Microclimate

The microclimate or miniature climate is the local or small-scale environmental conditions that influence plant growth and development, such as evapotranspiration and wind. This term is often used as an equivalent for a macroclimate, the seasonal or large-scale climate. As a result of the plant effect, we can observe different types of microclimates. 

A microclimate is more localized than the weather or local climate and is therefore generally much easier to understand and predict. Weather conditions, on the other hand, have a larger projection and, as a result, are more difficult to predict.

Factors that influence Microclimate

The microclimate is affected by the weather, and the weather is affected by the wind, temperature, relative humidity, precipitation, and atmospheric pressure. There is a clear relationship between wind and temperature: the temperature is cooler in an area with light wind and warmer in an area with heavier wind. 

This concept of microclimate is very important, as it plays an important role in the growth of plants. In a greenhouse, there are two types of microclimates:

• A sheltered microclimate is present in the greenhouse. This microclimate results from the greenhouse itself, which may protect the plant from the sun. 

• A natural microclimate is that which is present outdoors. The temperature of the soil is affected by the amount of shade cast by the surrounding vegetation and by the presence or absence of water. Air movement caused by the wind may also be important. This can also contribute to increased humidity. Plant growth is related to microclimates that support high levels of light and heat.

Microclimates play a critical role in how people experience various climate zones in different seasons.

There are a lot of factors that determine what a microclimate is and in fact, the term.

"microclimate" itself is a misnomer because there are really many different climate zones and microclimates, which can vary greatly.

But to get to the point, what is the temperature of the microclimate?

This is a critical aspect of climate zones because as the microclimate temperature approaches the dew point, the temperature of the airdrops and dew forms at the same time, the winds start to be warmer and that means the air is starting to be loaded with water vapor.

What you are seeing is the combination of temperature and humidity dropping and the air becoming heavy with water vapor, which explains why the air becomes heavy and becomes more prone to precipitation. This occurs most visibly in fog, but it also occurs in clouds, and when the air gets heavy with water vapor, it is able to produce precipitation.

A microclimate is a small region, such as a square meter or a meter-cube, that has its own environmental conditions, with its own conditions of heat and cold, light, and humidity.

For example, many of the plants in a small garden can have their own unique microclimates with particular conditions such as soil moisture, air humidity, and wind direction. A specific plant can be placed in a certain place in order to obtain the desired microclimate. For example, a potted plant can be kept in a location that is shaded most of the day. In a greenhouse, the microclimate can be used to regulate the relative humidity, temperature, and airflow.

In some of the literature, the microclimate is also called a site environment or a local environmental condition.

Causes

In a microclimate, the sun is closer to the ground (more direct sunlight) than it is to an observer, usually resulting in lower temperatures for that observer. This situation can be created by different types of vegetation. For example, tall trees shade smaller plants. However, in dense forests, the canopy shade is a secondary factor as the foliage is too dense to permit sunlight to reach the ground.

For a greenhouse or other structure that receives direct sunlight throughout the day, the effect of canopy shading is more important.

The intensity of direct sunlight in a given microclimate is a function of a number of factors: 

• The difference in elevation between the microclimate and an observer

• The tilt of the solar path relative to the surface

• The angle of the solar surface is relative to the vertical. In an example, the direct sunlight of noon is 10 percent of that of noon. This factor may be used to estimate the solar exposure of a microclimate.

Some types of plants, such as vines and deciduous trees, reduce the temperature of their leaves by evapotranspiration. Leaves are evaporative surfaces, and evaporative cooling reduces the temperature of the leaves. However, in the case of most vines, their water-conserving behavior is a function of soil moisture, while evaporative cooling occurs when soil moisture is greater than the plants' root zone capacity. The water-conserving behavior is a function of soil moisture that allows the plants to maximize the quantity of water that is available to the plant. Evaporative cooling is a function of both leaf and soil moisture.

Light intensity is also an important factor. A shade tree can be planted in a sunnier location to provide shade for the rest of the garden. A structure can be built to collect the light and redirect it. The building can be located on a different day from the light that reaches the ground, or it can be located at a different time of day.

The wind pattern affects the shape and distribution of a greenhouse, and it affects the distribution of light and air humidity. The effect of wind on the air inside a greenhouse is often called a wind shadow. Many different forms of wind, such as the wind gusts, the wind direction, and the wind speed, are significant factors in the design of a greenhouse. The microclimate is sometimes used synonymously with the microclimate of a plant.

