NorthAmericanRainfall: Observed North American summer precipitation from the...

In fields: Tools for Spatial Data

Observed North American summer precipitation from the historical climate network.

Description

Average rainfall in tenths of millimeters for the months of June, July and August (JJA) for the period 1950-2010 (old version, 1700+ locations) or 1971-2023 (new version, 4800+ locations) and for North America. The old version uses monthly data from the Global Historical Climate Network (GHCN) version 2 and the new version uses Version 4.

Format

For both versions the format is a list with components: "longitude" "latitude" "precip" "elevation" "precipSE" "trend" "trendSE" "type" "x.s" "sProjection" with elevation in meters, longitude as (-180,180), latitude as (-90, 90) and precipitaion in 1/10 mm ( precip/254 converts to inches of rainfall). Note that the usual convention is to report a total amount of rainfall over the season. Divide by 3 to get the mean.

precip is the intercept for 1980.5 (1997 for new version) when a straight line least squares regression is fit to each station's record. SE is the companion standard error from the least squares fit. If the station is complete, then precip and precipSE will just be the mean and standard deviation adjusted for a linear trend. The estimated trend trend and and its standard error trendSE are also included.

Also due to the centering, for complete data the intercept and trend estimate will be uncorrelated. The component type indicates whether the station has been "adjusted" (see below) or is still in "unadjusted" form.

x.s is a useful transformation of locations into stereographic coordinates that reduces the inflation of North Canada due to the usual lon/lat coordinates. Specifically it is found by:

  library(mapproj)
  xStereo<- mapproject( NorthAmericanRainfall$lon,NorthAmericanRainfall$lat, projection="stereographic")
  NorthAmericanRainfall$x.s<- cbind( xStereo$x, xStereo$y)
  hold<- .Last.projection()
   NorthAmericanRainfall$orientation<- hold$orientation
   NorthAmericanRainfall$projection <- hold$projection

Source

The monthly data used to construct NorthAmericanRainfall this summary was generously provided by Xuebin Zhang, however, the orignal source is freely available as the Global Historical Climate Network Version 2 Precipitation quality controlled, curated and served by the US National Center for Environmental Information. The adjusted data from this archive has been modified from its raw form to make the record more homogenous. Heterogenities can come from a variety of sources such as a moving the station a short distance or changes in instruments. See the National Centers for Envrionmental Information then Access Data and then GHCN.

The new version NorthAmericanRainfall2 uses the GHCN "Version 4" data product. There are substantially more stations reported in this data set. To reduce the size the stations for this R data set stations were selected if they had more than 80 percent of the months reported over the period 1971-2023. This subset amounts to 4893 locations. A simple linear regression was fit to each station record and the OLS trend, trend SE, trend line at 1997 is evaluated to get a "mean" rainfall estimate for this location.

See the fields github repository for the source code and source data to create this data set.

Examples

data(NorthAmericanRainfall)
x<- cbind(NorthAmericanRainfall$longitude,  NorthAmericanRainfall$latitude)
y<- NorthAmericanRainfall$precip
quilt.plot( x,y)
world( add=TRUE)

Zstat<- NorthAmericanRainfall$trend / NorthAmericanRainfall$trendSE
quilt.plot( x, Zstat)

## Not run: 
# with a better projection
library( maps)
library( mapproj)
bubblePlot( NorthAmericanRainfall$x.s, 
NorthAmericanRainfall$precip,
size=.3, col=rev(tim.colors()) )
map("world", 
projection=NorthAmericanRainfall$projection,
orientation= NorthAmericanRainfall$orientation,
add=TRUE, col="grey30")

## End(Not run)
# note station sparsity outside CONUS and lower CA.

# comparing older and newer versions 

data(NorthAmericanRainfall)
bubblePlot( NorthAmericanRainfall$lon, NorthAmericanRainfall$lat,
NorthAmericanRainfall$precip,
size=.3, col=rev(tim.colors()) )
world( add=TRUE, col="grey30")

data(NorthAmericanRainfall2)
bubblePlot( NorthAmericanRainfall2$lon,NorthAmericanRainfall2$lat,
NorthAmericanRainfall2$precip,
size=.3, col=rev(tim.colors()), xlim= c(-130,-50))
world( add=TRUE, col="grey30")

fields documentation built on June 28, 2024, 1:06 a.m.