NASA Technical Reports Server (NTRS) 20080023285: Cloud-System Resolving Models: Status and Prospects

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by  NASA Technical Reports Server (NTRS)

Cloud-System Resolving Models: Status and Prospects

Kun Tao! and Misch Moueriefi®

| Leborator: for Atmospheres
NASA Goddard Space Might Center
Greenbelt, MD 2071

NCAR
P.O. Bax 3000
Boulder, CO 30307-3000

Submitted to Reviews of Geophysics

Corresponding wathar addsss: Dr, Wei-Kuy Tai, Viwnsesle Aumospberie Processes
ranch, Code 6 4.1, NASA GSFC, Gteenbelt, MDD 20771

Tema: [email protected]

age L
ARSTRACT.

(Cloud-system resolving models (CIRM), which are based in the numydrostatic equations of
motion aed typically have a grid-spacing of abont a Kilometer, originated as lowd-provess
models in the easly 1970s, This paper reviews the status andl proqpeuts af CRM. across a
wide mnge of isu, such as uerophysios and procipitation; interaction between clouds and
radiation; Beouasue che ofteets of boundary-layer ant surtace-processes 0a cloud systems
Siace CRMs resolve organized convection, tropital waves and the large-feale circulation,

there is praspect for several advances in both basic knowledge af scale interaction requisite
eanerparamerctization, CRMs

ler paramecteuizing miesoscale processes in climate models
represent convection explicitly raplasing many of de assumptions necessary in
comemporsry parameterization, Glubal CRMs have been ma om an experimental hasis,
giving prospeut ul a new yeneratian climate weather prodistion ia a decade and climate
models due caure, CRMs play a major role ie the retrievals of surfie-rain aul Tuten
roe) satellite measurements, Finally, snore wide dynumie range of CRM

went

sSmulatians presents now challenges for model validation against observations

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1. Introd

“The global hydrologic! eyele is eontzal to understanding snd predicuing the weather-climate
system, where provipitalion physics and moist phyvical processes in general are major
challenges. Approximately cvo-thirds of the global preipilalion occurs in the “Tropics,
where organized previpitaling systems account for a lange pereentaye of rainfall (Nesbiet ot
al, 2006), Acuampanying latent heating accounts fr ahuut three-quarters of the total heat
encigy for the Farth’s etmosphere (Riehl and Simpson 1979). The vertical distribution of
latent heating strongly effec the lage-scale tropical circulation, such ag the 3-60-day
intrasenumal oscillation (Hartmann of al. 1984; Sui and Lau 1988), as well as the gal
circulate. Peesh water provided by tropical rainfall atfeets the state of the upper-ocean und
eean-atmasphere interaction, Tropical convection afters midlatinde weather anil climate
Urrough planetary wave televonnection, notably in association with FI Niiy Southern
Oscillecion (HNO), Variabitty in che global eiulation ea: cause proloryed deoupbts and

foods which ienpel the biosphere. agricuttre and humankind. Improved hapwledge of the

nrecheuiems responsible tar the distribution, variability, and effects of precipitating

tc.

convective systems iv roquitice to ont knovwledge of the gluhal energy and watec

(A Firemist challenge lics in the aoswrule puranneteeization of precipitating, elrud

systems in glohal medefs, a prablem of nunlineur inlersetion among inictophysical seules

(103 = 20" rm, secouds-to-mnircies), aasoncales (10% 10° my; hours-to-days) an che large

seule envieoctnent, Since messssule cnvective organization is contrary at the assumption of

nut scale-separstion assumed by contemporary parametsrizations, ew eppronches ate

requited, The mie of cloud-radiacion interaction in weather, elimace and bydrological

to advance in these areas is

systenus is snathsr major challenge. The comprehersion requi
Foucdable, Basically, this is why clouds and radiation is a prio-ity of dhe Global Chauge
Research Program (GCRP) and the Global Energy andl Water Cycle Experiment (GEWEX)
inaugurated the GEWTX Cloud System Smdy (GCSS). In ucknowledgement of their
emerging importance, cliud ensemble medels (CEM), als knawa ak eloud-rosolving
nodels (CRM) nnd cloud-system scsalving models (CSRM), were selected as the approach

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‘oF chive by GCSS in ti

ty 1990s (GUNS Sciences Phin 1993; Mamerieff etal. 1997). tn
‘his paper we will use the tertas CEM, CRM and CSRM interchamgably.

