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Paul, I was refering to you title: >> >PRESS WDIR WSPD UWND VWND >> > MB DEG KNTS KNTS KNTS In particular, if you are plotting UWND and VWND in GEMPAK, then the units are m/s not knts as you have labled. If you want to use knts in GEMPAK, then use UKNT and VKNT. I was assuming you were refering to data as listed by GEMPAK, though you did not refer to using GEMPAK. Since the 4 characater parameter names are simmilar to GEMPAK, but certainly not "PRESS"- I believed you were refering to snlist with some cooked up column lables from your own since that listing you provided is definitely not GEMPAK. Otherwise, I have no idea what you mean in your response below. Steve Chiswell Unidata User Support >From: Paul Ruscher <address@hidden> >Organization: . >Keywords: 200001182100.OAA16583 >Thanks, doh! My bad - I think he got this example from Albany - in any >case, it is round off error, of course! My site includes data to two >digits and does not have this problem. 1 digit rounding for both u and v >can lead to +/1 5% error or so, which is enough to explain his >problem. I'll write him again! > >Paul > >On Tue, 18 Jan 2000, Unidata Support wrote: > >> >> Paul, >> >> UWND/VWND is meters per second. UKNT/VKNT are knots. If you want units >> in knots, you need to use the appropriate parameter. >> >> The units column label is not from GEMPAK, but apparently something you >> have tacked on. You need to maintain that label to be consistent >> with the parameter usage above. >> >> Steve Chiswell >> Unidata User Support >> >> >> >> >From: Paul Ruscher <address@hidden> >> >Organization: . >> >Keywords: 200001181842.LAA08774 >> >> >Gempak decoding problem here, perhaps? I've checked and I think Chris is >> >correct - happens in other soundings, too. Paul Ruscher >> > >> >---------- Forwarded message ---------- >> >Date: Tue, 18 Jan 2000 15:10:32 +0000 (GMT) >> >From: Chris Walcek <address@hidden> >> >To: address@hidden, address@hidden >> >Subject: unit errors in decoded sounding data >> > >> >To whom it may concern, >> > >> >I regularly download and use decoded soundings >> >from your web pages. There is an error in the >> >units of the wind speeds presented in these tabulated >> >data. For example, here is a excerp of Tuscon AZ >> >0Z sounding, 18 January 2000 >> > >> >PRESS WDIR WSPD UWND VWND >> > MB DEG KNTS KNTS KNTS >> >----- ----- ---- ----- ----- >> >929.0 310.0 4.0 1.6 -1.3 >> >925.0 310.0 4.0 1.6 -1.3 >> > >> > >> >First, wind directions and speeds are presented >> >in degrees and "KNTS". Speed I assume is in >> >nautical miles per hour. >> > >> >Later, U(west-east) and V(south-north) winds >> >are tabulated, also in units of KNTS. However, >> >when I take the square root of the sum of >> >the squares of U and V (sqrt(U^2 + V^2) one >> >does not get the original wind speed. In fact >> >there is a discrepancy of a factor of 1.94 which >> >is precisely the conversion of nautical miles per >> >hour to meters per second. >> > >> >It looks like the units of U and V are WRONG and >> >should be in meters per second (m/s)???? >> > >> >Is this correct? If so please change the table >> >headings appropriately. Other explanations >> >of this discrepancy are possible. >> > >> >Thanks >> >Chris Walcek >> > >> >(beware the Mars pathfinder fiasco where >> >sloppy unit conversions were responsbile for >> >disaster!!) >> > >> > >> >> **************************************************************************** >> Unidata User Support UCAR Unidata Program >> (303)497-8644 P.O. Box 3000 >> address@hidden Boulder, CO 80307 >> ---------------------------------------------------------------------------- >> Unidata WWW Service http://www.unidata.ucar.edu/ >> **************************************************************************** >> >