davidcarslaw/ggopenair
Tools for the Analysis of Air Pollution Data

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importKCL: Import data from King's College London networks

importKCL: Import data from King's College London networks
In davidcarslaw/ggopenair: Tools for the Analysis of Air Pollution Data

Description Usage Arguments Details Value Author(s) See Also Examples

Description

Function for importing hourly mean data from King's College London networks. Files are imported from a remote server operated by King's College London that provides air quality data files as R data objects.

Usage

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importKCL(site = "my1", year = 2009, pollutant = "all", met = FALSE,
  units = "mass", extra = FALSE)

Arguments

site

Site code of the network site to import e.g. "my1" is Marylebone Road. Several sites can be imported with site = c("my1", "kc1") — to import Marylebone Road and North Kensignton for example.

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.

pollutant

Pollutants to import. If omitted will import all pollutants from a site. To import only NOx and NO2 for example use pollutant = c("nox", "no2").

met

Should meteorological data be added to the import data? The default is FALSE. If TRUE wind speed (m/s), wind direction (degrees), solar radiation and rain amount are available. See details below.

Access to reliable and free meteorological data is problematic.

units

By default the returned data frame expresses the units in mass terms (ug/m3 for NOx, NO2, O3, SO2; mg/m3 for CO). Use units = "volume" to use ppb etc. PM10_raw TEOM data are multiplied by 1.3 and PM2.5 have no correction applied. See details below concerning PM10 concentrations.

extra

Not currently used.

Details

The importKCL function has been written to make it easy to import data from the King's College London air pollution networks. KCL have provided .RData files (R workspaces) of all individual sites and years for the KCL networks. These files are updated on a weekly basis. This approach requires a link to the Internet to work.

There are several advantages over the web portal approach where .csv files are downloaded. First, it is quick to select a range of sites, pollutants and periods (see examples below). Second, storing the data as .RData objects is very efficient as they are about four times smaller than .csv files — which means the data downloads quickly and saves bandwidth. Third, the function completely avoids any need for data manipulation or setting time formats, time zones etc. Finally, it is easy to import many years of data beyond the current limit of about 64,000 lines. The final point makes it possible to download several long time series in one go. The function also has the advantage that the proper site name is imported and used in openair functions.

The site codes and pollutant names can be upper or lower case. The function will issue a warning when data less than six months old is downloaded, which may not be ratified.

The data are imported by stacking sites on top of one another and will have field names date, site, code (the site code) and pollutant(s). Sometimes it is useful to have columns of site data. This can be done using the reshape function — see examples below.

The situation for particle measurements is not straightforward given the variety of methods used to measure particle mass and changes in their use over time. The importKCL function imports two measures of PM10 where available. PM10_raw are TEOM measurements with a 1.3 factor applied to take account of volatile losses. The PM10 data is a current best estimate of a gravimetric equivalent measure as described below. NOTE! many sites have several instruments that measure PM10 or PM2.5. In the case of FDMS measurements, these are given as separate site codes (see below). For example "MY1" will be TEOM with VCM applied and "MY7" is the FDMS data.

Where FDMS data are used the volatile and non-volatile components are separately reported i.e. v10 = volatile PM10, v2.5 = volatile PM2.5, nv10 = non-volatile PM10 and nv2.5 = non-volatile PM2.5. Therefore, PM10 = v10 + nv10 and PM2.5 = v2.5 + nv2.5.

For the assessment of the EU Limit Values, PM10 needs to be measured using the reference method or one shown to be equivalent to the reference method. Defra carried out extensive trials between 2004 and 2006 to establish which types of particulate analysers in use in the UK were equivalent. These trials found that measurements made using Partisol, FDMS, BAM and SM200 instruments were shown to be equivalent to the PM10 reference method. However, correction factors need to be applied to measurements from the SM200 and BAM instruments. Importantly, the TEOM was demonstrated as not being equivalent to the reference method due to the loss of volatile PM, even when the 1.3 correction factor was applied. The Volatile Correction Model (VCM) was developed for Defra at King's to allow measurements of PM10 from TEOM instruments to be converted to reference equivalent; it uses the measurements of volatile PM made using nearby FDMS instruments to correct the measurements made by the TEOM. It passed the equivalence testing using the same methodology used in the Defra trials and is now the recommended method for correcting TEOM measurements (Defra, 2009). VCM correction of TEOM measurements can only be applied after 1st January 2004, when sufficiently widespread measurements of volatile PM became available. The 1.3 correction factor is now considered redundant for measurements of PM10 made after 1st January 2004. Further information on the VCM can be found at http://www.volatile-correction-model.info/.

All PM10 statistics on the LondonAir web site, including the bulletins and statistical tools (and in the RData objects downloaded using importKCL), now report PM10 results as reference equivalent. For PM10 measurements made by BAM and SM200 analysers the applicable correction factors have been applied. For measurements from TEOM analysers the 1.3 factor has been applied up to 1st January 2004, then the VCM method has been used to convert to reference equivalent.

The meteorological data are meant to represent 'typical' conditions in London, but users may prefer to use their own data. The data provide a an estimate of general meteorological conditions across Greater London. For meteorological species (wd, ws, rain, solar) each data point is formed by averaging measurements from a subset of LAQN monitoring sites that have been identified as having minimal disruption from local obstacles and a long term reliable dataset. The exact sites used varies between species, but include between two and five sites per species. Therefore, the data should represent 'London scale' meteorology, rather than local conditions.

While the function is being developed, the following site codes should help with selection. We will also make available other meta data such as site type and location to make it easier to select sites based on other information. Note that these codes need to be refined because only the common species are available for export currently i.e. NOx, NO2, O3, CO, SO2, PM10, PM2.5.

Value

Returns a data frame of hourly mean values with date in POSIXct class and time zone GMT.

Author(s)

David Carslaw and Ben Barratt

See Also

importAURN, importADMS, importSAQN

Examples

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## import all pollutants from Marylebone Rd from 1990:2009
## Not run: mary <- importKCL(site = "my1", year = 2000:2009)

## import nox, no2, o3 from Marylebone Road and North Kensignton for 2000
## Not run: thedata <- importKCL(site = c("my1", "kc1"), year = 2000,
pollutant = c("nox", "no2", "o3"))
## End(Not run)

## import met data too...
## Not run: my1 <- importKCL(site = "my1", year = 2008, met = TRUE)

# see example in importAURN about how to reshape the output

davidcarslaw/ggopenair documentation built on May 14, 2019, 10:37 p.m.

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