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gsn_csm_pres_hgt_streamline

Creates and draws a pressure/height contour plot overlaid with streamlines.

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"  ; These two libraries are automatically
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"   ; loaded from NCL V6.2.0 onward.
                                                          ; No need for user to explicitly load.

	function gsn_csm_pres_hgt_streamline (
		wks      [1] : graphic,  
		data  [*][*] : numeric,  
		xcomp [*][*] : numeric,  
		zcomp [*][*] : numeric,  
		res      [1] : logical   
	)

	return_val [1] :  graphic

Arguments

wks

A Workstation identifier. The identifier is one returned either from calling gsn_open_wks or calling create to create a Workstation object.

data

The two-dimensional data to contour. The leftmost dimension must contain a one-dimensional coordinate array of pressure values, and the values must be in the correct units. This is determined by examining the "units" attribute of the coordinate variable. Some accepted units are "hpa", "hPa", "Pa", "pa", "mb", "millibars", etc. If the units attribute doesn't exist or has the wrong value, an error will be issued.

xcomp
zcomp

The data for the streamline plot; must be two-dimensional.

res

A variable containing an optional list of plot resources, attached as attributes. Set to True if you want the attached attributes to be applied, and False if you either don't have any resources to set, or you don't want the resources applied.

Return value

A scalar id of the streamline plot created is returned. The id of the streamline data object is returned as an attribute called vfdata, and the id of the scalar data object is returned as an attribute called sfdata. If a separate contour plot is created, then an attribute called contour is also returned. These ids are useful if you want to use setvalues to change some data or plot options after this function has been called.

Description

This function creates and draws a pressure/height contour plot with streamlines overlaid.

xcomp usually refers to either the east-west (e.g., u) or north-south (e.g., v) component of the horizontal wind. If the plot is a pressure-longitude plot then xcomp refers to the east-west wind component (u). In this case the bottom (x-axis) is labeled with longitude labels (e.g., 90E) if a longitude coordinate array exists. If the plot is a pressure-latitude plot then xcomp refers to the north-south wind component (v). In this case the bottom (x-axis) is labeled with latitude labels (e.g., 30N) if a latitude coordinate array exists.

The left Y-axis will be labeled with reverse log pressure values, and the right Y-axis with height values in km. The height values are a logarithmic interpolation from Standard Atmosphere of the pressure array. The pressure coordinate array values must lie between 1013.25 mb and 0.010 mb.

To turn off the "height" title on the right Y axis, set the special gsnPresHgtHeightLabelOn resource to False.

If xcomp, zcomp, or data have a _FillValue attribute, these values will be used as missing values.

If xcomp has an attribute called "long_name", and gsnLeftString hasn't explicitly been set, then the value of this attribute is used for the left string title. If xcomp has an attribute called "units", and gsnRightString hasn't explicitly been set, then the value of this attribute is used for the right string title. You likely will want to set gsnLeftString and gsnRightString yourself, to more correctly represent the information on the streamlines being overlaid.

To maximize the area that the plot is drawn in, set the special resource gsnMaximize to True.

Examples

For some application examples, see: