VGAM (version 1.1-8)

venice: Venice Maximum Sea Levels Data

Description

Some sea levels data sets recorded at Venice, Italy.

Usage

data(venice)
data(venice90)

Format

venice is a data frame with 51 observations on the following 11 variables. It concerns the maximum heights of sea levels between 1931 and 1981.

year

a numeric vector.

r1,r2,r3,r4,r5,r6,r7,r8,r9,r10

numeric vectors; r1 is the highest recorded value, r2 is the second highest recorded value, etc.

venice90 is a data frame with 455 observations on the following 7 variables.

year, month, day, hour

numeric vectors; actual time of the recording.

sealevel

numeric; sea level.

ohour

numeric; number of hours since the midnight of 31 Dec 1939 and 1 Jan 1940.

Year

numeric vector; approximate year as a real number. The formula is start.year + ohour / (365.26 * 24) where start.year is 1940. One can treat Year as continuous whereas year can be treated as both continuous and discrete.

Details

Sea levels are in cm. For venice90, the value 0 corresponds to a fixed reference point (e.g., the mean sea level in 1897 at an old palace of Venice). Clearly since the relative (perceived) mean sea level has been increasing in trend over time (more than an overall 0.4 m increase by 2010), therefore the value 0 is (now) a very low and unusual measurement.

For venice, in 1935 only the top six values were recorded.

For venice90, this is a subset of a data set provided by Paolo Pirazzoli consisting of hourly sea levels from 1940 to 2009. Values greater than 90 cm were extracted, and then declustered (each cluster provides no more than one value, and each value is at least 24 hours apart). Thus the values are more likely to be independent. Of the original (2009-1940+1)*365.26*24 values about 7 percent of these comprise venice90.

Yet to do: check for consistency between the data sets. Some external data sets elsewhere have some extremes recorded at times not exactly on the hour.

References

Smith, R. L. (1986). Extreme value theory based on the r largest annual events. Journal of Hydrology, 86, 27--43.

Battistin, D. and Canestrelli, P. (2006). La serie storica delle maree a Venezia, 1872--2004 (in Italian), Comune di Venezia. Istituzione Centro Previsione e Segnalazioni Maree.

See Also

guplot, gev, gpd.

Examples

if (FALSE) {
matplot(venice[["year"]], venice[, -1], xlab = "Year",
        ylab = "Sea level (cm)", type = "l")

ymat <- as.matrix(venice[, paste("r", 1:10, sep = "")])
fit1 <- vgam(ymat ~ s(year, df = 3), gumbel(R = 365, mpv = TRUE),
             venice, trace = TRUE, na.action = na.pass)
head(fitted(fit1))

par(mfrow = c(2, 1), xpd = TRUE)
plot(fit1, se = TRUE, lcol = "blue", llwd = 2, slty = "dashed")

par(mfrow = c(1,1), bty = "l", xpd = TRUE, las = 1)
qtplot(fit1, mpv = TRUE, lcol = c(1, 2, 5), tcol = c(1, 2, 5),
       llwd = 2, pcol = "blue", tadj = 0.1)

plot(sealevel ~ Year, data = venice90, type = "h", col = "blue")
summary(venice90)
dim(venice90)
round(100 * nrow(venice90)/((2009-1940+1)*365.26*24), dig = 3)
}