Source: WeatherSTEM
A Skew-T diagram is a chart used to plot the upper air observations taken by the radiosonde. This thermodynamic diagram helps meteorologists get a better understanding of the structure of the atmosphere. There are six different sets of lines on the Skew-T diagram for plotting data. Temperature lines are drawn at a 45-degree angle on the diagram, and this is how it gets its name. Values of temperature increase from the upper-left-hand corner of the diagram to the lower-right-hand corner. Pressure lines are drawn horizontally on the diagram. The distances between the lines represent the changes in atmospheric density with respect to height. The wind staff is located on the right-hand side of the diagram. It is used to display the windspeeds and directions at different pressure levels in the atmosphere. The dark lines on the Skew-T diagram are used to plot the mixing ratio, sometimes called the mass ratio. This ratio is the mass of the water vapor in the air compared to the mass of the dry air that is present in the atmosphere. The brown curved lines on the chart are called the dry adiabats. These lines represent the rate an unsaturated air parcel cools as it rises. Known as the dry adiabatic clouds rate, unsaturated air will cool at a rate of 5.5 degrees Farenheit per 1,000 feet until the relative humidity becomes 100 percent. The green lines on the chart are known as the moist adiabats and represent the rate at which saturated air cools as it rises. Because water vapor releases heat as it cools and condenses, the rate at which moist air cools is different than if it were dry.