# Presentation: 250279

## “Trials & Tribulations with Clouds  and Radiation ... Continued”12/4/03 Branch Meeting          Brad Ferrier

**Thanks to**
**Hsin-Mu Lin for all his efforts in this endeavor**
**Eric Rogers for adding many cloud, radiation, & LSM fields to the 32-km and 12-km parallel web pages**
**Yu-Tai Hou for his radiation expertise and support**
**Ken Mitchell, Mike Ek, Jesse Meng, and others in the LSM group**
**Mary Hart for providing first look at AFWA cloud products, Russ Treadon for looking at cloud water paths**

**Conclusion:  The GFS radiation is not yet ready for operational implementation into the Eta.  May not even be ready for the Eta’s final implementation next spring/summer.  **

## 32-km Parallel Tests  (early Oct – Nov 25)

**EtaV - control**
**Correct posting of instantaneous solar fluxes at top of hour**

**EtaY – parallel test with EDAS cycling**
**GOES-12 radiances, modified precipitation assimilation, modified LSM, new GFS radiation**
**Developed a pronounced cold bias, esp. at high latitudes**
**Cold bias primarily due to clouds “blocking” too much radiation ****(absorption, reflection, scattering)**** from reaching the ground**

**EtaL – parallel test without cycling, initiated from EtaY restart**
**Lots of changes to clouds & optical properties ******** described later!**

## Two-Pronged Strategy

**Sensitivity experiments by Hsin-Mu Lin testing changes to:**
**Cloud optical properties  ****(cloud fractions, cloud & ice water paths, effective radius of water & ice, single scattering albedos for water)**
**Aerosol effects, diurnal variation of albedos for direct (beam) component of radiation**
**Cloud microphysics ****(glaciation temperature, ice nucleation rates, & autoconversion threshold of cloud to rain)**

**Test ideas in uncycled 32-km EtaL runs (before Nov 25) **
**Forecast executable in scripts were pointing to a link**
**The link to the actual executable could be changed w/o affecting the scripts**
**16 different versions of EtaL were run from 10/4 to 11/25**

## Summary of Cloud-Radiation Issues

**New radiation is very sensitive to clouds**
**Large reduction in surface insolation below low-level clouds, esp. if liquid water is present**
**Results from Y.-T. Hou at last GMoB Mtg showed this may be *****partly***** due to the GFS radiation when compared against the more accurate AER solar radiation package for multi-layered clouds with partial overcast**
**Parameterizing the radiative effects of snow based on geometric optics (Q. Fu, personal communication) was abandoned in favor of treating cloud ice & snow the same.  **

**Improved surface albedos**
**SW****up****/SW****dn**** are more accurate ******** lower midday albedos over land (0.10-0.15 vs. 0.20-0.25), higher albedos at low sun angles (see examples from **_**[12Z 11/17 ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etavetay.effalb_animate.html)**_**& **_**[00Z 11/20 ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etavetay.effalb_animate.html)**_**runs)**

## Cloud-Radiation Issues (cont.)

**Possible errors in Eta grid-scale clouds**
**Forecast total cloud cover too high compared to AFWA’s WWMCA, esp. at higher latitudes**
**Concerns that AFWA product may be missing some low-level clouds over cold surfaces?  (Ken M.)**
**Higher Eta cloud water paths (CWP) than in the GFS and AMSU (microwave) retrievals  (Russ T.) **

**Arctic stratus – a challenge  ****(Curry *****et al*****., 2000; Dong and Mace, 2003)**
**Shallow (tops often below 1 km), presence of supercooled liquid water (esp. near cloud top)**
**Incident radiation at low sun angles, underlying snow surfaces ******** surface albedo issues?  **
**Greater *****relative errors***** in radiative forcing?**

