Microclimate | Types of Microclimate

Micro-climate 

Micro-climate means a garden, park, valley, or a part of a city. The small area has a specific climate. Weather-related changes in temperature, rainfall, air or humidity, which occur in micro-climates, may be somewhat different from the conditions in the entire region. Several factors are responsible for the micro-climate. like:

1. The ability to maintain heat in urban areas
2. Mountain slopes
3. Absence of vegetation in areas such as the city's Central Business District (CBD)
4. Intensive vegetation presence in protected areas
5. Types of soil

Different types of micro-climate exist in different types of environment on the surface of the Earth:

1-Upland Regions   

• The altitude areas have a distinct type of climate, which is different from the surrounding lowlands. Generally there is a decrease in altitude as well as temperature which depends on the humidity of the air. It is noteworthy that the rate of temperature drop is between 5 and 10 degrees Celsius per 1000 meters. This means that even the areas at normal elevation are on average much cooler.
• Occasionally, the air in areas at high altitudes becomes warm due to temperature derivatives, but such conditions do not exist for long. Temperatures in high mountainous and mountainous regions are, on average, so low that winters are too long and summers are too short.
• Catabatic air also creates cool conditions in the valleys. It is because of these conditions that the plants and animals found here differ from those living in the lower places.

2-Coastal area

• The climate of coastal areas is affected by both land and sea as coastal areas form a boundary line between terrestrial and oceanic regions. Due to the thermal properties of the water, the daily sea temperature is relatively constant against the site. The seas take longer to warm up during summers and conversely, it also takes longer to cool during winters.
• Coastal micro-climates exhibit different types of characteristics, depending on the variations of the surface. In tropical regions there is little change in sea temperature. The coastal climate is affected by the daytime heating in terrestrial areas and the cooling process in the night.
• In temperate latitudes, the coastal climate is more affected by the sea area than the site. In winter the coastal parts are pleasant compared to the interior areas and cool in summer. Due to the presence of snow around the polar regions, the temperature of the sea areas is low. The position of the coast in these areas varies due to the melting of ice and the re-freezing of sea water.

3-Forest Regions

Although tropical rainforests are found on only about 6% of the Earth's surface, they contribute significantly to the transfer of atmospheric water vapor. This process is caused by the evaporation of green leaves. The forest areas are less windy and cool than their surrounding grasslands. The reason for this is that trees block the way of air and also block the fraction of sun radiation from them.

4-Urban Regions

Urban areas are the most complex of all microclimate areas. The temperature of these areas is higher than the surrounding areas. The details of rainfall in a town or city depends very much on the topography of the area. For example, the amount of rainfall is found more in hilly areas and lowest in lowlands. In fact, the nature of rainfall varies throughout the year in these areas. In summer, the rainfall is generally showery in nature and in the short time more rainfall is received. Usually this rainfall is more intense than in winter.

4.1-Urban Climate

Green regions of the world have a distinct type of climate different from regional characteristics. Today the process of rapid urbanization has drastically changed the physical environment. This climate change is a clear example of the role of humans. There has also been a change in the surface energy, humidity and wind speed conditions of the urban climate.

City-Rain-Women-Urban-Climate-Umbrella

• Urban development constrains the surface and climatic characteristics of the atmosphere. Land use change, desalination, drainage and construction projects create a new micro-climate around them and a group of these diverse human-affected micro-climates create an urban climate. The urban area has also changed the composition of air, temperature and rainfall etc.
• Wind speeds are slower than open areas due to the structure of the resistant nature of cities. During the daytime, the speed of the winds in the cities is much slower than the surrounding areas but at night, the disturbance varies over the cities. The strongest winds prevail in the rural-urban transition areas and its effects are more pronounced in winter than in summer.
• Most urban areas being built from concrete (concreteization) absorb much less water per area than rural areas. For this reason, heavy rainfall in some areas increases the risk of local urban flooding and specific measures need to be taken to reduce this risk. Due to heavy construction activities in floodplains, both duration and intensity of urban floods increase.
• Cities tend to have lower humidity than rural or forest covered areas. Due to the concrete surface, water runoff becomes faster. Low vegetation cover and general absence of water bodies in urban areas also reduce humidity and evaporation.
• On the other hand it seems that in some circumstances the thermal and turbulent conditions of cities cause rain or thunderstorms. Urban areas sometimes receive more rainfall and storms than surrounding areas. As a result, these areas grow relatively.
• Pressure fluctuations are much greater during winter than in summer. During the winter the average high pressure system is found to have more high pressure and lower pressure system with lower pressure. This causes more rapid flow of air in this system. Due to this instability, much variation in temperature is observed during winter. Although most days of summertime have almost the same temperature, the temperature of winter season fluctuates dramatically.

