# [ncl-talk] Vertical motion with zonal wind

Barry Lynn barry.h.lynn at gmail.com
Sun Feb 25 23:46:48 MST 2018

```Hi:

What did you plot?  Is that omega or vertical velocity?  I am wondering why
the northern hemisphere winds are not convergent with the positive vertical
motion values like they are in the southern hemisphere.

Barry

On Mon, Feb 26, 2018 at 8:32 AM, Jenny Taylor <jenny63taylor91 at gmail.com>
wrote:

> at my attached output figure. Kindly inform me it is in proper shape or
> not. I think this time it makes some sense.
>
> Thanks again,
> Jenny
>
>
> On Sat, Feb 24, 2018 at 2:14 AM, Adam Phillips <asphilli at ucar.edu> wrote:
>
>> Hi Jenny,
>> You are reading in OMEGA. Note that OMEGA has opposite signs and
>> different units from the conventional W variable.
>>
>> For upward motion:  W is positive and OMEGA is negative
>> for downward motion: W is negative and OMEGA is positive
>>
>> A basic, simple relationship
>>    omega = -rho*grav*w              ; Pa/s
>> Hence:
>>    w          = -omega/(rho*grav)    ; (say) m/s
>>
>> Note the sign ....
>> -----
>> I believe all you have to do is flip the sign of your W variable:
>>    W = in->OMEGA
>>    W = -W
>> assuming you want upward arrows for upward motion.
>>
>> Also note that NCL has a omega_to_w function:
>> https://www.ncl.ucar.edu/Document/Functions/Contributed/omega_to_w.shtml
>>
>> Hope that all makes sense! If not or if you have further questions please
>> respond to the ncl-talk email list.
>>
>>
>> On Fri, Feb 23, 2018 at 1:24 AM, Jenny Taylor <jenny63taylor91 at gmail.com>
>> wrote:
>>
>>> Mary,
>>>
>>> I was trying with the following attached script. But vertical motion
>>> near the equator, as well as the 30S and 30N, shows rising motion in the
>>> output which is not correct in real term. Please kindly look into my script
>>> and figure and inform me what I am missing or doing any wrong in this.
>>>
>>> Data structure is below;
>>>
>>> Variable: t
>>> Type: float
>>> Total Size: 655360 bytes
>>>             163840 values
>>> Number of Dimensions: 4
>>> Dimensions and sizes:   [time | 1] x [lev_p | 20] x [lat | 64] x [lon |
>>> 128]
>>> Coordinates:
>>>             time: [ 791.. 791]
>>>             lev_p: [950..50]
>>>             lat: [-87.8638..87.8638]
>>>             lon: [ 0..357.1875]
>>> Number Of Attributes: 1
>>>   _FillValue :  9.96921e+36
>>>
>>> Variable: u
>>> Type: float
>>> Total Size: 655360 bytes
>>>             163840 values
>>> Number of Dimensions: 4
>>> Dimensions and sizes:   [time | 1] x [lev_p | 20] x [lat | 64] x [lon |
>>> 128]
>>> Coordinates:
>>>             time: [ 791.. 791]
>>>             lev_p: [950..50]
>>>             lat: [-87.8638..87.8638]
>>>             lon: [ 0..357.1875]
>>> Number Of Attributes: 1
>>>   _FillValue :  9.96921e+36
>>>
>>> Variable: v
>>> Type: float
>>> Total Size: 655360 bytes
>>>             163840 values
>>> Number of Dimensions: 4
>>> Dimensions and sizes:   [time | 1] x [lev_p | 20] x [lat | 64] x [lon |
>>> 128]
>>> Coordinates:
>>>             time: [ 791.. 791]
>>>             lev_p: [950..50]
>>>             lat: [-87.8638..87.8638]
>>>             lon: [ 0..357.1875]
>>> Number Of Attributes: 1
>>>   _FillValue :  9.96921e+36
>>>
>>> Variable: w
>>> Type: float
>>> Total Size: 655360 bytes
>>>             163840 values
>>> Number of Dimensions: 4
>>> Dimensions and sizes:   [time | 1] x [lev_p | 20] x [lat | 64] x [lon |
>>> 128]
>>> Coordinates:
>>>             time: [ 791.. 791]
>>>             lev_p: [950..50]
>>>             lat: [-87.8638..87.8638]
>>>             lon: [ 0..357.1875]
>>> Number Of Attributes: 1
>>>   _FillValue :  9.96921e+36
>>>
>>>
>>> Thanking you,
>>> Jenny
>>>
>>>
>>> On Thu, Feb 22, 2018 at 1:17 AM, Mary Haley <haley at ucar.edu> wrote:
>>>
>>>> Jenny,
>>>>
>>>> In order to do plot overlays of different variables, you need to use
>>>> the "overlay" procedure in NCL.