The Fine spatial resolution of CRMs {compared to global models) enables explicic
interaction among clouds, radiation, precipitation, and surfaes procssies moans CRMs ure
flexiie tools for moist processes and scaleinteraetion reseurch. Collaborative studies
conducted by the GCSS and the Department of Enorgy Atmospheric Radiation Measurement
ADOBARKN show that CRMs arc superior to single-column models (SCMs) wherein
paysical processes are paramcterized (Rundall el ul. 200%), Observationally veufiod CRMs
provide a physical basis for not only improving fix a runge of parameretizations global

‘models but also cloud mmicrophysies! parumeterisulians (iar CRMs,

Table | shows selected highlights: CRMs for the past four decades. The eories kind
of cloud model, the one-dimensional {1D} entrsining bubble ur plume simply represents (he
lateral enttainmear of envuoumental ait, Lhis model wus wed extensively in cloud-seeding
research (Simpson ef al. 1965, 1967) andl is wil as the umpor: module in convective
parameterizations. ‘Isvo- dimensions] (210) vloul models represent cloud development aud
anterastions with the near-onviran-nent (Ogure and Philips 1962), “Le 197U's witoessed the
developracat of thrve-dimensional (31) cloul models with geid-lengths of about a kiometer
(Steiner 197%; Withelmson 1974; Miller and Pearce 1974; Somameris 1976; Klemp und
Wilhelmsim 19784; Cousin and Tripoli, 1978: Schlesinger 1978: and Clark 1979). The
effects of raadel neomevy {ie slab ssunmettio vs axi-syammetsie; two-dimensional vs threc-

eyoles were examine 4s. Saemg said Ogura 1973}. Orher carly

Amnensional) on closd Uf
studics inelne the simulation of rvidlatitude supercells (2-g., Klemp and Wallietmson 19786:
Wilhelmsen and Klemp. 1978) and squall systems (c.g, Mouctiei and Green 1972:
Moncvicf md Viiler 1976).

amine the collective

‘Subsequent to GATE, clond suscmble mndela! were used t
effects of cosy and interaction with the cuvivonrasnt and thereby improve cusmulus
panumsterivations (e., Soong and Tan 19805 Lav ane Soong 1986: Tipps and Heleser [9X6

2 Te lobed Atm er + Ress Prgranin GARE) Atlante Topical aperizaal be Wok pace 8974

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Tao et al. 1987; und many ocbers). ‘Ihe challenging quest of improving parameterization
ceninues to ths day, Other studies inckude the effoers of ice-proceuses, radiative processes,
an precipirating systems and sind-shese on convective organization (ee, Thorpe et al
LoD, 1982; Moncrieff 1984; Nakajima and Matsuno 1988; Rotuono ef of. 4988; Favell and
‘Ogura I9RK; Tao and Simpucm 1989; Redelsperger and Sommmeria 1986; Jafore of ul. L9H;

perger and Lafore 1988; Lalore 2nd Monosicff 1988; I'a0 1993, among others)

Ret

In the 1990's, advancing comp

power enablod CRMs to examine the large-scale
celfects of cloud system cod investigate the dynamical bavin af muli-seale convective
‘ripoli and Cotter: 1949, cloud.
‘chemistry interaction (see review by Thompson er al 1997), idleuized climate varlabsliey

‘argeninacion (c.g. Grubowski el al. 1998, Wu et al. 1998:

eg, Held ot al 1993; Lau or af 1993, 1994; Sui et of. 1954; Tan ef af 1999; aud Kig. 1);

orogiaphic effects on snow (Le, Saito er af, 1996); surface processes (Le, Lynn er ah
199% Wang of al. 2008: Zeng er af. 2007): und the develapunent of retrieval algovithas for
sitellite minal (see sevlew by Slompson 27, 1996) and latent heating (see review by Tuo et

at, 20065).