4.2- Urban Heat Island

Temperature is generally higher in urban areas than in open and rural areas. The most important reason for this is that the amount of sunlight absorbed during the day by the buildings and other concrete construction of the city is radiated at night. Temperatures are generally higher during the day than at night and this is even more pronounced when the air flow is slow.

Urban heat island (UHI) is a metropolitan area that is much warmer than its surrounding rural areas due to human activities. The temperature difference between the urban center and its surrounding areas is excessive, which can be up to 10 ° C.

The following factors are responsible for the construction of the urban heat island:

• High buildings: High buildings, narrow lanes cause a decrease in net long wave radiation, as these buildings decrease the visibility of the sky. Different surfaces are provided for the reflection and absorption of sunlight by tall buildings, which increases the heating efficiency of urban areas.

• Heat absorbing structural structures: For example, concrete used in buildings absorbs more sunlight due to the thermal properties of asphalt. Later this heat is released at a slow rate in the form of long waves, which slows down the cooling process.

• Population growth: As the population increases in urban areas, the average temperature also increases with the expansion of the area. For example, in Los Angeles, there was rapid urban development after World War II, which caused the average temperature in urban areas to increase by about 0.5 ° C each decade.

• Pollution: The chemicals emitted by vehicles and industries also react differently in sunlight, due to which often more heat is produced. Blanketing effect generated by atmospheric pollution in the Earth's radiation is also a cause of heat.

• Absence of vegetation: Due to the land without vegetation, the rate of evaporation is low. Also, the various benefits (shade and cooling effect, albido) effect they get and the absorption of carbon dioxide deprive urban areas.

• Industrial and Household Appliances: Direct emission of heat is caused by industries and homes in urban areas.

The urban heat island effect of different cities varies according to the urban structure as well as the temperature range also varies. Parks and green belts help to reduce temperatures while the Central Business District (CBD), commercial areas and even suburban residential areas are high-temperature areas. Each house, building and street affects the micro-climate around them and thus contribute to the urban heat island effect.

Impact on Urban dwellers

• A lot of energy is consumed to keep buildings cool.
• The urban heat island effect increases the production of pollutants such as ozone, which leads to a decrease in air quality.
• Water quality deteriorates due to the flow of hot water into streams. Hence, there is pressure on the ecosystem.
• The increased heat increases the photochemical reaction, which increases the amount of particles in the air and thus contributes to the formation of smog. London, for example, receives about 270 hours less sunlight from the surrounding rural area due to smoke and cloud.

4.3-Atmospheric pollution in cities

• The problem of atmospheric pollution arises when humans emit unwanted elements and energy in the environment to the extent that it cannot be assimilated by the ecosystem. This creates health problems and damages the environment and property.
• The urban environment is affected by soot, ash, gas, smoke and sulfur, carbon, nitrogen oxides. Green house gases such as carbon dioxide and methane are mainly responsible for the increase in Earth's temperature. They also produce blanketing effects for urban radiation, increasing the albedo of the urban area. Sulfur dioxide and related chemicals are considered primarily primary factors of acid rain. These particles also act as condensation nuclei.
• Under normal conditions, most of the pollution is transmitted upwards into the atmosphere due to disturbance and flows with high winds at high altitudes. However, high-rise buildings in cities impede the smooth transmission of these particles. The highest concentration of smoke is found in places with slow air speed, temperature inversion and high relative humidity.
• To deal with this problem, with the active participation of civil society and urban population, several strategies will be required. The government is taking various measures to curb air pollution through legislation, tax benefits and other schemes on a long-term level. Civil society can play an important role in spreading environmental awareness among the people and helping in urban forestry etc.