>>>>
>>>> ----------------------------------------------------------------
>>>>
>>>> The overlay procedure works one of two ways:
>>>>
>>>> [1] It overlays data from one plot (called the "overlay" plot) into the
>>>> data space of another plot (called the "base" plot).
>>>>
>>>> The two plots must have intersecting data spaces for this to work. By
>>>> "data space", I mean the range of the X and Y axes of the two plots must
>>>> intersect. Otherwise, you will not see the overlay plot at all.
>>>>
>>>> For an example, see overlay_8.ncl at:
>>>>
>>>> http://www.ncl.ucar.edu/Applications/overlay.shtml#ex8
>>>>
>>>> [2] It simply "lines up" the two plots in the same rectangular region
>>>> and draws them. It's not as common to do overlays this way, because it
>>>> requires that you do all the work of making sure the two plots are in the
>>>> same data space.
>>>>
>>>> For an example, see overlay_9.ncl at:
>>>>
>>>> http://www.ncl.ucar.edu/Applications/overlay.shtml#ex9
>>>>
>>>> ----------------------------------------------------------------
>>>>
>>>> It doesn't matter whether you are doing contour plots, vector plots, or
>>>> XY plots: you can overlay any of these on another one using the "overlay"
>>>> procedure.
>>>>
>>>> The "overlay" examples page has several other scripts showing how to
>>>> use the overlay procedure. In particular, you might want to look at
>>>> overlay_1.ncl, overlay_6.ncl, and/or wrf_gsn_5.ncl:
>>>>
>>>> http://www.ncl.ucar.edu/Applications/overlay.shtml
>>>>
>>>> If you continue to have problems, please post back to ncl-talk and
>>>> include your script and a "printVarSummary" of the data you are trying to
>>>> plot.
>>>>
>>>> Thanks,
>>>>
>>>> --Mary
>>>>
>>>>
>>>> On Fri, Feb 16, 2018 at 9:59 AM, Jenny Taylor <
>>>> jenny63taylor91 at gmail.com> wrote:
>>>>
>>>>> Dear NCL Users,
>>>>>
>>>>> I am trying to plot vector wind field at different pressure level for
>>>>> latitute range 40N-40S. I am following the below mention script;
>>>>> https://www.ncl.ucar.edu/Applications/Scripts/h_lat_7.ncl
>>>>>
>>>>> I am trying to overlay vertical motion (rising/sinking) in vector
>>>>> arrows and zonal wind in color scheme.
>>>>>
>>>>> Can anyone suggest me, in that case which funtion I need to use in it?
>>>>> Any help will be appriciated.
>>>>>
>>>>> Thanks,
>>>>> Jenny
>>>>>
>>>>> _______________________________________________
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>>>>> ncl-talk at ucar.edu
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>>>>>
>>>>>
>>>>
>>>
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>>
>>
>> --
>> Associate Scientist,  Climate and Global Dynamics Laboratory, NCAR
>> www.cgd.ucar.edu/staff/asphilli/   303-497-1726 <(303)%20497-1726>
>>
>> <http://www.cgd.ucar.edu/staff/asphilli>
>>
>
>
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--
Barry H. Lynn, Ph.D
Senior Lecturer,
The Institute of the Earth Science,
The Hebrew University of Jerusalem,
Givat Ram, Jerusalem 91904, Israel
Tel: 972 547 231 170
Fax: (972)-25662581

C.E.O, Weather It Is, LTD
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