natural environments the atmosphere ge 101 spring 2007 boston university l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University PowerPoint Presentation
Download Presentation
Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University

Loading in 2 Seconds...

play fullscreen
1 / 15

Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University - PowerPoint PPT Presentation


  • 50 Views
  • Uploaded on

Myneni Lecture 03: Rotating Sphere Jan-22-07 (1 of 15). Further Reading: Chapter 03 of text book. Outline. - Introduction. - Latitudes and Longitudes. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University. - Map Projections. - Time.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University' - wattan


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
natural environments the atmosphere ge 101 spring 2007 boston university

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(1 of 15)

Further Reading: Chapter 03 of text book

Outline

- Introduction

- Latitudes and Longitudes

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

- Map Projections

- Time

slide2

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(2 of 15)

Earth as Rotating Sphere

  • Let us begin to lay the foundation for the first part of the course, which is -
  • Energy balance of the earth system
  • that is, What energy comes in, how it changes form, what goes out
  • The energy source for the earth is the sun. Therefore, we need to look at the earth-sun
  • “astronomical relationship”
  • We begin by looking at the earth as a Rotating, Orbiting Sphere
  • From this we will be able to answer many questions about the basic climate of the earth
  • - Why are there seasons?
  • - Why is there such a temperature difference between the equator and poles?
  • - What effect does this temperature difference have on the circulation of the
  • atmosphere and oceans
slide3

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(3 of 15)

Shape of the Earth

  • We begin by looking at the earth as a Rotating, Orbiting Sphere

N

  • Approximately spherical
  • Actually an “oblate ellipsoid”
  • Slightly compressed from north to south
  • Slightly bulging from east to west
  • - But, we treat it as a sphere

12756 km

12714 km

S

The Blue Marble

slide4

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(4 of 15)

Great and Small Circles

  • Because earth is effectively a sphere, the geometry,
  • (meaning, how we define where we are on the sphere)
  • is more difficult than if the earth was flat.
  • We introduce two concepts for drawing lines on the surface -

Great Circles

Small Circles

slide5

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(5 of 15)

Parallels and Meridians

  • From these concepts we can draw systematic set of coordinates on the earth’s surface called
  • “Meridians and Parallels”
  • Parallels
  • Parallel to one another
  • - Intersect meridians at 90-degree angles
  • Meridians
    • - Not parallel to one another
    • - Intersect at the poles
slide6

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(6 of 15)

Geographical Coordinate System: Latitude

  • From these sets of lines, we can define a “geographic coordinate system” based on the relation
  • of our position on the globe to the fixed meridians and parallels

Fixed Meridian

Parallel

Equator

Latitude

Latitude

Position measured in degrees of arc (along a fixed meridian) from the Equator

slide7

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(7 of 15)

Geographical Coordinate System: Longitude

Meridian

Fixed Parallel

Prime Meridian

Longitude

Longitude

Position measured in degrees of arc (along a fixed parallel) from a fixed meridian Called the “Prime Meridian” - passes through Greenwhich, England and is defined as 0-degrees longitude

slide8

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(8 of 15)

Geographical Coordinate System: Example

  • Location of point P is:
  • 50 degrees North, 60 degrees West
  • So P would be located….?
slide9

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(9 of 15)

Maps and Projections

  • To make life easier, cartographers usually represent three-dimensional objects in two
  • dimensions using cartographic projection systems, that is, maps
  • But, such transformations introduce various
  • types of distortions.
  • Typically, selection of a projection requires
  • trade-off between direction preserving vs.
  • area preserving maps.

Equal Angle, Un-equal Areas

slide10

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(10 of 15)

Common Projections: Goodes

Preserves area but not shape

slide11

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(11 of 15)

Earth’s Rotation

  • Rotation of the earth produces “time”
  • We count time with respect to the position of the sun either over a:
    • - Fixed point, which is “solar time” - will discuss later
    • - Imaginary point, which is “standard time” - will discuss later
  • Remember, the Earth spins in a counter-clockwise direction when looking down on the
  • North pole (one revolution or 360 degrees defines 1 day)
slide12

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(12 of 15)

Solar Time

Solar Time: time relative to position of sun over a fixed point

Midpoint of the day (i.e. when the sun is highest overhead) called “solar noon”

Midpoint of night (i.e. when the earth has rotated 180-degrees from solar noon)

Sunrise and sunset = time when earth rotates into and out of illumination

Sunrise

Sun

Solar noon

Solarnight

Sunset

slide13

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(13 of 15)

Problem with Solar Time

  • Define time at a point on Earth’s surface relative to passage of Sun
  • Angular rate of rotation = 360 degrees/ 24 hours
  • Therefore, 15 degrees/hour

11:00 am

15 West

Solar noon

1:00 pm

  • Problem: Does not provide fixed/universal time system!!
    • Local time varies continuously with longitude
slide14

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(14 of 15)

Standard Time

  • Therefore, we create something called ‘Standard Time”
  • Define “time zones” - swaths of approximately 15-degree longitude where we
  • define time to be the same everywhere
  • - “Standard time” - time as defined by a given time zone
  • - “Standard meridian” - imaginary longitude whose solar time is defined to
  • be the standard time for an entire time zone
slide15

Natural Environments: The Atmosphere

GE 101 – Spring 2007

Boston University

Myneni

Lecture 03: Rotating Sphere

Jan-22-07

(15 of 15)

U.S. Time Zones

  • US Time Zones
    • Eastern time ~ 75W
    • Central time ~ 90W
    • Mountain time ~105W
    • Pacific time ~ 120W
  • Note – within any time zone
    • Local solar time > standard
    • time E of standard meridian,
    • and vice versa

“Daylight savings time” is a political

construct which relates to an arbitrary

selection of the time for a given time

zone. Hawaii and Arizona follow

Standard Time all year long.