Simulated Observed Radiosonde Soundings: Applications of Boundary Layer Sounding Modification in Forecasting and Numerical Weather Prediction

This study outlines the process of boundary layer sounding modification and the creation of simulated observed radiosonde soundings in order to determine optimal collection frequency and measurement depth of boundary layer thermodynamic profile measurements acquired by unmanned aircraft systems. In recent years, various tests such as the SUMO (Small Unmanned Meteorological Observer) and operations at the University of Oklahoma's KAEFS (Kessler Atmospheric and Ecological Field Station) have been conducted to demonstrate how UAS's (Unmanned Aircraft Systems) can be used to obtain measurements of boundary layer conditions. However, field tests have been limited due to Federal Aviation Administration (FAA) height restrictions that have contained UAS flights to the lower boundary layer (less than 3000 ft AGL). Due to these limitations, questions remain regarding the most effective boundary layer depth to measure and timeframes over which new boundary layer measurements between radiosonde launches are useful.

In order to simulate unrestricted boundary layer measurements and test temporal resolution between soundings, similar to how a UAS might sample in time and space, hourly radiosonde sounding data was obtained from Yuma Proving Grounds in Yuma, AZ (1Y7) to create sets of simulated observed soundings (SimOS's). Hourly boundary layer profiles (temperature and dew point) were combined with a constant upper atmosphere profile and displayed on Skew-T Log-P diagrams in SHARPpy (Sounding/Hodograph Analysis and Research Program in Python). Variations between each hour's SimOS and the official observed sounding were recorded and analyzed using regression analysis techniques to determine the accuracy of each SimOS and the point at which the creation of a SimOS becomes ineffective. Additionally, multiple variations of each SimOS were created using different boundary layer depths to allow for correlation between SimOS accuracy and the scale of the boundary layer measurements.

Preliminary analysis for various surface based thermodynamic parameters and overall profile structure revealed minimal variance in 1 to 3 hour modified soundings with consistently increasing variance after hour 3. Mid and upper level parameters have shown minimal variance in 1 to 3 hour modified soundings and inconsistent variance after hour 3. Additionally, shallow depth boundary layer measurements were shown to increase variance in surface based thermodynamic parameters as well as increase inconsistent variance in mid and upper level parameters. The results of this statistical analysis support numerous potential benefits associated with matching observed radiosonde soundings with UAS measurements in real time forecasting applications as well as improving observational input for data assimilation in numerical weather models.