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[IDV #ZRG-103304]: Converting between knots and m/s with flow vectors

> > > Hi Yuan,
> > > The barbs indicate winds twice stronger than the data shows.
> > > If you look at the location of the cross, it reads 21.7 and 9.6 knots. 
> > > This translates well to the contours in the background (12.2 m/sec).
> > >
> > > But, the barb shows 45 knots, as if IDV calculated the speed in knots 
> > > (~23.7) and converted again to knots, giving ~46.
> > >
> > > I am using IDV2.9 on WinXP.
> > >
> > > Thanks,
> > >
> > > Ilan
> >
> > Hi Ilan,
> > I think you are right, the u component is no larger than 26.4 knot, and v 
> > is no larger than 15.2, the IDV should not display anything larger 30 in 
> > the wind barb. I will check to see what is wrong.
> >
> >
> 
> Hi Ilan,
> There is some difference between "Make flow vectors from grid relative u and 
> v data" and "Make flow vectors from u and v data", I believe you were using 
> the later one, if you choose the other one, it should get the correct result.
> 

Hi Ilan,
     I have checked your data, it contains "True wind ..." in both x and y, so 
you should use the "Make flow vectors from grid relative u and v data", which 
calculate the True Wind vector, the other one may have a bug when the 
projection is not lat/lon base.


Yuan
> 
> Yuan
> >
> > Yuan
> > >
> > >
> > >
> > > 9.
> > >
> > > -----Original Message-----
> > > From: Unidata IDV Support [mailto:address@hidden]
> > > Sent: August 16, 2010 2:02 PM
> > > To: Sills,David [Ontario]
> > > Cc: Levy,Ilan [Ontario]; Sills,David [Ontario]; address@hidden
> > > Subject: [IDV #ZRG-103304]: Converting between knots and m/s with flow 
> > > vectors
> > >
> > > > Hello Julien,
> > > > Attached are two small sample files.
> > > >
> > > > Ilan Levy
> > > >
> > >
> > > Hi Ilan,
> > > I don't know which version of the IDV you are running, I am running the 
> > > IDV2.9 on your data, the result looks correct to me, the highest wind is 
> > > about 50 knot in my display, and compared to the u and v data, it is 
> > > right. see the attached image.
> > >
> > >
> > > Yuan
> > > > -----Original Message-----
> > > > From: Sills,David [Ontario]
> > > > Sent: August 13, 2010 4:50 PM
> > > > To: Levy,Ilan [Ontario]
> > > > Subject: FW: [IDV #ZRG-103304]: Converting between knots and m/s with
> > > > flow vectors
> > > >
> > > > Hi Ilan,
> > > >
> > > > The data files are far too large to send to him. Would it be possible 
> > > > to generate a file that had just one time and one level?
> > > >
> > > > I'm on vacation starting tomorrow, so if you could send along to him 
> > > > I'd appreciate it.
> > > >
> > > > Thanks,
> > > >
> > > > Dave
> > > > ______________________________________
> > > > David Sills, Ph.D.
> > > > Severe Weather Scientist | Scientifique du temps rigoureux Cloud
> > > > Physics and Severe Weather Research Section | Section de la recherché
> > > > sur la physique des nuages et du temps violent National Laboratory for
> > > > Nowcasting and Remote Sensing Meteorology | Laboratoire national de
> > > > prévision immédiate et de météorologie par télédétection Environment
> > > > Canada | Environnement Canada
> > > > 4905 Dufferin Street | 4905, rue Dufferin Toronto (Ontario) M3H 5T4
> > > > address@hidden
> > > > 905-833-3905 x235 Telephone | Téléphone
> > > > 905-833-0398 Facsimile | Télécopieur
> > > > Government of Canada | Gouvernement du Canada Website | Site web
> > > >
> > > > -----Original Message-----
> > > > From: Unidata IDV Support [mailto:address@hidden]
> > > > Sent: Friday, August 13, 2010 4:47 PM
> > > > To: Sills,David [Ontario]
> > > > Cc: address@hidden
> > > > Subject: [IDV #ZRG-103304]: Converting between knots and m/s with flow
> > > > vectors
> > > >
> > > > Hi, David
> > > >
> > > > Would it be possible to send (attach) one of the data files in question?
> > > >
> > > > Thanks,
> > > >
> > > > -Julien
> > > >
> > > > > Hello,
> > > > >
> > > > > I have data files with wind in knots. When I plot them as wind
> > > > > barbs, it appears as though IDV treats the data as m/s, and then
> > > > > does a conversion to knots. This results in the winds being much
> > > > > higher in the plot than they should be.
> > > > >
> > > > > What is the best way to get around this problem?
> > > > >
> > > > > Many thanks,
> > > > >
> > > > > Dave
> > > > > ______________________________________
> > > > > David Sills, Ph.D.
> > > > > Severe Weather Scientist | Scientifique du temps rigoureux Cloud
> > > > > Physics and Severe Weather Research Section | Section de la
> > > > > recherché sur la physique des nuages et du temps violent National
> > > > > Laboratory for Nowcasting and Remote Sensing Meteorology |
> > > > > Laboratoire national de prévision immédiate et de météorologie par
> > > > > télédétection Environment Canada | Environnement Canada
> > > > > 4905 Dufferin Street | 4905, rue Dufferin Toronto (Ontario) M3H 5T4
> > > > > address@hidden
> > > > > 905-833-3905 x235 Telephone | Téléphone
> > > > > 905-833-0398 Facsimile | Télécopieur Government of Canada |
> > > > > Gouvernement du Canada Website
> > > > > <http://www.ec.gc.ca/scitech/default.asp?lang=En&n=F97AE834-1&xsl=sc
> > > > > it echprofile,form&formid=A9E422E3-F382-4017-A64E-E58E6BC14CC9>  |
> > > > > Site web
> > > > > <http://www.ec.gc.ca/scitech/default.asp?lang=Fr&n=F97AE834-1&xsl=sc
> > > > > it echprofile,form&formid=A9E422E3-F382-4017-A64E-E58E6BC14CC9>
> > > >
> > > >
> > > > Ticket Details
> > > > ===================
> > > > Ticket ID: ZRG-103304
> > > > Department: Support IDV
> > > > Priority: Normal
> > > > Status: Open
> > > >
> > > >
> > > >
> > >
> > >
> > > Ticket Details
> > > ===================
> > > Ticket ID: ZRG-103304
> > > Department: Support IDV
> > > Priority: Normal
> > > Status: Closed
> > >
> > >
> > >
> > >
> >
> 


Ticket Details
===================
Ticket ID: ZRG-103304
Department: Support IDV
Priority: Normal
Status: Closed