# [ncl-talk] Vertical motion with zonal wind

Dennis Shea shea at ucar.edu
Mon Feb 26 15:16:38 MST 2018

```Hybrid levels are a form of terrain following vertical coordinate
formulation.
Unlike isobaric levels where the vertical levels are the same at every grid
point,
hybrid levels differ at each grid point *(j,i) *because they are a function
of surface pressure
which varies with time and location. The climate atmospheric model uses the
following
formulation:

* p([t,] k,j,i) = a(k)*p0 + b(k)*ps([t,] k,j,i)        *; t=>time,
k=>level, j=>latitude; i=longitude

Each calculated pressure level is called the '*m*id-level' (hya*m* and hyb
*m*).  Each
'*m*id-level' has an upper and lower boundary called the* i*nterface levels
(hya*i*, hyb*i*).

http://www.ncl.ucar.edu/Document/Functions/Built-in/pres_hybrid_ccm.shtml

There are other hybrid level formulations so be aware of what is being used.

A detailed description with some pictures is here:

https://rda.ucar.edu/datasets/ds627.0/docs/Eta_coordinate/index.html

====
You should talk with an advisor about these topics. ncl-talk is really for
language issues.

Good luck

On Mon, Feb 26, 2018 at 2:23 PM, Adam Phillips <asphilli at ucar.edu> wrote:

> Hi Jenny,
> With regards to whether the plot looks correct: It looks like you took
> NCL's vector_5 example script, and modified it slightly.  That script uses
> the atmos.nc NetCDF file, which according to the global history attribute
> is an old NCAR-CSM file. The data may be October averages. You're selecting
> 20E as the longitude to plot, but are basing your weights on 160E. All that
> being said, it is honestly up to you to investigate the file you are
> reading in, and to interpret the results. I am not an expert at looking at
> this kind of diagnostic.
>
> With regards to your question about hyam and hybm, that information is
> given within the NetCDF file, which you can see by doing a ncdump atmos.nc.
> More information on hyam/hybm can be found by entering either term within
> the NCL website search engine.
>
> If you have any further questions please respond to the ncl-talk email
> list.
>
> On Mon, Feb 26, 2018 at 4:33 AM, Jenny Taylor <jenny63taylor91 at gmail.com>
> wrote:
>
>> Hello,
>>
>> I am sending you the script based on which it is made. Kindly find the
>> script attached below. I have one question on this matter. In the dataset (
>> atmos.nc) what are those variables named as 'hyam' and 'hybm'?
>> It is showing as 'hybrid A coefficient at layer midpoints' and 'hybrid B
>> coefficient at layer midpoints'.
>>
>> Kindly also inform me what I am doing wrong as per your observation over
>> NH.
>>
>> Thanks,
>> Jenny
>>
>>
>> On Mon, Feb 26, 2018 at 12:16 PM, Barry Lynn <barry.h.lynn at gmail.com>
>> wrote:
>>
>>> 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:
>>>
>>>> look 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/omeg
>>>>> a_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
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> ncl-talk mailing list
>>>>>>>> ncl-talk at ucar.edu
>>>>>>>> List instructions, subscriber options, unsubscribe:
>>>>>>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
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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
>>> Weather and Climate Focus
>>> http://weather-it-is.com
>>> Jerusalem, Israel
>>> Local: 02 930 9525
>>> Cell: 054 7 231 170
>>> Int-IS: x972 2 930 9525
>>> US 914 432 3108 <(914)%20432-3108>
>>>
>>
>>
>
>
> --
> 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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