## Final Two Versions of EtaL (prior to Nov 25)

**11-14-03 version**
**Glaciation temperature increased from -40 ****o**** C to -10 ****o**** C**
**Enhanced ice nucleation at 0 ****o**** C to -10 ****o**** C**
**N****cw**** = 50 cm****-3**** ******** reduced cloud autoconversion threshold by 1/4 from 0.84 g m****-3**** to 0.21 g m****-3**
**Removed effects of rain in calculating grid-scale cloud fractions and in cloud water paths**
**Reduced grid-scale cloud fractions ****(simplified Ek & Mahrt, 1991)**** ********  ****(f****c****)****strat**** = 0% - 100% linearly for RH****tot**** = 90% - 110%****RH****tot**** = (q****v****+q****w****+q****i****+q****s****)/q****sat****, q****sat**** is w/r/t water (******** 0****o****C) or ice (< 0****o****C)**
**Removed aerosol effects**
**Reduced cloud fractions further by (f****c****)****1/2****  (Hou, Moorthi)**

## Final Two Versions of EtaL (prior to Nov 25)

**11-14-03 version of EtaL **_**[increased surface](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etal.diffna.dswf_animate84.html)**__**[ ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etal.diffna.dswf_animate84.html)**__**[SW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etal.diffna.dswf_animate84.html)**__**[dn](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etal.diffna.dswf_animate84.html)**__**[ ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etal.diffna.dswf_animate84.html)**__**[w/r/t EtaY](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etal.diffna.dswf_animate84.html)**_**, but could not remove cold bias over Canada & Alaska**

**11-18-03 version of EtaL added two more changes**
**(R****eff****)****ice**** varies from 150 ********m at 0****o****C to **_**75 **__****__**m**_** at -46****o****C**
**No diurnal variation of surface albedos for the direct (beam) component of solar radiation**

**Both versions of EtaL **_***have more net surface insolation than the EtaV***_** over CONUS at “midday”, and yet **_***they still have a cold bias***_** **_***w/r/t to the EtaV***_**  over Canada & Alaska**

**Note the EtaV has a cold bias over Alaska (60h fcst **_**[v00Z](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/verif/sfc7days/2m_TEMP_SAK_VLD00Z_BIAS_F60.gif)**_**, **_**[v12Z](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/verif/sfc7days/2m_TEMP_SAK_VLD12Z_BIAS_F60.gif)**_**)**

**The original goal was to reduce the high bias in Eta insolation**

## Current 32-km Parallels

**Corrected error in cloud amounts and cloud-base levels in longwave calculations for clouds at the ground (fog)**
**Currently running in latest versions of the parallels, which are now focusing on trying to get the latest set of LSM changes into this fall/winter implementation**
**Slight increase in downward longwave fluxes, addressing the low bias over New England found by ETL**
**Should help reduce early morning cold bias, though the change occurs in isolated spots and its impact is expected to be minor**

## Links

**Copies of some of the web pages are available for preview**
_**[32-km parallel forecast page for the 12Z Nov 17 cycle ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/)**_**shows an example of how the 11-14-03 version of EtaL performed**
_**[32-km parallel forecast page for the 00Z Nov 20 cycle ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/)**_**shows an example of how the 11-18-03 version of EtaL performed**
_**[2-week time series of regional surface verification](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/verif/sfc7days/)**_**, focusing only on the period prior to Nov 27**
_**[Time series for November ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/verif/bias7days/)**_**of 850-T, 700-RH, 500-Z, 250-V**
**850-hPa T shows improvement in EtaL over EtaY, comparable to EtaV control**

