A “New” One-moment 4ICE Scheme for the GCE

Stephen Lang, SSAIW.-K. Tao, NASA GSFC

Jiundar Chern, Morgan State U.Xiaowen Li, Morgan State U.

Di Wu, SSAIXiping Zeng, Morgan State U.

Toshi Matsui, ESSIC

September 11, 2012Mesoscale Atmospheric Processes Branch Laboratory Meeting

Lang et al. (2007) -- no dry growth, reduced snow collection efficienciesLess overall graupel, improved CFADs

Lang et al. (2011) -- lots of changes, added snow/graupel size mappingLowered excessive penetration of 40 dBZ echoes, improved CFADs

Lang et al. (2011) applied to KWAJEX MCSLowered excessive penetration of 40 dBZ echoes, improved CFADs

THE NOTCH and THE TAIL

Actually not really “new”…..

Added hail processes from the Lin et al. (1983) 3ICE hail scheme to the improved (Lang et al. 2007, 2011) Rutledge and Hobbs (1983, 1984) 3ICE graupel scheme. Applied some lessons learned to the hail processes…

UnchangedHail rimingHail collection of ice and snow during wet growth***Hail accretion of rainHail deposition/sublimationHail melting and shedding

New/modifiedRain freezes to hail not graupelIce or Snow collecting rain becomes hail not graupelHail collection of graupel during wet growthHallett-Mossop rime splintering of hail via rimingHail transferred to graupel via deposition

OmittedHail collection of ice or snow as dry growth

Other modifications…..

Added a snow density mapping (smaller=higher density, Heymsfield et al.)

Modified the Lang et. al. 2011 graupel/snow size mapping (reduced sizes in tail)

Modified the saturation adjustment:cloud ice can persist in sub-saturated air down to RHI=70%allows for a 5% background super-saturation w.r.t. icecloud evaporation only when W > -0.1 m/s (limit spurious evaporation, Reisner)

Added “physical” rain evaporation correction based on bin (Li et al. 2010) but with limits

Added two-tier graupel density scheme (0.3 < 2.0 g/m3 > 0.5) including fall speeds

Snow size/density mapping

rsnow = 0.1 g/m3 rsnow = 0.05 g/m3

Graupel size mapping

rgraupel = 0.4 g/m3 rgraupel = 0.3 g/m3 rgraupel = 0.3 g/m3 rgraupel = 0.5 g/m3

Maximum Reflectivity

Reflectivity CFADs

Hydrometeor Profiles

Summary and Future Plans

The 4ICE scheme improves the GCE’s radar signature in two ways:

1) it eliminates the occurrence of elevated reflectivity maxima (most likely via

higher hail fall speeds) and could perhaps even help in less intense cases, and

2) with its ability to produce high reflectivity values, it eliminates the need for

graupel and snow to produce those values, allowing for more “stable” snow/graupel size mappings and mappings better suited to produce reflectivity values with the highest occurrence.

Test and refine the rain evaporation correction, transfer of hail/graupel to snow,and changes to the saturation adjustment.

Test the 4ICE scheme in WRF and the MMF to make sure it works well in a variety ofenvironments.

Validate with radar CFADs and hydrometeor classifications for a variety of cases. Use CloudSat or other similar instrument(s) to get a better picture of cloud top performance with PDFs.

Validate/modify snow/graupel size/density maps using in situ and/or bin data.