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How much water is locked up in our oceans and glaciers?

Nearly all of the earth's water is contained in the world's oceans. Fresh surface and soil water make up only a small fraction of the total volume of global water. Ice sheets and glaciers are the second largest reservoir of water.

Hydrologic Cycle

Circulation of water in the atmosphere, a continuous cycle of evaporation, condensation, and precipitation. Water is continually transferred from one state to another as a liquid, vapor, or solid. Precipitation has three fates. Water from the oceans and from land surfaces evaporates, changing state from liquid to vapor and entering the atmosphere. Once in the atmosphere, water vapor condense or deposit to form clouds and precipitation which falls to Earth as rain, snow, or hail

Precipitation Three fates

It can evaporate and return to the atmosphere as vapor. It can soak into the soil and into the surface rock layers below. Subsurface water emerges from below to feed rivers, lakes, and ocean margins. Precipitation can run off land into streams and rivers that eventually carry it to the ocean or lakes... aka runoff

What is humidity?

Amount of water vapor in the air

Warm air versus cold air and capacity to hold water

Warm air can hold more moisture than cold air

How does relative humidity change with temperature throughout the day?

As air temperature rises relative humidity drops, therefore relative humidity tends to be highest first thing in the morning when temperatures are lowest

The Adiabatic Process

Adiabatic Cooling, Adiabatic Heating, Rising and Cooling air parcel, DALR, WALR

Adiabatic Cooling

The cooling of clouds when a parcel of air rises. The rising parcel of air expands as it encounters decreasing atmospheric pressure with altitude

Adiabatic Heating

Air descending through the atmosphere is compressed by the increasing pressure and increases air temperature

Rising and Cooling air parcel

The rising and cooling air parcels will eventually reach the dew point temperature and water vapor will condense and form cloud droplets. After condensation occurs, the adiabatic cooling of a rising parcel will decrease at a lower rate because latent heat of condensation is being released into the air


Dry Adiabatic Lapse Rate, 10 degrees Celsius/1000 m, rate at which air is cooled by expansion when no condensation is occurring (before condensing)


Wet Adiabatic Lapse Rate, 5 degrees Celsius/1000 m, rate at which rising air is cooled by expansion when condensation is occurring (after condensing)

Condensation Nuclei

A tiny bit of solid matter (aersol) in the atmosphere, on which water vapor condenses to form a tiny water droplet

Stratus Clouds

Appear at lower altitudes from the surface up to almost 6000 meters, basic characteristic is horizontal appearance, in layers of fairly uniform thickness


Aka nimbus, meaning precipitation (rain) is falling

What are the four primary way clouds form?

High Cloud, Middle Clouds, Low Clouds, Clouds of vertical development


Advection, Radiation, Upslope


Horizontal transport of air, warm air over cold surface, common over oceans


Fog produced by radiational cooling, clear skies and cooling of the ground chills the layers just near the surface


Form when air moving in hilly or mountainous terrain cools to condensation

Where is the foggiest place in North America and why?

Libby Islands (coast of Maine), Air flowing off of the warm waters of the North Atlantic drift crosses the cold water of the Labrador Current. Warmer air cools below its dew point and fog results

What type of fog is common to San Francisco and why?

Advection fog, Cold California current hugs the coast and air moving in from the warmer pacific waters comes in contact with it.

Air Masses

Extremely large body of air whose properties of temperature and humidity are fairly similar in any horizontal direction at any given altitude. Air masses are classified according to temperature and moisture properties of their source regions. Based on moisture of Source Region, Based on Temperature of SR.

