rNOMADS (version 2.5.3)

BuildProfile: Get model data at a specific point.

Description

Takes the output of ReadGrib or DODSGrab and extracts data at a specific point, performing interpolation if required.

Usage

BuildProfile(model.data, lon, lat, spatial.average, points = 4)

Value

profile

A list with as many elements as profile points, with fields:

profile$profile.data

A levels x variables x time matrix with data at a specific point

profile$location

The location for which the profile is generated

profile$forecast.date

What dates and times the profile contains

profile$variables

The variables the profile contains

profile$levels

The levels the profile contains

Arguments

model.data

Data structure returned by ReadGrib or DODSGrab.

lon

Longitudes of points of interest.

lat

Latitudes of points of interest.

spatial.average

Whether to interpolate data using b-splines to obtain value at the requested point (spatial.average = TRUE) or use the nearest model node (spatial.average = FALSE).

points

How many points to include in the interpolation, will be ignored if spatial.average = FALSE.

Author

Daniel C. Bowman

Details

It is much more efficient to download a large chunk of data and extract profile points from that as opposed to downloading individual small model chunks in the vicinity of each point of interest.

See Also

ReadGrib, DODSGrab

Examples

#Get temperature profile in Chapel Hill, NC.

#First, define each location
lon <- -79.052094
lat <- 35.907562

#Get second to latest GFS 0.5 model, use analysis forecast
#(this ensures the data's fully up on NOMADS)

if (FALSE) {
model.url <- CrawlModels(abbrev = "gfs_0p50", depth = 2)[2]
pred <- ParseModelPage(model.url)$pred[1]
}

#Get levels
pressure <- c(1, 2, 3, 5, 7,
10, 20, 30, 50, 70,
seq(100, 1000, by = 25))
levels <- paste(pressure, " mb", sep = "")

#Variables - temperature and height only
variables <- c("TMP", "HGT")

if (FALSE) {
grib.info <- GribGrab(model.url, pred, levels, variables,
   model.domain = c(-85, -75, 37, 32))
grib.data <- ReadGrib(grib.info[[1]]$file.name, levels, variables)

profile <- BuildProfile(grib.data, lon, lat, TRUE, points = 8)
plot(profile[[1]]$profile.data[,2, 1] - 272.15, 
   profile[[1]]$profile.data[,1, 1], xlab = "Temperature (C)",
   ylab = "Height (m)", main = "Temperature Profile above Chapel Hill, NC")
}