LPT Main Options Tab

Owned by Kester Scandrett
Last updated: 12 Aug, 2016
2 min read

Figure 1 shows the LPT Main Options tab. Within the LPT Computational Method and Timing frame the user must switch on drifters with the Compute Drifters check box before LPT can be implemented. Here the user will set the global computational period starting and ending days for the particle tracking in Julian days for all of the groups. The frequency (in minutes) of writing the particle positions to the EE_Drifters file is specified here.  This frequency of output is for all groups and is independent of the normal EE output frequency.



Figure 1  LPT Options: Main Options.


The Vertical Movement Option frame provides the user the option of fixing the temporal position of the particles at their initial seeding depths. If this is unchecked the particles will drift vertically as Fully 3D Lagrangian Neutrally Buoyant Particles.  A sub-option is Adjust Particle Depth.  This is the default option and adjusts particle depth with change in water depth. In some cases the user may wish to disallow this so that particles are not adjusted by change in water depth, and so can turn off this adjustment by unchecking this box. If the Adjust Particle Depth is selected, the amount of adjustment in the vertical direction depends on the ratio of particle depth and water depth. The formula of the vertical adjustment is:

dzp=  pdep/wdep*dH

In which dzp is the adjustment of vertical particle depth, pdep is particle depth, wdep is water depth and dH the discrepancy of water depth of the current and previous timestep.

Within the Initial Particle Vertical Position Input Option the user may  specify whether the vertical positions provided are elevations or depths.

If the Random Walk checkbox is checked the user has a number of options for the Random Walk Dimensional Options. The user may select the random walk in only the vertical direction, in only the horizontal direction, or in both vertical and horizontal directions at the same time. In addition the user may specify the Random Walk Size Options by selecting to allow EFDC Diffusion calculations to be used for the AH and AV. Alternatively there is the option for Specified Constant Diffusivities that should be inputted by the user.