Contouring and Analysis Meteorology 311 Fall 2010Contouring and Analysis • Aids in organizing and displaying an enormous quantity of data in a meaningful manner. • Isopleth: Line of constant value of any parameter.Isopleths • List on page 33 of course notes. • Isobar – pressure • Isallobar – pressure tendency • Height contour – height • Isotherm – temperature • Isallotherm – temperature tendency • Isohume – humidityTypes of Analysis • Subjective: hand analysis (manual) • Objective: computerized (automated), making use of interpolation schemes. • Contours should fit the data, yet be smooth enough so that features that are smaller scale than the spacing between observations do not appear.Method • Pre-analysis orientation: General inspection – Previous weather maps • Isopleth analysis – Lightly at first being sure to fit the data, maintain some smoothness, establish continuity with previous maps. • Data representativeness – Interpret the results, decide which features are significant on the analyzed map. • Frontal Analysis • Weather AnalysisRules of Isopleths • The interval between isopleths doesn’t normally change. – Dash or color isopleths that don’t match the interval • Isopleths are continuous and should never fork or cross. • Isopleths of the same value should never cross. • Field is usually smoothed to be consistent with the spacing of the data analyzed. • By agreement, saddle points, ridge lines, and trough lines are not used (see course notes).Rules of Isopleths cont. • Isopleths often do not close off, but run off the edge of the map. • Do not contour data sparse areas. – Use dashed contours in these areas if data is present, but sparse. – If data is not present, do not contour. • Always sketch isopleths lightly with a soft, easily erased pencil line. – Darken once final positions are