importTraj: 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

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/'

Value

Returns a data frame with pre-calculated back trajectories.

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).

Examples

Run this code



## 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")
## ---------------------------------------------

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