Riawasets on precipitaing comvection accumulated from radar. instrumented aircrll,
satellites, and tawinsondes deployed ie (eld campaigns during the past yemeratin, (6.8
GATR, TOGA COARH, SCSMFX, KWAIEX, DOL/ARM? among others} stow the
‘ubiquity of tropical neeunic mesoscale convective system. A prevalenl cioud-system type
consists oF dep cunulonimbys convostien embedlat in leadingtalting stariforma reyiors

fog, Howe ol al, 1980, Zipsor 1977; Houze amt Betis 198; Houze 2004). Dataests on

precipitating comveerion accumolanst from rudur, instrumented airerafl, satellites, and

ruvvinsondes depleyed in fsld carcpalyns during the gast generation. (@.g.. GATT, TOGA,

COARF, SCSMEX, KWAJKX, DOFYARM* amang others! show the ubiquity: of Uropical

occanic mesosoule convective systema. A prevalunl type ef convective organization of deep

F Caml ameintle masi elow seve soventvn clouds (0 dow-ap ames, Spieat'y wing yeti
laa rear sions.

J Chouan Aanosphere Repuase

mest, RWAIBS for Kaagln,

armcephere Roden Vienne

TOG FOARE for topical Itesptere (IGA = Ceupled ecm Ammoepbere Rex
perinent (COARL);ACSMES for Sou Cian Seu Musa hepa, RWATER tor Kean

einen: oud tke LAO AR fo Dearest ot Basi acephere cae Viste

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cmmmulonimbus convection eeidedded in leading‘talling statiform regions, namely
mscsoseale convertive systems, MCS (e.g, (louse etal. 1980, Zipser 1977; Houze ancl Betts
1982; Howse 2004).

CRMG represoa: subgrid-scale processes mare cinmpletely than lange-seale models,
sare compre ts dynamics at the cloud seale: 1) spetral-bin

because physical proves

riccaphysical processes which represent cloud aerosol-ehemistry interscrious: iy elowd-

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radiation interavton; if) turbulence; and iv) atmosphere-surtace models simulate che water
and euctgy eyoles, her the past four decades, CRM inteyrativa Limes have extended ftom
hows to months, and le umber of grid points frum Jess than 1000 to abour 106 asillio.
Cucial mist mesosuule dynanical processes and their large-scale effects are represented

cexplieitly in 10,000 kan computational domains in two spatial dimensions (i2., Peng eral

2wvl; Grabowski und Monerief? 2001) and 1,000 x 1,000 Yom? —douisins en three
Aimensions (Yoshizaki ot ai. 2008; Saito xr at 2606), Prototype glohal cloud-system

resolving madels exist (Miura e: a1 2007),

EG Tag a Ee

‘com Gn Mt Cis Homann

Table 1: Hightights of cloud mel development over the past finer devudes. jAdapted trom
Taso and Moneriel} (20031: Tao 2H03) and madlifiad in Jung of ob. (20079).

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ized inte 11 sections, ‘The physical propestics of CRMs are

Thin paper 8 ong

marized in section 2, follewod by the effects of microphysics pursmeterizalicms in

Section 3. The etfects of aerosol, surface-cxchange and radiative provewes are reviewed in
swelions 4, 5 and 6, respectively. ‘tthe diumual variation of precipitation is summarized in
sectian 7 and satettite applications in soction 8. Mesoscale convective urganization is he
theme of section 9, aud fiture developmen in section 10, The paper eoclus in section 11

Faysical characteristics of CRMs

es. First, in classics

‘There ure two eomplementary CRM-based spproac cloud models,
which wan awe be sun at eaey bigh resolution, a focal issue is convective initiagion and
yrocess interaction over short pcviods (hours). Whe verified agsinst field eampaiym sata,
auch sunwat.ons provide a detailed symthosis of variety of cloull processes. Secand, in tse
second approach (Soong and Ognra #980; Soong und Tan {980 Lipps and Helmer 1986:"Ts0

and Soong 1986; Kruoger 1988: und many cteny ORM un af a lower cesointion (acid

spacing about | km) enable fislds of clouds ir various stages of thelt Ile eyele to interact

across a wide dynamic range. When constrained by spcciticd large-scale advoction of

levnpsrature and moisture (large-scale thermodynamic forcing) derived fram observations,

