gstat (version 2.0-3)

wind: Ireland wind data, 1961-1978

Description

Daily average wind speeds for 1961-1978 at 12 synoptic meteorological stations in the Republic of Ireland (Haslett and raftery 1989). Wind speeds are in knots (1 knot = 0.5418 m/s), at each of the stations in the order given in Fig.4 of Haslett and Raftery (1989, see below)

Usage

data(wind)

Format

data.frame wind contains the following columns:

year

year, minus 1900

month

month (number) of the year

day

day

RPT

average wind speed in knots at station RPT

VAL

average wind speed in knots at station VAL

ROS

average wind speed in knots at station ROS

KIL

average wind speed in knots at station KIL

SHA

average wind speed in knots at station SHA

BIR

average wind speed in knots at station BIR

DUB

average wind speed in knots at station DUB

CLA

average wind speed in knots at station CLA

MUL

average wind speed in knots at station MUL

CLO

average wind speed in knots at station CLO

BEL

average wind speed in knots at station BEL

MAL

average wind speed in knots at station MAL

data.frame wind.loc contains the following columns:

Station

Station name

Code

Station code

Latitude

Latitude, in DMS, see examples below

Longitude

Longitude, in DMS, see examples below

MeanWind

mean wind for each station, metres per second

References

These data were analyzed in detail in the following article:

Haslett, J. and Raftery, A. E. (1989). Space-time Modelling with Long-memory Dependence: Assessing Ireland's Wind Power Resource (with Discussion). Applied Statistics 38, 1-50.

and in many later papers on space-time analysis, for example:

Tilmann Gneiting, Marc G. Genton, Peter Guttorp: Geostatistical Space-Time Models, Stationarity, Separability and Full symmetry. Ch. 4 in: B. Finkenstaedt, L. Held, V. Isham, Statistical Methods for Spatio-Temporal Systems.

Examples

# NOT RUN {
dev.off()
data(wind)
summary(wind)
wind.loc
library(sp) # char2dms
wind.loc$y = as.numeric(char2dms(as.character(wind.loc[["Latitude"]])))
wind.loc$x = as.numeric(char2dms(as.character(wind.loc[["Longitude"]])))
coordinates(wind.loc) = ~x+y
# fig 1:
if (require(mapdata)) {
    map("worldHires", xlim = c(-11,-5.4), ylim = c(51,55.5))
    plot(wind.loc, add=TRUE, pch=16)
    text(coordinates(wind.loc), pos=1, label=wind.loc$Station)
}

wind$time = ISOdate(wind$year+1900, wind$month, wind$day)
# time series of e.g. Dublin data:
plot(DUB~time, wind, type= 'l', ylab = "windspeed (knots)", main = "Dublin")
dev.off()

# fig 2:
#wind = wind[!(wind$month == 2 & wind$day == 29),]
wind$jday = as.numeric(format(wind$time, '%j'))
windsqrt = sqrt(0.5148 * as.matrix(wind[4:15]))
Jday = 1:366
windsqrt = windsqrt - mean(windsqrt)
daymeans = sapply(split(windsqrt, wind$jday), mean)
plot(daymeans ~ Jday)
lines(lowess(daymeans ~ Jday, f = 0.1))
dev.off()

# subtract the trend:
meanwind = lowess(daymeans ~ Jday, f = 0.1)$y[wind$jday]
velocity = apply(windsqrt, 2, function(x) { x - meanwind })

# match order of columns in wind to Code in wind.loc:
pts = coordinates(wind.loc[match(names(wind[4:15]), wind.loc$Code),])

# fig 3, but not really yet...
dists = spDists(pts, longlat=TRUE)
corv = cor(velocity)
sel = !(as.vector(dists) == 0)
plot(as.vector(corv[sel]) ~ as.vector(dists[sel]),
	xlim = c(0,500), ylim = c(.4, 1), xlab = "distance (km.)", 
	ylab = "correlation") 
# plots all points twice, ignores zero distance 
dev.off()

# now really get fig 3:
ros = rownames(corv) == "ROS"
dists.nr = dists[!ros,!ros]
corv.nr = corv[!ros,!ros]
sel = !(as.vector(dists.nr) == 0)
plot(as.vector(corv.nr[sel]) ~ as.vector(dists.nr[sel]), pch = 3,
	xlim = c(0,500), ylim = c(.4, 1), xlab = "distance (km.)", 
	ylab = "correlation") 
# add outlier:
points(corv[ros,!ros] ~ dists[ros,!ros], pch=16, cex=.5)
xdiscr = 1:500
# add correlation model:
lines(xdiscr, .968 * exp(- .00134 * xdiscr))
# }