Table of Contents

Satellites

Shadowing Satellite Science

The CloudSat Ground Validation Program

Canadians have a natural fascination with cold weather – especially with our unpredictable winter season filled with everything from wet snow to icy rain. Scientists would like to have a better understanding of the physics behind winter clouds that are a mix of ice and water droplets mix and the resulting weather conditions.

By unlocking the microphysics of cloud formation, especially the more complex winter clouds, researchers hope to improve weather forecast models. Until recently, atmospheric scientists have known about the consequences of certain cloud formations (for instance, freezing rain, drizzle, or sleet) but have had a hard time testing their computer-based models.

Reliable, continuous meteorological information provides insight not only into the inner workings of cloud systems but more importantly, helps improve long-term forecasts of our climate. This is the big picture behind the CloudSat mission; but to make sure data from above the clouds is correct, it has to first be verified and calibrated from below. That's where the Canadian Space Agency's Ground Validation Campaign plays a critical role in the success of the satellite program by independently evaluating, diagnosing, and improving CloudSat measurements.

A sizeable challenge

During winter 2007, Canadian researchers flew 28 precision flights aboard the National Research Council's Convair 580 research aircraft, shadowing CloudSat as it passed along its orbital path above eastern Canada. The aircraft carries the same type of radar and lidar instruments as CloudSat, so researchers probe the same clouds as the satellite.

As the satellite races by at seven kilometres per second measuring ice and water content across the depth of clouds, researchers on the plane take simultaneous measurements of the same location as the satellite passes overhead. Timing and precision make each three-hour long aircraft flight a serious technical challenge, like flying along CloudSat's relatively tiny 1.4 kilometre-wide radar footprint at 6,000 metres through turbulent clouds, and even snow squalls, over the Great Lakes.

Revealing data

With the completion of the field portion of the data validation campaign earlier this year, the Canadian Space Agency is hosting a workshop to discuss all aspects of the field project and application areas. The results are now being analyzed and prepared for publication. CloudSat has already provided data of parts of Canada where no data previously existed. The Ground Validation Program has proven its worth by improving data from the satellite when it was having difficulty accurately analyzing multi-layered clouds.