ATM OCN (Meteorology) 100 - Lecture 3

Answers for Homework 5

Fall 1997

The total maximum points were 60.

ATMOSPHERIC MOTIONS

1. Identify the following characteristics associated with each of the force components in the atmospheric equation of motion:

[30 pts at 2 pts each]

A. VERTICAL PRESSURE GRADIENT FORCE

DIRECTION: Vertical and upward (from high pressure near the surface toward low pressure aloft, or opposite of down). MAGNITUDE depends upon: Altitude (also it depends upon the vertical spacing of the pressure surfaces, which depend upon the average temperature of the layer).

B. HORIZONTAL PRESSURE GRADIENT FORCE

DIRECTION: Horizontal and upward pointed from high pressure toward low pressure (as seen on a weather chart). MAGNITUDE depends upon: Packing of the isobars on a horizontal, constant altitude weather chart.

C. GRAVITATIONAL FORCE or "GRAVITY"

DIRECTION: Vertical and downward (toward the center of the earth). MAGNITUDE depends upon: The masses of the earth and the object and upon the separation between their centers (or equivalently, upon altitude).

D. CORIOLIS EFFECT or "FORCE" (Horizontal Component)

DIRECTION: To the right of the direction of the intended motion in the Northern Hemisphere and to the left in the Southern Hemisphere. MAGNITUDE depends upon: a. .Speed of the object b. .Latitude [Two (2) separate variables] NOTE: It also depends upon the rotation rate of the earth

E. FRICTIONAL FORCE (Horizontal Component)

DIRECTION: To opposite of the motion. MAGNITUDE depends upon: a. .Wind speed b. .Type of surface, or altitude above the surface. [Two (2) separate variables]

F. CENTRIPETAL FORCE

DIRECTION: Inward toward the center of rotation. MAGNITUDE depends upon a. .Speed b. .Radius of curvature [Two (2) separate variables]

2. What is the primary physical significance of the hydrostatic balance relationship?

[4 pts]

3. From this hydrostatic balance relationship, how does the magnitude of the vertical pressure gradient in a warm air column compare with the vertical pressure gradient in a column of cold air?

[4 pts]

4. a) What forces are balanced in the geostrophic wind model?

[4 pts.]

b) Name three separate assumptions used to describe the geostrophic wind model.

[6 pts or 2 pts. each]

5. On the horizontal surface pressure map in the Northern Hemisphere (within the friction layer), locate the regions of high and low pressure, placing a large block H and L, respectively. Make a force diagram by neatly drawing thin arrows to signify the direction and relative magnitudes of the horizontal pressure gradient force (FHPG), the Coriolis force (FCOR), the friction force (FFRC). Label each of these forces. Neatly draw a thick, double bladed arrow to represent the resultant wind (VRES); label this wind vector:

[12 pts]

Last revision 12 November 1997