| 1 | !*********************************************************************** |
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| 2 | subroutine neutral(u10_mps,ustar_mps,obklen_m, & |
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| 3 | u10n_mps ) |
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| 4 | !----------------------------------------------------------------------- |
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| 5 | ! subroutine to compute u10 neutral wind speed |
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| 6 | ! inputs |
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| 7 | ! u10_mps - wind speed at 10 m (m/s) |
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| 8 | ! ustar_mps - friction velocity (m/s) |
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| 9 | ! obklen_m - monin-obukhov length scale (m) |
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| 10 | ! outputs |
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| 11 | ! u10n_mps - wind speed at 10 m under neutral conditions (m/s) |
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| 12 | ! following code assumes reference height Z is 10m, consistent with use |
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| 13 | ! of u10 and u10_neutral. If not, code |
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| 14 | ! should be changed so that constants of 50. and 160. in equations |
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| 15 | ! below are changed to -5 * Z and -16 * Z respectively. |
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| 16 | ! Reference: G. L. Geernaert. 'Bulk parameterizations for the |
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| 17 | ! wind stress and heat fluxes,' in Surface Waves and Fluxes, Vol. I, |
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| 18 | ! Current Theory, Geernaert and W.J. Plant, editors, Kluwer Academic |
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| 19 | ! Publishers, Boston, MA, 1990. |
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| 20 | ! subroutine written Feb 2001 by eg chapman |
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| 21 | ! adapted to LMD-ZT by E. Cosme 310801 |
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| 22 | ! Following Will Shaw (PNL, Seattle) the theory applied for flux |
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| 23 | ! calculation with the scheme of Nightingale et al. (2000) does not |
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| 24 | ! hold anymore when -1<obklen<20. In this case, u10n is set to 0, |
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| 25 | ! so that the transfer velocity computed in nightingale.F will also |
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| 26 | ! be 0. The flux is then set to 0. |
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| 27 | !---------------------------------------------------------------------- |
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| 28 | ! |
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| 29 | USE dimphy |
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| 30 | ! |
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| 31 | real :: u10_mps(klon),ustar_mps(klon),obklen_m(klon) |
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| 32 | real :: u10n_mps(klon) |
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| 33 | real :: pi,von_karman |
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| 34 | ! parameter (pi = 3.141592653589793, von_karman = 0.4) |
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| 35 | ! pour etre coherent avec vk de bl_for_dms.F |
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| 36 | parameter (pi = 3.141592653589793, von_karman = 0.35) |
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| 37 | ! |
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| 38 | real :: phi, phi_inv, phi_inv_sq, f1, f2, f3, dum1, psi |
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| 39 | integer :: i |
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| 40 | |
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| 41 | |
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| 42 | psi = 0. |
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| 43 | do i=1,klon |
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| 44 | |
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| 45 | if (u10_mps(i) .lt. 0.) u10_mps(i) = 0.0 |
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| 46 | |
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| 47 | if (obklen_m(i) .lt. 0.) then |
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| 48 | phi = (1. - 160./obklen_m(i))**(-0.25) |
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| 49 | phi_inv = 1./phi |
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| 50 | phi_inv_sq = 1./phi * 1./phi |
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| 51 | f1 = (1. + phi_inv) / 2. |
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| 52 | f2 = (1. + phi_inv_sq)/2. |
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| 53 | ! following to avoid numerical overruns. recall tan(90deg)=infinity |
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| 54 | dum1 = min (1.e24, phi_inv) |
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| 55 | f3 = atan(dum1) |
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| 56 | psi = 2.*log(f1) + log(f2) - 2.*f3 + pi/2. |
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| 57 | else if (obklen_m(i) .gt. 0.) then |
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| 58 | psi = -50. / obklen_m(i) |
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| 59 | end if |
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| 60 | |
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| 61 | u10n_mps(i) = u10_mps(i) + (ustar_mps(i) * psi /von_karman ) |
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| 62 | ! u10n set to 0. if -1 < obklen < 20 |
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| 63 | if ((obklen_m(i).gt.-1.).and.(obklen_m(i).lt.20.)) then |
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| 64 | u10n_mps(i) = 0. |
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| 65 | endif |
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| 66 | if (u10n_mps(i) .lt. 0.) u10n_mps(i) = 0.0 |
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| 67 | |
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| 68 | enddo |
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| 69 | return |
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| 70 | end subroutine neutral |
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| 71 | !*********************************************************************** |
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