# Presentation: 184354

## NMM Physics Group - 9/19/05 Mtg

- NAMX & NAMXF (full cycling) 2005/9/15/12 changes
- Modified module_radiation_driver so that it skipped code that should not run when using the GDFL radiation. This code block, when run in the NMM, would re-calculate (and reduce) the the downward solar flux and also re-calculated the total downward longwave flux
- Net effect was to change (usually reduce) the incident shortwave by the factor (1-A*)/(1-A), whereA=midday albedo (ALBEDO array),A*=diurnally corrected (from RADFS),and often A*>A, esp when cos(zenith) is small (sun low in sky)

## NAMX & NAMXF 2005/9/15/12 changes (cont.)

- Revert back to 7 July change to RADFS: the downward solar fluxes in RADFS are obtained from the array DF rather than as a sum of the four components - i.e., direct visible and near-IR and diffuse visible and near-IR components, represented by the GDFxx arrays.
- Systematic embedded prints verified that SW fluxes from DF were up 20 W m-2 larger than from the GDFxx
- SW are derived from UF arrays, “sister” of DF arrays
- Calculated albedos (_****_ = SW/SW) >1.0 and net SW fluxes (SWnet = SW - SW)< 0 from GDFxx arrays
- Even  from the DF arrays were at least 5-6% larger than diurnal-adjusted albedos – i.e., the inputs to the radiation calculations!  You can glean this under clear-sky conditions.
- Yu-Tai warned H.-S. Lin and I about these possibilities.  The “sins” of a circa ’70s / early ’80s

## Impact on calculated albedos ()

- Purple in NAM (>90%) is due to use of less accurate GDFxx arrays under clear skies
-  >60% in NAMXF (full cycling) from more accurate DF arrays.  Larger area of lower albedos due to more extensive clouds

## Impact on SW near sunset - low cos(zenith)

- Over west and central land masses (ignore cloudy oceans), larger SW in NAMXF (left) near sunset in clear skies – see area enclosed in circle
- (SW)clear – SW (right) is an objective way of identifying “clear sky conditions”.  It’s like a net cloud forcing impact on SW - see area enclosed in circle

## Effectiveness of “SW cloud forcing” 

- Total column-integrated condensate (water + ice, left)
- (SW)clear – SW (right) -> “SW cloud forcing”
- Still a large impact of NAMXF clouds:
- _[Comparison of SW cloud forcing for this cycle](http://www.emc.ncep.noaa.gov/mmb/mmbpll/nampll12_fullcyc/Sun/12z/na.clrdswf_animate.html)_
- _[Differences in SW cloud forcing for this cycle](http://www.emc.ncep.noaa.gov/mmb/mmbpll/nampll12_fullcyc/Sun/12z/diff.na.clrdswf_animate.html)_ (grows w/ time), similar to but of opposite sign to _[differences in SW](http://www.emc.ncep.noaa.gov/mmb/mmbpll/nampll12_fullcyc/Sun/12z/diff.na.dswf_animate.html)__[](http://www.emc.ncep.noaa.gov/mmb/mmbpll/nampll12_fullcyc/Sun/12z/diff.na.dswf_animate.html)_ - ie, SWNAM-SWNAMXF
- _[Comparison of column-integrated liquid water for this cycle](http://www.emc.ncep.noaa.gov/mmb/mmbpll/nampll12_fullcyc/Sun/12z/na.cldrain_animate.html)_

## Impact of “SW Cloud Forcing” still big by 6 h

## Other fixes

- New code should lead to correct posting of convective cloud base/top arrays (currently zero’ed out due to calling radiation before top of hour)
- Found bug in time-averaged total cloudiness.  Quick fix provided to Hui-ya, more elegant fix will need changes to Registry & radiation driver (sorry)
- In addition to cosmetic changes above, more substantial changes to cloud-radiation and to cloud physics listed in following 2 slides.

## More cloud-rad changes tested in 3h runs

- Convective cloud changes in radiation
- Eliminated subgrid condensate
- Using only Slingo scheme in absence of grid-scale clouds
- Subgrid variability of grid-scale condensate
- Gaussian distribution of RHtot assumed within grid, but standard deviation of this distribution (RHtot) increased from 1% to 2% - more partial clouds
- RHtot = 8% if convective clouds coexist with grid clouds
- Cloud optical thickness/depths (cld) :
- Absorption coefficients for water reduced by 62.5% from “800” to “500”; for ice reduced from “500” to “250”
- cld scaled by cloud fraction for Cu & grid-scale clouds
- Put upper limit on diurnal clear-sky albedos to 0.5

## Microphysics changes

- RHgrd = 1.0 (was 0.976)
- NLImax = 5.e3 (was 20.e3)
- NLImin=1.e3 (was 100)
- NCW=50.e6 or 50 cm-3 (was 200.e6 or 200 cm-3)
- T_ice=-30C (was -10C)
- Net effect of the first 4 changes is to reduce amount of suspended cloudiness and increase solar transmission through clouds
- Net effect of last change is to make scheme more intelligent and do what it was designed to do