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0002 <TITLE>module diffusivity</TITLE>
0003 <BODY BGCOLOR="#AABBCC" TEXT="#332211" >
0004
0005 <DIV ALIGN="CENTER"> <FONT SIZE=1>
0006 <A HREF="#INTERFACE">PUBLIC INTERFACE</A> /
0007 <A HREF="#ROUTINES">ROUTINES</A> /
0008 <A HREF="#NAMELIST">NAMELIST</A> /
0009 <A HREF="#CHANGES">CHANGES</A> /
0010 <A HREF="#ERRORS">ERRORS</A> /
0011 <A HREF="#REFERENCES">REFERENCES</A> /
0012 <A HREF="#NOTES">NOTES</A>
0013 </FONT>
0014 <BR><BR></DIV><HR>
0015
0016
0017 <H2>Module diffusivity_mod</H2>
0018 <A NAME="HEADER">
0019 <PRE>
0020 <B>Contact:</B> Steve Klein and Isaac Held
0021 <B>Reviewers:</B>
0022
0023 <B><A HREF=".doc.log#diffusivity.f90">Tags/Status</A></B>
0024 </PRE>
0025 </A>
0026
0027 <A NAME="OVERVIEW">
0028 <HR>
0029 <H4>OVERVIEW</H4>
0030
0031 <PRE>
0032
0033 This routine computes the atmospheric vertical diffusivity
0034 coefficients of momentum and temperature plus tracers at all
0035 half-levels interior to the atmosphere.
0036
0037 </PRE>
0038 </A>
0039
0040 <A NAME="DESCRIPTION">
0041
0042 <PRE>
0043
0044 The vertical diffusivity coefficients are calculated separately
0045 for the planetary boundary layer (PBL) and the free atmosphere.
0046 Note that the diffusivity coefficient for temperature is the same
0047 as that for all tracers.
0048
0049 In the PBL, the default prescription of diffusivities is the
0050 K-profile boundary layer scheme. A second method is to do the
0051 Old Climate Model's version. In the free atmosphere there
0052 there are two options, one of which duplicates that used in
0053 the old Skyhii model.
0054
0055 A full description can be found <A HREF="diffusivity.tech.ps">here</A>.
0056
0057 </PRE>
0058 </A><!-- END DESCRIPTION -->
0059 <!--------------------------------------------------------------------->
0060 <A NAME="MODULES_USED">
0061 <HR>
0062 <H4>OTHER MODULES USED</H4>
0063 <!-- BEGIN MODULES_USED -->
0064 <PRE>
0065
0066 utilities_mod
0067 constants_mod
0068 monin_obukhov_mod
0069
0070 </PRE>
0071 </A><!-- END MODULES_USED -->
0072 <!--------------------------------------------------------------------->
0073 <A NAME="INTERFACE">
0074 <HR>
0075 <H4>PUBLIC INTERFACE</H4>
0076 <!-- BEGIN INTERFACE -->
0077 <PRE>
0078
0079 use diffusivity_mod [,only: diffusivity]
0080
0081 diffusivity - called every physics time step to compute diffusivity
0082 coefficients.
0083
0084 Notes:
0085
0086 1) A namelist interface controls runtime options
0087 2) An initialization routine is called upon the first call to
0088 diffusivity.
0089 2) No restart file is generated by this module.
0090 3) No other data files are needed.
0091
0092 </PRE>
0093 </A><!-- END INTERFACE -->
0094 <!--------------------------------------------------------------------->
0095 <A NAME="ROUTINES">
0096 <HR>
0097 <H4>PUBLIC ROUTINES</H4>
0098 <!-- BEGIN ROUTINES -->
0099 <PRE>
0100
0101 <b>call diffusivity</b> (t, q, u, v, p_full, p_half, z_full, z_half,
0102 u_star, b_star, h, k_m, k_t, kbot)
0103
0104 input:
0105
0106 t : temperature (K) [real, dimension(:,:,:) -- (:,:,pressure),
0107 third index running from top of atmosphere to bottom]
0108
0109 q : water vapor specific humidity (nondimensional)
0110 [real, dimension(:,:,:)]
0111
0112 u : zonal wind (m/s) [real, dimension(:,:)]
0113
0114 v : meridional wind (m/s) [real, dimension(:,:,:)]
0115
0116 p_full : pressure at full levels (pascals)
0117
0118 p_half : pressure at half levels (pascals)
0119
0120 z_full : height of full levels (m)
0121 [real, dimension(:,:,:), size(z_full,3) = size(t,3)]
0122
0123 z_half : height of half levels (m)
0124 [real, dimension(:,:,:), size(z_half,3) = size(t,3) +1
0125 z_half(:,:,size(z_half,3)) must be height of surface
0126 (for non-eta models)!]
