Radar Observations of Storms for Education: Real Storm Examples for the Mesoscale Course Classroom

STEM education research indicates that the learning value of conceptual models is maximized when students are able to compare and contrast the model with real data and identify weaknesses in the simplified model. The Radar Observations of Storms for Education (ROSE) project uses high-resolution dual-polarimetric and dual-Doppler radar data to construct a series of dynamic examples of storms that can be used to supplement current static conceptual models in upper level undergraduate and graduate courses. The overarching goal of the project is provide materials for classroom use that facilitate the interpretation of authentic data by distinguishing among different types of mesoscale storms and explaining key features. Vertical cross-sections (radar RHIs) are particularly useful to explain storm structures to students. Prior to this project, there were few RHIs available for educational purposes within the community since operational radars do not scan RHIs and use of research radars for this purpose requires informed real-time decisions on where to scan.

A dedicated field phase for ROSE was conducted from 20 May – 20 June 2014 using the CSU CHILL and NCAR EOL SPOL radars in Colorado. Data were obtained in coordinated scanning modes during 18 storms including supercells, a tornadic supercell, hail storms, and multicellular storms with and without stratiform precipitation. Undergraduate students made daily forecasts and decisions on when to schedule radar operations. Once storms were in the radar domain, the students anticipated storm motion and development and made real-time decisions on where to scan vertical cross-sections. Both the CSU CHILL and NCAR EOL SPOL radar were operated remotely by the students in Raleigh, NC.

Lessons utilizing radar data examples from the literature often center on inferring velocity structures (esp. vertical velocity) from radar reflectivity and often include an implicit assumption of steady state kinematics. The reality is that storms rarely have steady state wind fields that closely align with radar reflectivity structures. Storm dynamics respond quickly to changes in the buoyancy and pressure fields. In comparison, microphysics represents the time-integrated result of the sequence of velocity structures along the particles' paths 10's of minutes prior to the scan. The set of particles in a individual radar resolution volume at time t often do not remain together at time t + 10 min. Our modules will employ static images as well as user-controllable radar data movies to emphasize that warm-season storms can evolve dramatically over time scales of minutes and the relations between instantaneous velocity and hydrometeor fields.

Novice users such as students are frequently distracted by radar data artifacts. Consequently, subsequent to the completion of the field phase we have spent considerable time on radar quality control issues including removal of non-meteorological echo and radial velocity dealiasing. The goal is to make our presentations of storm structures easy to understand by novice users of radar data. Our radar plots use a 1:1 aspect ratio which allows the student to more easily interpret horizontal and vertical flow within the storm. We are also simplifying the interpretations of the data by emphasizing hydrometeor categories rather than radar reflectivity. Additionally, we are exploring use of Doppler spectral width to illustrate channels of airflow and where speed/directional shear is present within the storm.