[gradsusr] To Plot Ocean Current streams

[Eric Altshuler]

Hello Anil, 


You need to do 'set gxout stream' before displaying the variables. By default, the gxout type for displaying two variables ('display U;V') is 'vector', so you'll get a vector plot unless you tell grads you want something different. To control streamline appearance, use 'set strmden …' The plot you attached was probably made by manually drawing the currents, and grads can't do this automatically. 


Best regards, 


Eric L. Altshuler 
Research Scientist 
Center for Ocean-Land-Atmosphere Studies 
253 Research Hall, Mail Stop 6C5 
George Mason University 
4400 University Drive 
Fairfax, VA 22030 USA 

E-mail: ela at cola.iges.org 
Phone: (703) 993-5725 
Fax: (703) 993-5770 

----- Original Message -----
From: "Anil Kumar Sharma" <aanil649 at gmail.com> 
To: "GrADS Users Forum" <gradsusr at gradsusr.org> 
Sent: Thursday, April 3, 2014 3:13:38 AM 
Subject: [gradsusr] To Plot Ocean Current streams 


Hi Everyone, 


I have NetCDF data downloaded for Ocean Current from NOAA website and is attached for reference. Below is the NCDump 



netcdf rtofs_glo_2ds_f024_daily_prog { 
dimensions: 
lat = 360 ; 
lev = 1 ; 
lon = 720 ; 
time = 1 ; 
variables: 
double lat(lat) ; 
lat:grads_dim = "y" ; 
lat:grads_mapping = "linear" ; 
lat:grads_size = "2160" ; 
lat:units = "degrees_north" ; 
lat:long_name = "latitude" ; 
lat:minimum = -90. ; 
lat:maximum = 89.90947 ; 
lat:resolution = 0.08333f ; 
double lev(lev) ; 
lev:grads_dim = "z" ; 
lev:grads_mapping = "levels" ; 
lev:units = "millibar" ; 
lev:long_name = "altitude" ; 
lev:minimum = 1. ; 
lev:maximum = 1. ; 
double lon(lon) ; 
lon:grads_dim = "x" ; 
lon:grads_mapping = "linear" ; 
lon:grads_size = "4320" ; 
lon:units = "degrees_east" ; 
lon:long_name = "longitude" ; 
lon:minimum = 74.16 ; 
lon:maximum = 434.06227 ; 
lon:resolution = 0.08333f ; 
double time(time) ; 
time:grads_dim = "t" ; 
time:grads_mapping = "linear" ; 
time:grads_size = "9" ; 
time:grads_min = "00z13mar2014" ; 
time:grads_step = "1dy" ; 
time:units = "days since 1-1-1 00:00:0.0" ; 
time:long_name = "time" ; 
time:minimum = "00z13mar2014" ; 
time:maximum = "00z21mar2014" ; 
time:resolution = 1.f ; 
float u_velocity(time, lev, lat, lon) ; 
u_velocity:_FillValue = 1.26765e+030f ; 
u_velocity:missing_value = 1.26765e+030f ; 
u_velocity:long_name = "eastward_sea_water_velocity (m/s) " ; 
float v_velocity(time, lev, lat, lon) ; 
v_velocity:_FillValue = 1.26765e+030f ; 
v_velocity:missing_value = 1.26765e+030f ; 
v_velocity:long_name = "northward_sea_water_velocity (m/s) " ; 


// global attributes: 
:title = "2D Sfc Daily Prognostic 00Z13mar2014: Forecast, downlo 
aded Mar 13 15:18 UTC" ; 
:Conventions = "COARDS\n", 
"GrADS" ; 
:dataType = "Grid" ; 
:history = "Thu Mar 13 11:21:41 EDT 2014 : imported by GrADS Data Server 2.0" ; 
:NCO = "20140314" ; 
} 




I need to Plot the current Streams as output, Attached image can be treated as output sample. 
currently, I am using below command for displaying u_velocity and v_velocity variables 



d skip(u_velocity*1.95,14,14);skip(v_velocity*1.95,14,14) 


with skip function I am only able to plot arrow but no stream (we can say axis of current) 


I really don't know how to get this working. Any help on it please 


-- Anil 


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