The model you select determines which FORTRAN program is executed. Note that not all function buttons and field parameters are used in each model. To run a model: 1) Select the model to run with the Model function button, 2) Make sure the function buttons and field settings are correct, 3) Click on the Execute/Plot button on the button left of the widget interface.
Band 4 and Band 4 minus Band 5 brightness temperature pairs are simulated for different particle radii and optical depth. The AVHRR data are fitted to this model by plotting the theoretical curves and the AVHRR Band 4 and Band 4 minus Band 5 brightness temperature. The Radius-Optical Depth Model is used to determine the value of the Cloud-Base temperature. The Cloud-Base temperature value should be adjusted until the data from the eruption fit into the theoretical curves. Note that the AVHRR data may not fit into the theoretical curves if the correct cloud aerosol type is not choosen.
The Range of Radius Model plots effective radius and normalized negative temperature domain areas. A discussion of the normalized area parameter is given in Wen and Rose (1194) on pages 5423-5424. It indicates the retrieval will work properly for particles with an effective radius over a range in which is monotonically decreasing. This Range of Radius Model can be run serveral times to find a size range that will allow the retrievals to work.
The Radius-Optical Depth Model should be used in conjuction with the Range of Radius Model to determine the minimum and maxiumum radius which can be uniquely retrieved. The minimum and maximum radius depends on composition and size distribution of the aerosols.
This model is used to calculate particle radius, optical depth, and then retrieve the total mass retrieval. The Radius-Optical Depth and Range of Radius Models must be run first to determine the correct cloud-base temperature, minimum radii and maximum radii.
A uniform distribution assumes that all particles are the same size. The uniform distribution gives a lower bound on the volcanic cloud's mass estimate.
A gamma distribution can be used to describe the size distribution of water/ice clouds.
A volcanic cloud is considered to have a lognormal size distribution. Of the three particle distribution types considered, the lognormal size distribution gives the largest estimate of the volcanic cloud's aerosol mass.
The assumed type of aerosol in the volcanic cloud. The type of aerosol is determined from data of the ash fall out or in-situ aircaraft samples or by choosing the material type that produces the best fits to the theoretical curves in the Radius-Optical Depth Model. The type of material determines the refiractive index and the particle density to used in the radiative transfer calculations.
Display the plots on the Screen.
Creates a Postscript file in portrait mode. The file is saved with the filename "idl.ps" in the current directory. The utility function "Print PS" can be used to print the file.
Creates a Postscript file in Landscape mode. The file is saved with the filename "idl.ps" in the current directory. The utility function "Print PS" can be used to print the file.
Creates a Encapsulated Postscript file. The file is saved with the filename "idl.eps" in the current directory. This file can be imported into word processing programs like FrameMaker.
The type of symbol to use in the Radius-Optical Depth Plot.
This parameter is used only in the mass calulation. If Frame Scale Type is selected, the average particle radius for the whole frame is used as the effective radius for the mass calulation. If Pixel Scale Type is selected, the effective radius is different for each pixel in the frame. Note that for a lognormal distribution, only a Frame Scale Type can be selected. This is not much of a problem because usually only a small range of radii can be uniquely retrieved for a lognormal distribution.
If this button is set, labels are placed on the output plots
If this button is set, the input data file is assumed to contained latitude and longitude values.