Re: ncl-talk Digest, Vol 119, Issue 15

From: Tiffani Drew <tiffani_drew_at_nyahnyahspammersnyahnyah>
Date: Sun Oct 13 2013 - 06:52:59 MDT

I have a spinning disk 1 meter in radius and I want to calculate the difference in the speed between innermost point and the outermost point. I know that the centre of the disk spins fast and as you move out you spin slower, what is the formula for that? ________________________________ From: "ncl-talk-request_at_ucar.edu" <ncl-talk-request_at_ucar.edu> To: ncl-talk_at_ucar.edu Sent: Saturday, 12 October 2013 11:00 AM Subject: ncl-talk Digest, Vol 119, Issue 15 Send ncl-talk mailing list submissions to     ncl-talk_at_ucar.edu To subscribe or unsubscribe via the World Wide Web, visit     http://mailman.ucar.edu/mailman/listinfo/ncl-talk or, via email, send a message with subject or body 'help' to     ncl-talk-request_at_ucar.edu You can reach the person managing the list at     ncl-talk-owner_at_ucar.edu When replying, please edit your Subject line so it is more specific than "Re: Contents of ncl-talk digest..." Today's Topics:   1. Re: area_global_rectilinear_grid (Dennis Shea) ---------------------------------------------------------------------- Message: 1 Date: Fri, 11 Oct 2013 13:13:32 -0600 From: Dennis Shea <shea_at_ucar.edu> Subject: Re: area_global_rectilinear_grid To: Soumik Basu <sbasu_at_iarc.uaf.edu> Cc: "ncl-talk_at_ucar.edu" <ncl-talk_at_ucar.edu> Message-ID: <52584DDC.4070102_at_ucar.edu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Actually, there is an undocumented function in shea_util.ncl ;------------------------------- undef("area_polar_region") function area_polar_region (lat[1]:numeric, opt[1]:logical) ; Area from pole to latitude. local rearth, pi, rad, rr, twopi, parea begin   rearth = 6371.220d0            ; default; kilometers   if (opt .and. isatt(opt, "rearth")) then       rearth = opt_at_rearth   end if   pi    = 4d0*atan(1.0d0)   rad    = pi/180d0   twopi  = 2.0d0*pi   parea  = twopi*rearth*rearth*(1.0d0-sin(rad*lat))   parea_at_long_name = "Polar Area"   parea_at_units    = "km^2"   return(parea) end On 10/8/13 5:49 AM, Dennis Shea wrote: > This is *NOT* correct. Not sure what I was thinking. > > Sorry > D > > On 10/7/13 11:47 AM, Dennis Shea wrote: >> As noted the function is an approximation. >> >> The surface area of a sphere is >> >>    A = 4*pi*R^2    ; area of sphere; R is radius of earth >> >> Area of a hemisphere: >> >>    diff = 90-0.0 >>    Ahem = A*(diff/180.0) = A*0.5 >> >> Area of the 'cap' >> >>    diff = 90-88.92773 >>    A889 = A*(diff/180.0) >> >> On 10/2/13 7:37 PM, Soumik Basu wrote: >>> Hi, >>> >>> I am trying to calculate the sea ice extent from sea ice fraction data >>> for CAM3.1 in T85 grid. >>> I used the area_global_rectilinear_grid function to calculate the area >>> of each of the grid box. But I am trying to estimate the area over the >>> pole as the latitudes ends at 88.92773. For doing that I tried >>> calculating in the following way. But what confused me is that why the >>> sum of the grid areas calculated using the function is greater than the >>> surface area of the earth. Is there any better way to estimate the area >>> of the small circle over the pole? >>> >>> >>> ;**************************************************** >>> ; Calculate area at each grid point >>> ;**************************************************** >>> ; T85 >>> >>> nlat = 128 >>> lat  = latGau(nlat, "lat", "latitude", "degrees_north") >>> mlon = 256 >>> lon  = lonGlobeF(mlon, "lon", "longitude", "degrees_east") >>> print(lat) >>> area = area_global_rectilinear_grid (lat, lon, False) >>> >>> areaa = dble2flt(area) >>> >>> printVarSummary(areaa) >>> printMinMax(areaa, True) >>> >>> R = 6371.220 ; in km >>> >>> pi = 4d0*atan(1d0) >>> >>> S_Area = 4d0*pi*R^2  ;Total surface area of the earth >>> >>> print(S_Area) >>> >>> Area_total = sum(areaa) ; Total area from the grid boxes >>> >>> print(Area_total) >>> >>> Pole_area = (S_Area - Area_total)/(10^6)*2  ; Area over the pole in 10^6 >>> sq km >>> >>> print(Pole_area) >>> >>> Here are the printVarSummary results: >>> >>> Variable: areaa >>> Type: float >>> Total Size: 131072 bytes >>> 32768 values >>> Number of Dimensions: 2 >>> Dimensions and sizes:    [lat | 128] x [lon | 256] >>> Coordinates: >>> lat: [-88.92773..88.92773] >>> lon: [ 0..358.5938] >>> Number Of Attributes: 8 >>> long_name :    area of each grid cell >>> units :    km^2 >>> area_total :    5.101007e+08 >>> area_lat :    <ARRAY of 128 elements> >>> rearth :    6371.22 >>> area_sphere :    5.100997e+08 >>> area_ratio :    1.000002 >>> typeConversion_op_ncl :    double converted to float >>> (0) >>> (0)    area of each grid cell: min=451.99  max=24355.4 >>> >>> >>> Variable: S_Area >>> Type: double >>> Total Size: 8 bytes >>> 1 values >>> Number of Dimensions: 1 >>> Dimensions and sizes:    [1] >>> Coordinates: >>> (0)    510099745.7121028 >>> >>> >>> Variable: Area_total >>> Type: float >>> Total Size: 4 bytes >>> 1 values >>> Number of Dimensions: 1 >>> Dimensions and sizes:    [1] >>> Coordinates: >>> (0)    5.101245e+08 >>> >>> >>> Variable: Pole_area >>> Type: double >>> Total Size: 8 bytes >>> 1 values >>> Number of Dimensions: 1 >>> Dimensions and sizes:    [1] >>> Coordinates: >>> (0)    -0.04953257579445839 >>> >>> >>> Thanks, >>> Soumik >>> ------------------------------ _______________________________________________ ncl-talk mailing list ncl-talk_at_ucar.edu http://mailman.ucar.edu/mailman/listinfo/ncl-talk End of ncl-talk Digest, Vol 119, Issue 15 *****************************************

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Received on Sun Oct 13 06:53:13 2013

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