WEATHER PATTERNS, JET STREAM, AND OCEAN CURRENTS

WEATHER PATTERNS

Weather pattern’s are described as prolonged temperature changes over a specific area for example seasons.

Weather patterns can also be described as a period for which natural disasters are prevalent ex. Hurricane season, tornado season, blizzards

Weather patterns ARE affected by climate and the conditions of the atmosphere at the time

WEATHER VS. CLIMATE The average weather conditions for an area over a long period of time are

referred to as climate. Climates are chiefly described by using the average temperature and

precipitation of an area. Latitude is one of the most important factors that determines a regions

climate. Different latitudes on Earth’s surface receive different amounts of solar energy. Solar energy determines the temperature and wind patterns of an area, which influence the average annual temperature and precipitation.

Climate is different from weather in that weather is the condition of the atmosphere at a particular time. Weather conditions, such as temperature, humidity, wind, and precipitation, vary from day to day.

Weather Climate

AIR MASSES PG 603 A mass of air that remains over a region of a few days acquires the characteristics

of the area over which it occurs. A large body of air throughout which temperature and moisture are similar is

called an air mass. Air masses that form over frozen polar regions are very cold and dry , air masses that form over tropical oceans are warm and moist. There are 6 different types of air masses Continental air mass: form over large landmasses dry air Maritime air mass: form over oceans moist air Tropical air mass: form over the deserts of the southwestern U.S. Warm air Polar Air Masses: form over ice and snow covered land. Cold air

Is an air mass considered part of climate or weather?

FRONTS Weather patterns are also described

as fronts. There are three specific types of front that affect us: cold front, warm front, occluded front

Where air masses of different temperatures meet, a boundary between them called a front is created.

Along a front, the air doesn’t mix, this happens because hot air rises and cold air sinks.

Cold Fronts – When a cold, dense air mass advances and pushes under a warm air mass, the warm air is forced to rise.

WARM FRONT If air is advancing into a region of colder air,

the warmer front is formed. The warm less dense air slides up ad over

the colder, denser air mass.

STATIONARY AND OCCLUDED FRONTS A stationary front, is a front

where a warm air mass and a cold air mass meet but neither advances.

An Occluded front is when a fast moving cold front overtakes a slower warm front.

CAN YOU LABEL THIS MAP?

OCEAN CURRENTS The water in the ocean moves in giant streams (like

rivers) called currents. Because there are continents in between the large

bodies of water, the currents move in different directions depending on which continent they are in between

Currents that move on or near the surface of the ocean and are driven by winds are called surface currents. Surface currents are controlled by three factors: air currents, Earth’s rotation, and the location of the continents.

Because wind is moving air, wind has kinetic energy. The wind passes this energy to the ocean as the air moves across the ocean surface causing the water to move.

MAJOR SURFACE CURRENTS Equatorial Currents: located in the Atlantic, Pacific, and Indian

Ocean. Currents in the southern hemisphere: in this hemisphere the currents

move in a counter clockwise direction. In the most southern region of the ocean, the westward wind produces the Antartic Circumpolar Current, no continents interrupt this current.

Gulf Stream : in the north Atlantic ocean, warm water moves thru the Caribbean Sea and gulf of Mexico and north along the east coast of North America in a swift, warm current.

DEEP CURRENTS Deep currents are cold, dense, slow moving

currents that flow far below the surface. They form as cold water sinks to flow below warm water.

GLOBAL WIND BELTS PG 633 Because Earth received different amounts of solar energy at different latitudes, belts

of cool, dense air form at latitudes near the poles, while belts of warm, less dense air form near the equator.

Differences in air pressure create wind Global wind belts, such as the trade winds and westerlies, are a major factor

affecting the flow of ocean surface water. The trade winds are located just north and south of the equator. In the northern

Hemisphere they blow from the northeast, in the southern hemisphere they blow from the southeast. In both hemispheres, trade wind belts push currents westward across the tropical latitudes of all three major oceans.

The westerlies are located in the middle latitudes. They push ocean currents eastward in the higher latitudes of the northern and southern hemispheres. In the equatorial

belt of low pressure, called the doldrums, the air rises and cools, and water vapor condenses. The region has large amounts of precipitation. The amount of precipitation generally decreases as latitude increases.

The subtropical highs are between 20-30 degrees. Air sinks, warms, and dries. There is little precipitation (deserts)

Winds are caused by the uneven heating of the atmosphere. Variations in air temperature lead to variations in air density and pressure.

Air always moves from an area of high pressure to an area of low pressure, therefore there is a general, worldwide movement of surface air from the poles toward the equator.

At high altitudes, the warmed air flows from the equator toward the poles

These differences in temperatures and air pressures create three wind belts in the southern hemisphere.

The Coriolis effect also influences wind patterns. The Coriolis effect occurs when winds are redirected by Earth’s rotation. This process affects storms like hurricanes

CORIOLIS EFFECT As we learned earlier, the coriolis effect occurs

when winds are redirected by Earth’s rotation.BUT WHAT DOES THAT MEAN????

Neither wind belts nor ocean currents flow in straight lines. They all follow a curved or circular pattern caused by Earth’s rotation. As Earth spins on its axis, ocean currents and wind belts curve.

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JET STREAMS Jet streams – Narrow bands of high-speed winds

that blow in the upper troposphere and lower stratosphere. These winds exist in the Northern Hemisphere and Southern Hemisphere.

One type of jet stream is the polar jet stream. These bands of winds, can reach speeds of up to 500km/h and can affect airline routes and the paths of storms.

Another type of jet stream is a subtropical jet stream. In subtropical regions, very warm equatorial air meets the cooler air of the middle latitudes and this jet stream forms. Unlike the polar jet streams the subtropical jet streams do not change much in speed or position.

LOCAL WINDS Winds also exist on a scale that is much smaller

than a global scale. Movements of air are influenced by local conditions and local temperature variations.

There are two types of local winds/breezes: Land and sea breezes: during the day, the land’s

temperature increases where as the sea’s temperature stays the same. As the hot air over the land rises the cooler air over the ocean sinks creating a sea breeze. At night when the opposite happens (land cools faster than water) the sea breeze is replaced by a land breeze.

Mountain and valley breezes: during the day, a valley breeze forms when warm air from the valleys moves upslope. At night, mountains cool more quickly than the valleys do creating a mountain breeze.