In order to assure that all users can access the HYSPLIT web system we are limiting the number of HYSPLIT model runs to 100 per UTC day per IP address effective June 4, 2007.

Many additional features were recently added to the registered users web version of HYSPLIT trajectories.

• GFS Forecast Data - an option has been added to the forecast trajectories to enable trajectories that run off the chosen meteorology grid (in time or space) to continue running with the current Global Forecast System (GFS) meteorological data if the date range is available. The current GFS forecast dataset contains 48 hours of analysis and 84 hours of forecast data. CAUTION: the initialization times of the chosen meteorological dataset and the GFS may be different depending on the time of day.
• 3 Source Locations - Users now can enter up to 3 different trajectory source locations instead of just one. All trajectories will be calculated for all specified levels (1, 2 or 3) for a total of up to 9 trajectories per run.
• Trajectory Matrix Option - A trajectory matrix option will produce a grid of trajectories bounded by the first 2 entered source locations (trajectory 1 is the lower left grid point and trajectory 2 is the upper right grid point) and evenly spaced with a grid increment given by the distance between the lower left grid point (trajectory 2) and trajectory 3. Only one height is allowed.
• Trajectory Ensemble Option - A trajectory ensemble option will produce multiple trajectories from the first user-selected starting location. Each member of the trajectory ensemble is calculated by offsetting the meteorological data by a fixed grid factor (one grid meteorological grid point in the horizontal and 0.01 sigma units in the vertical). This results in 27 members for all-possible offsets in X,Y, and Z. Note: the starting height should be greater than 250 m for optimal configuration of the ensemble.
• Source Location Symbol - An option has been added to allow users to turn on or off the source location symbol on the trajectory map. This is useful for the trajectory matrix display.
• Rerun the model using user-defined defaults - A much needed option has been implemented to allow users to rerun a trajectory calculation by modifying the user entered defaults of that particular run to produce a new calculation with its own Job ID number.

A generic Postscript color fill program was created to show values on a global concentration grid. The program also works with regional grids. The standard concentration plotting program had difficulty with global grids. The concentration probability programs were revised to output values consistent with a typical frequency box plot. A box plot routine was added to the ensemble display menu. A testing script was created to check out the executables created from a UNIX compilation. The temporal emissions file program was modified to permit multiple species to reside on the same particle when the mass dimension namelist variable was set to a value equal to the number of pollutant species. The minimum particle emission rate was set to one per processor, when the model is run in a multi-processor environment. The puff split-merge algorithm was improved to avoid the situation during very long-duration simulations when the number of puffs reaches the array limits cause further splitting to shutdown while puff growth continues. In this revised version, the onset of splitting is delayed and the merging parameters are relaxed to permit more distant puffs to merge. Due to the removal of all GRIB-1 formatted meteorological data from NOAA-NCEP servers, the GUI programs to download and convert GRIB-1 data to HYSPLIT format have been removed. The GRIB-1 conversions for local data files is unchanged. Users will be required to convert their data from GRIB-2 to GRIB-1 prior to using the GUI conversion programs. Future versions of the code may directly incorporate GRIB-2. However, to compensate for the loss of direct GRIB-1 downloads, additional options were added to the HYSPLIT formatted meteorological data download menus.

The trajectory and concentration plotting routines were modified in terms of map centering, colors, and clipping lines outside of the map domain. Units were changed in the source-attribution code to be consistent in converting measurement concentrations to release rates. The routine to compute the model's internal vertical grid structure was corrected to handle very high resolution input data. The emission start-stop tests were corrected to handle releases shorter than the model's integration time step. The termination message was expanded to determine if a starting point fell outside of the meteorological data in terms of space or time. Additional puff split-merge factors were moved from the compiled constants to the namelist input file. A multi-trajectory geo-location option based upon measurment data was added to the GUI menu. Cluster number labels were added to the trajectory plotting program. A new procedure, callable from the GUI, was added to update various executables and scripts from the web server, as they become available and before a new complete download is posted.

Primarily the mixed layer depth is now computed by the temperature difference from minimum temperature rather than from the surface temperature. This accounts for small super-adiabatic layers that may be present near the surface when using high resolution meteorological data. Also the default turbulence option for short range applications has been modified to use the wind and temperature profiles rather than heat and momentum fluxes due to the variability in the way fluxes are computed from different meteorological inputs. The height initialization method was modified when starting trajectories relative to mean sea level to account for large terrain gradients. Two new source-attribution options were added to the GUI to determine emission location and emission rates from measured sampling data by using backward (upwind) integrations and a coefficient matrix solution method.

Numerous GUI changes including updated namelist menus integrated with new help files, resolved name conflicts with postscript conversion menus, and now more than six starting locations can be specified in the GUI. Substantial updates to the graphical programs, especially for concentration, resolved problems with particle cross-sections, and added the minutes field. The point-source emissions file for complex scenarios can now be used for backward as well as forward integrations. Other changes include a new option to plot trajectory frequencies and increased the number of files that can be processed by the probability display programs. The main trajectory and dispersion executables now create namelist files that can be directly imported into the GUI. Computational changes include sorting meteorological files by forecast time to use the most recent forecast first and corrected the sign on the derivative for backward integrations using the non-data vertical motion options.

Most of the changes since the last release are cosmetic relating the various post-processing mapping features such as correcting problems over the prime meridian and the dateline, new options to control the latitude-longitude lines, an option for a cylindrical-equidistant projection, adding the minutes field to the map labels. Numerous changes were made to the graphical user interface, including adding trajectory clustering examples, directory selection option in several addional menus, options to define the FTP data servers, adding a progress widget during FTP data downloads, and streamlined namelist configuration menus. More substantial changes were made to the way the model computes mixing when the TKE field is available, adding an option to define the anisotropy ratio for both day and night, and an option to output the maximum concentration or the maximum average concentration.

Version 4.8 supports staggered meteorological data grids in WRF as well as use of the time averaged fields from the AER version of WRF. Data conversion routines are available (UNIX only) for NetCDF output from LAPS and WRF. Internally, a problem was corrected that caused problems with multiple meteorological grids when the calculation switched from a regional to global grid. Now when the mixed layer depth is provided as input, it is used for calculations rather than the height determined internally from the temperature profile. The temporal emissions input file was modified to handle more complex release scenarios, including the heat released by the emission to compute a dynamic plume rise option based upon the bouyancy terms of the Briggs equations. Options to convert GIS output to a format compatible with Google Earth were added to the concentration and trajectory plotting programs. In addition to the standard meteorological offset ensemble, a new ensemble option was added to compute concentration probabilities based upon variations in the turbulence and varying the random seed. Trajectory clustering programs have been added to the distribution and are part of the GUI. Additional options were added to many of the GUI menus. The trajectory and concentration examples were reduced to 12 hour duration simulations to illustrate shorter-range applications. The concentration model defaults were modified such that if a a run run durations is <= 12 hours and the concentration grid is <= 5 km, then the model configuration is automatically modified to an isotropic and 1000 3D- particle simulation.

Further details can be found at: http://www.arl.noaa.gov/ready/hysp_info.html