Chapter 23. Weather and Climate. Cloud Forming Processes. A cloud with a volume of 1 cubic km contains about a million liters of water. You see a white cloud when you are between the cloud and the sun, since you see reflected sunlight from the cloud.
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Weather and Climate
The clouds filter the sunlight.
between the sun and the
Clouds-You see reflected
sunlight from the cloud.
1. Cumulus clouds are heaped and puffy. They can be of low or middle altitudes in the atmosphere.
2. Stratus clouds are layered. They can be of low or middle altitude in the atmosphere.
3. Cirrus clouds are wispy. These clouds are of high altitudes in the atmosphere.
1. Low altitudes (below 2000 m): Stratus, Nimbostratus, Cumulus, Stratocumulus, Cumulonimbus
2. Middle altitudes (2000-6000 m): Altocumulus, Altostratus
3. High altitudes (above 6000 m): Cirrus Cirrocumulus Cirrostratus
3. Continental tropical (cT) -Dry, warm air
4. Maritime tropical (mT) -Warm, moist air
Polar air mass moving southeast over the southern US. Clouds form over the warmer
waters of the Gulf of Mexico and the Atlantic Ocean, showing the state of atmospheric
Instability from the temperature differences.
Fronts – boundary between air masses
This weather map of the US shows two fronts with associated low pressure areas and
Five areas with high pressure.
Cold Front – cold air moving into a region of warmer air.
Warm Front – warm air advances over cooler air.
Different parts of a thunderstorm cloud develop centers of electric charge. Lightning
Is a giant electric spark that discharges the accumulated charges.
Lightning heats, expands atmosphere creating large pressure wave - thunder.
This hailstones fell from a thunderstorm in Iowa, damaging automobiles, structures,
Tornadoes – smallest, most violent weather disturbance on Earth.
This zone is near the equator and receive the greatest amount of sunlight throughout the year, so the overall climate is hot. The average monthly temperatures are above 64oF.
2. High altitudes- Those that some time during the year receive no solar radiation at noon. They receive a maximum amount of radiation during one part of the year and none during another part. Overall temperatures are low, and there is a large range of annual temperatures. This is called the polar climate zone and it occurs north of latitude 66.5oN or south of latitude 66.5oS.
The sun never sets here during some summer days and never rises during some winter days. The overall climate is cold and the average monthly temperature stays below 50oF even during the warmest month of the year.
3. Middle Latitudes-Between the low and the high latitudes. They receive a higher amount of incoming radiation during one part of the year and a lower amount during the other part. Overall temperatures are cooler than in the low latitudes and have a wide seasonal variation. This is the temperate climate zone and is between 23.5oN and 66.5oN and between 23.5OS and 66.5OS.
The temperature is neither very cold or very hot, the average monthly temperature stays between 50oF and 64oF throughout the year.
Regional climate groups
Rain Shadows, regions of little or no precipitation.
Regional climate groups
Carson City, Nevada; east of the Sierra Nevada mountains.
Lake Tahoe, Nevada; west of the Sierra Nevada mountains.
3. Large bodies of water:
Regional climate groups
San Diego, California
Oceans (or other large bodies of water) minimize large temperature fluctuations.
San Diego’s summer is 13°F cooler and winter is 9°F warmer than Dallas.
Regional climate groups
Northern hemispheric temperature range is 25°F while the Southern is 13°F.
4. Ocean Currents:
Ocean currents affect local climates. U.S. eastern coast, warm ocean currents travel northward. U.S. western coast, cold currents travel southward.
2. Continental Climate:
3.Other ways to describe climate:
# 1, 2, 3, 4, 5, 10, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22
New Book: p. 622-625 # 1, 2, 3, 4, 5, 6, 7, 8, 13, 14, 15, 18, 19, 22, 27, 29, 30, 31, 32, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 47.
The hydrologic cycle: More water evaporates from oceans than is returned as rain. Deficit is from streams and rivers flowing into the ocean.
After tiny droplets condense in the atmosphere and form clouds condensation nuclei are needed before larger droplets can form.
White clouds-You are between the sun and the clouds. Grey clouds-The clouds are between you and the sun.
Dew and frost-not precipitation. Rain, hail, snow-precipitation.
Near ocean-clouds form water droplets around large salt crystals and precipitation occurs. Away from oceans clouds are higher and ice crystals grow; for these precipitation is liquid in summer, could be solid if winter.
Cumulus clouds (puffy)-shorter rain showers; stratus clouds (layered)-longer rain drizzle or snow; cirrus clouds (wispy, high altitudes)-no rain showers.
Cumulus and stratus clouds are of low and middle altitudes. The prefix nimbo or the suffix nimbus means rain. Prefix alto means middle altitudes.
Close to the equator the earth receives more sunlight and the air is warmer, rises, then sinks back towards the surface at around 30oN and S. Part of the air then comes back towards areas close to the equator and part towards the poles. Low pressure over equator, high pressure over 30oN and S.
Changing weather is attributed to: movement of air masses, fronts of air masses, high and low pressure systems.
Air masses-Continental polar (cold, dry), continental tropical (warm, dry), maritime polar (moist, cold), continental tropical (dry, warm).
A front is the boundary between air masses of different temperatures and they don’t mix-density of cold air higher than warm air. Shown as a bulging line on weather map. Bulge is in the direction of movement of front.
Cold fronts produce high P systems and result in cumulus clouds and thunderstorms. Warm fronts produce low sloping fronts and cirrus clouds followed by stratus clouds which produce long periods of fog, drizzle and rain.
Stationary fronts produce major storms. Cold and warm fronts moving in opposite directions.
Thunderstorms develop in very warm, moist and unstable air. Often July afternoons. Thunder, lightning, strong winds, rain, hail generated. Different parts of a thunderstorm cloud develop centers of electric charge. Lightning is a giant electric spark that discharges the accumulated charges.
Tornadoes are the most powerful weather disturbances on earth. Occur in great plains states-tornado alley.
A tropical depression (<35mph winds), a tropical storm(>35,<75mph winds) and a hurricane(>75mph winds) are all storms with cyclonic surface wind circulation. Occur over tropical or subtropical waters and are not associated with a weather front. Storm intensities according to the speed of the maximum sustained surface winds.
Called a hurricane if over the Atlantic Ocean or the Pacific Ocean east of the international date line. Called a typhoon if it occurs over the North Pacific Ocean west of the international date line.
Climate-weather following a yearly pattern of seasons. Low latitudes-tropical, middle altitudes-(between tropic of cancer and arctic circle or tropic of capricorn and antarctic circle)-temperate, high altitudes-polar.
Dry climate 30oN and S and poles, wet climates equator and 60oN and S.
Four factors affecting regional climate: altitude (T decreases), mountains (W of Rockies-wet, E of Rockies-dry), large bodies of water (Southern hemisphere, more water, less T changes), ocean currents (warmer water upwards, cooler water downwards, moderate temperatures near the coast) .
Ocean currents give rise to marine (warmer winters and cooler summers) vs. continental climates (colder winters, hotter summers).
Arid, humid and semiarid are based on amounts of precipitation.Summary Chapter 23