Based on moisture of Source Region

Continental (dry) - land, Maritime (moist) - oceans

Based on temperature of Source Region

Tropical (warm), Polar (cold), Arctic (extremely cold)

Continental Polar (cP) AIr Masses

Formed over high-latitude land masses, Northern Canada, Siberia, Very low temperatures, stable conditions, extremely dry (low relative humidity), clear-sky conditions

Continental Arctic (cA) Air Masses

Similar to cP, but colder

Maritime Polar (mP) Air Masses

Usually unstable air masses, forms over North Pacific from air moving out of Asia, Affects West coast of North America (Pacific), mP air masses on the Atlantic seldom affect weather on the eastern coast because this air mass is located in the westerlies belt

Continental Tropical (cT) Air Masses

Forms over hot, dry, low latitude regions during summer, Southwest US and Northern Mexico, Cloud-free

Maritime Tropical (mT) Air masses

Forms over warm tropical waters, Atlantic and Gulf of Mexico, warm and moist, unstable near the surface, clouds and precipitation, over land, additional surface heating more unstable, heavy, short-lived precipitation thunderstorms, the mT from the Gulf of Mexico provides the greatest amount of moisture to the U.S. east of the Rockies


Surface of contact between two unlike air masses, identifies a zone of transition between air of different properties. Ex. often represents the boundaries between polar and tropical air. (great temperature differences). Cold, Warm, Occluded, Stationary

Cold front

Moving weather front along which a cold air mass moves underneath a warm air mass, lifting the warm air mass. Cold air is much denser than warm and remains in contact with the ground. Cold air mass overtakes and replaces warm air.

Cold front Cloud types

Cumuls, Cumulonimbus clouds (can produce hail)

Cold front weather


Warm front

Warm air mass replaces cold air, moving weather front along which a warm air mass slides over a cold air mass, producing stratiform clouds and precipitation

Warm front cloud types

Stratus, nimbostratus

Warm front weather

steady precipitation, sometimes thunderstorms


Closed or shut off, a front formed when colder air surrounds a mass of warm air and forces it aloft


A front that is stationary with winds blowing almost parallel and from opposite directions on each side of the front. The two air masses are in contact with one another but with little motion

What are the three types of cyclones?

Wave cyclone, Tropical cyclones, tornado

Wave Cyclone

Midlatitudes, Arctic, Antarctic zones

Tropical Cyclone

Tropical and subtropical zones

Midlatitude Cyclone and theory

Storms, neither tropical nor hurricanes, form along a front in the middle and high latitudes. Synoptic scale low pressure system that has cyclonic (counter-clockwise in the northern hemisphere) flow. Characterized by the presence of frontal boundaries. It travels great distances bringing precipitation and sometimes severe weather to wide areas.

Polar Front Theory

Jacob Bjerknes provided insight into the development, movement, and dissipation of middle latitude cyclones

What is the life cycle of the midlatitude cyclone (cyclogenesis)?

Stage 1-6

Stage 1

Trough of low pressure with high pressure on both sides of the polar front, the two anticyclones come into contact on the polar front. One contains a cold dry air mass, and the others a warm, moist maritime air mass

Stage 2

A wavelike kink forms on the front known as a "frontal wave". Cold front pushing southward and warm front pushing northward. Region of lowest pressure is the junction of the two fronts. A low-pressure trough forms. Wave cyclone begins to form.

Stage 3

Steered by winds aloft, the system moves east or northeastward. Strong cyclonic flow - winds swirl counterclockwise and inward toward low pressure. Precipitation - wide band head of warm front. Narrow band along cold front.

Stage 4

System continues eastward and central pressure decreases and winds blow more vigorously. Fast cold front inches closer to warm and eventually overtakes warm front.

Stage 5

Occluded front (in purple) - the cold front overtakes the warm front. It will gradually dissipate because cold air now lies on both sides of the occluded front. Without rising warm, moist air, the supply of energy is gone and system dies out

Stage 6

Pocket of warm air above surface moves north. These systems help more energy poleward. Most start in the Leeward side of the Rockies and end in the location of the Ohio Valley or around Maine.


Life cycle of a typical mid-latitude cyclone (wave cyclone), they are guided alonga path reflecting the configuration and speed of the upper air westerlies or the jet stream, a general west-to-east pattern prevails

Tropical Cyclone

Always from over warm oceans, temperatures > 26.5 degrees Celsius, move towards west through trade-wind belt, Usually occur late summer or early autumn; water temperature at highest, different names around the globe.

Different names of Tropical Cylones around the world

Hurricane, Typhoon, Cyclone


Northern Atlantic, Eastern Pacific


North Pacific


South Pacific, Indian Ocean

How do Tropical Cyclones derive their power?

