Clouds and Fog 13.11 pg. 530-534 Energy in the Water Cycle Water in the hydrosphere picks up energy from the Sun. This causes the water to vaporize and to rise high in the atmosphere where the pressure and temperature drops. As a result condensation occurs and precipitation forms How Clouds Form There are three main categories of cloud formation: Convective clouds Frontal clouds Orographic clouds Convective Clouds Convective clouds: air near the ground picks up energy from the ground, warms and rises carrying vapor with it. It expands and cools as it rises into the cool, low pressure region of the atmosphere. This usually occurs wherever solar energy is absorbed by water and other surfaces Frontal Clouds Frontal clouds: Form when the leading edge or front of an air mass meets another at different temperature. This happens if a warm air mass moves over a cold one or if a cold air mass pushes under a warm one. Orographic Clouds Orographic clouds: Forms when air moves up a mountain, expands at low pressure and cools. (“oro” comes from the Greek oros meaning mountain) Moisture in the rising air condenses in the colder air as it goes up the mountain, producing clouds Fog Fog Actually a cloud that forms near the ground. Fog commonly forms: On clear nights when energy radiates upward and is not reflected back When warm air passes over snow covered ground When moist sea air drifts over a cold current (coastal regions) When moist air rises up mountains during orographic lifting Classifying Clouds Classified in three ways: 1.General Shape Cumulus (‘heap’) Clouds- have a billowing, rounded shape. Grow vertically, mean unstable weather. Form from convection currents, orographic lifting or when a cold air front pushes into a warm air mass Stratus (‘spread out’) Clouds- flattened and layered,grow horizontally, stable conditons, form when warm air mass overruns a cold one Classifying Clouds 2.Altitude Low level- usually called stratus or cumulus Medium level- start with alto meaning higher High level- starting with cirrus (‘curly lock of hair’) are the highest 3.Rain-holding: Nimbus-a rain holding cloud Name the 10 different types of clouds (see pg. 533)
"Clouds and Fog"