1 | subroutine hanna_short(z) |
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2 | ! i |
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3 | !***************************************************************************** |
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4 | ! * |
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5 | ! Computation of \sigma_i and \tau_L based on the scheme of Hanna (1982) * |
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6 | ! * |
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7 | ! Author: A. Stohl * |
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8 | ! * |
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9 | ! 4 December 1997 * |
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10 | ! * |
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11 | !***************************************************************************** |
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12 | ! * |
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13 | ! Variables: * |
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14 | ! dsigwdz [1/s] vertical gradient of sigw * |
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15 | ! ol [m] Obukhov length * |
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16 | ! sigu, sigv, sigw standard deviations of turbulent velocity fluctuations * |
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17 | ! tlu [s] Lagrangian time scale for the along wind component. * |
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18 | ! tlv [s] Lagrangian time scale for the cross wind component. * |
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19 | ! tlw [s] Lagrangian time scale for the vertical wind component. * |
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20 | ! ust, ustar [m/s] friction velocity * |
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21 | ! wst, wstar [m/s] convective velocity scale * |
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22 | ! * |
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23 | !***************************************************************************** |
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24 | |
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25 | use par_mod |
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26 | use com_mod |
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27 | use hanna_mod |
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28 | |
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29 | implicit none |
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30 | |
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31 | real :: z |
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32 | |
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33 | |
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34 | |
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35 | !********************** |
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36 | ! 1. Neutral conditions |
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37 | !********************** |
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38 | |
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39 | if (h/abs(ol).lt.1.) then |
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40 | ust=max(1.e-4,ust) |
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41 | sigw=1.3*exp(-2.e-4*z/ust) |
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42 | dsigwdz=-2.e-4*sigw |
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43 | sigw=sigw*ust+1.e-2 |
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44 | tlw=0.5*z/sigw/(1.+1.5e-3*z/ust) |
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45 | |
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46 | |
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47 | !*********************** |
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48 | ! 2. Unstable conditions |
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49 | !*********************** |
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50 | |
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51 | else if (ol.lt.0.) then |
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52 | |
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53 | |
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54 | ! Determine sigmas |
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55 | !***************** |
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56 | |
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57 | sigw=sqrt(1.2*wst**2*(1.-.9*zeta)*zeta**0.66666+ & |
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58 | (1.8-1.4*zeta)*ust**2)+1.e-2 |
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59 | dsigwdz=0.5/sigw/h*(-1.4*ust**2+wst**2* & |
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60 | (0.8*max(zeta,1.e-3)**(-.33333)-1.8*zeta**0.66666)) |
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61 | |
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62 | |
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63 | ! Determine average Lagrangian time scale |
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64 | !**************************************** |
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65 | |
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66 | if (z.lt.abs(ol)) then |
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67 | tlw=0.1*z/(sigw*(0.55-0.38*abs(z/ol))) |
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68 | else if (zeta.lt.0.1) then |
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69 | tlw=0.59*z/sigw |
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70 | else |
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71 | tlw=0.15*h/sigw*(1.-exp(-5*zeta)) |
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72 | endif |
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73 | |
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74 | |
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75 | !********************* |
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76 | ! 3. Stable conditions |
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77 | !********************* |
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78 | |
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79 | else |
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80 | sigw=1.e-2+1.3*ust*(1.-zeta) |
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81 | dsigwdz=-1.3*ust/h |
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82 | tlw=0.1*h/sigw*zeta**0.8 |
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83 | endif |
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84 | |
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85 | |
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86 | tlu=max(10.,tlu) |
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87 | tlv=max(10.,tlv) |
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88 | tlw=max(30.,tlw) |
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89 | if (dsigwdz.eq.0.) dsigwdz=1.e-10 |
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90 | |
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91 | end subroutine hanna_short |
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