10.9. Surface Maps Contour Parameters#
We previously introduced hand analysis when we looked at the difference between an isobaric (pressure) surface and a constant height surface. In this lab you will complete a hand analysis of a surface map. The surface map can be more difficult because we cannot use the same atmospheric relationships, such as geostrophic or gradient wind balance, to aid in the drawing contours at the surface. This is the result of need to account for the friction that is present at and near the surface. However, it is through the analysis of one-year worth of surface data that the Bergen School was able to develop the early theories and life cycles of mid-latitude cyclones.
Surface Analysis
Contouring is accomplished in just the same way as it would be for upper-level maps, separating warmer air from colder air or higher pressure from lower pressure. At the surface there are three main parameters that re analyzed by contouring: mean sea-level pressure (MSLP), temperature, and dewpoint temperature. The details of the contours are summarized below and are also part of the initial handout regarding map analysis.
Surface#
Parameter |
Contour Interval |
Color |
Style |
|---|---|---|---|
Mean Sea Level Pressure (MSLP) |
4 mb centered on 1000 mb (e.g., 984, 988, 992, 996, 1000, 1004, 1008) |
Black |
Solid |
Temperature |
Every 10°F on the 10’s or 5°C on the 10’s and 5’s |
Red |
Dashed |
Dew Point |
Every 10°F on the 10’s or 5°C on the 10’s and 5’s |
Green |
Dashed |
Shading on surface maps:
Precipitation is shaded in light green pencil, fog in yellow. When shading avoid a polka dot look when shading areas of precipitation. Thunderstorm symbols should be circled in red pen. Occasionally, the clear regions are delineated by scalloped blue lines.
There are additional features that are important to mark while analyzing a surface map. Generally, you want to indicate areas of precipitation, shading areas in light green. You may wish to differentiate different precipitation types with different colors. For example, you might shade snow in light blue, rain in light green, and mixed precipitation types in pink. The shading is done to help the analyzer better understand the current weather situation present on the map.