Weather and Climate S2 End of Year Review

Climate encompasses long-term patterns and averages of weather conditions, typically assessed over a minimum of 30 years. This distinction highlights that while weather represents short-term atmospheric changes at a specific location, climate provides a broader understanding of what to expect in terms of temperature, precipitation, and other atmospheric elements over extended periods. Thus, climate is a more stable and predictable measure compared to the variability of daily weather.

As temperature rises, air expands and its capacity to hold moisture increases. Relative humidity, which is the ratio of the current amount of water vapor to the maximum amount the air can hold at that temperature, decreases because the same amount of water vapor now represents a smaller percentage of the air's increased capacity. Thus, even though the total water vapor remains constant, the relative humidity drops as the air can accommodate more moisture.

Dew point temperature refers to the specific temperature at which air reaches saturation, causing moisture in the air to condense into liquid water. When air cools to this temperature, it can no longer hold all of its water vapor, leading to the formation of dew, fog, or clouds. Understanding the dew point is crucial in meteorology as it helps predict weather conditions and humidity levels.

Coalescence is a key process in cloud formation where small water droplets in the atmosphere collide and combine to create larger droplets. As these tiny droplets come together, they overcome surface tension and grow in size, eventually becoming heavy enough to fall as precipitation. This process is crucial for the development of rain and other forms of precipitation, as it enhances the efficiency of water droplet growth within clouds.

In orographic rainfall, the windward side of a mountain receives the most rainfall because it faces the prevailing winds. As moist air approaches the mountain, it is forced to rise. This rising air cools as it ascends, leading to condensation and cloud formation, which results in precipitation. The leeward side, in contrast, experiences descending air that warms and dries, resulting in significantly less rainfall. Thus, the windward side is characterized by higher moisture levels and more rainfall due to the orographic lifting effect.

At higher altitudes, the atmosphere becomes less dense, resulting in fewer air molecules to absorb and retain heat. This reduced density leads to lower temperatures as there is less thermal energy available. Additionally, snow and ice commonly found at mountain tops reflect sunlight rather than absorbing it, further contributing to the cooler conditions. Combined, these factors explain why temperatures decrease at higher elevations compared to the base of the mountain.

An albedo of 70% indicates that the surface reflects 70% of the incoming solar radiation. Albedo is a measure of reflectivity, with higher values representing greater reflection. Therefore, if a surface has an albedo of 70%, it absorbs only 30% of the solar energy that strikes it, reflecting the majority back into the atmosphere. This property plays a crucial role in climate and temperature regulation, as surfaces with high albedo can help cool the environment by reflecting sunlight.

Convectional rainfall occurs when warm, moist air rises rapidly, cools, and condenses to form clouds, often leading to thunderstorms. This type of rainfall is characterized by intense precipitation over a short duration, frequently accompanied by lightning and thunder. It typically happens in warm climates, especially during the summer months, when surface heating is strongest. The rapid upward movement of air creates the conditions necessary for severe weather phenomena, making convectional rainfall the most common type associated with thunderstorms.

Cloud cover influences the diurnal temperature range by acting as an insulating layer. During the day, clouds can block sunlight, resulting in lower daytime temperatures. At night, clouds trap heat emitted from the Earth's surface, preventing it from escaping into the atmosphere, which raises nighttime temperatures. This combination leads to a smaller difference between the maximum and minimum temperatures over a 24-hour period, effectively decreasing the diurnal temperature range.

The tropics are characterized by high levels of solar radiation, which significantly increases evaporation rates. This region's proximity to vast oceans and lush forests further enhances humidity by providing a continuous source of moisture. The combination of intense sunlight and abundant water sources creates an environment where moisture is readily available, leading to the high humidity levels typical of tropical climates. This contrasts with other regions that may not benefit from such consistent solar energy and moisture availability.