To find the answer to a question, click on the symbol.
HYSPLIT in General
meteorological archive data sets can I use to model Europe with
archived data are available on the web to run HYSPLIT with?
data is used to calculate the trajectories and what is the the
vertical resolution of the data?
have a question about section five "meteorological input data" in
the HYSPLIT_4 USER's GUIDE. In page 49, what are the meanings
of "pole latitude & longitude", "reference latitude & longitude", "synch
latitude & longitude", "synch point X and Y" and the relation
(or difference) between "reference grid size" and "number X & Y
points"? Or would you tell me what are their values if I have
gridded meteorological data within lat. 5 N to 60 N and long.
110 E to 140 E., one degree resolution and I want to plot the
back-trajectory within the same area?
am trying to better understand what the best approach is for
calculating the HYSPLIT trajectories I need. I have mostly looked
at using the EDAS data, but it has a lot of holes in it for the
period I am interested in, so we wind up with trajectories truncated
or not calculatable. I tried to fill in the holes with the FNL
data. However, in one case when I calculated 120-hour backward
trajectories from Potsdam, NY at 1800 on April 8, 1999 using
both the EDAS and FNL data bases, I found that the EDAS data
suggested the air was in the upper midwest 5 days prior, but
the FNL put it into northern Quebec. Why the difference?
can I find gridded meteorological data to simulate the Chernobyl
have FNL meteorological files, which I use to compute trajectories
with HYSPLIT. I need to extract the numerical value of some fields
(geopotential at 700 hPa at each i,j grid point). I ran your
program example which extracts the first field (precipitation),
but I do not know how modify the program to extract geopotential
at 700 hPa.
would like to extract surface winds from the archived EDAS data
into ESRI Shape "shp" format, MapInfo "mif" format, or something
similar. Is this possible?
archived data can I use prior to the start of the FNL dataset?
I use surface observations in HYSPLIT?
do you parse GRIB files? NCAR/NCEP reanalysis data has all fields
for a certain variable for an entire year in one large GRIB file.
I'd like to extract (keeping the data in GRIB format) just one
or several of the grid numbers from different files into one
file containing all data for a given date/time. This is a requirement
to run the ARL HYSPLIT converter to get the data in a format
compatible with HYSPLIT. Does any one have a GRIB extractor or
editor that allows one to parse grib files?
want to extract the u and v fields from the FNL archive according
to the pressure level in some locations. Is this possible?
HYSPLIT read other forms of meteorological data?
will be converting ECMWF grib files into ARL-packed format for
use in calculating backward trajectories in Europe using your
HYSPLIT model. What fields do I need to have for HYSPLIT to properly
calculate my trajectories?
do I convert my ECMWF GRIB data files into ARL format using ecm2arl
on the PC?
you explain the equation (Zagl = ak2 + bk + c) used by HYSPLIT?
What is the different between Ztop, Zgl, Zmsl and Zagl?
trajectory run today looks different than the same trajectory I ran
yesterday using the GDAS current7days archive. How often is the GDAS
archive current7days file updated?
use WRF data with HYSPLIT?
are used for computing the mixing depth from the NCAR/NCEP reanalysis data?
What is the
smallest horizontal resolution allowed by the code, e.g., 10x10 meters, or 1x1 km?
Model Setup & Parameters
HYSPLIT be setup to run a short-range dispersion calculation?
If so, how?
value should I input as the start height (MAGL)? What does "above
model ground level" mean?
computed a vertical sounding at position (40.24, -3.40) with
the FNL archived data. In the text results, the PRSS and the
MSLP are 923.3 and 1021 mb, respectively. Assuming a hydrostatic
atmosphere the model terrain height at this point can be estimated
as 977 MASL. But in the text an Estimated Surface Height of 634
MASL is also reported, which is very close to the actual terrain
height of 667 MASL. What should I consider as the model terrain
height ASL at this point, 977 or 634 MASL?
have a question regarding what start height to make the trajectories
and the correction factor for MAGL...
If I choose AGL for the start height, does that
mean that for the entire model run the computed heights are
relative to the ground? I'm concerned about this because of the
terrain in the mountains. I don't want values to be
I get backward trajectories starting at a rural East Coast site
in NJ, which starting height(s) do you suggest is (are) appropriate?
The terrain of the site is flat and near sea level. I am also
wondering how long of a trajectory duration is recommended.
am attempting to calculate back trajectories for event based
precipitation samples to trace sources of atmospheric pollutants
(mercury, nitrogen, pesiticides). I am uncertain as to what height
or pressure I should use in the model.
