NASAPrecipitation.jl

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Downloading and Reading NASA Precipitation Datasets ​

In this page we show how you can download data for a given NASAPrecipitation dataset.

Setup ​

julia
using NASAPrecipitation
using CairoMakie
using DelimitedFiles

download("https://raw.githubusercontent.com/natgeo-wong/GeoPlottingData/main/coastline_resl.txt","coast.cst")
coast = readdlm("coast.cst",comments=true)
clon  = coast[:,1]
clat  = coast[:,2]
nothing

Required dependencies ​

Since we are downloading from NASA's EOSDIS OPeNDAP servers, you are required to perform the following:

  1. You need to register an account with Earthdata and allow access to the NASA EOSDISC on it.

  2. Create a .netrc file with the following information: machine urs.earthdata.nasa.gov login <your login> password <your password>

  3. Create a .dodsrc file with the following lines: (1) HTTP.COOKIEJAR=/<home directory>/.urs_cookies and (2) HTTP.NETRC=/<home directory>/.netrc

If this sounds complicated however, fear not! You need only perform the first step yourself (i.e. create your own account), for NASAPrecipitation.jl will automatically set up the .dodsrc file (if you don't already have one), and once you have your <login> and <password>, you can use the function setup() to set up your .netrc file.

setup(
    login = <username>
    password = <password>
)

Downloading NASAPrecipitationDatasets ​

Downloading NASA Precipitation data is as simple as

julia
npd = NASAPrecipitationDataset(args...)
geo = GeoRegion(args...)
download(npd,geo)

Let us download the IMERGMonthly Dataset for 2020 over the Caribbean (as defined by the AR6 IPCC), for example

@example
# npd = IMERGMonthly(start=Date(2020),stop=Date(2020),path=pwd())
# geo = GeoRegion("AR6_CAR")
hroot = "https://gpm1.gesdisc.eosdis.nasa.gov/opendap/AUXILIARY"
npdnc = "GPM_IMERG_LandSeaMask.2/GPM_IMERG_LandSeaMask.2.nc4"
npdds = NCDataset(joinpath(hroot,npdnc),"r")
npdds["landseamask"][1]
# lsd = getLandSea(npd,geo)
# download(npd,geo)

Reading data for a downloaded NASAPrecipitationDataset ​

And now that you have downloaded the data, you can use the function read() to call the NCDataset that points towards the downloaded data.

@example
ds = read(npd,geo,Date(2020))

As shown in the printout of the NCDataset, the precipitation data is saved under the field name precipitation, and is in units of kg m**-2 s**-1, or alternatively mm s**-1.

@example
prcp = ds["precipitation"][:,:,:] * 3600
close(ds)

fig = Figure()
_,_,slon,slat = coordGeoRegion(geo)
aspect = (maximum(slon)-minimum(slon))/(maximum(slat)-minimum(slat))

ax = Axis(
    fig[1,1],width=350,height=350/aspect,
    title="February 2020",xlabel="Longitude / º",ylabel="Latitude / º",
    limits=(minimum(slon)-2,maximum(slon)+2,minimum(slat)-2,maximum(slat)+2)
)
contourf!(
    ax,lsd.lon,lsd.lat,prcp[:,:,2],colormap=:Blues,
    levels=range(0,0.5,length=11),extendlow=:auto,extendhigh=:auto
)
lines!(ax,clon,clat,color=:black)
lines!(ax,slon,slat,color=:red,linewidth=5)

ax = Axis(
    fig[1,2],width=350,height=350/aspect,
    title="August 2020",xlabel="Longitude / º",
    limits=(minimum(slon)-2,maximum(slon)+2,minimum(slat)-2,maximum(slat)+2)
)
contourf!(
    ax,lsd.lon,lsd.lat,prcp[:,:,8],colormap=:Blues,
    levels=range(0,0.5,length=11),extendlow=:auto,extendhigh=:auto
)
lines!(ax,clon,clat,color=:black)
lines!(ax,slon,slat,color=:red,linewidth=5)

hideydecorations!(ax, ticks = false,grid=false)

resize_to_layout!(fig)
fig

Where is the data saved to? ​

You can check where the data is saved to for a given dataset, georegion and datetime by using the function npdfnc()

@example
fnc = npdfnc(npd,geo,Date(2020))

API ​

NASAPrecipitation.setup Function
julia
setup(;
    login     :: AbstractString = "",
    password  :: AbstractString = "",
    overwrite :: Bool = false
)

Function that sets up your .ncrc and .netrc files for you. If you do not provide the keyword arguments for login and password, the .netrc file will not be created.

Keyword arguments

  • login : Your Earthdata username. You need to specify both login and password arguments.

  • password : Your Earthdata password. You need to specify both login and password arguments.

  • overwrite : If true, overwrite existing .ncrc and .netrc files with the data provided.

source
Base.download Function
julia
download(
    npd :: NASAPrecipitationDataset,
    geo :: GeoRegion = GeoRegion("GLB");
    overwrite :: Bool = false
) -> nothing

Downloads a NASA Precipitation dataset specified by npd for a GeoRegion specified by geo

Arguments

  • npd : a NASAPrecipitationDataset specifying the dataset details and date download range

  • geo : a GeoRegion (see GeoRegions.jl) that sets the geographic bounds of the data array in lon-lat

Keyword Arguments

  • overwrite : If true, overwrite any existing files
source
Base.read Function
julia
read(
    npd :: NASAPrecipitationDataset,
    geo :: GeoRegion,
    dt  :: TimeType;
    smooth   :: Bool = false,
    smoothlon  :: Real = 0,
    smoothlat  :: Real = 0,
    smoothtime :: Real = 0,
    quiet  :: Bool = false
) -> NCDataset

Reads a NASA Precipitation dataset specified by npd for a GeoRegion specified by geo at a date specified by dt.

Arguments

  • npd : a NASAPrecipitationDataset specifying the dataset details and date download range

  • geo : a GeoRegion (see GeoRegions.jl) that sets the geographic bounds of the data array in lon-lat

  • dt : A specified date. The NCDataset retrieved may will contain data for the date, although it may also contain data for other dates depending on the NASAPrecipitationDataset specified by npd

Keyword Arguments

  • smooth :

  • smoothlon :

  • smoothlat :

  • smoothtime :

  • quiet :

source
NASAPrecipitation.npdfnc Function
julia
npdfnc(
    npd :: NASAPrecipitationDataset,
    geo :: GeoRegion,
    dt  :: TimeType
) -> String

Returns of the path of the file for the NASA Precipitation dataset specified by npd for a GeoRegion specified by geo at a date specified by dt.

Arguments

  • npd : a NASAPrecipitationDataset specifying the dataset details and date download range

  • geo : a GeoRegion (see GeoRegions.jl) that sets the geographic bounds of the data array in lon-lat

  • dt : A specified date. The NCDataset retrieved may will contain data for the date, although it may also contain data for other dates depending on the NASAPrecipitationDataset specified by npd

source