Cloud Formation Formation of clouds

Compression and Expansion  When air expands its temperature drops  When air is compressed it heats up –These effects come are called adiabatic temperature changes –The temperatures change without heat being transferred from one object to another  As altitude increases temperature drops by 10°C for every 1000 meters

Expansion & Cooling  A large amount of air that is rising decreases its pressure as its altitude increases –This is called the dry adiabatic rate –This leads to air expanding; which leads to air cooling  At some point the air that is rising reaches its dew point –This causes condensation (releasing energy)  These begin to form clouds

Still expanding still cooling (BRRR)  As the moisture in the air condenses it releases energy working against the cooling of the rising air to slow the rate air cools –This is called the wet adiabatic rate  This ranges from 5-9°C per 1000 meters  The line between the dry & wet adiabatic rates happen when the moisture begins to condense

That’s great but how often does this actually happen? Seriously?  Air in the atmosphere doesn’t usually like to change its height –Air close to the surface tends to stay at the surface  It has four mechanisms that can cause air to change altitude –Orographic lifting –Frontal wedging –Convergence –Localized convective lifting

Mountains aka Orographic  When air runs into elevated terrains it is forced up the side of the mountain increasing its altitude –When this occurs it goes through the dry & wet adiabatic lowering of temperature  As the moisture condenses it is often released in the form of precipitation –The rainiest places in the world on the “windward” side of mountains

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Fronts aka Fronts  This is what we in Kansas experience most of the time –If orographic was the only process the Midwest would be a desert  In this process warm and cold masses of air run into each other –This makes the warm air rise causing adiabatic cooling

BAM (aka convergence)  Sometimes the two masses of air have roughly the same temperature and they run into each other –The air stuck in the middle will then rise producing adiabatic temperature changes  Florida experiences this due to its shape as a peninsula –Air over land get squished upward from moderate air from the gulf of Mexico & Atlantic ocean

Hot air (aka localized convective lifting)  When air becomes hotter then its surrounding it will rise –Think hot air balloon  Causes of this could be due to the makeup of the surface –A black asphalt parking lot will heat air above it quicker then a park with trees and vegetation  This air is called Thermals –Some birds use these rising air to get to high altitudes

Stability  Hot air rises Cold air sinks –The reason hot air rises is because it has a lower density –It will raise until it is surrounded by air of the same density –Rising air is called unstable air –Air that remains at the same height is generally called stable

Measuring Stability  Stability is measured by checking the temperature of the atmosphere as altitude increases  The most stability in the atmosphere is when the temperature above is warmer then below –This is called a temperature inversion  These happen often on clear nights

Stability still  When air is rising it is said to be unstable –Rising air can produce very menacing clouds  Generally stable air can still produce clouds but they tend to not be very tall and little to no rain  Unstable air can produce tall clouds that can lead to thunderstorms

Condensation  Follow the steps –Air rises –Rising air cools –Cold air can’t hold moisture as well as warm –The relative humidity increases (saturated air) –Moisture that was in the air then condenses –Moisture condensing forms clouds & fog  The moisture in the clouds condense on dust particles & Ocean Sand particles