NOAA ARL

• Currently I am a chemistry major at a major university. In the future, I would like to work in the air pollution field. What area of study is better for a future career in air pollution and which area did people working in NOAA study in college?
• What is the Air Resources Laboratory and what do you do?

READY Web Server

Accounts & Linking

• How come I can no longer automate the way I get READY meteorological products and why do I now need to enter a random password for every product I request?
• I am having trouble getting meteograms and other products. A message pops up that says I don't have permission to get the information. Can you tell me if I now need to get an account?
• I'd very much like to set up some shortcuts to the Current Meteorology products in a similar way that some others have done for Europe and Australia, for the regions and locations that I most frequently access. If you'll allow this, do you have any documentation available on the CGI parameters, etc?

Meteograms

• Do you have a description of the meteogram or profile program for soaring pilots? (March 2004)

Stability Plots

• With regard to the stability time series plots from the EDAS data, exactly what am I looking at? Are these model output fields (forecasts), or am I looking at the results from assimilated data?
• What does it mean by vertical mixing in the stability plots? Does this represent thermal height? If so, how's that different than the boundary layer? Also, is instability simply a measurement of lapse rate? One of the reasons for asking is that I noticed that for one of the WMO stations I look at the vertical mixing spike was off the chart, but the same sounding was showing a so-so lapse rate. On another day the spike was lower while the sounding for the same day was indicating a much stronger lapse rate.

Vertical Profiles (soundings)

• In the text format of the forecast-model soundings, there is a section at the beginning of the file that has four-character abbreviations followed by numerical values. I can figure out easily what some of these are, e.g., PRSS=pressure, T02M=temperature at 2 m, but other abbreviations aren't so obvious to me. Is there a complete list of the abbreviations and units?
• What is the meaning of red line and green lines on the vertical profile? Where can I learn more about the plot?
• I'd like to get the dT/dz and the potential temperature. Could you explain me how to get those values?

Maps

• Why can't I plot GDAS archive data using the Interactive Map programs?
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Meteorological Data on READY

Archived Data

• What are the differences between EDAS, FNL, REANALYSIS, and NGM meteorological datasets, because I got quite different HYSPLIT results between them?
• What is the source of the Reanalysis meteorological data on your web-site, and what is it's resolution and content?
• In reference to your FNL archive products, when we retrieve a map corresponding to a specific date do we get a model predicted field or an actual one?
• Did anyone else archive EDAS data prior to 1997?
• What is the difference between the FNL and CDC Reanalysis data sets?

Forecast Data

• Is there a sanctioned way of retrieving the GFS data 4 times a day? I don't want to use the READY web interface in an automated script. http://www.windguru.cz/ is a good example of what I want to do, but with a subset of data a balloonist would find useful.
  I have been using the GFS model data to get soundings to assist me in the running of advanced gliding courses in Australia. I have been using the information for the last two years and, to date, I have been extremely impressed by the accuracy of the information. My query is, how is the information derived? The nearest sites that have sounding information are Moree, Charleville and Brisbane, the nearest being some 250km from my location. Many thanks for a great service.
• What is the difference between the AVN, MRF and GFS models? (March 2004)

HYSPLIT in General

Meteorological Data

• What meteorological archive data sets can I use to model Europe with HYSPLIT?
• What archived data are available on the web to run HYSPLIT with?
• What data is used to calculate the trajectories and what is the the vertical resolution of the data?
• I 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?
• I 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?
• Where can I find gridded meteorological data to simulate the Chernobyl accident?
• I 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.
• I 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?
• What archived data can I use prior to the start of the FNL dataset?
• Can I use surface observations in HYSPLIT?
• How 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?
• I want to extract the u and v fields from the FNL archive according to the pressure level in some locations. Is this possible?
• Can HYSPLIT read other forms of meteorological data?
• I 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?
• How do I convert my ECMWF GRIB data files into ARL format using ecm2arl on the PC?
• Could you explain the equation (Zagl = ak2 + bk + c) used by HYSPLIT? What is the different between Ztop, Zgl, Zmsl and Zagl?
  

