UNIT 2

WORLD CLIMATE PATTERNS

Weather – the day-to-day or short-term conditions of the atmosphere.

Describe 9 features of the weather today.1. Temperature2. Amount of precipitation3. Type of precipitation4. Atmospheric pressure5. Wind direction 6. Wind speed7. Cloud cover8. Hours of sunshine9. Humidity

Climate - the average weather conditions of a region over a long period of time.

Identify each statement as either a weather or climate reference.

1. Heavy snowfall and whiteouts have reduced visibility to 30%.2. The highest air temperature on record was reached on

September 13, 1922 in Libya: 58 0 C.3. Vancouver has an annual frost-free period of 233 days.4. We expect rain in the early afternoon and continuing on through

the evening.5. The greatest average annual precipitation – 11,684 mm – falls on

Mount Waialeaie, Hawaii.6. High winds of over 50 km/h are fanning the forest fires north of

Marseille.7. Residents in the gulf region are preparing to take shelter from the

hurricane.

ROTATION AND REVOLUTION

Rotation – the earth spinning on its axis once every 24 hours. This causes day and night.

Day – Exposed to the sun

Night – Away from the sun

In the morning it appears that the sun rises in the east. In actual fact you are rotating towards the sun from the west.

Revolution – the earth travels around (orbits) the sun once in a year.

The earth is tilted on its axis at 23.5 0 This and the revolution of the earth around the sun, cause the seasons.

When the northern hemisphere is tilted towards the sun it has summer.

About 3 months later the north is not tilted towards or away from the sun and it is fall.

In 3 months the northern hemisphere is tilted away from the sun and it is winter.

Again in 3 months the earth is not tilted towards or away from the sun and it is spring.

This is all opposite for the southern hemisphere, so it has opposite seasons than the northern hemisphere.

Date North SouthJuneSept.

Dec.

March

Equinox & Solstice

SOLSTICE

1. From Latin for sun stand still

2. Sun is directly over head @ 12 noon on 23.5o North or South.

3. Occurs Dec 21 (Winter) which is the shortest day of the year (North)

4. & June 21 (Summer) which is the longest day of the year (North)

EQUINOX

1. From Latin for equal day & night.

2. Sun is directly over head @ 12 noon on the equator.

3. In the North, occurs Sept. 21 (Autumnal/Fall) & March 21(Vernal/Spring)

4. Equal length of night & day everywhere on earth.

Differences in Day Length

The tilt of the earth’s axis combined withthe earth’s rotation in orbit around thesun results in different day lengths.

• Northern Hemisphere – June

• Because of the tilt on the earth's axis, the north pole points towards the sun.

• It now receives more hours of exposure to the sun giving it longer days.

• The southern hemisphere rotates out of the sun for long periods.

• Sunrise at 5:30 AM Light until 9:30 PM

• Northern Hemisphere- December

• Because of the tilt on the earth's axis, the north pole points away from the sun.

• It now receives fewer hours of exposure to the sun giving it shorter days.

• The northern hemisphere rotates out of the sun for long periods.

• Sunrise at 8:00 AM Dark at 5:30 PM.

Temperature difference in summer and winter.

There are two reasons for the difference in temperature:

1. More direct sunlight gives greater intensity of heat - longer summer.

2. Longer summer daylight hours means there are more heating hours and fewer cooling hours.

NORTH

NORTHSOUTH

SOUTH

SEASONS??? DATE???

LENGTH of DAY??? EQUINOX/SOLSTICE?

Where are these seasons experienced?

Northern Hemisphere or Southern Hemisphere?

How do you know?

Southern

Cloud Cover Affects Temperatures From Day to Night.

Cloud cover reduces the range of temperature from day to night.

Clouds reflect heat waves back into the atmosphere during the day.

During the night the clouds reflect heat back to earth.

Cooler day and warmer night = lower temperature range.

Lack of Clouds in a Desert Affects Temperatures From Day to Night.

No cloud cover increases the range of temperature from day to night.

No clouds allow more heat waves to reach the earth during the day.

During the night the lack of clouds allow heat to escape.

Warmer day and colder night = higher temperature range.