Uses

A microclimate can be used for the following:

• Plant phenology: the observation of growth, flowering, fruiting, and the death of a plant

• Water balance: the calculation of the evaporation and transpiration of water from plants

• Climatic studies: the comparison of a microclimate with the seasonal climate of a region

• Plant selection: the placement of plants that have specific needs for microclimate

• Design: the specification of a structure in terms of space usage

• Air quality and air pollution: the reduction of harmful gasses, like carbon dioxide and nitrous oxide

The microclimate is the aggregate of environment variables, including temperature, humidity, radiations, and to which plant is exposed. It is the climate near the Earth's surface and it is distinct from the local climate or weather projection microclimate because of the earth effects and, most importantly, the presence of vegetation.

Microclimates occur, for example near the water bodies, which may cool the atmosphere, or in heavily urban areas where brick, concrete and asphalt absorb the sun's energy, heat up and radiate that heat to the ambient air then the resulting urban heat island is a kind of microclimate.

The term "microclimate" is first introduced in publications such as "Climates in Miniature": A Study of Microclimate Environment (Thomas Bedford, Franklin).

Microclimatology

The term microclimatology is defined as the scientific investigation of microclimate, and it's concerned with the atmospheric layer that extends from the Earth surface to a height where the consequences of the features of the supporting surface can no longer be differentiated from the local climate (American Meteorological, 2000).

Urban Microclimate

Urban microclimate can be defined as the local climate observed in the urban areas, which differs from the climate of the surrounding rural areas. Several factors are responsible for creating an unhealthy urban microclimate.

Human-generated heat is the biggest factor and much of it is caused by internal combustion by car engines that use fossil fuels. Cars also cause pollution and moisture to the air. All the heat- retaining covered surface required for cars makes the climate more unhealthy. Other factors that are responsible for creating unhealthy urban microclimates are poor building constructions and designs, inferior insulating materials, and inefficient building management practices. 

Microclimate Parameters

Two microclimate parameters that define microclimate within a certain area are temperature and humidity. 

Macro and Micro Climate

A microclimate is defined as the variations in localized climate around a building, whereas a microclimate is the climate of larger areas such as a region or country. The macro and microclimate have a crucial effect on both the energy and atmospheric performance of buildings during the summer season.

The construction site affects exposure to the prevailing wind, the solar radiation the building receives, pollution level, temperature and rain penetration.

Factors Affecting Microclimate And Microclimate

The factors that adversely affect macroclimate and microclimate are discussed below.

Macroclimate is Affected By the following factors:

• Topography- The Shape of the land

• Sun angle exposure

• Vegetation

• Waterbody

• Physical Infrastructure

• Urban Layout

• Energy Demand

• Open Spaces

• Vehicle Population

A microclimate is Affected by the following factors:

Outsiders Designer Control

• Area and local climate

• Site surrounding

• Site shape

• Topography features

• Surrounding Buildings

Within Designer's Remit

• Location of open areas

• Spacing and orientation of buildings

• Form and height of a building

• Fenestration

• Tree covers

• Windbreak

• Ground Profiling

• Surrounding Surface (paving grass etc.)

Climate and Microclimate

Weather is defined as the atmospheric condition at a certain point in time or a short period of time. It is characterized by distinct methodological events such as air velocity, temperature, air pressure, and their interactions. On the other hand, climate can be defined as the average state of the atmosphere and related characteristics of the underlying water or land in a particular region for a long duration. The term microclimate can be used to describe an indoor climate, i.e., the condition of the area in a certain closed space. 

Difference between the Climate and Microclimate

The difference between climate and microclimate is that the climate is an area of the Earth's surface between two parallels of latitude, whereas microclimate is a small, local region retaining a unique pattern of weather or weather effects that differs from the local climate. 

Did You Know?

• North California above the Bay Area is renowned for microclimate with significant temperature differences.

• San Francisco is a city with microclimate and sub microclimates.

• The Chesapeake Bay is also known for its subtropical climates.

• The wind microclimate around buildings is the result of the layout of the building.

• A microclimate is advantageous for gardeners who carefully choose and position their plants.

• Tall buildings in urban areas create their own microclimate both by overshadowing larger areas and by channelizing strong wind to ground level.

• Halixa, Nova Scotia has varied microclimates.