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 24.43 54.408 2012-2013 ah Aston Hill 52.5038 -3.04178 1988-2013 auch Auchencorth Moss 55.7928 -3.24257 2006-2013 berlin Berlin, Germany 52.52 13.4 2000-2013 birm Birmigham Centre 52.4797 -1.90808 1990-2013 boston Boston, USA 42.329 -71.083 2008-2013 bot Bottesford 52.9303 -0.814722 1990-2013 bukit Bukit Kototabang, Indonesia -0.19805 100.318 1996-2013 chittagong Chittagong, Bangladesh 22.37 91.8 2010-2013 dhaka Dhaka, Bangladesh 23.7 90.375 2010-2013 ed Edinburgh 55.952 -3.19577 1990-2013 elche Elche, Spain 38.27 -0.69 2004-2013 esk Eskdalemuir 55.3153 -3.20611 1998-2013 gibraltar Gibraltar 36.134 -5.347 2005-2010 glaz Glazebury 53.4601 -2.47206 1998-2013 groningen Groningen 53.4 6.35 2007-2013 har Harwell 51.5711 -1.32528 1988-2013 hk Hong Kong 22.29 114.17 1998-2013 hm High Muffles 54.335 -0.8086 1988-2013 kuwait Kuwait City 29.367 47.967 2008-2013 lb Ladybower 53.4034 -1.75201 1988-2013 london Central London 51.5 -0.1 1990-2013 lh Lullington Heath 50.7937 0.18125 1988-2013 ln Lough Navar 54.4395 -7.90033 1988-2013 mh Mace Head 53.33 -9.9 1988-2013 ny-alesund Ny-Alesund, Norway 78.9176 11.8947 2009-2013 oslo Oslo 59.9 10.75 2010-2013 paris Paris, France 48.862 2.339 2000-2013 roch Rochester Stoke 51.4562 0.634889 1988-2013 rotterdam Rotterdam 51.9166 4.475 2010-2013 saopaulo Sao Paulo -23.55 -46.64 2000-2013 sib Sibton 52.2944 1.46397 1988-2013 sv Strath Vaich 57.7345 -4.77658 1988-2013 wuhan Wuhan, China 30.583 114.28 2008-2013 yw Yarner Wood 50.5976 -3.71651 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 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. 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.

trajPlot, importAURN, importKCL,importADMS, importSAQN

David Carslaw

## 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 merge(mytraj, theData, by = "date"): object 'mytraj' not found