If a skyscraper is structurally sound or a pedestrian area is pleasant for strolling or sitting, thank an atmospheric scientist. CPP has a few of these professionals on their team and we spoke to Anke Beyer-Lout and Kelly Gassert about what they do and why they do it.
But first, about that title. An atmospheric scientist is a meteorologist, but what does that last word make you think of? Someone who studies meteors? The weatherperson on local TV?
The title atmospheric scientist suggests a broader view of the study of climate and the analysis of atmospheric events. Having trained extensively in the specialization, Beyer-Lout and Gassert considered typical meteorological careers in government and academia, but they chose the private sector and CPP for the greater freedom and applicability of their work, meaning “the chance to be immediately helpful to people,” said Gassert.
Atmospheric scientists play a critical role with CPP’s work. “Every project we do starts with the wind,” said Beyer-Lout. The local wind climate drives building design and what safety measures must be put in place. Beyer-Lout and Gassert sometimes find themselves examining temperature, humidity, and even snow and ice, but most projects focus on wind — over years and decades, in averages and extremes.
“We get involved early in the project lifecycle,” said Gassert, “by determining the wind climate for a project location.”
Wind data comes from many sources, the best being the National Centers for Environmental Information. Through a website, Beyer-Lout and Gassert download climate data for a particular building site, or as close as they can get. Most data are collected at airports, every hour on the hour, although universities, businesses — such as a wind farm — and even private citizens record data through their own instruments and make it available to the public. Quality varies.
Data quality is essential, and has improved in recent decades. Prior to the 1970s, wind observations were often taken manually and recorded by hand. Fortunately, advances led to automated collection and the accumulation of solid historical data. “Going back forty years gives us a good foundation,” said Beyer-Lout. “From that we can extrapolate to paint a picture of 700 years, even 1,700 years, of climate behavior.”
Beyer-Lout and Gassert explained that some projects begin with only ten years of data, which is considered inadequate. Consequently, the range of potential error goes up, and the resulting design must account for the uncertainty. A building might require greater reinforcement and associated expense. In short, wind data quality correlates to project cost.
Gassert described a typical project. After being downloaded, the climate data is subjected to a series of quality-assurance procedures. Data arriving in many formats must be consolidated, and in huge quantities. “These are massive data sets, well beyond what a spreadsheet could handle,” Beyer-Lout explained. CPP uses proprietary software tools, which constantly evolve.
Next, the results of the wind climate assessment are applied to a specific project site. CPP conducts tests in atmospheric boundary layer wind tunnels, blasting scale models of several city blocks with air from all directions, as delicate sensors record resulting pressures and wind speeds along facades and on street corners. The wind climate for the area is then used to scale the non-dimensional wind tunnel results, providing clients with actual extreme wind pressures or average wind speeds they can expect for their building.
“Our deliverables to the project engineers vary widely, depending on the type of project,” explained Gassert. For a structural job like the construction of a new building, engineers care most about gusts. After all, a building has to be designed to withstand the worst the environment could deliver. For a pedestrian comfort project, designers pay closer attention to average wind speeds and direction. Direction can be as simple as north, south, east, and west, but the need for greater precision may demand data from sixteen directions or more.
What makes for a challenging project? “Take Colorado’s Front Range where CPP is headquartered,” explained Beyer-Lout. “Plains butt up against mountains, creating tremendous wind and weather variances.” Can airport data from a flat landscape be trusted in designing a building for the foothills?
Gassert described the challenge of designing for New York City, where wind data can come from a number of nearby airports, all unique. Newark International Airport to the west frequently experiences severe thunderstorms, while data at JFK and LaGuardia Airports on Long Island suggest weaker thunderstorms. “Which dataset applies best to Manhattan? It’s an interesting puzzle.”