Urban Heat Islands and Climate Phenomena
Urban Heat Island Effect
The urban heat island effect refers to the difficulty of heat dissipation during nighttime hours in urban areas. While non-urban areas cool down considerably due to a lack of heat buildup, downtown areas with buildings and asphalt radiate heat accumulated during the day. This causes local winds to blow from the outside inward. The phenomenon of temperature rise in densely built urban areas is caused by a combination of factors, including construction, lack of green spaces, and gaseous or heat generation. The urban heat island effect intensifies with increasing city size.
Why Polar Winds Don’t Reach Ecuador
Polar winds do not reach Ecuador because of the Coriolis effect. The rotational speed of the winds is greatest at the poles and lowest at the Equator (Ecuador). Therefore, air masses moving from the poles towards Ecuador lag behind the Earth’s surface, undergoing a deflection to the right in the Northern Hemisphere and a clockwise deflection in the Southern Hemisphere.
Understanding the El Niño Phenomenon
The El Niño phenomenon occurs in the tropical waters of the South Pacific, near the coast of South America. Normally, trade winds blow from the continent, pushing surface waters offshore. This allows for the upwelling of nutrient-rich deep waters, increasing productivity. The climate is typically dry on the American coast, while the moist trade winds reach the coast of Asia, resulting in heavy rainfall.
However, every 3-4 years on average, the position of cyclones and storms in the Pacific shifts, reversing the situation. Winds blow from the ocean towards the continent, bringing heavy rains to the South American coast. This causes the upwelling of deep water to cease, drastically reducing fish stocks.
Photochemical Smog Explained
Photochemical smog is created by a mixture of nitrogen oxides and other volatile hydrocarbons. Sunlight acts upon these compounds, causing a reaction that produces highly toxic gases, such as ozone. The primary contributor to this type of smog pollution is the high volume of vehicles in cities.
Application Questions
1. Windward and Leeward Effects on Rainfall
The windward side of a mountain range is characterized by the development of orographic convective clouds, leading to heavy rainfall. By the time these clouds reach the leeward slope, they have already released most or all of their moisture, resulting in minimal or no rainfall on that side.
2. Temperature Differences: Windward vs. Leeward
On the windward side, the cooling of an air mass from a given altitude begins at the value of the Dry Adiabatic Lapse Rate (DALR). Once the saturation point is reached, the cooling rate changes to the Saturated Adiabatic Lapse Rate (SALR), which is lower. This means the decrease in temperature with altitude is less than if it had continued at the DALR. On the leeward side, descending air masses are devoid of moisture and are heated at the DALR throughout the entire descent.
At the same height, the temperature of the air mass on the leeward side will be higher than on the windward side. This difference is approximately equal to the difference between the DALR and the SALR, multiplied by the height at which the air mass rose at the SALR. Furthermore, the leeward area may receive increased energy due to a clearer sky (lack of clouds).
3. Risks Associated with Windward and Leeward Climates
- Windward: Storms and risks arising from erosion.
- Leeward: Drought. Atmospheric stability hinders the dispersion of pollutants.