18-3 Flashcards
what are cirrus clouds? appearance, weather, level?
wispy, white, feathery, curly, high clouds that contain ice crystals. fair weather or indicates appraoching storm. bases above 6000 m
what are cumulus clouds? appearance, weather?
puffy white clouds (like piles of cotton), with flat bases.
As air currents rise they may lower, fair weather when clouds are not very tall while towering clouds indicate approaching storm
what are stratus clouds? appearance, how do they form, weather?
form in flat layers, uniform dull, gray clouds, usually cover all or most of sky. Forms when layers of air cool below dew point temperatures, usually at low altitudes, associated with fair weather or light precipitation. bases below 2000 m
what are the 3 types of high clouds? describe them.
Cirrus clouds: feathery appearance, made of ice crystals, sometimes forms halos around moon or sun
Cirrocumulus clouds: like rows of cotton balls
Cirrostratus clouds: layered, high clouds that look like veils, usually not rain makers, low temperatures and low water vapor present
what are the 2 middle clouds? describe.
Altocumulus clouds: rounded masses are larger and denser than cirrocumulus, higher than regular cumulus clouds
Altostratus clouds: create white to grayish sheet covering sky, sun or moon visible as bright spot through them, continuous light snow/drizzle may accompany clouds
both have bases between 2000 m and 6000 m
what are the 3 low clouds? describe.
Stratus clouds: uniform, fog-like layer of clouds, may produce light precipitation
- Nimbostratus: dark colored rain making clouds, long steady rain, so full of water sun cannot penetrate cloud
Stratocumulus clouds: have long parallel rounded patches
Cumulus clouds: larger rounded puffy clouds
how do cumulus clouds form into cumulonimbus clouds?
cumulus may grow dramatically on hot days with strong lift, once upward movement is triggered acceleration of cloud is powerful.
Cumulonimbus clouds may form and produce rain or even thunderstorm, some so large they start near the ground and tower
what is fog?
clouds that form at or near the ground; clouds result from air rising and cooling adiabatically
what is fog a result of?
radiational cooling: air moving over cold surface or enough water vapor added to the air to bring about saturation
how is fog caused by cooling?
when ground cools at night after warm humid day. it cools the air above the ground to air’s dew point, next day the warmth of the sun burns the fog off as water droplets evaporate because temperature rises above dew point
how is fog caused by evaporation?
when cool air moves over warm water.
Moisture evaporates from water to produce saturation of the air, as rising water vapor meets cold air it condenses.
precipitation occurs when..?
droplets are too heavy to remain suspended so it falls out of clouds
what are the two things size of rain depends on?
- Updrafts that keep rain in sky longer making them bigger
- Rate of evaporation, if low humidity in air the rain drops will be smaller
different types of precipitation form depending on?
temperature profile of the air, changes with altitude
what is the most common type of precipitation? explain the different sizes and how it starts.
rain. it starts as snow, then melts. droplets are biggest, then drizzle, then mist.
how does snow occur?
when water vapor changes directly to a solid at high altitude and falls to ground as a solid.
what is sleet?
when snow passes through a layer of warm air and melts then refreezes in colder air mass above the ground
what is glaze?
freezing rain; when falling snow hits warm air and melts, then falls into colder air but does not have time to freeze. Forms a thick layer of ice on surface
what is hail?
when water drops freeze in layers around a small nucleus of ice, tossed up by updraft, forms new layer of ice then falls down by gravity, then tosses up again by another updraft, cycle repeats. Eventually gets too large and falls to the ground
what is cloud seeding? was it successful?
experiment used to try and create rain in a drought location, shoots silver iodine or dry ice particles into cloud, proving nuclei for water molecules to cluster around and freeze.
Has been successful in less fog, more snow and some rainfall but most have been unsuccessful, not able to modify weather that much
how is snowfall measured?
two ways:
1. Using meter stick to measure amount of snow
2. Melting collected snow and measuring depth of water it produces
what is a rain gauge? is it accurate?
open-ended can/tube that collects rainfall, increases accuracy, the top of the rain gauge may have funnel, has calibrated scale on the tub.
Narrower tub = less evaporation, more accurate