0127
0128 u_star: friction velocity (m/s)
0129 [real, dimension(:,:)]
0130
0131 b_star: buoyancy scale (m/s**2)
0132 [real, dimension(:,:)]
0133
0134 surface stress = ustar*ustar
0135 surface buoyancy flux = ustar*bstar
0136 bstar > 0 => upward flux
0137
0138 (u_star and b_star are output from
0139 mo_drag in monin_obukhov_mod
0140 along with the drag_coeffcients )
0141
0142
0143 output:
0144
0145 h : pbl depth (meters) [real, dimension(:,:)]
0146
0147 k_m : momentum diffusivity coefficient ((meters)**2./second)
0148 [real, dimension(:,:,:)]
0149
0150 k_t : temperature, vapor and scalars diffusivity coefficient
0151 ((meters)**2./second)
0152 [real, dimension(:,:,:)]
0153
0154 defined at half-levels
0155 size(k_m and k_t,3) should be at least as large as size(t,3)
0156 only the returned values at
0157 levels 2 to size(t,3) are meaningful
0158 other values will be returned as zero
0159 That is k_m(:,:,2) is the diffusivity coefficient
0160 between full model levels 1 and 2. (Full model level 1
0161 is the top level of the model.)
0162
0163 optional input:
0164
0165 kbot : lowest true model level (for use with eta grid point model)
0166 [integer, dimension(:,:)]
0167
0168
0169
0170 </PRE>
0171 </A><!-- END ROUTINES -->
0172 <!--------------------------------------------------------------------->
0173 <A NAME="NAMELIST">
0174 <HR>
0175 <H4>NAMELIST</H4>
0176 <!-- BEGIN NAMELIST -->
0177 <PRE>
0178
0179 <b>&diffusivity_nml</b>
0180
0181 fixed_depth should the boundary layer depth be fixed?
0182 [logical, default: fixed_depth = .false.]
0183
0184 depth_0 height of fixed depth boundary (meters)
0185 [real, default: depth_0 = 5000.]
0186
0187 frac_inner height of the surface layer as a fraction of
0188 the boundary layer depth
0189 [real, default: frac_inner = 0.1]
0190
0191 rich_crit_pbl critical richardson number used to compute
0192 boundary layer depth in the neutral or stable
0193 case
0194 [real, default: rich_crit_pbl = 1.0]
0195
0196 entr_ratio ratio of entrainment buoyancy flux to surface
0197 buoyancy flux (must be >= 0.)
0198 [real, default: entr_ratio = 0.2]
0199
0200 parcel_buoy scaling factor for the excess buoyancy of the
0201 parcel used to determine the boundary layer
0202 depth in the unstable case
0203 [real, default: parcel_buoy = 2.]
0204
0205 znom nominal boundary layer depth used only in the
0206 calculation of surface layer vertical velocity
0207 scale. this velocity scale is used only in
0208 the calculation of parcel buoyancy in the unstable
0209 case (meters)
0210 [real, default: znom = 1000.]
0211
0212 free_atm_diff should there be richardson number dependent
0213 mixing in the free atmosphere?
0214 [logical, default: free_atm_diff = .false.]
0215
0216 free_atm_skyhi_diff should the free atmospheric diffusion
0217 depend on model level thickness and the
0218 prandtl number depend on the richardson number
0219 (as in the formulation previously used in skyhi)?
0220 [logical, default: free_atm_skyhi_diff = .false.]