From warm tropical waters and latent heat released as water vapor condenses into clouds

How do Tropical Cyclones dissipate?

Dissipate rapidly when they move from ocean over land due to friction and loss of moisture supply

Tropical Cyclone Development

Tropical Disturbance, Tropical Depression, Tropical Storm, Hurricane

Tropical Disturbance

Small clusters of thunderstorms, weak pressure gradients, no rotation

Tropical Depression

Storm intensifying

Tropical Storm

Wind speeds above 37 mph - officially given a name


Wind speeds 74 mph +

What is the Saffir Simpson Scale

A scale that measures strength of Tropical Cyclones, and orders Minimal, Moderate, Extensive, Extreme, Catastrophic

Storm Surge

Rise in sea level due to intense low pressure in the center of the storm. When a storm surge moves in at high tide it can inundate and destroy a wide swatch of coastal lowlands.

Two processes create storm surges

Piling up of water due to drag of surface waters and low atmospheric pressure - for every millibar the pressure decreases, the water level rises .4 inches


Rotating column of air around an area of intense low pressure with a circulation that reaches the ground, small, very intense wind vortex with extremely low air pressure in the center, formed below a dense cumulonimbus cloud in proximity to a cold front.

Tornadoes are most associated with

Thunderstorms in midlatitude fronts, with tropical cyclones

Favorable conditions for Tornadoes

Cold front of mP air lifts mT air

Where are tornadoes most frequent?

in U.S., in "Tornado Alley" in the Central Plains

Tornadoes can have wind speeds up to

100 m/s (225 mph)

What is the Fujita Scale?

Shows strengths of Tornadoes, F0-F5


The daily conditions at a particular location


The average weather (temperature and precipitation) over a region (30-year average)

What are the controls of climate?

Radiation, rotation, topography, latitude


Primary driving force for weather - it is the flow of solar energy received by the Earth and the atmosphere


Energy flow varies on daily cycles (also on annual cycles with revolution). It imposes these cycles on temperature and precipitation regimes.


The arrangement of high and low elevations on a land surface. Local variations in elevation can cause local variations in climate. Climate zones coincide roughly with elevation ranges.


There is variation in insolation with latitude which in turn affects temperature. In general, temperatures drop from equator to poles.

What is a climograph?

A graph on which two or more variables are plotted for each month of the year. Shows annual cycles of monthly mean (average) air temperature (line) and monthly mean (average) precipitation (bars) for a location. Some may also show location, climate type, latitude/longitude coordinates, and average temperature and range

What is the ITCZ?

The Intertropical Convergence Zone, the tradewinds from tropics of both hemispheres converge on the equatorial region. Air rises here. Equatorial low - notice the band of cloud cover in this region associated with low pressure.

What is the STHP?

Subtropical High Pressure Zone, air sinks - calm winds, sunny, dry, rainless especially along west coasts

What are Koppens Climate Classifications?

A, B, C, D, E, H


Tropical Climates, low latitude climates, basically seasonless, for the most part lie between the Tropics of Cancer and Capricorn, warm year round with high insolation, sun's rays at noon are never far from overhead, dominated by the ITCZ, trade winds, and STHP


Dry Climates, dominated by Subtropical high pressure (STHP), usually found between 20-35 degrees N & S latitude, irregular and unreliable rainfall, highest percentage of sunshine of any climate, little to no precipitation most of the year, world's greatest deserts - lie primarily on the west coasts of continents, Sahara, Atacama, Sonoran, Steppe


Cf, Cw, Cs, a, b, c


wet all year


dry winter


dry summer


hot summer


warm/long summer


short summer

Climate Controls of Mediterranean Csa Csb

STHP in summer, in winter, STHP shifts southward and westerlies blow through bringing cyclonic storms

Climate Characteristics of Mediterranean Csa Csb

Hot, Dry summers, Mild, wet winters

Geographic Distribution of Mediterranean Csa Csb

30-40 N/S latitude, Confined to the western coastlines - California, Chile, Mediterranean Sea borderlands, SW Australia

