monitor_nowcast: Apply Nowcast Algorithm to ws_monitor Object
In PWFSLSmoke: Utilities for Working with Air Quality Monitoring Data

Description Usage Arguments Details Value References Examples

A Nowcast algorithm is applied to the data in in the ws_monitor object. The version argument specifies the minimum weight factor and number of hours to be considered in the calculation.

Available versions include:

pm: hours=12, weight=0.5
pmAsian: hours=3, weight=0.1
ozone: hours=8, weight=NA

The default, version='pm', is appropriate for typical usage.

1	monitor_nowcast(ws_monitor, version = "pm", includeShortTerm = FALSE)

`ws_monitor`	ws_monitor object
`version`	character identity specifying the type of nowcast algorithm to be used
`includeShortTerm`	calcluate preliminary NowCast values starting with the 2nd hour

This function calculates the current hour's NowCast value based on the value for the given hour and the previous N-1 hours, where N is the number of hours corresponding to the version argument (see Description above). For example, if version=pm, then the NowCast value for Hour 12 is based on the data from Hours 1-12.

The function requires valid data for at least two of the three latest hours; NA's are returned for hours where this condition is not met.

By default, the funtion will not return a valid value until the Nth hour. If includeShortTerm=TRUE, the function will return a valid value after only the 2nd hour (provided, of course, that both hours are valid).

Calculated Nowcast values are truncated to the nearest .1 ug/m3 for 'pm' and nearest .001 ppm for 'ozone' regardless of the precision of the data in the incoming ws_monitor object.

A ws_monitor object with data that have been processed by the Nowcast algorithm.

https://en.wikipedia.org/wiki/Nowcast_(Air_Quality_Index)

https://aqicn.org/faq/2015-03-15/air-quality-nowcast-a-beginners-guide/

https://forum.airnowtech.org/t/the-nowcast-for-ozone-and-pm/172

https://forum.airnowtech.org/t/the-aqi-equation/169

https://forum.airnowtech.org/t/how-does-airnow-handle-negative-hourly-concentrations/143

library(PWFSLSmoke)

N_M <- monitor_subset(Northwest_Megafires, tlim=c(20150815,20150831))
Omak <- monitor_subset(N_M, monitorIDs='530470013_01')
Omak_nowcast <- monitor_nowcast(Omak, includeShortTerm=TRUE)
monitor_timeseriesPlot(Omak, type='l', lwd=2)
monitor_timeseriesPlot(Omak_nowcast, add=TRUE, type='l', col='purple', lwd=2)
addAQILines()
addAQILegend(lwd=1, pch=NULL)
legend("topleft", lwd=2, col=c('black','purple'), legend=c('hourly','nowcast'))
title("Omak, Washington Hourly and Nowcast PM2.5 Values in August, 2015")
# Zooming in to check on handling of missing values
monitor_timeseriesPlot(Omak, tlim=c(20150823,20150825))
monitor_timeseriesPlot(Omak_nowcast, tlim=c(20150823,20150825), pch=16,col='red',type='b', add=TRUE)
abline(v=Omak$data[is.na(Omak$data[,2]),1])
title("Missing values")