If I know the in-situ measured SO2 concentration
(pptv), corresponding location, altitude (4 km), and time of
measurment, is it possible to calculate a back trajectory of that
SO2 plume to know about the spreading over that source region?
interested in the backward trajectories at the costal site Baia
Terra Nova, Antarctica, for aerosol studying. As in most of the
Antarctic Plateau there are mountains, and I wonder if this is
the reason why the meteorological model used by HYSPLIT "sees" the
Antarctic continent so high (even though it is a coastal site)?
Can I obtain backward trajectories at a lower height than the
model terrain height (say at sea level), and if not, can I be
confident in those trajectories starting from a much higher level
than the level of the site under study?
would be the most accurate way to determine back trajectories
(BT) for airmass sources at a particular field site. The sampling
time at the field site was ~24 hours. Should I run a 24 hr BT
for every hour during sampling? Would I then combine all of these
BT's to get an accurate BT for the airmass collected over the
24 hr sampling period? Also what height would you suggest to
end the BT at, 10 m or 950 h Pa? (April 2004)
terrain included in the HYSPLIT model and how accurate are surface
trajectories computed for complex terrain?
there anyway to change the simulation specification so that the
concentration measurements are standardized across both:
One location at different points in time and
Different locations at the same point in time?
Is the model designed only to model slow
releases of chemicals or could it also be used in the case of
Would HYSPLIT work to model an atmospheric release of a biological toxin?
Can I run 1 trajectory every 6 hours every day for an extended period of time?
Is there a batch job that can be submitted to the server to obtain 10-d back-trajectories
for the time period specified?
Is there a way to run multiple trajectories with a single command in hysplit?
Is the time used to calculate trajectories UTC or local time?
Interpretation of Trajectory Results
calculating backward isentropic trajectories on the PC and looking
at the plot, particularly the vertical motion plot at the bottom,
I see motion across theta surfaces. My question is, shouldn't
I see vertical motion on a constant theta (potential temperature)
calculating backward isobaric trajectories I see that the pressure
is not constant and looking the vertical motion plot at the bottom
of the plot, I see vertical motion (about 500m difference from
the starting point to some other points ). Why is this?
am trying to do trajectory analysis for an event in which we
have observed meteorological data. Is it possible to download
HYSPLIT to the PC and feed it observed data from meteorological
I ran a foward trajectory from a location on a previously computed
backward trajectory, I did not return to the starting location
of my backward trajectory. Why?
you tell us how the precipitation rates are determined which
accompany the air parcel trajectories in the tdump file?
it possible to overlay several trajectories onto one map?
trajectories can I draw in the same plot when I enter different names in trajectory Display
GUI using a + symbol and what is the minimum number of tdump files which I need to create a cluster?
do I estimate the absolute (in km) and relative (%) errors when
using the HYSPLIT trajectory model? Where does the error mostly
come from (e.g., truncation error, interpolation error or wind
are the levels of uncertainty associated with back trajectory
calculations in HYSPLIT?
are the levels of uncertainty associated with back trajectory
calculations of ambient and potential temperature in the Hysplit
model meteorological outputs? I am trying to use the model, to
do 5-day backward trajectories of two air parcels (200m and 1000m)
starting at my study location. I would like to use the temperature
outputs to understand processes within my study region and would
like to know its accuracy. (April 2004)
does HYSPLIT consider the vertical coordinate. If a trajectory
meets the surface how does HYSPLIT work? Does it reflect, or
use another method to solve it?
calculated three isentropic back trajectories simultaineously
for the same latitude and longitude, but for three different
altitudes. Then we calculated one back trajectory by itself.
To my surprise the results are different. Why are the back trajectories
different if you calculate them jointly or separately?
the effect of the boundary layer considered when the model computes
I have been running trajectories every hour for
24 hours to get a general idea of the airmass origin a single
point during this period. Is there a way to obtain an average
visual trajectory for a 24 hour period?
Why are there small differences in my trajectories when I run more than one at a time
versus running just one trajectory?
Interpretation of Concentration Results
it possible to interpolate between two lines of equal concentration
or between a maximum and a line?
is concentration defined in HYSPLIT and how does it relate to
the radiation units of Bacquerel?
there any way to obtain the concentration and deposition information
in a data file instead of a graphic?
running HYSPLIT concentrations I got 10E-11 ... 10E-17 for values
of concentration. I understood that the unit is mass/m3.hr. My
question is that in order to apply the numbers to total emission
from a power plant stack, how can I calculate real plume concentration?
Suppose it is 167381 ton/yr and converted 19 ton/hr, then, can
I just multiply 19 ton/hr by 10E-11... to get real level?
