This lab is an introduction to locating important features on the 500mb chart.
The assignment is to locate and draw various features on the provided 500mb map.
The map is linked HERE.
As is the custom, the height contours are draw using 60 meter intervals. As is also the custom, the contours are labeled in DecaMeters (1Dm = 10Meters). In other words, the last zero is dropped from the labeling. These height contours are from the numerical model analysis for this time and date.
The upper air observations (from radiosondes) are also plotted on the map. These are plotted in a way that is somewhat similar to the surface station models. The winds are plotted the same way as for surface observations. On this map, the winds are in knots. The number in the upper left is temperature in Celsius. In the lower left is the dewpoint in Celsius. In the upper right is the geopotential height in DecaMeters (multiply by 10 to get meters). See page 213 in Vasquez (the textbook) for additional info.
1) The ridges and troughs. See Vasquez, page 57. The ridges are usually drawn in blue (zig-zag), and the troughs in red. As was discussed in the lecture last Thursday, look at the points of greatest curvature of the height contours for locating the troughs and ridges. Also look at the wind field, and try to locate the troughs and ridges where the winds are changing direction most rapidly -- cyclonic for troughs, anti-cyclonic for ridges. (Note: In Vasquez, there is a discussion on using the vorticity to locate ridges and troughs. We have not fully covered vorticity as yet in the class.)
2) Identify the two major areas of diffluence on this map, and circle them (or shade them). See Vasquez Page 59. Please do not locate other regions of diffluence or confluence (hint: The two areas of diffluence are near NW US and the S. Central US).
3) Shade the region where the wind speed is 70 knots or greater. This can be done by shading the stations with winds of 70 or greater, then shading in-between those stations as appropriate. Another approach is to draw the 70 Knot Isoline (called an Isotach), and then shade the region it encloses.
4) There are three stations on this map whose height values differ by more than 20 meters (2 Dm) from the height contours. For these three stations, the location of the contour lines violates the rules you were taught in Lab 1. Locate these stations. Identify these stations by circling the height value at those station locations (in red).
See Vasquez, pages 216 to 221, for additional information on contouring.
