1 | !********************************************************************** |
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2 | ! Copyright 1998,1999,2000,2001,2002,2005,2007,2008,2009,2010 * |
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3 | ! Andreas Stohl, Petra Seibert, A. Frank, Gerhard Wotawa, * |
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4 | ! Caroline Forster, Sabine Eckhardt, John Burkhart, Harald Sodemann * |
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5 | ! * |
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6 | ! This file is part of FLEXPART. * |
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7 | ! * |
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8 | ! FLEXPART is free software: you can redistribute it and/or modify * |
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9 | ! it under the terms of the GNU General Public License as published by* |
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10 | ! the Free Software Foundation, either version 3 of the License, or * |
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11 | ! (at your option) any later version. * |
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12 | ! * |
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13 | ! FLEXPART is distributed in the hope that it will be useful, * |
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14 | ! but WITHOUT ANY WARRANTY; without even the implied warranty of * |
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15 | ! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * |
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16 | ! GNU General Public License for more details. * |
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17 | ! * |
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18 | ! You should have received a copy of the GNU General Public License * |
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19 | ! along with FLEXPART. If not, see <http://www.gnu.org/licenses/>. * |
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20 | !********************************************************************** |
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21 | |
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22 | subroutine centerofmass(xl,yl,n,xcenter,ycenter) |
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23 | ! i i i o o |
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24 | !***************************************************************************** |
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25 | ! * |
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26 | ! This routine calculates the center of mass of n points on the Earth. * |
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27 | ! Input are the longitudes (xl) and latitudes (yl) of the individual * |
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28 | ! points, output is the longitude and latitude of the centre of mass. * |
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29 | ! * |
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30 | ! Author: A. Stohl * |
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31 | ! * |
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32 | ! 24 January 2002 * |
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33 | ! * |
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34 | !***************************************************************************** |
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35 | |
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36 | use par_mod |
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37 | |
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38 | implicit none |
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39 | |
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40 | integer :: n,l |
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41 | real :: xl(n),yl(n),xll,yll,xav,yav,zav,x,y,z,xcenter,ycenter |
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42 | |
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43 | |
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44 | xav=0. |
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45 | yav=0. |
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46 | zav=0. |
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47 | |
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48 | do l=1,n |
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49 | |
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50 | ! Convert longitude and latitude from degrees to radians |
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51 | !******************************************************* |
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52 | |
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53 | xll=xl(l)*pi180 |
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54 | yll=yl(l)*pi180 |
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55 | |
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56 | ! Calculate 3D coordinates from longitude and latitude |
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57 | !***************************************************** |
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58 | |
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59 | x = cos(yll)*sin(xll) |
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60 | y = -1.*cos(yll)*cos(xll) |
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61 | z = sin(yll) |
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62 | |
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63 | |
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64 | ! Find the mean location in Cartesian coordinates |
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65 | !************************************************ |
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66 | |
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67 | xav=xav+x |
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68 | yav=yav+y |
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69 | zav=zav+z |
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70 | end do |
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71 | |
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72 | xav=xav/real(n) |
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73 | yav=yav/real(n) |
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74 | zav=zav/real(n) |
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75 | |
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76 | |
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77 | ! Project the point back onto Earth's surface |
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78 | !******************************************** |
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79 | |
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80 | xcenter=atan2(xav,-1.*yav) |
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81 | ycenter=atan2(zav,sqrt(xav*xav+yav*yav)) |
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82 | |
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83 | ! Convert back to degrees |
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84 | !************************ |
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85 | |
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86 | xcenter=xcenter/pi180 |
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87 | ycenter=ycenter/pi180 |
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88 | |
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89 | end subroutine centerofmass |
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