Table of Contents

IDV Vertical Profiles and Skew-T Plots in HTML


Vertical Profiles

Here is a plot of temperature in the atmosphere by height.


The temperature profile location is shown in the IDV main display by a vertical line of the same color as the plot line. You can better see the profile location line by rotating the main display in 3D by dragging the mouse with the right button down over the main display.

Move the profile line around by dragging the colored square at the top of the line with the left mouse button. The plot here will change.

To zoom into the plot in this page, drag the right button and mouse cursor upwards, with Shift held down. To pan, drag the right mouse button.

Skew-T Plots

This HTML code automatically connects the IDV to an online data source on a remote server, reads the data, and makes this Skew-T plot.

In the Skew-T display, move the mouse pointer over the
plot and watch the changing values in the table.

This Skew-T is made from temperature and relative humidity output from the July 18, 2002, 12 Z RUC run at NCEP.

The Skew-T location is shown in the IDV main display by a vertical line of the same color as the plot line. The data for this display covers the U.S. (RUC model). You can better see the location line by rotating the main display in 3D by dragging the mouse with the right button down over the main display.

You can move the Skew-T position line over the map by dragging the colored square point on top of the line with the left button. A label at the top of the Skew-T window shows the latitude-longitude position. This data set is not the same one as in the vertical profile on the top of this page, it only covers the US so you can move the line off the data area.

You can zoom the Skew-T diagram by holding down the Shift key and dragging the mouse pointer up while pressing mouse button 3 (usually the right button); drag down to zoom out. You can pan the diagram by dragging the mouse pointer in any direction while pressing mouse button three.

The temperature and dew-point traces can be modified via the pointer. Because the coordinate system of a Skew-T diagram is skewed, however, a sawtooth-like pattern must be used. Press mouse button 1 (usually 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 button 1.

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 pseudoadiabatic lifting) are determined from the environmental sounding (i.e. the temperature and dew-point profiles) according to the mode indicated by Parcel mode check. 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 mouse button 2 (usually the middle button) is pressed. Thus, pressing button 2 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 mouse button 2 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 mouse button 2 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 both 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 Skew-T 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 inital 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).

The aerological table also shows values from any position on the diagram, in the section "Background." Move the mouse cursor over the table to the position desired.