Model Setup & Parameters

• Can HYSPLIT be setup to run a short-range dispersion calculation? If so, how?
• Which value should I input as the start height (MAGL)? What does "above model ground level" mean?
• I 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?
• I 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 "underground."
• When 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.
• I 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?
• I'm 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?
• What 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)
• Is terrain included in the HYSPLIT model and how accurate are surface trajectories computed for complex terrain?
• Is there anyway to change the simulation specification so that the concentration measurements are standardized across both
  (1) one location at different points in time and,
  (2) 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 explosions?
• Would HYSPLIT work to model an atmospheric release of a biological toxin?
• Can a run 1 trajectory every 6 hours every day for an extended period of time?

Interpretation of Trajectory Results

• After 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) surface?
• After 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?
• I 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 stations?
• When 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?
• Could you tell us how the precipitation rates are determined which accompany the air parcel trajectories in the tdump file?
• Is it possible to overlay several trajectories onto one map?
• How 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 field error)?
• What are the levels of uncertainty associated with back trajectory calculations in HYSPLIT?
• What 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)
• How 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?
• We 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?
• Is the effect of the boundary layer considered when the model computes the trajectory?
• 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?

Interpretation of Concentration Results

• Is it possible to interpolate between two lines of equal concentration or between a maximum and a line?
• How is concentration defined in HYSPLIT and how does it relate to the radiation units of Bacquerel?
• Is there any way to obtain the concentration and deposition information in a data file instead of a graphic?
• When 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?
  

Running HYSPLIT on the READY Server

Trajectories

• How do I calculate and visualize backward and forward trajectories for our air pollution monitoring station on the READY website?
• My 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?
• What is the longest period over which trajectories can be calculated on the web?
• Is 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?

Concentration/Deposition

• The 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?
• Does HYSPLIT output 3 dimensional concentrations?

Misc.

• How 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?

Running HYSPLIT on your PC

Downloading, Installing and Running the Model

• Where can I download the HYSPLIT PC version?
• What RAM and HD requirements are needed for running the trajectory and dispersion models on the PC?
• Is it necessary for the CONTROL file to be named "CONTROL"?
• How 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?
• Can I produce the particle display on the PC version?

Trajectories

• How do I run a BACKWARD trajectory using the PC version of HYSPLIT?
• When 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?
• Is there a way to run the model in "batch mode" that would generate trajectory endpoints?
• I 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?
• An 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.
• Is it possible to represent in the same map both forward and backward trajectories in order to make a comparision of the integration time step?
• For 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?
• I 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?
• When 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)
• Please 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.

Concentration/Deposition

• The 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?
• I 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 each endpoint?
• I 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.
• I 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.
• I 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.
• How do I calculate deposition?

Errors

• I 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 this problem?
• I 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:
• I 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?
• Why 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.
• When 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"?
• I 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
  "*ERROR* runset: Numb meteo grids exceed DEFGRID limit - 12"
  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 year?
• 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 concplot create?
• I 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

Atmospheric Transport and Dispersion Modeling in General

• What research is being conducted on the long-range atmospheric transport of pesticides in NOAA or other related organizations?
• I would like to know what kind of research is done concerning air quality in New York City so far. Is there a permanent sampling of air quality parameters? Where are these stations located?
• Many previous aerosol studies have used 850 and 750 mb pressure levels in back trajectory calculations. Why is this significant? Are surface back trajectory calculations (at 1000 mb) more accurate, due to presumably greater spatial resolution of meteorological data?
• What is the definition of the boundary (or mixed) layer?
  
  
• Is there is a way to calculate or predict how far a certain organic molecule will travel from an oil refinery on any given day? Are there any models or sites out there that could answer that question?
  
  
• We want to use HYSPLIT to model both a Chlorine and an Ammonia spill. We have looked all over the internet for the Henry's Actual and Effective constants, as well as the surface reactivity and diffusivity ratios for both Chlorine and Ammonia. Do you know where we can find this information?
  
