Inventory a Site’s Climate Better Than Al Gore

Former Vice-President Al Gore may be an climate expert, but nobody is better an inventorying a site’s climate details like a landscape architect.

Climate and microclimate are natural existing conditions that need to be identified during the site inventory phase of a project. There may be a few questions on the California Supplemental Exam for landscape architects. This article will give you the basic knowledge needed for the exam.

What is Climate?

Climate is the average long-term weather pattern for a region. Thirty years of data are used to describe a location’s climate. Several factors influence climate, such as, latitude, elevation, vegetation, and bodies of water. In this article, we will refer to this “big picture” climate as the macroclimate.

Why Is Climate important to Landscape Architects?

In addition to being an existing natural condition that we are expected to master for the CSE, there are other reasons why landscape architects inventory climate information.

First, landscape architects create comfortable outdoor spaces. Infringing comfortable outdoor living environments for people requires a thorough understanding of existing climate and microclimate information. Landscape architects use data collected during the inventory to inform sit analysis and design.

Second, landscape architects have many design tools that we can use to modify a space’s microclimate. But, we need to understand what the existing conditions are first. Modify and improve the environment for human comfort, productivity, or resource conservation.

Third, we can modify microclimate conditions to improve energy efficiency.

Three Climate Types

There are three types of climate that landscape architects typically discuss. Macro and microclimate are, by far, the most common. Topoclimate is a relatively new term that discusses how landform and topography modify the macroclimate. We will exam the three types of climate and discuss what role they play in a site inventory.

  • Macroclimate
  • Microclimate
  • Topoclimate

Macroclimate

Macroclimate is the regional climate and is a generalization for a region. Due to the modifying factors of topography and microclimate influences, the macroclimate may not accurately reflect site conditions. For example, we can generalize that areas along the coast have a maritime Mediterranean climate. But that does not tell us how the climate is modified by slope aspect or a variety of other influencing factors.

Microclimate
Have you ever noticed that some tender plants survive a killing frost while others do not? Some of the survivors just happen to grow in a slightly more protected microclimate that protected their delicate leaves from climatic extremes. For example, a building overhang trapped just enough radiant heat to protect delicate begonias. Or, the water in a water feature retained enough heat to keep a courtyard above freezing. These climate-modifying factors are just one example of how microclimates make a big difference to both plants and people.

Microclimate site inventory information is the most useful data for landscape architects. The site’s numerous microclimates are the actual climate condition experience by people and plants.

Microclimate data is the hardest climate data to inventory but provides the most value for landscape architects during the site analysis and design phases of a project.

Landscape architects try to predict how existing and proposed conditions will affect a site’s microclimates.

Factors that affect microclimates include:

  • Surface materials
  • Landform and topography
  • Buildings and structures
  • Vegetation
  • Water

Surface Texture & Color
Surface colorant texture can profoundly affect the microclimate of the space. For example, broad expanses of light-colored pavement reflect light and heat and can make a space and surrounding buildings unbearably hot on a sunny summer day. Dark pavement absorbs heat during the day and releases it at night. For example, a parking lot at your local shopping center gets hot during the day and releases it’s heat at night, contributing to their an heat island effect. Surface texture and color make all the difference.

Landform & Topography
The topographic form of a site can affect its microclimate. If you have ever gone hiking in the mountains, you probably noticed that trains on the north slopes are cooler in the summer and south-facing slopes are much warmer. The shape of the land affects how energy flows through a site.

Buildings & Structures
Like topography, buildings channel energy flow on a site. South facing walls absorb or reflect light and heat depending on their surface color and texture. Buildings also cast shadows and create shady nooks. Enclosed courtyards are protected from macro clumsy extremes. Walls can reflect and store heat which modifies the surrounding environment. Additionally, walls and structures can increase or decrease wind velocity by their placement in the landscape. These are just a few ways that built objects can modify the macroclimate.

Vegetation
Site vegetation is another factor that creates microclimate modifications to the regional climate. Plant life on a site can modify temperature and humidity levels on a site through transpiration. Air blowing across a sports field of well-maintained turf is cooler than a summer breeze coming from an asphalt parking lot. Another way that trees modify the climate is through shading the ground. By increasing tree canopy coverage on a site, the ability for the ground to absorb and radiate heat is reduced. Trees also create shade and cool the air around them through evaporative cooling. These are just a few ways that plants can affect a site’s microclimates.

Water
Have you ever seen those products that claim to magically protect your tomatoes from frost and allow you to plant them early in the season? What is their secret? Water. Wall-O-Water and similar products use the heat storage potential of water to create a microclimate that protects plants from frost. Larger bodies of water do the same thing on a larger scale.

There are a few different ways that water can affect microclimate. First, water absorbs heat slower and releases it slower. Thus, areas adjacent to water bodies are less prone to extremes of heat and cold. Second, evaporation helps cool the air. That is why fountains are so common in dry-climate courtyard gardens. Water has a temperature-regulating effect in the landscape.

The best ways for landscape architects to inventory a site’s microclimate is by visiting the site and experience the site’s microclimates firsthand. Look for climate modifying factors that are on the site. Record your observations for future reference.

Topoclimate
Topoclimate is a fairly recent term used to describe how landform and topography modify an area’s climate. Topoclimate affects areas larger than a microclimate but smaller than the macroclimate.

Slope exposure affects a site. South-facing slopes are warmer and dryer because they directly intercept solar radiation. North-facing slopes are cooler and moister because the sun’s rays strike the slope less directly.

Landform affects wind flow through a site. Ridges perpendicular to the dominant wind direction reduce wind speed on the back-side. Valleys that run perpendicular to the wind will be less well ventilated while valleys that run in the same direction of the wind can be funnel wind and create breezy spaces.

How to landscape architects inventory the topoclimate?

There are two recommended ways to survey a site’s topoclimate. Topographic maps and surveys can help you understand the bigger picture (particularly on large sites). From maps and aerial photos, you can assess the climate-modifying landforms and make reasonable inferences as to how the macro climate is modified on the site. Test out your assumptions by experiencing the site firsthand. Check your assumptions about microclimates created by landforms with actual observations to test the validity of your conclusions.

Climate Site Inventory Checklist

A climate site inventory contains information on macro, micro, and topoclimate. This checklist covers some items you may find on the California Supplemental Exam for landscape architects.

  • Min/Max temperatures and average monthly temperatures
  • First and last frost dates
  • Average annual precipitation
  • Annual snowfall rates
  • Air quality
  • Humidity
  • Wind speed and direction
  • ETo rate
  • Climate type or classification
  • (climate map thingy)
  • California Climate Classification (energy map)
  • Microclimates at various places on site
  • Proximity to water that can modify the climate
  • Topography that modifies the climate
  • Sun and shade patterns
  • Sunset Climate Zone
  • Dominant Vegetation type.
  • Climate-related natural disasters

Can you think of something else that needs to be on the list? Post your suggestion in the comments.

Final Thoughts on Climate Inventories

You don’t need to be a climate “rock star” like Al Gore to inventory a site’s climate. Landscape architects have the perfect skill set to observe and record a site’s climate and microclimate information.

Climate is another natural factor that landscape architects include in a site inventory. Macroclimate information is the easiest to gather. Microclimate information takes some detailed site investigation. Identifying climate factors on your site during the inventory process will help focus site analysis and the rest of the design process.

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About

John is a landscape architect who is currently preparing to take the California Supplemental Exam to become licensed in California. He is currently a licensed professional landscape architect in Georgia and Florida. John graduated from California State University, Pomona with a BSLA degree in landscape architecture in 1997 and has extensive practice experience in residential and commercial landscape design.

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