BuildProfile: Get model data at a specific point.

In rNOMADS: An R Interface to the NOAA Operational Model Archive and Distribution System

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)

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.

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.

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

Note

The “outside of model domain” warning may occur if the profile point is very close to the prime meridian (in the case of a 0-360 longitude definition) or the antipode of the prime meridian (+/- 180 degrees longitude in the case of -180 to 180 degrees definition). For a full download of a global model (e. g. the GFS), this does not mean the point is actually outside of the model domain. For example, the 0.5 degree GFS has nodes from 0 to 359.5 degrees longitude; a profile point requested at 359.9 degrees longitude will cause this warning even though it is within the global GFS model domain.

Author(s)

Daniel C. Bowman [e-mail]

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)

## Not run: 
model.url <- CrawlModels(abbrev = "gfs_0p50", depth = 2)[2]
pred <- ParseModelPage(model.url)$pred[1]

## End(Not run)

#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")

## Not run: 
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")

## End(Not run)

rNOMADS documentation built on May 29, 2024, 6:44 a.m.