oce (version 0.1-76)

plot.sealevel: Plot sealevel data

Description

Plot a summary diagram for sealevel data.

Usage

## S3 method for class 'sealevel':
plot(x, focus.time=NULL, \dots)

Arguments

x

A sealevel object, e.g. as read by read.sealevel.

focus.time

if provided, the the time interval on which to focus, each a string in a format suitable for interpretation by as.POSIXct; see the example.

...

optional arguments passed to plotting functions.

Value

• None.

Details

Creates a plot for a sea-level dataset, in one of two varieties.

If a focus.time is provided, then the plot is a simple time series extending between the two times.

If a focus.time is not not provided, then a multi-panel display is drawn. The top panel shows the entire timeseries; since this typically extends over a year, the graph mainly shows low-frequency modulations of the tide, such as spring-neap cycles. The second panel focusses on the first month of data, providing a quick visual signal as to the nature of the tide, e.g. mainly semidiurnal, mainly diurnal, or mixed. In both of these panels, the sealevel is plotted as an anomaly in excess of the mean over the whole timeseries. This mean value is indicated in the right-hand margin. If the sealevel series contains missing values, then only these two panels are drawn. However, if it has no missing values, then two spectral representations are also drawn. The first of these is a power spectrum, with some common tidal constituents being indicates with lines and labels. The units are $m^2$ per cycle-per-day. The second, and thus the lower of the four panels, is a cumulative graph of the square root of the power spectrum. The unit for this graph is $m$, so that the step for each tidal constituent may be interpreted as the amplitude of that constituent, and the largest value on the graph gives the standard deviation of sealevel height.

References

The example refers to Hurricane Juan, which caused a great deal of damage to Halifax in 2003. Since this was in the era of the digital photo, a casual web search will uncover some spectacular images of damage, from both wind and storm surge. The wikipedia entry http://en.wikipedia.org/wiki/Hurricane_Juan provides a good entry to the topic, with the Canadian Hurricane Centre's http://www.atl.ec.gc.ca/weather/hurricane/juan/summary_e.html filling in some more technical details.

See Also

summary.sealevel summarizes the information, while read.sealevel scans it from a file.

Examples

library(oce)
data(sealevel.hal)
# Overall plot
plot(sealevel.hal)
# Focus on 2003-Sep-28 to 29th, the time when Hurricane Juan caused flooding
plot(sealevel.hal, focus.time=c("2003-09-23","2003-10-05"))
abline(v=as.POSIXct("2003-09-28 23:30:00"), col="red", lty="dotted")
mtext("Hurricane
Juan", at=as.POSIXct("2003-09-28 23:30:00"), col="red")