Proposed 2013 PBL upgrade to - PowerPoint Presentation

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Proposed 2013 PBL upgrade to the operational HWRF

Young Kwon, Vijay Tallapragada, Weiguo Wang, HWRF team and Jun Zhang

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Baseline

(H130)

Physics upgradesCombined(H213)PBL(H131)Meso-SAS (H132)RRTMG (H133)Ocean(H135) Final configurationDescriptionRevised init/GSI,New nest parent interpolations,Radiation bug fix,Revised nest movement,Increased frequency of Physics callsVariable RicMeso SASRadiationMPI-POMBaseline+ physicsPersonQingu, In-HyukSam TrahanMingjing, YoungYoung/WeiguoQingfuChanhBiju Thomas (URI)AllCasesWhole 2011 and 2012 storms and some 2010 stormsWhole 2011 and 2012 storms and some 2010 stormsWhole 2011 and 2012 storms and some 2010 stormsPriority casesWhole 2011 and 2012 storms and some 2010 stormsWhole 2011 and 2012 storms and some 2010 storms

2013 HWRF pre-implementation test planSlide3

Variable Critical Richardson number

(Vickers & Mahrt, 2003)

PBL

  z (1 - z/h) p Motivation: The GFS PBL scheme used in HWRF model has been known to produce too diffusive boundary layer in hurricane condition. Thanks to HRD’s effort to improve the hurricane PBL in HWRF model, the diffusivity and PBL height of HWRF model greatly improved based on composite dropsonde observations (e.g., Gopalakrishnan et al. 2013, JAS; Zhang et al. 2013, TCRR) However, outside of hurricanes, the GFS PBL behaves quite well and some underestimation of PBL height is reported (Jongil Han, personal communication). Therefore, it may worth trying to revise the current PBL scheme to work well in both inside and outside of hurricane area seamlessly.3Inverse of surface bulk Richardson number Slide4

Critical Richardson number function of Ro (Vickers and Mahrt, 2003)

Hurricane cases

Vickers and

Mahrt(2003) Critical Richardson number is not a constant but varies with case by case.Ric = 0.16(10−7 )−0.18  The magnitude of Ric modifies the depth of PBL and diffusivity, so the Ric varying with conditions would fit both hurricane condition and environments.4Slide5

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“ We conclude that if a constant critical Richardson number is used, the bulk Richardson number method based on two atmospheric levels is superior to the surface bulk Richardson number method. However, the better approach is to use the surface bulk Richardson number with a variable Critical Richardson number” (Vickers and

Mahrt

, 2003).Slide6

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PBL height difference

(new PBL scheme with var Ric – PBL scheme in 2012 HWRF with constant Ric=0.25)PBL height over the ocean and hurricane area becomes shallower while that over land area becomes deeperBoth configurations have  set to 0.5Hurricane Katia (20110829018+96hr)Slide7

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2012 operation

H131 (H130+new PBL)KmKmRed: radial windsBlack: vertical windsOBSHWRFSlide8

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resultsSlide9

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ATL track

EP track

ATL intensityEP intensity~ 3.1% ~ 7.2% ~ 3.8% ~ 6.5% Slide10

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bias

34kt radius

Earl intensity Nadine intensity Slide11

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~ 4.6%

After removing Igor and Nadine

ATL intensityATL intensity biasSlide12

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Earl track

Igor track

Irene trackLeslie trackSlide13

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SUMMARY

Variable critical Richardson number method suggested by Vickers and

Mahrt(2003) is implemented and tested on the 2013 baseline HWRF .Verification stats show the HWRF system with new PBL performs comparable or better than the 2013.The storms size and PBL structure(Km, pblh) are better with the new variable critical Richardson number method.The degradation of intensity is mainly caused by Igor(2010) and Nadine(2012).Overall, tracks seems perform better with the new PBL scheme, and it may be resulted from improved large scale flows.