Climate Controls of Humid Subtropical Hot - Summer Cfa

Weak western side of STHP, Brings in mT into Texas in summer

Climate Characteristics of Humid Subtropical Hot - Summer Cfa

Humid summers - warm moderated by the coast, becomes hotter inland, mild winters with occasional fronts, precipitation all year, long growing season, ex. Florida - citrus fruit

Geographic Distribution of Humid Subtropical Hot - Summer Cfa

East Coasts, 20-40 N/S latitude

Climate Controls of Marine West Coast Cfb, Cfc

In Westerlies wind belt all year

Climate Characteristics of Marine West Coast Cfb, Cfc

Wet all year, mild winters & summers, frequent cyclonic storms, no frozen winter

Geographic Distribution of Marine West Coast Cfb, Cfc

West coasts, Europe, Spain, Great Britain, Oregon and Washington Coast


Microthermal Humid (Severe winter) D

Microthermal Humid (Severe winter) D

Mean temperature of coolest month is below 26.6F (-3C)

Controls of Humid Continental Hot-Summer, Dfa, Dwa

Cyclonic storms along polar front, prevailing westerlies, continentality

Climate Characteristics of Humid Continental Hot-Summer, Dfa, Dwa

Hot summers, cold winters, large annual temperature range, year round precipitation

Geographic Distribution of Humid Continental Hot-Summer Dfa, Dwa

Middle - 35-45 degrees, Eastern and Midwestern states in U.S., Poleward of C climates, east central europe, approximate 140-200 day growing season

Controls of Humid Continental Mild - Summer Climates Dfb, Dwb

Cyclonic storms along polar front, prevailing westerlies, Continentality

Climate Characteristics of Humid Continental Mild-Summer Cliamtes Dfb, Dwb

Brutally cold winters, not so hot summers - more moderate, long winters with frequent clear and cold weather, large annual temperature range, less total precipitation that areas south

Geographic Distribution of Humid Continental Mild-Summer Climates Dfb, Dwb

Locations in the mid-latitudes (45-55 degrees), Canada, Siberia, New England, Great Lakes region, growing season = 90-130 days

Controls of Subarctic Climates, Cool Summers Dfc, Dwc, Dwd, Very Cold Winters, Dfd, Dwd

Extreme continentality, high latitudes 50-70 degrees, westerlies in the summer, occasional cyclonic storms, strong polar anticyclone in winter

Climate Characteristics of Subarctic Climates, Cool Summers Dfc, Dwc, Dwd, Very Cold Winters Dfd, Dwd

Brief cool summers with bitter cold winters, largest annual temperature ranges, low precipitation annually, growing season approximately 50-80 days, Permafrost

Geographic Distribution of Subarctic Climates, Cool Summers Dfc, Dwc, Dwd, Very Cold Winters, Dfd, Dwd

Northern North America (Newfoundland to Alaska), Northern Eurasia (Scandinavia through Siberia), Boreal forest or Taiga vegetation (Dfc, Dfd climates)


Tundra Climates (ET) and Ice Cap and Ice Sheet Climates (EF)

Controls of ET

location in high latitudes, polar high pressure system (polar anticyclone), proximity to coasts

Climate Characteristics of ET

Average temperature of warmest month is below 50 degree F but greater than 32 degree F, low precipitation (below 10 inches) low evaporation, summerless - 9+ months below freezing

Geographic Distribution of ET

Arctic Ocean Borderlands, Greenland, Eurasia, the landscape is a mixture of grasses, flowering herbs, mosses, lichens, and low growing shrubs

Controls of EF

Polar Marine Climate, latitude, continental interior, year round influence of polar high pressure

Climate Characteristics of EF

Summerless, all months below freezing - average temperature of warmest month is 32F or below, world's coldest temperatures

Geographic Distribution of EF

Antarctica, Interior Greenland, Ice Cover


Highland (mountainous regions)


A transition between desert and wetter climate

What are the four primary ways clouds form?

Convectional precipitation, orographic precipitation, frontal precipitation, and convergence

Convectional Precipitation

Uplift due to intense surface heating

Orographic Precipitation

Uplift due to physical barrier (mountain)

Frontal Precipitation

Uplift due to meeting of air masses (fronts)


Air flow from all directions into a low pressure

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