  

Volcanic Ash Model (VAFTAD)

• As an airline pilot I always check the VAFTADs 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 VAFTAD 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 VAFTAD's, 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 a graphic?
• On the VAFTAD page is lists current VAFTAD eruptions, but when you click on it, it says there are none.
• 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?

Modeling Support Programs

• What information is available on the CMAPF mapping function used by many of your programs?
  
• Which way does the wind blow at the north pole?
  
• Can you give me a brief history on the origins of latitude, longitude and the division of degrees into minute and seconds. How old is this system and who developed it?

Climate - Humidity - Temperature

• What is atmospheric humidity and how is it measured?
• Where can I find a current emissions report on the greenhouse gases, carbon dioxide, nitris oxide, and methane?
• I am a 7th Grade student and would like to know why is it always cold in Antarctica?
• What information is available on how climate affects air quality and vice versa?
• Why is it, for example, that at 27 degrees C in both Calgary, Canada and Osaka, Japan with a relative humidity of 60% one would barely perceive any humidity in the air in Calgary and yet one would feel very uncomforable and "wet" in Osaka?

Air Quality - Pollen - Atmospheric Chemistry - Acid Rain

Acid Rain

• What are the major pollutants found in acid rain? How much acid (percentage of total rain) would have to be present in rain for it to be considered: low-acidity rain, medium-acidity rain, and high-acidity rain; and what would be their respective pH levels?
• Could you tell us the origin of the air that contributed to the rainfall sample we measured on 12/15/99 in Front Royal, Virginia?
• Could you offer a detailed answer on why/how the nitrogen deposition from nitrate and ammonium is so high in the northeast states, lower in the midwest states and very low in the west. What is causing this atmospheric deposition condition?
• My son, a 7th grader, is working on a science fair project that will hopefully show varying levels of acid rain in our county. Is the HYSPLIT trajectory model the best way to show wind current origins for rain falling on a given day, or is there another way to show this? Also, can you recommend any other sites/sources for middle school level research on acid rain effects, sources, detection, etc.?

Atmospheric Chemistry

• How much carbon dioxide is there in non-urban and indoor air?
• How much oxygen and carbon dioxide is there in the air we breath? Does it change with the seasons? Does it change with the location on our planet?
• How can lead be removed from the air, especially related to exhaust gasses from internal combustion engines? Is there a chemical process that can accomplish this instead of filtration?
• Does anyone monitor the levels of carbon monoxide (CO) in the air in Albuquerque, New Mexico? I need the data for my science fair project. If that is not available, is there a way I can calculate it through weather, etc. archives for the past month in Albuquerque NM, and where would I find that data?
• What pollutants and how much are in the atmosphere?
• Where can I find the latest research on aerosols?
• Could you please provide me with Nitrogen Oxides content/index in the atmosphere from year 1950 to year 2000? Please include the industrial contribution numbers as well. Or could you please direct me to another link to obtain the information?
• Is there a Comprehensive directory or guide that would include all organic or volatile organic chemicals and their compounds? Also, where can I find the concentrations of gaseous organic and inorganic substances in typical outdoor air. (April 2004)
• Do you have any historical data or "rule of thumb" information regarding the amount of salt (seasalt) contained in the moisture in the air around coastal areas?
• Do you have a database or maps for SO2 emissions in all the world?

Air Quality

• What cities do you suggest have the best air quality?
• Do you have air quality information specific to a region other than the Chesapeake Bay?
• What kind of impact does the air quality in the Kanawha Valley of West Virginia have on my daughter and her asthma. I have the option of moving west of Charleston about 30 miles, out of the valley, and I wanted to see what kind of data there is to show the differences in air quality between South Charleston, WV and Milton, WV. Is there a way I can sample the air myself?

Pollen

• I am looking for historical data on pollen and mold counts and humidity data. Any information or websites you can direct me to will be greatly appreciated.
• Is there any plans in the future to have a segment that tracks pollen/air particals on a daily basis for those of us have allergies real bad? (March 2004)