students chart microclimates in pavilion gardens
sciences professor Bruce Hayden (left) and other students
watch while Tara Zimet (center) points an infrared thermometer
in the air to get a temperature reading. The students are
looking at how, even in the same garden, the climate varies
from spot to spot, depending on aspects of the landscaping,
from trees and plants, to terraced or sloping ground, to brick
gardens where the University's first students grew vegetables,
sciences majors taking a new class, "Climate of Engineered
Landscapes," are studying how plantings create microclimates.
it's a student research-oriented course, I'm using the Grounds,"
said Bruce Hayden, environmental sciences professor. "The Pavilion
gardens are very specific landscapes, walled off from one another,
each with a different design" -- and a slightly different climate.
gardens on the East Range, for instance, are steeply terraced,
except one that is sloped, and they only get morning sun, so they
tend to be cooler.
"We know that cold air runs downhill," said Hayden, whose research
focuses on climate and vegetation interactions. "If you sit in
a lower garden just after sundown, you can feel that little river
of cold air come down and rush past you."
The students make sky maps of the gardens using an infrared thermometer
that allows them to take several kinds of measurements, he said,
adding that each of the 10 students in the class has a different
garden to study. Hayden concedes that the students could just
as easily learn the physical principles in the classroom and then
go look at the gardens. But he prefers a hands-on approach. "When
we're taking measurements, it's hard to put it all together into
one picture, to answer questions like, 'Do gates and cross walls
make a difference?'
takes hours and hours to take these kinds of measurements; but
this is an empirical course where they're trying to discover something.
You can sit in a room and read about the productivity of others,
or you can go out and [do your own research]."
students will point a thermometer directly above them at the sky
or the trees' canopy, measuring the temperature, he said. On a
clear October day when the temperature is in the upper 60s, the
sky is about 22°F, while the canopy is about 77°F.
three-dimensional architecture of the garden plays a large role
in determining where it's warm and where it's cold," Hayden said.
"Plants don't produce heat, but they do give off energy; there's
always a balance between the energy the plant [releases] and the
energy it gains from its surroundings."
In mapping the temperature of the sky and trees all over the garden,
students gain a better understanding of the balance of energy.
are designed and placed on the landscape to make life more comfortable,
so they tend to reduce temperature extremes. In some cases they're
designed to increase or decrease the humidity as well," he said,
adding that gardens in the desert often have fountains in them.
Plants keep a garden cool during the day by using sunlight that
would otherwise be heating the air to evaporate water, he explained.
The coolest garden on the Lawn is the evergreen one on the East
Range, which has a canopy that's nearly closed. The warmest gardens
are the most open ones on the West Range, which get plenty of
these flat gardens, without cold air runoff, Hayden said, it's
the materials in the garden that make the difference in temperature.
A brick walk with sand between the bricks is 15° cooler than one
with cement between the bricks, because the sand holds moisture
that evaporates during the day, keeping the bricks cool. The use
of certain building materials to influence air temperature has
broad implications for cities, he said, noting that some are looking
for ways this kind of technology can "make the whole city more
comfortable. There's been a movement in the last 15 years to increase
the shading of streets. Chicago is proposing rooftop gardens,
and cities like Phoenix and Los Angeles are trying to use more
reflective surface materials that retard heat."
students are surprised by the effects different materials can
have in engineered landscapes, he said, as well as by the presence
of cold air drainage, which they typically associate with river
who has taught at U.Va. since 1970, said he also learns a great
deal from his students in courses like this. "Empirical work involves
generating theories as well as testing them; it's hard to have
one without the other. The students are critical to the capacity
to generate ideas. Questions we wouldn't dream of asking, the