TRACER Forecast Exercise Comes With a Surprise Twist

Published: 20 July 2020

Editor’s note: Scott Collis, an atmospheric scientist and ARM radar data translator from Argonne National Laboratory (ANL), sent in this blog post. Collis is a co-investigator on the upcoming TRacking Aerosol Convection interactions ExpeRiment (TRACER).

In just under a year’s time, the U.S. Department of Energy’s ARM user facility will deploy one of its mobile facilities to Houston, Texas, for TRACER. During a four-month intensive operational period (IOP), ARM will launch weather balloons—balloons with special sensors that allow scientists to study how winds, temperatures, and moisture vary with height—every 1.5 hours. In comparison, National Weather Service (NWS) offices launch balloons every 12 hours, and ARM will normally launch every six hours during the rest of TRACER.

Radar reflectivity factor seen from WSR-88D radar system in Galveston, Texas
Figure 1 provides the radar reflectivity factor as seen from the WSR-88D radar system in Galveston, Texas, on June 25, 2020. These radar data allow scientists to understand how storms evolve and change. During TRACER, ARM plans to deploy the second-generation C-Band Scanning ARM Precipitation Radar (CSAPR2), which will allow imaging of fine-scale storm structure through the use of storm tracking software, restricting the radar’s imaging volume to small parts of the storm.

The incredibly rapid launching of balloons during the TRACER IOP will allow the study of how the thin (around 3,000-foot) layer of air next to the ground, called the boundary layer, changes before storm clouds form. To get as much value from the soundings as possible, TRACER scientists will put their forecast skills to the test to try to predict the perfect day for these rapid weather balloon launches.

In preparation for this, and to gain a better understanding of the meteorology of the Houston region, scientists from across the DOE labs, other federal agencies, and partnered universities led a forecast exercise over three weeks (June 13 to July 2, 2020). These scientists—joined by a local weather expert, Lance Wood, the science and operations officer for NWS Houston—used this exercise to “game out” various weather scenarios as well as to develop procedures on how forecast data will be presented and archived to guide operations and future analysis.

While a 2019 paper led by NASA’s Ann Fridlind helped to statistically frame the “typical weather” expected during the TRACER IOP, the actual weather that occurs can vary quite dramatically from the statistical average (also known as climatology). This happened in two ways during the TRACER forecast exercise:

  • During the start of the forecast period, the team saw a lot more “organized” large storms than expected (such as the example shown in figure 1).
  • Strong winds over Africa and a persistent weather system called a Bermuda high helped transport a large amount of dust from the Sahara to the local region (see figure 2). This unusual event spawned a lot of discussion on the TRACER Science Team about what operational mode we would request of the ARM soundings during such a phenomenon, given how valuable the data would be to the community.
Saharan dust event from June 22, 2020
Figure 2 shows PhD student Amber Schlessiger (Texas A&M University) discussing the Saharan dust event that occurred over the TRACER domain during the forecast exercise.

Overall, the forecast exercise was a great success, allowing the team to not only hone our skills, but also to build excitement for the TRACER deployment next year. As new partners come aboard, the team plans to transition the ARM-focused forecast exercise to a multi-agency-focused implementation. If there are any partners needing forecast support or who can provide extra resources, please reach out to TRACER Principal Investigator Mike Jensen or forecast lead Scott Collis.

The team would like to extend our thanks to those who provided forecast help: Robert Jackson (ANL), Mike Jensen (Brookhaven National Laboratory), Chris Nowotarski (Texas A&M University), Amber Schlessiger (Texas A&M University), Laura Judd (NASA Langley Research Center), Steve Nesbitt (University of Illinois at Urbana-Champaign), Marcus van Lier-Walqui (Columbia University/NASA Goddard Institute for Space Sciences), Toshi Matsui (NASA Goddard Space Flight Center), Brian Wittemann (Brookhaven/SUNY Oneonta), and Eric Bruning (Texas Tech University), and a special thanks to Lance Wood (NWS Houston) for his expert advice and feedback.