Unit 2

World Climate Patterns… An Introduction

Distinguish between the terms weather &

climate. P. 54Weather = the state of the atmosphere at any one place or time. (short term)

Climate = the average weather conditions of a region over the LONG term. (Season, Month Annually)

Both refer to temperature, rain fall, humidity etc.

Practice:

Do the following phrases refer to weather or climate?

1. Annual precipitation of 200 mm.2. Rain forecasted for tomorrow.3. Normal July temperature averages

22 oC.4. Temperatures this week will range

between 20 & 30 oC.5. Vancouver has an annual frost free

period of 233 days.6. The greatest annual precipitation

11, 680 mm falls on Mt. Waialeaie in Hawaii.

7. Residents in Florida are preparing to take shelter from a hurricane.

ClimateWeatherClimate

Weather

Climate

Climate

Weather

In describing today’s weather:

9 features are often used!!

1. Temperature

2. Amount of precipitation

3. Type of precipitation

4. Atmospheric pressure

5. Wind direction

6. Wind speed

7. Cloud cover

8. Hours of sunshine

9. Humidity

Explain why only about ½ of the sunlight

directed at earth actually reaches the earth.

6% is scattered in the atmosphere

24 % is reflected by clouds

4 % is reflected by the earth’s surface.

17 % is absorbed by Green House gases & dust

49% of sun’s radiation actually reaches the earth’s surface

While the 4 % that reflects from the earth’s surface is small it does vary with location & with time.

How/Why do you think it varies?

Winter vs. Summer?

Poles Vs. equator?

Land vs. ocean?

HINT: Precipitation (Snow & water), reflection vs absorption, dust, cloud cover, angle of sun,

Lack of cloud cover Day AND Night…

the effect…

DAY : No clouds = higher day temperatures

NO clouds to deflect / block heat from reaching the surface.

NIGHT: NO cloud cover = cold nightlytemperatures. (heat escapes, nothing to TRAP it.)

Ex. Day 24o C, Night 15o C

Clear Day AND clouds over BEFORE night…the

effect…

DAY : No clouds = higher day temperatures

NO clouds to deflect / block heat from reaching the surface.

cloud cover PRIOR to night = = warmer and muggy nights.

heat being TRAPPED during the night…like a blanket AND precipitation in the clouds.

Ex. Day 24o C, Night 21o C

Cloudy Day AND NO clouds at Night…

the effect…

DAY : Cloud cover = lower daily temperatures

Clouds deflect/block out sun & heat.

NIGHT : NO cloud cover = even COLDER nightly temperatures.

Already cooler temperatures become even lower.

Ex. Day 15o C, Night 9o C

Cloudy Day AND cloudy Night…the effect…

Day: Cloud cover = lower daily temperatures

Clouds deflects/blocks out heat

Night: Cloud cover = relatively constant temperatures in the night.

Clouds traps current air temperatures and keeps them relatively constant.

Ex. Day 15o C, Night 12o C

Explain how cloud cover influences the range

of temperature from day to night.

Clear day / Clear Night = largest temp range (24–15=9)

Clear day, cloudy night = small/low temp range (24-21=3)

Cloudy day, clear night = moderate range (15-9=6)

Cloudy day / cloudy night = small temp range(15-12=3)