DEPARTMENT OF GEOSCIENCES NAME_________________________ SAN FRANCISCO STATE UNIVERSITY Meteorology 201

Synoptic Metr Homework 3

Due Tuesday 29 April 2009

Part I. You are provided the 500 mb analysis (without data plots) for 12 UTC 9 February 2005.  Note the station in southeastern Oklahoma (indicated by the square).  The line segment shown is a portion of the "n" axis (normal to the flow) at that location, with the segment length shown there (delta n) = 300 km.

1.  The geostrophic wind speed can be calculated from the expression

where g is gravity, 9.8 m s-2 , f is the Coriolis parameter, numerically equal to approximately 10 X 10-5 s-1 at around the latitude of the station shown, delta z is the difference in 500 mb heights normal to the flow measured along the increment delta n (remember, to estimate a gradient, take the value at location 2, furthest along the positive directon of the given axis, and subtract from it the value at location 1.)

Estimate the value of the geostrophic wind in meters per second, kilometers per hour and knots at the location shown and plot the value with conventional weather map symbols for wind directon and wind speed (knots) on the map.

Caution, Caution:  the challenge here will be to keep units consistent initially.  Please remember that when you solve for the geostrophic wind speed using the above expression, your result will initially be in meters per second.  You will need to convert that to kilometers per hour and knots. Remember that a nautical mile is 6040 feet.

2.  With a long arrow/streamline drawn right on the chart, locate the position of the fastest current (the polar jet stream).

Fig. 1: 500 mb chart for 1200 UTC 9 February 2005

Part II. You are provided with the time-averaged topography of the ocean (cm) relative to mean sealevel for the period 1992–2002   Note the two locations at 40N in the eastern and western Pacific. The line segment shown is a portion of the "n" axis (normal to the flow) at that location, with the segment length shown there ∆n = 300 km.

1.  The speed of the geostrophic current can be calculated from the expression

where g is gravity, 9.8 m s-2 , f is the Coriolis parameter, numerically equal to approximately 10 X 10-5 s-1 at 40N, ∆ z is the difference in sea-surface height topography normal to the flow measured along the increment ∆n (remember, to estimate a gradient, take the value at location 2, furthest along the positive directon of the given axis, and subtract from it the value at location 1.)

Estimate the value of the geostrophic current meters per second, kilometers per hour and knots at the locations shown.

Caution, Caution:  the challenge here will be to keep units consistent initially.  Please remember that when you solve for the geostrophic wind speed using the above expression, your result will initially be in meters per second.  You will need to convert that to kilometers per hour and knots. Remember that a nautical mile is 6040 feet.

2.  With a long arrow/streamline drawn right on Fig. 2a, locate the position of the fastest current north of the Tropic of Cancer.

Fig 2a: Time-averaged topography of the ocean (cm) relative to mean sealevel for the period 1992–2002

Fig 2b: North Pacific Zoom of Fig. 2a