## More Links   Examples of ...

**reduced grid-scale cloud fractions in the EtaL compared to the EtaV for the **_**[12Z Nov 17 ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etavetal.totcfall_animate.html)**_**and **_**[00Z Nov 20 ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etavetal.totcfall_animate.html)**_**cases**
**reduced liquid water paths in the **_**[EtaL ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etal.cldrainall_animate.html)**_**compared to the **_**[EtaV ](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etav.cldrainall_animate.html)**_**for the 12Z Nov 17 case associated with the change in the cloud water autoconversion threshold**
**EtaL-EtaV differences in **_**[SW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.dswf_animate84.html)**__**[dn](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.dswf_animate84.html)**_**, **_**[SW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netswfall_animate84.html)**__**[dn](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netswfall_animate84.html)**__**[-](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netswfall_animate84.html)**__**[SW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netswfall_animate84.html)**__**[up](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netswfall_animate84.html)**_**, **_**[LW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netlwfall_animate84.html)**__**[dn](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netlwfall_animate84.html)**__**[-](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netlwfall_animate84.html)**__**[LW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netlwfall_animate84.html)**__**[up](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003111712/etaletav.diffna.netlwfall_animate84.html)**_** for 12Z Nov 17 case (*****v11-14-03*****)**
**EtaL-EtaV differences in **_**[SW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.dswf_animate84.html)**__**[dn](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.dswf_animate84.html)**_**, **_**[SW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netswfall_animate84.html)**__**[dn](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netswfall_animate84.html)**__**[-](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netswfall_animate84.html)**__**[SW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netswfall_animate84.html)**__**[up](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netswfall_animate84.html)**_**, **_**[LW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netlwfall_animate84.html)**__**[dn](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netlwfall_animate84.html)**__**[-](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netlwfall_animate84.html)**__**[LW](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netlwfall_animate84.html)**__**[up](http://wwwt.emc.ncep.noaa.gov/mmb/bf/presentations/Branch_12-4-03/eta32.2003112000/etaletav.diffna.netlwfall_animate84.html)**_**, and Rnet=SW****dn****-SW****up****+LW****dn****-LW****up ****for 00Z Nov 20 case (v*****11-18-03*****)**
**the lower albedo in the morning & afternoon in the EtaL-EtaY for 00Z Nov 20**
**the lower 2-m T in EtaL-EtaV for 00Z Nov 20**
**a comparison of the GOES-retrieved vs. fcst SW****dn**

## A Retrospective View

**Recent documentation of improved Eta solar insolation since the July 8 implementation**
**Improved agreement against SURFRAD observations**
**High biases reduced by ~ 1⁄2 from 2002 to 2003 over NE**

**Latest LSM changes further reduce 2-m T midday warm bias**

**Target for reducing high surface insolation of 100-200 W m****-2**** was based on the operational Eta prior to the July 8 change**

**Net result ... an overcompensation in the radiation and LSM changes, resulting in a cold EtaY parallel**

**Recent realization that Eta-forecast radiation fields may not be so crucial for next summer’s CMAQ effort**

## Proposed Two-Pronged Approach

**Continue work on modified clouds and GFS radiation**
**Starting from a variant of the 11-14-03 version of the EtaL**
**Evaluate forecast SW****dn**** and SW****up**** ****against GOES-retrieved values over CONUS**
**Incorporate new radiation and modified clouds into WRF-NMM and conduct further tests if not ready for spring/summer Eta implementation**

**Modify clouds in current Eta radiation scheme**
**Improve shallow convection**
**Less triggering over broad areas**
**Make cloud top based more on parcel theory**
**Use simple, modified grid-scale cloud fraction scheme to calculate cloud fractions for shallow convection (currently fixed at 10%)**

## Future Considerations

**Improving 2-m T will require careful adjustments to parameters in both the land-surface and cloud schemes**
**Extra challenges for higher latitudes ******** midlatitude winter?**
**Sparse surface and sounding data**
**Absence of GOES-retrieved fields for verification**
**Low sun angles, snow-covered surfaces ******** higher albedos, reduced net solar fluxes (SW****dn**** - SW****up****) at surface**
**Reduced cloud cover (EtaL) was intended to increase net solar fluxes, but instead this was counteracted by reduced LW****dn**** and enhanced cooling.  **
**Dominance of low clouds with partial cloud cover amplifies impact of low bias in surface SW****dn**** in GFS radiation**

## Preliminary Comparison of SWdn from 32-km Parallel Runs vs. GOES retrievals

- (return)