Custom PressureLevel variables

In ERA5Reanalysis.jl, we have predefined all the pressure-level variables that are available directly from the CDS. As such, all custom PressureLevel variables are defined under the PressureCustom type.

Defining Custom PressureLevel Variables

PressureCustom variables are defined using the PressureVariable() function, as follows:

ERA5Reanalysis.PressureVariable — Type
PressureVariable(
    ST = String;
    varID :: AbstractString,
    lname :: AbstractString = "",
    vname :: AbstractString,
    units :: AbstractString,
    hPa   :: Int = 0,
    throw :: Bool = true
) -> evar :: PressureCustom

Create a custom Pressure-Level variable that is not in the default list exported by ERA5Reanalysis.jl. These variables are not available in the CDS store, and so they must be separately calculated from other variables and analyzed.

Keyword Arguments

  • varID : variable ID (in string format) used in the NetCDF file
  • lname : long-name for variable (used in specifying variable for CDS downloads)
  • vname : user-defined variable name
  • units : user-defined units of the variable
  • hPa : Pressure level specified in hPa. Default is 0, which indicates all levels.
  • throw : if hPa level does not exist and throw is true, throw error, otherwise find nearest pressure level

Removing Custom PressureLevel Variables

To remove a PressureCustom variable, we can use the rmPressure() function:

ERA5Reanalysis.rmPressure — Method
rmPressure( varID :: AbstractString ) -> nothing

Remove the Pressure-Level Variable with the ID varID from the lists.

Arguments

  • RegID : The keyword ID that will be used to identify the Pressure-Level Variable that is to be removed

An Example!

Let us define the custom variable "vt" for Virtual Temperature, which is a proxy to buoyancy in the atmosphere. Virtual Temperature is calculated from both the water vapour mixing ratio and atmospheric temperature and is given by the formula:

\[T_v = T(1+0.61q)\]

Virtual Temperature has the units "K", and for this example let us define the pressure level height we are interested in to be at 1000 hPa. The resultant PressureCustom variable is given by:

julia> using ERA5Reanalysis
julia> PressureVariable(
           varID = "vt",
           units = "K",
           hPa   = 1000,
           lname = "virtual_temperature",
           vname = "Virtual Temperature"
       )ERROR: 2023-04-03T03:55:12.682 - ERA5Reanalysis.jl - The PressureVariable "vt" has already been defined, please use another identifier.
julia> tablePressures()ERROR: MethodError: no method matching pretty_table(::Matrix{Any}, ::Vector{String}; alignment=[:c, :c, :l, :c, :l], crop=:none, tf=PrettyTables.TextFormat(' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', '-', [:begin, :header, :end], :all))
Closest candidates are:
  pretty_table(!Matched::IO, ::Any; kwargs...) at ~/.julia/packages/PrettyTables/pZvTh/src/print.jl:705
  pretty_table(!Matched::Type{String}, ::Any; color, kwargs...) at ~/.julia/packages/PrettyTables/pZvTh/src/print.jl:707
  pretty_table(!Matched::Type{HTML}, ::Any; kwargs...) at ~/.julia/packages/PrettyTables/pZvTh/src/print.jl:713
  ...
julia> rmPressure("vt")ERROR: UndefKeywordError: keyword argument hPa not assigned
julia> isPressure("vt",throw=false) # don't throw error, just show warningtrue