient air during night-time ascents, due to adiabatic cooling of the gas inside the balloon (which also occurs in the daytime, but is smaller than the daytime warming effect). In particular we report on thermal wake characterization using (Neulog) thermocouple sensors, as compared to (HOBO) thermistors and (Arduino-logged) DS18B20 digital temperature sensors. We also present additional results from X-shaped 2-dimensional wake booms or “X-Booms” which allow us to compare wake temperatures on the sun side versus the shade side of the balloon, looking for asymmetries in the horizontal temperature profile.