I found a case where there are deposition
contours where there are no corresponding air
concentration contours. Why?
do I calculate and visualize backward and forward trajectories
for our air pollution monitoring station on the READY website?
research is to use wind trajectories to find pollutant sources
in Chicago. How do I translate longitude and latitude into the
exact location, say Sears Tower or United Center?
is the longest period over which trajectories can be calculated
on the web?
it possible to extract the the trajectory-data into an ascii-file?
I am trying to do a backward trajectory for
parcels involved in historical weather events, and I know that
even minor changes in the point or time can yield much different
results for the parcel origin. Is there a way to do an "ensemble"
run, slightly perturbing the starting point?
model always gives a deposition plot. Can this influence the
concentration plot? I mean: If you have a gas with no deposition
at all, is the the concentration plot then still valid?
HYSPLIT output 3 dimensional concentrations?
come when I use the back button on the browser, my settings to
the HYSPLIT Model Setup form are returned to the default settings?
Which datum do you use for the output from your models?
NGVD 29? NAD27? NAD83? WGS84? Clarke Spheroid?
And what does datum mean, anyway?
RAM and HD requirements are needed for running the trajectory
and dispersion models on the PC?
it necessary for the CONTROL file to be named "CONTROL"?
do you specify more than one meteorological
file in the 'set Meteo_file' line of the Auto_traj.tcl script so
the loop can run through many months of data?
I produce the particle display on the PC version?
Why do I get this message when trying to run PC Hysplit: "C:\hysplit4\guicode\hysplit4.tcl is not a valid Win32 application"?
do I run a BACKWARD trajectory using the PC version of HYSPLIT?
I ran a backward trajectory from a location on a previously computed
forward trajectory, I did not return to the starting location
of my forward trajectory. Why?
there a way to run the model in "batch mode" that would generate
am running a statistical program that groups hundreds of trajectories
over one another and creates probability fields. My problem is
that generating one trajectory at a time and converting the ASCII
trajectory endpoint data into Excel format is far too time consuming.
Is there a way to run a number of trajectories at once?
FAQ question under HYSPLIT in General explains how to adjust
the start height to account for differences between model terrain
and actual terrain. I'm assuming that it's most accurate to
use actual elevation plus my desired trajectory height as a
starting height, and specify the option KMSL=1 in the setup.cfg
file on the PC. Is this correct? Occasionally these trajectories
are wildly different f rom those with KMSL=0 and the start
height specified as meters above ground level.
it possible to represent in the same map both forward and backward
trajectories in order to make a comparision of the integration
the web version of HYSPLIT, we can get temperature, potential
temperature, precipitation, etc., along the trajectory. Can we
do the same with the PC version?
purchased NCEP reanalysis GRIB data for summer 2001, downloaded
the PC HYSPLIT model, and figured out how to convert the GRIB
format to the HYSPLIT format using the compiled fortran program: ncr2arl.
However, I am unsure about what latitude and longitude to input.
I read that lat and lon are at the center of a 100x100 grid that
is extracted from the GRIB file. So if my study area is around
the North Eastern Pacific/West Coast of the US, should I just
input my center lat and lon from my study area? I am trying to
do backward air parcel trajectories of the marine atmospheric
air located off Oregon. I am worried that if the grid extracted
is only 100x100 from my center lat/lon that long duration backward
trajectories might cover a larger area than the grid extracted.
How should I deal with this? Finally, when using display.exe (or
HYSPLIT GUI interface) to display contour maps, should I again
enter the center lat/lon of my study area (in other words is
the diplay.exe plotting the extracted 100x100 grid?) and what
is meant by the radius (degLat)? What value of radius should
I put in and how does different values change my contour map?
I set up a matrix run and have the heights specified at a certain
altitude (using MSL), why do the results show the starting points
at different heights instead of at a constant one? (April 2004)
let me know is it possible to classify the trajectories by cluster analysis
and draw a mean trajectory of each cluster using the PC version of Hysplit.
model prints on a large scale (all of Europe), while the concentration
area itself is sometimes rather small. Is it perhaps possible
to reduce the scale of the map?
have several months of the EDAS data files on my PC and wish
to run several months at one time. Is there a way to run the
model in "batch mode" that would generate deposition and concentration for
downloaded the latest version of HYSPLIT for the PC. How do I
run the dispersion simulation backwards? I tried a negative number
of hours run time, as for backward trajectories, but I got the
same result as with positive number of hours.
am trying to run HYSPLIT (PC version) for Mercury (emit in gas
phase). For chemical depositon set up, the model asks f or Surface
Reactivity Ratio, Diffusivity Ratio, and Effective Henry's Constant.
