The temperature and dew-point traces can be modified via the cursor. Press the left button on the first data-point to be modified and drag it horizontally along an isobar to the desired position, then move the pointer diagonally along an isotherm to keep the data-point at the desired position and to pick-up the next data-point. Repeat until done and then release the mouse button.

The check box labeled Parcel mode selects the origin of the path of a parcel of air lifted pseudo-adiabatically from the initial point to the top of the diagram. Check Parcel path to display the path of a lifted parcel.

The initial conditions of the pseudo-adiabatically lifted air-parcel (i.e. the parcel's pressure, temperature, and moisture content at the start of the pseudo-adiabatic lifting) are determined from the environmental sounding (i.e. the temperature and dew-point profiles) according to the mode indicated by Parcel mode. The modal choices are Bottom of Sounding, Below Cursor, At Cursor Pressure, and At Cursor (Press, Temp).

In Bottom of Sounding mode, the initial conditions of the parcel are determined from the temperature and dew-point at the lowest (i.e. highest pressure) data-point of the environmental profiles.

In Below Cursor mode, the initial conditions of the parcel are determined from the temperature and dew-point profiles by computing the pressure-weighted mean potential temperature and water-vapor mixing-ratio of the atmosphere that lies below the cursor when the middle mouse button is pressed. Thus, pressing the middle button at 950 hPa for a sounding that starts at 1000 hPa will effectively mix the lower 50 hPa of the atmosphere and lift the resulting parcel starting at 975 hPa.

In At Cursor Pressure mode, the initial pressure, in-situ temperature, and moisture content of the parcel are taken from the the temperature and dew-point profiles at the pressure of the cursor when the middle mouse button is pressed.

In At Cursor (Press, Temp) mode, the initial pressure and in-situ temperature of the parcel equal the pressure and temperature values under the cursor when the middle mouse button is pressed. The initial moisture content is determined from the dew-point profile at the initial pressure.

The computed path of a lifted parcel is automatically updated when appropriate. In Below Cursor, At Cursor Pressure, and At Cursor (press, temp) modes, the path will update as the cursor is dragged. In all modes, the path will update whenever the profiles change.

The check box labeled Virtual Temperature controls whether or not the virtual temperatures of the environmental profile and pseudo-adiabatically lifted air-parcel are displayed.

The check box labeled Spatial Loci controls whether or not the location of the sounding data is displayed in the main, 3-D window. For aircraft data, the track of the aircraft will be displayed; for RAOB data, the locations of the stations will be displayed; and for gridded data, the grid points will be displayed.

The table to the left of the sounding diagram contains aerological parameters determined from the atmospheric sounding displayed in the diagram. The following abbreviations are used:

LCL

Lifting Condensation Level: the level at which a pseudo-adiabatically lifted air-parcel becomes saturated with water-vapor.

LFC

Level of Free Convection: the level at which the virtual temperature of a pseudo-adiabatically lifted air-parcel changes from being less than the environment's virtual temperature to being greater than the environment's.

LNB

Level of Neutral Buoyancy: the level above the LFC at which the virtual temperature of a pseudo-adiabatically lifted air-parcel equals the environment's virtual temperature.

CAPE

Convective Available Potential Energy: the area between the virtual temperature trace of the pseudo-adiabatically lifted air-parcel and the virtual temperature trace of the environment from the LFC to the LNB in which the parcel's virtual temperature is greater than the environment's (positive CAPE connotes convective development).

CIN

Convective Inhibition: the negative of the area between the virtual temperature trace of the pseudo-adiabatically lifted air-parcel and the virtual temperature trace of the environment from the parcel's initial conditions to the LFC in which the parcel's virtual temperature is less than the environment's (negative CIN connotes initial positive work to lift the parcel).

Unidata IDV Workshop for version 6.3 > Accessing and Displaying Data > Upper Air Displays