Re: u and v wind component values ?

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Wed Apr 27 2011 - 16:07:42 MDT

Your variable u and v are type short (16-bit signed integers)

> Variable: u
> Type: short

They have the attributes

> add_offset : 202.65
> scale_factor : 0.01

They must be 'unpacked' before use

    u = short2flt( f->uwnd )
    v = short2flt( f->vwnd )

http://www.ncl.ucar.edu/Document/Functions/Contributed/short2flt.shtml

On 4/27/11 3:44 PM, Ed Martino wrote:
> Hi
>
> I am having some difficulty plotting and interpreting wind vectors using
> the NCEP reanalysis files. The data values seem too large, I think?.
>
> I used ncl's "min" and "max" functions to generate variable summaries
> for u and v winds.
>
> The NCEP u and v wind component files are
> uwnd.mon.mean.p.nc
> vwnd.mon.mean.p.nc
>
> I used the following statement to generate the output copied below.
> print("min/max slp_anom = " + min(slp_anom) + "/" + max(slp_anom))
>
> Magnitude of min and max values seem too large as indicated by the
> copied output of variable summaries below.
> Do min and max values seem OK? Am I missing something in interpreting
> the variable values?
>
> Thanks.
> Ed
>
>
> *************************************************************************
> Variable: u
> Type: short
> Total Size: 271272672 bytes
> 135636336 values
> Number of Dimensions: 4
> Dimensions and sizes: [time | 759] x [level | 17] x [lat | 73] x [lon
> | 144]
> Coordinates:
> time: [17067072..17620752]
> level: [1000..10]
> lat: [90..-90]
> lon: [ 0..357.5]
> Number Of Attributes: 16
> long_name : Monthly mean u wind
> actual_range : ( -66.37, 124.4 )
> unpacked_valid_range : ( -125, 160 )
> units : m/s
> add_offset : 202.65
> scale_factor : 0.01
> missing_value : 32766
> precision : 2
> least_significant_digit : 1
> var_desc : u-wind
> dataset : CDC Derived NCEP Reanalysis Products
> level_desc : Multiple levels
> statistic : Mean
> parent_stat : Other
> valid_range : ( -32765, -4265 )
> _FillValue : 32766
> (0) min/max u = -26902/-7825
>
>
>
> Variable: v
> Type: short
> Total Size: 271272672 bytes
> 135636336 values
> Number of Dimensions: 4
> Dimensions and sizes: [time | 759] x [level | 17] x [lat | 73] x [lon
> | 144]
> Coordinates:
> time: [17067072..17620752]
> level: [1000..10]
> lat: [90..-90]
> lon: [ 0..357.5]
> Number Of Attributes: 16
> long_name : Monthly mean v wind
> actual_range : ( -66.65, 66.39 )
> unpacked_valid_range : ( -125, 160 )
> units : m/s
> add_offset : 202.65
> scale_factor : 0.01
> missing_value : 32766
> precision : 2
> least_significant_digit : 1
> var_desc : v-wind
> dataset : CDC Derived NCEP Reanalysis Products
> level_desc : Multiple levels
> statistic : Mean
> parent_stat : Other
> valid_range : ( -32765, -4265 )
> _FillValue : 32766
> (0) min/max v = -26930/-13626
>
>
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Received on Wed Apr 27 16:07:51 2011

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