MTEOR 411/511 WEEK 11 SUPPORTING MATERIAL

Week 11 - Isentropic Analysis

Despite losing World War II, Germany actually won a meteorological war, and some atmospheric scientists today regret that! Prior to the war, weather data were often plotted on isentropic surfaces, or maps of constant potential temperature. After the war, the U.S. generally adopted the German way of plotting maps on constant pressure surfaces. Although there are some advantages and disadvantages to both approaches, there are some interesting features seen when using isentropic maps. On an isentropic map (such as a 290 K surface), flow will generally stay in the map (as opposed to rising up above it or sinking down below it) as long as conditions are adiabatic. Thus, unlike a 500 mb map, you can look at an isentropic map and know exactly where upward and downward motion are occurring. Isentropic vertical cross-sections are often used to point out fronts at all levels in the atmosphere, the tropopause, regions of instability, and can be used to diagnose areas of ascent or descent (if the flow is following the cross-section).