Assessment of Multi-Thermistor Radiosonde Air Temperature and Sensor Uncertainty

The National Weather Service (NWS) currently uses several radiosonde types within their upper air network to conduct routine synoptic soundings for weather prediction. These radiosondes have unique error characteristics that can adversely affect weather prediction and climate records if not well quantified. Therefore, to better quantify the temperature aspect of their error, the NWS is considering the use of multi-thermistor radiosonde (MTR) technology as an independent reference for upper air temperatures. This technology, originally developed by NASA Wallops scientists – primarily Frank Schmidlin, has proven to be effective at correcting soundings' raw temperature measurements of in-situ radiative effects. A typical MTR system consists of three thermistors with unique radiative properties that are used to make these corrections. The NWS has further matured this technology and developed an algorithm called the Advanced Multi-thermistor (AMT) to determine air temperature solutions for MTR systems.

This study assesses the precision of the AMT solution relative to the thermistor temperature measurements. The MTR systems used in this study have five thermistors; three thermistors deposited with aluminum, one thermistor coated with black paint, and one thermistor coated with white paint. The precision of the aluminum thermistors is easily ascertained for this MTR system but the precision of the black and white thermistors are not. Therefore, specialty MTR systems, with all five thermistors painted either black or white, are utilized in addition to the regular MTR system.

Soundings of specialty and regular MTR systems attached to a single balloon, in a dual bar configuration, will be conducted to evaluate the precision of the thermistor measurements and AMT solution simultaneously. These soundings will take place during the day at the NWS Sterling Field Support Center (SFSC) in Sterling, VA. There will be six of these dual bar soundings conducted for both respective specialty MTR systems. Each of the soundings will offer six white or six black thermistor profile measurements which will allow 18 possible temperature solutions. This report will present the uncertainty statistics from these soundings as a function of cloud cover and solar angle. The results of this analysis will be used to determine the plausibility of using the MTR system as an upper air temperature reference.