CUBE-TRACER

In the summer of 2022 I got the chance to participate in TRACER, a DoE funded atmospheric field experiment investigating if pollution makes thunderstorms more severe.

The D.o.E. operates ARM, the mobile Atmospheric Radiation Measurement lab. It’s a sort of moving village of shipping containers, full of the best atmospheric sensing equipment money can buy, which travels around the world performing observational campaigns. The data from these campaigns helps to improve weather and climate models, and to further understanding of atmospheric science principles.

Timelapse setting up a flux tower on a convectively active day.

The T.R.A.C.E.R. Campaign or “Tracking Aerosol Convection Interactions Experiment” was specifically investigating the effects anthropogenic aerosols have on thunderstorm formation.

All data collected by the DoE is made publicly available, and as such, atmospheric scientists from all around the world follow the mobile ARM unit, conducting their own experiments. This data is shared as well, creating an intensive observation period where dozens of smaller experiments coincide with the larger ARM campaign.

Scouting out sensor positions with our generous host from the University of Houston, Dr. James Flynn, and scintillometer tests on the rooftop of our engineering building with Gabriel Rios.

Our laboratory was one of these groups conducting our own experiment, C.U.B.E., the “Convective Urban Boundary Layer Experiment.” We deployed sensors at three sites- a coastal location, an urban location, and a rural location, gathering data across the city to characterize the coastal-urban boundary layer.

Deploying a Net Radiometer and Ceilometer, two different devices for vertical profiling.

It may seem a bit odd for a Mechanical Engineering group to be preoccupied with atmospheric science, but the same numerical solution methods and Navier-Stokes equations that describe “conventional” fluid mechanics (think: wing aerodynamics) scale up to the movement of air in the atmospheric boundary layer.

Releasing a Sparv Embedded Windsonde at our urban site-- these little radiosondes have a genius design, a single PCB inside a styrofoam cup, light enough to fly with a normal birthday balloon.

The bulk of my work for the experiment was logistical– testing all our sensors, shipping them down to texas, and getting everything networked and collecting data. Modern sensors and data loggers have fairly easy plug and play networking connections, but for some older models the data stream involved a bit of creativity with messy GUI-interacting auto hot key scripts.

Another timelapse at our rural site in the northwest of the city.

Getting a handle on the variety of sensors took the majority of the academic year leading up to the campaign, and the whole experience was a fun crash course in atmospheric boundary layer science. In total, we deployed:
 

• Three Eddy Covariance Flux Towers (Campbell Scientific)

  These sensors are a combination of a 3D sonic anemometer, which measures a 3D wind vector at ~18hz using ultrasonic sensors, and an open path gas analyzer, which yields concentrations of CO2 and H2O. Simultaneous measurements of the upwelling/downwelling of the wind and gaseous concentrations allow for net flux measurements of those gasses.
   

• A Ceilometer (Vaisala CL31)

  A ceilometer is a small Lidar, which shoots up and receives a signal bouncing off particulates or clouds in the atmosphere. This is a reliable remote sensing method to determine the boundary layer height.
   

• A Net Radiometer (Radiometrics)

  A radiometer on the other hand is a passive sensing device, using microwave detection to determine temperature and humidity in the atmosphere. The operating principals on these are really neat, and they require an interesting field calibration for a zero set point, using a liquid nitrogen cooled target.
   

• A Scintillometer (Scintec)

  Scintillometers work by analyzing the changes in the refractive index of air, similar to the mirage-like “scintillations” you can see around a fire or above hot tarmac. They’re composed of two parts, an emitter and receiver, which can be set up spanning any line of sight distance up to 6000m. The disturbance to the emitters signal can be interpreted to yield heat flux and turbulence values along the path line.
   

• Forty-something Radiosondes (Sparv Embedded)

  Launching this many sondes inside an urban environment was something special, and only possible with the organization of the larger tracer campaign.  

Thanks to Dr. Prathap Ramamurthy and Dr. Jorge Gonzalez for the opportunity to take part in the project, to Dr. James Flynn and the team at the University of Houston for hosting us, and to Harold Gamarro, Kalimur Rahman, and M.V.P. Gabriel Rios for their contributions to the team.

Special thanks to Houston's Electronics Part Outlet which managed to have every possible obscure connector or component needed to fix whatever was breaking at the time. An absolute gem of an electronics shop if you are in the area.