Shade Where It Counts

• ○A. Energy absorbed by city surfaces during daylight can affect temperatures after dark.
• ○B. Waste heat prevents city temperatures from changing between day and night.
• ○C. City surfaces begin absorbing most of their solar energy after sunset.
• ○D. Limited air movement is the only reason cities remain warm after dark.

• ○A. “Buildings can also limit air movement, while vehicles and air-conditioning equipment add waste heat.”
• ○B. “The strength of an urban heat island changes with weather, time of day, and the arrangement of buildings and surfaces.”
• ○C. “They can release stored heat after sunset, slowing nighttime cooling.”
• ○D. “Many roofs and paved surfaces absorb solar energy during the day.”

• ○A. The cooling provided by trees stays similar despite differences in water availability.
• ○B. The shade of a small sapling cools as much pavement as the shade of a mature tree.
• ○C. The movement of water into the air provides a cooling process in addition to shade.
• ○D. The water beneath a tree cools a street mainly by blocking sunlight from the pavement.

Trees influence heat in more than one way.Their leaves intercept sunlight, shading pavement, walls, and people.Water also evaporates from soil and passes from leaves into the air through transpiration; these processes use heat.The amount of cooling depends on conditions, including available water and the size and density of the canopy.A small sapling cannot immediately provide the shade of a mature tree.

• ○A. Whether the planting total is larger than the city's previous planting total
• ○B. Whether the trees cast shade on waiting areas when passengers use them
• ○C. Whether the trees are evenly spaced along both sides of every street
• ○D. Whether the bus stops are close to streets with the largest number of trees

• ○A. “Where a tree stands matters as well.”
• ○B. “A tree across the street might cast its shade elsewhere at that hour.”
• ○C. “A tree beside an afternoon bus stop may shade people during a long wait.”
• ○D. “Planners can study the sun's path and the times people use a space.”

• ○A. The budget can treat watering as unnecessary once a tree enters the ground.
• ○B. The budget can assume suitable species will grow despite limited root space.
• ○C. The budget should favor buying more trees over checking planting conditions.
• ○D. The budget should include care after planting, not just the purchase of trees.

• ○A. “Without follow-up care, some planted trees die before developing a large canopy.”
• ○B. “A suitable species must tolerate local conditions and fit the available space.”
• ○C. “Roots need room, air, and water, but urban soil may be compacted beneath pavement.”
• ○D. “Planting is only the beginning of a tree's life on a street.”

• ○A. A map can explain why each neighborhood developed its current amount of shade.
• ○B. A map can establish how frequently people walk along each exposed route.
• ○C. A map is less useful than a citywide average for locating blocks without trees.
• ○D. A map may need to be supplemented with residents' knowledge of local routes.

• ○A. “Asking residents about exposed walking routes can reveal needs that a broad map misses.”
• ○B. “Existing shade is not distributed evenly among neighborhoods.”
• ○C. “A citywide canopy average can hide blocks with very few trees.”
• ○D. “Planners can combine canopy maps with information about summer temperatures and places where people spend time outdoors.”

• ○A. The result could be useful if its measurement conditions are documented.
• ○B. The nearby air must be cooler by the same amount as the pavement.
• ○C. The time and weather conditions matter when comparing the measurements.
• ○D. The report should identify the kind of temperature that was measured.

• ○A. “Checking results requires care, too.”
• ○B. “Comparing similar locations at similar times helps researchers separate the effect of shade from changes in weather.”
• ○C. “A shaded pavement surface may be much cooler than nearby sunlit pavement, but that difference is not automatically the same as the difference in air temperature.”
• ○D. “Reports should identify what was measured and under what conditions.”