Chapter 5

Global Temperature (Continued)

Lecture 122 February, 2005

Land versus ocean differences

Clouds and Temperature Changes

Clouds reduce surface insolation

Clouds trap net radiation in

lower troposphere

Little seasonal change in

ocean surface temp

warmest ocean waters occur in

the western tropical Pacific

notice the changes in sea

ice in the northern and

southern hemispheres

focus on differences between the northern and southern hemispheres

why should northern Siberia

have the greatest seasonality?

why should the seasonality in N.

America be smaller than in Asia at similar

latitudes?

Difference between January & July

Seasonal Temperature Range in Siberiathe seasonality in northern

Siberia is extreme for several reasons:

continentalitysolar angles

clear, dry air with little cloud cover (think of albedo & greenhouse

cloud effects)Verkhoyansk, Russia has a 105 °C min-max range!

Marine and Continental Climates

WitchitaKS

San FranciscoCA

Marine and Continental Climates

VerkhoyanskRussia

TrondheimNorway

Gulf Stream & Temperature inWestern Europe

think of the Gulf Stream as a gigantic river of warm water in the Atlantic (moving about

6.4 kph/4 mph)the amount of water flow in this ‘river’ is

~100 sverdrups (100 million cubic meters per second)

Not exactly the whole story…

the Gulf Stream was named and partly discovered by Benjamin Franklin

The Gulf

Stream

The Gulf Stream and Temperatures in Western Europe

the Gulf Stream largely explains why Iceland is mostly green, even though it sits just below the

Arctic Circlevariations in the Gulf Stream have had huge implications for human societies, such as

allowing the Vikings to reach eastern Canada and the little Ice Age

water-to-land heat transfers are accomplished via latent heat transfers and

direct sensible heating of air overlying warm water

Movie: ‘The Day After Tomorrow’

California current & temperatures

in coastal Californiawater can directly warm or

cool nearby land masses - compare California’s cool

coastal Mediterranean climate with the warm coastal climate of Italy

Air temperature patterns

isotherm - a line connecting points of equal temperature - analogous to a line on a topo map connecting points of equal elevation

some definitions

thermal equator - a line connecting all points of highest average temperature

notice the thermal

equator over land

notice the influence of

large mountain

ranges

see how isotherms

shift poleward

over continental interiors?

where would the hottest places be?

why?

•Show energy budget animation

Air Temperature and the Human Body

•Wind chillCorrelates cold and wind speed

•Heat indexCorrelates heat and humidity

Wind Chill Table

Heat Index Table

Figure 2

Chapter 6Atmospheric and Oceanic Circulation

Concepts in this chapterair pressure

winds (global, regional, and local)global circulation systems

four driving forces in the atmosphereprimary high and low pressure areas in the atmosphere

upper air circulationocean currents & circulation

“We live submerged at the bottom of an ocean of the element air.”

-Evangelista Torricelli

Air Pressure

Air pressurerecall that air pressure is force per unit

area

Ideal Gas LawP V = n R T

where R is a constantPressure*Volume = Moles*constant*Temperature

With Moles of air constant, Pressure increases

• as Volume decreases (Temperature constant)• as Temperature increases (constant Volume)

Ideal Gas LawPV = nRT

I. pressure increases if # molecules increases (constant volume)

II. pressure increases if volume decreases (constant temperature)

III. pressure increases if temperature increases (constant volume)

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I. II.

Pressure*Volume = Moles*constant*Temperature

III.

a quick and dirty estimate of air pressure at the surface

1. define pressure: force per unit area

2. force = mass*acceleration due to gravity

(F = m g)3. mass of the atmosphere = 5x1018

kggravitational acceleration = 9.81 m s-2

4. surface area of Earth = 4R2

= 4(6,400km)2 = 5x1014 square meters5. plug it all in ….

Pressure = F / A = m g /A= 5x1018 kg * 9.81 m s-2 / 5x1014 m2

~ 100,000 kg /(m s2) Newtons per m2 (Pascal)

~ 1000 millebar (mb)

sea level pressure = 1013 mb = 101.3 kPa = 14.5 lbs/sq. in = 29.92” mercury = 760 mm mercury = 1

atmosphere

the weight of air literally pushes mercury up the

column

what would the column’s height be on

top of Mt. Everest?

elevation is ~8 km~ 75% of air is below

-> 0.25 * 29.92 in ~ 7.5 in

Barometer

Pressure in the Atmosphere and Ocean

to calculate atmospheric pressure (in mb) by height (Z):

P(Z) = 1014*[1-0.0226*Z]^5.26

to calculate water pressure (in mb) by depth (D, in m):

P(D) = 100*D

Total Pressure by Depth

0

2

4

6

8

10

12

14

1013

1023

13

2036

13

3049

13

4062

13

5075

13

6088

13

7101

13

8114

13

9127

131E

+061E

+061E

+06

Pressure (mb)

Dep

th (

km)

even though gravity is pulling on both air and water, air is compressible (water

is not)

Scuba Diving & Pressurerule of thumb in scuba diving:

Each 10 m (33 ft) increase in depth increases the pressure on every square

inch of your body by 1 atmosphere

Dive to 30 m, you have 4 atmospheres of pressure pushing on you (3 ocean + 1

atmos)