At this time I could not find any of the se properties for (Hg+2
or HgO). I wonder is there anyone who did this pollutant simulation
before. Any suggestion about where to obtain this information
would be appreciated.
am looking to run concentrations for about 300 plants in HYSPLIT
for use in an econometric analysis. I am running the concentration
model for each plant and producing a GIS map for each model output.
My problem is that generating one concentration and one GIS map
at a time is very time-consuming and I am wondering if there
is a way to do all 300+ of the concentrations at the same time?
I want the model (time, pollutant characteristics, etc.) to be
all the same for each model run, the only difference is the emission
source and the height.
do I calculate deposition?
am using the PC version of the model on a Windows NT computer
and am having trouble running it. I downloaded some archived
files from the ftp site, and when I ask the model to use them
I get the following error:
HYSPLIT4 (Dec 98) - Initialization
Unable to find file: JUN98.BIN
On local directory : C:/HYSPLIT4/METDATA
Check input CONTROL file for correct values
Stop - Program terminated.
I edited the control file by taking out the relative reference
pathfile and put in the specific fully qualified directory path
C:/hysplit4/metdata/ Do you have any suggestions on how to correct
purchased FNL meteorological files from NCDC for 1998, and they
sent me a tape with the files. When I run the HYSPLIT model however,
I get the following message:
have been quite successful running the trajectories off the website,
but have not been able to get the downloaded software to work
correctly. It seems to put out the default example graph every
time, even after other meteorological data has been entered.
Since I have been using HYSPLIT on the web, it doesn't really
matter. But I was wondering if the website accesses the hard
drive, or if the software is actually not necessary and the website
can be used instead? Are there things I can do using the software
that are not available on the web? If so, what?
can't I run a back trajectory from 1900 UTC on 31 July, 2001
using downloaded FNL data? I attached my CONTROL file for you.
using trajplot.exe to plot multiple HYSPLIT output files, we
are having trouble getting trajplot to recognize output files
unless they are named tdump, tdump1, tdump2, ..., tdumpn. Is
it necessary for the file name to contain "tdump"?
am trying to calculate trajectories using my own MM5 output files.
I compiled the mm5toarl routine and created the arl formatted
files compatible with HYSPLIT, but it still doesn't work. I used
the chk_file program and there is an error with the header.
Should I change something in the mm5toarl routine?
I am attempting to run the HYSPLIT model daily
for a 10 year period. I received the error message:
Is there a restriction of the length the model can run for? If so
how do I get around this or do I have to restrict it to a single
I have been trying to use the convert program to
trim the white space around the edge of the hysplit plots using
the ImageMagik 'convert -trim' command. This seems to have no
effect on the image. The '-crop IxJ' option has limited success.
Is this an underlying issue with the .ps files that trajplot and
received the following error. What could be wrong?
> Model started ...
> HYSPLIT48 (March 2007) - Initialization
> Calculation Started ... please be patient
> *ERROR* metpos: start point not within (x,y,t) any data file
> xp,yp : 7.800000 12.60000
> time (min) : 53864640
Why are the results different for the same run on the web versus the PC?
When I "Run Standard Model" after saving the "Trajectory Setup", I get a static message
> Model started ...
> HYSPLIT48 (February 2008) - Initialization
Volcanic Ash Model (currently HYSPLIT, formerly VAFTAD)
As an airline pilot I always check the volcanic
ash dispersion forecasts for Colima and Popoctptl whenever I fly
Toronto-Mexico City, however I'm a little uncertain as to just how
much gravity I should treat them with. If I was flying, say, from
Miami to Mexico City at 18000ft can you tell me just what I might
encounter if VAFTAD has a big red "blotch" along my route? Should
I be planning to avoid it altogether or is the ash likely to be
too dissipated to cause a problem?
The HYSPLIT distribution models will often
show significant areal coverage. Is there a threshold particle
density that defines the plume boundaries and if so, is it one
that corresponds to a known aircraft danger/non-danger threshold ?
I am doing a project on air pollution due to
Volcanic activity. I am missing one major part of the project: a
model for the plume so that I can calculate the contaminant
dispersion. I was wondering if one of you were familiar with such
models and if I could get any information about them.
Is it true that the VAAC's do not issue
volcanic ash dispersion model forecasts (sometimes called VAFTADs
using the name of an earlier model), but use them as guidance,
like the PUFF and AVHRR? If I wanted to see your forecast, then
would need to look up your bulletin and the attached VAAC chart
along with the SIGMETS bulletin, or do you send the VAFTAD out as
I saw a program on TV that stated volcanic gas
and/or ash is necessary for earth's healthy atmosphere, and that
volcanic erruptions cause a protective layer between us and the
sun. Is this in fact true?