R: Import pre-calculated HYSPLIT 96-hour back trajectories

importTraj {openair} | R Documentation

## Import pre-calculated HYSPLIT 96-hour back trajectories

### Description

Function to import pre-calculated back trajectories using the NOAA HYSPLIT model. The trajectories have been calculated for a select range of locations which will expand in time. They cover the last 20 years or so and can be used together with other `openair` functions.

### Usage

    importTraj(site = "london", year = 2009, local = NA)

### Arguments

`site` | Site code of the network site to import e.g. "london". Only one site can be imported at a time. The following sites are typically available from 2000-2012, although some UK ozone sites go back to 1988 (code, location, lat, lon, year):
abudhabi | Abu Dhabi | 24.43000 | 54.408000 | 2012-2013
ah | Aston Hill | 52.50385 | -3.041780 | 1988-2013
auch | Auchencorth Moss | 55.79283 | -3.242568 | 2006-2013
berlin | Berlin, Germany | 52.52000 | 13.400000 | 2000-2013
birm | Birmigham Centre | 52.47972 | -1.908078 | 1990-2013
boston | Boston, USA | 42.32900 | -71.083000 | 2008-2013
bot | Bottesford | 52.93028 | -0.814722 | 1990-2013
bukit | Bukit Kototabang, Indonesia | -0.19805 | 100.318000 | 1996-2013
chittagong | Chittagong, Bangladesh | 22.37000 | 91.800000 | 2010-2013
dhaka | Dhaka, Bangladesh | 23.70000 | 90.375000 | 2010-2013
ed | Edinburgh | 55.95197 | -3.195775 | 1990-2013
elche | Elche, Spain | 38.27000 | -0.690000 | 2004-2013
esk | Eskdalemuir | 55.31530 | -3.206110 | 1998-2013
gibraltar | Gibraltar | 36.13400 | -5.347000 | 2005-2010
glaz | Glazebury | 53.46008 | -2.472056 | 1998-2013
groningen | Groningen | 53.40000 | 6.350000 | 2007-2013
har | Harwell | 51.57108 | -1.325283 | 1988-2013
hk | Hong Kong | 22.29000 | 114.170000 | 1998-2013
hm | High Muffles | 54.33500 | -0.808600 | 1988-2013
kuwait | Kuwait City | 29.36700 | 47.967000 | 2008-2013
lb | Ladybower | 53.40337 | -1.752006 | 1988-2013
london | Central London | 51.50000 | -0.100000 | 1990-2013
lh | Lullington Heath | 50.79370 | 0.181250 | 1988-2013
ln | Lough Navar | 54.43951 | -7.900328 | 1988-2013
mh | Mace Head | 53.33000 | -9.900000 | 1988-2013
ny-alesund | Ny-Alesund, Norway | 78.91763 | 11.894653 | 2009-2013
oslo | Oslo | 59.90000 | 10.750000 | 2010-2013
paris | Paris, France | 48.86200 | 2.339000 | 2000-2013
roch | Rochester Stoke | 51.45617 | 0.634889 | 1988-2013
rotterdam | Rotterdam | 51.91660 | 4.475000 | 2010-2013
saopaulo | Sao Paulo | -23.55000 | -46.640000 | 2000-2013
sib | Sibton | 52.29440 | 1.463970 | 1988-2013
sv | Strath Vaich | 57.73446 | -4.776583 | 1988-2013
wuhan | Wuhan, China | 30.58300 | 114.280000 | 2008-2013
yw | Yarner Wood | 50.59760 | -3.716510 | 1988-2013
`year` | Year or years to import. To import a sequence of years from 1990 to 2000 use `year = 1990:2000`. To import several specfic years use `year = c(1990, 1995, 2000)` for example.
`local` | File path to .RData trajectory files run by user and not stored on the Ricardo web server. These files would have been generated from the Hysplit trajectory code shown in the appendix of the openair manual. An example would be `local = 'c:/users/david/TrajFiles/'`.

### Details

This function imports pre-calculated back trajectories using the HYSPLIT trajectory model (Hybrid Single Particle Lagrangian Integrated Trajectory Model http://ready.arl.noaa.gov/HYSPLIT.php). Back trajectories provide some very useful information for air quality data analysis. However, while they are commonly calculated by researchers it is generally difficult for them to be calculated on a routine basis and used easily. In addition, the availability of back trajectories over several years can be very useful, but again difficult to calculate.

Trajectories are run at 3-hour intervals and stored in yearly files (see below). The trajectories are started at ground-level (10m) and propagated backwards in time.

These trajectories have been calculated using the Global NOAA-NCEP/NCAR reanalysis data archives. The global data are on a latitude-longitude grid (2.5 degree). Note that there are many different meteorological data sets that can be used to run HYSPLIT e.g. including ECMWF data. However, in order to make it practicable to run and store trajectories for many years and sites, the NOAA-NCEP/NCAR reanalysis data is most useful. In addition, these archives are available for use widely, which is not the case for many other data sets e.g. ECMWF. HYSPLIT calculated trajectories based on archive data may be distributed without permission (see http://ready.arl.noaa.gov/HYSPLIT_agreement.php). For those wanting, for example, to consider higher resolution meteorological data sets it may be better to run the trajectories separately.

We are extremely grateful to NOAA for making HYSPLIT available to produce back trajectories in an open way. We ask that you cite HYSPLIT if used in published work.

Users can supply their own trajectory files to plot in openair. These files must have the following fields: date, lat, lon and hour.inc (see details below).

The files consist of the following information:

date

  This is the arrival point time and is repeated the number of times equal to the length of the back trajectory — typically 96 hours (except early on in the file). The format is `POSIXct`. It is this field that should be used to link with air quality data. See example below.

receptor

  Receptor number, currently only 1.

year

  The year

month

  Month 1-12

day

  Day of the month 1-31

hour

  Hour of the day 0-23 GMT

hour.inc

  Number of hours back in time e.g. 0 to -96.

lat

  Latitude in decimal format.

lon

  Longitude in decimal format.

height

  Height of trajectory (m).

pressure

  Pressure of trajectory (kPa).

### Value

Returns a data frame with pre-calculated back trajectories.

### Note

The trajectories were run using the February 2011 HYSPLIT model. The function is primarily written to investigate a single site at a time for a single year. The trajectory files are quite large and care should be exercised when importing several years and/or sites.

### Author(s)

David Carslaw

### See Also

`trajPlot`, `importAURN`, `importKCL`,`importADMS`, `importSAQN`

### Examples

    ## import trajectory data for London in 2009
    ## Not run: mytraj <- importTraj(site = "london", year = 2009)

    ## combine with measurements
    ## Not run: theData <- importAURN(site = "kc1", year = 2009)
    mytraj <- merge(mytraj, theData, by = "date")
    ## End(Not run)

[Package openair version 2.8-5 Index]