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.
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 specific years useyear = 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/'.- progress
Show a progress bar when many receptors/years are being imported? Defaults to
TRUE.
Details
This function imports pre-calculated back trajectories using the HYSPLIT trajectory model (Hybrid Single Particle Lagrangian Integrated Trajectory Model. 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. 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).
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.
See also
Other import functions:
importADMS(),
importAURN(),
importEurope(),
importKCL(),
importMeta(),
importUKAQ()
Other trajectory analysis functions:
trajCluster(),
trajLevel(),
trajPlot()
Examples
## import trajectory data for London in 2009
if (FALSE) mytraj <- importTraj(site = "london", year = 2009)
## combine with measurements
if (FALSE) theData <- importAURN(site = "kc1", year = 2009)
mytraj <- merge(mytraj, theData, by = "date")
#> Error in eval(expr, envir, enclos): object 'mytraj' not found