Lake breeze captured during glider flight

Yesterday December 13, 2010 part of the PCAPS team and volunteers headed out again to the Great Salt Lake for more glider "sounding" data. With a strong possibility for lake breeze development, we hoped to capture at least some of the event mid-day. Meeting around solar noon allowed for time to setup and train our volunteers in initializing GRAW sondes and configuring radios for communications.

Some of the Team: Erik Crossman, Chris Santacroce, Chris Ander, David Reim, Neil Lareau

Our pilot, Chris Santacroce, met us shortly after noon. Surface winds were strangely calm at the lake's edge, and after waiting for several minutes, Chris decided to make a no-wind launch with his powered paraglider.

Chris setting up the powered paraglider

The flight plan was to fly long north-south cross sections, stepping up 100m each leg. Half way through the 50 minute flight we noticed a strong increase in surface winds pushing off the lake. Temps dropped rapidly and rh values spiked. We managed to capture the lake breeze as Chris was sampling data at the inversion top, so changed plan and sampled an east-west cross section at the mixing level as the lake breeze persisted inland. No one anticipated the lake breeze to penetrate deep into the Salt Lake Valley, but within the hour it had channeled across the length of the valley into Sandy. This helped strengthen the inversion and justified one more sounding transect the next day at 12 and 18 UTC across the valley before ending sub IOP 3 operations.

Chris flying north over the GSL at 6000 ft MSL.

More analysis is needed on the data collected, and we hope to review this last glider data-set during the upcoming downtime as the next series of troughs move through northern Utah.

Glider Test Flight Over Saltair a Success

In anticipation of today's potential mix out, local paraglider pilot Chris Santacroce and a small team from the U of U finally had a good window to test deploying an instrumented Powered Paraglider (PPG) at the edge of the Great Salt Lake over Saltair yesterday (December 2, 2010). The goal was to sample the land / lake interaction in a strong Cold Air Pool and capture the vertical structure in detail. By attaching a GRAW Sonde to the pilot controlling the glider we hoped to create a "new" type of instrumentation that could sample cross sections and vertical profiles of the air.

Paragliders can fly at very low speeds without stalling (around 15 to 20 mph) which allows unique sampling of the air by a human pilot. Imagine being able to ask a balloon to stop at a certain height, sample a cross section, spiral back to the ground, then ascend just above the cold pool and take pictures before returning to the launch location.

A powered paraglider is also unique because of the small space required to take off. This allows us to deploy the glider quickly and with few resources from any number of locations within the Salt Lake Valley. Of course, most first prototypes suffer in the glamor department but this is what we ended up with (sonde mounted on helmet):


The first flight attempt yielded no problems and good quality data. Chris flew for around 40 minutes completing cross sections out to the lake's edge, then back over I-80. Each transect was 100 meters higher than the last until finally the glider was above the Cold Air Pool, where he was met with a 20 knot south wind. We communicated by texting via iPhone and two-way radio. Chris was able to snap a few photos along the way to document the flight in a little more detail.

Photo by Chris Santacroce, Dec 2, 2010.

Looking south over Saltair from 350 meters AGL.

Photo by Chris Santacroce, Dec 2, 2010.
Looking NNW over Saltair from 325 meters AGL.

Yes. Those are feet at the bottom of the photos. Note in the second photo: the lake fog to the west of Lake Point was still quite thick mid day.

Initial analysis of the observations showed that within 150m starting at 250m AGL, temperatures increased just over 9C, which validated well with nearby balloon launches. And where a regular sonde only samples a single vertical profile with few observations in a shallow Cold Air Pool, we were able to maintain flight within the inversion and gather considerably more data.

Our thanks to Chris Santacroce for helping design a working prototype. Chris is a talented pilot and co-creator of the Red Bull Airforce team. We are extremely lucky to have his skills and time donated for PCAPS and we hope to deploy many more glider flights throughout the project.