0221
0222 pbl_mcm When .true., the pbl K profile is that of the Manabe Climate Model.
0223 [logical, default: pbl_mcm = .false.]
0224
0225 rich_crit_diff critical richardson number beneath which free
0226 atmospheric diffusion occurs
0227 [real, default: rich_crit_diff = 0.25 ]
0228
0229 mix_len mixing length used in free atmospheric diffusion
0230 (meters)
0231 [real, default: mix_len = 30.]
0232
0233 rich_prandtl Prandtl number used in the scaling of k_m to
0234 k_t in the free atmospheric diffusion
0235 [real, default: rich_prandtl = 1.]
0236
0237 background_m background value of K for momentum (m**2/sec)
0238 [real, default: background_m = 0.]
0239
0240 background_t background value of K for temperature and tracers
0241 (m**2/sec)
0242 [real, default: background_t = 0.]
0243
0244 Notes: (1) To get Climate Model's PBL diffusivities set
0245 pbl_mcm to TRUE, fixed_depth to TRUE,
0246 depth_0 to 5000. and frac_inner to 0.015.
0247
0248 (2) To get K-profile diffusivities, pbl_mcm
0249 must be FALSE (default) and fixed_depth must be
0250 FALSE (default).
0251
0252 (3) To have any vertical diffusion in the free atmosphere
0253 free_atm_diff must be set to TRUE.
0254
0255 (4) To get skyhi free atmospheric diffusivities, both
0256 free_atm_skyhi_diff and free_atm_diff must be set
0257 to true.
0258
0259 </PRE>
0260 </A>
0261
0262 <A NAME="CHANGES">
0263 <HR>
0264 <H4>CHANGE HISTORY</H4>
0265
0266 <PRE>
0267 <B><A HREF=".doc.log#diffusivity.f90">Revision history</A></B>
0268
0269 <b>changes</b> (10/4/1999)
0270
0271 MPP version created. Minor changes in open_file, error_mesg,
0272 and Fortran write statements. Answers should reproduce the
0273 previous version.
0274
0275 <b>changes</b> (8/16/1999)
0276
0277 Code to set background diffusivities is moved out of
0278 diffusivity_free subroutine and into the diffusivity subroutine
0279 so that it is possible to set a background level of diffusivity
0280 even if free_atm_diff = FALSE.
0281 (This was impossible in previous revisions).
0282
0283 </PRE>
0284 </A>
0285
0286 <A NAME="ERRORS">
0287 <HR>
0288 <H4>ERROR MESSAGES</H4>
0289
0290 <PRE>
0291
0292 diffusivity_init:
0293
0294 namelist parameters are checked to see if valid selections
0295 have been made. The following settings are prohibited and
0296 the model will shut down if any are chosen:
0297
0298 (1) frac_inner <= 0 or frac_inner >= 1.
0299 (2) rich_crit_pbl < 0.
0300 (3) entr_ratio < 0.
0301 (4) znom < 0.
0302 (5) free_atm_skyhi_diff = TRUE and free_atm_diff = FALSE
0303 (6) rich_crit_diff <= 0.
0304 (7) mix_len < 0.
0305 (8) rich_prandtl < 0.
0306 (9) background_m < 0.
0307 (10) background_t < 0.
0308
0309 </PRE>
0310 </A>
0311
0312 <A NAME="REFERENCES">
0313 <HR>
0314 <H4>REFERENCES</H4>
0315
0316 <PRE>
0317
0318 See <A HREF="diffusivity.tech.ps">technical documention</A>.
0319
0320 </PRE>
0321 </A>
0322
0323 <A NAME="NOTES">
0324 <HR>
0325 <H4>NOTES</H4>
0326
0327 <PRE>
0328
0329 None.
0330
0331 </PRE>
0332 </A>
0333
0334 <A NAME="PLANS">
0335 <HR>
0336 <H4>FUTURE PLANS</H4>
0337
0338 <PRE>
0339
0340 None.
0341
0342 </PRE>
0343 </A>
0344
0345
0346 <HR>
0347 </BODY>
0348 </HTML>
