[92fab65] | 1 | ! SPDX-FileCopyrightText: FLEXPART 1998-2019, see flexpart_license.txt |
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| 2 | ! SPDX-License-Identifier: GPL-3.0-or-later |
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[332fbbd] | 3 | |
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[e200b7a] | 4 | subroutine centerofmass(xl,yl,n,xcenter,ycenter) |
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| 5 | ! i i i o o |
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| 6 | !***************************************************************************** |
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| 7 | ! * |
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| 8 | ! This routine calculates the center of mass of n points on the Earth. * |
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| 9 | ! Input are the longitudes (xl) and latitudes (yl) of the individual * |
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| 10 | ! points, output is the longitude and latitude of the centre of mass. * |
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| 11 | ! * |
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| 12 | ! Author: A. Stohl * |
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| 13 | ! * |
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| 14 | ! 24 January 2002 * |
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| 15 | ! * |
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| 16 | !***************************************************************************** |
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| 17 | |
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| 18 | use par_mod |
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| 19 | |
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| 20 | implicit none |
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| 21 | |
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| 22 | integer :: n,l |
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| 23 | real :: xl(n),yl(n),xll,yll,xav,yav,zav,x,y,z,xcenter,ycenter |
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| 24 | |
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| 25 | |
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| 26 | xav=0. |
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| 27 | yav=0. |
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| 28 | zav=0. |
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| 29 | |
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| 30 | do l=1,n |
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| 31 | |
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| 32 | ! Convert longitude and latitude from degrees to radians |
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| 33 | !******************************************************* |
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| 34 | |
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| 35 | xll=xl(l)*pi180 |
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| 36 | yll=yl(l)*pi180 |
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| 37 | |
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| 38 | ! Calculate 3D coordinates from longitude and latitude |
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| 39 | !***************************************************** |
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| 40 | |
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| 41 | x = cos(yll)*sin(xll) |
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| 42 | y = -1.*cos(yll)*cos(xll) |
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| 43 | z = sin(yll) |
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| 44 | |
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| 45 | |
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| 46 | ! Find the mean location in Cartesian coordinates |
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| 47 | !************************************************ |
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| 48 | |
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| 49 | xav=xav+x |
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| 50 | yav=yav+y |
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| 51 | zav=zav+z |
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| 52 | end do |
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| 53 | |
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| 54 | xav=xav/real(n) |
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| 55 | yav=yav/real(n) |
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| 56 | zav=zav/real(n) |
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| 57 | |
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| 58 | |
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| 59 | ! Project the point back onto Earth's surface |
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| 60 | !******************************************** |
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| 61 | |
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| 62 | xcenter=atan2(xav,-1.*yav) |
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| 63 | ycenter=atan2(zav,sqrt(xav*xav+yav*yav)) |
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| 64 | |
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| 65 | ! Convert back to degrees |
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| 66 | !************************ |
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| 67 | |
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| 68 | xcenter=xcenter/pi180 |
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| 69 | ycenter=ycenter/pi180 |
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| 70 | |
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| 71 | end subroutine centerofmass |
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