These males sinvulate raialall, @rapelature and water vapo: distribution with eonsidenuble

realism 12.4, Tao 2003, Randall eta, 238 and ethers) and provide a wealth af statics
information usetil parasteriantion dewstogment. The secrnd upprsach isthe basis for globat

loud systom sesolv.ng models

Clyudlersierophysieal processes (quclealion, diMusion growth and collisions be-ween
stood and precipitation particles) ure parameterized in CRMs, sloug with anuospherie
lurbulenee, lrbulent exchange ul oceaniclerrestval boundavies, and radiative tusfes, Figure
5 shnows lypical chasustevstien deseeibod beiafly below.

Dynamical cures

ATI CRMs are based on the nonhydrosratis equatieus of motion, which is necessary for a

slastiv (Ogura unl Phillips 1942),

grid-spacing smuallec than about 10k, “They may he
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where sound waves are fitore by neylenting the local time-variation of Jemsily in the mass
continuity equation, of compressible in whieh sound waves arc retamod, Sound waves ure
-metenratogically unmportant, bul [heir lasl phase. speed (about 300-mvs) severely Vint the
time step (2, 2 tumo-step of 2 yoounds is meded at 1000m guid-spacing). Klemp xnd
Wilketwnson (1978) umproved ccamputational elfisieney by using a semi-impiieit time-
splitting schecne {equations are split ipto sound-wave and aeaviry-wave components). An

advinuye of che corapressil

em is Thal ihe set of prognostic equations are structurally

similar. To contrast, ths anclastic approach invol

BD dhagnostic (elliptic) preswure
‘oquation, although this can be solved eMiviectly using modern direst (eg. Pourier
‘Transfonm) o¢ iterative methods, Tkawa (1988) and Tao and Simpson (1999) showed that
compressible and anelastie formulations give similar results, for example, compured
Jifferences that arise due lo changing the cloud-aulerophysies parameterization

1B) Microphysiex und precipitation

In CRMs, mierophysival and precip.tarion proceswee are caupled al cloud-seale and sre,
therefore, more reiistie dian ia global models. Is one-moment bulk miraphysieal sciomes
(eg. Hin era. 1983 and Rutledge and Hobby 1984) with tvo-clas Tiguld feloud vearer and
rain) nnd three-slass ice (cloud ice, snow and graupelbail) che shapes of uou-precipitating,
fliquid andl ive) are assumed 9 be spierical, The size distibutions of the precipitating

particles (rin, smw and gcaupclehai2) follow a Urree-parameter yaonraa disteibution fonction
such thar MD) =A.,0"exp( AD), where No is the interespe parameter. A. the slope of the
particle sine divriution and « the shape parameter’ Orly the hydrometeor mass conten,
Proportional to ND is predicwel in tee-enorveut bulls schemes (i... Murakami 1990:
Thawa ef ai, 1991: Ferrier 1994; Meyers ef wl. 1997; Resincr er al 1998, Walk et af. 2000,
Mortison ef al, 2008; an Seifert end Deheng 2005), mass commn ard the toral umber

soncenteation arc predicted, In the mlti-tiomenr bulk microphysical scherne | Mifbrandt and
‘Yan 2005), e varies ana finetton of the meau-anass diameter. The effects of ice processes

5 Grampel has alow evry wala Wah intr ri, bigh wimber ceneematon}_ te cmt, al ae high
conity et sal icra. Tho choise of graupel of hl leer or whore th clos of cloud syster=
‘selopod {hcComber ov ai 19911 Pee spiel cloves, yrampel iw mune seprescomtice. ay bal Tor
trdladteds ob cone pons,

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on sorfie

ofall have hoen quantified identiGed (Favell and Ogura 1988; Tao er af. 1989,
G0 et. 2606a, among others

Explicit bin-microphysie:
nent and clond-aeresol interaction (@.¢4 Tekhashi 1976; Chen and Lamb 1994; Khain ofa

schemes developed for CRMs examine cirrus develop-

2014), Explicit hin-mierophysieal schera

s are based an che stachastic kinetic equations for
the size distribution and ure functions of water (elwud droplets anc raindrops) and ice
pirticley of different tuhits (ie, evhunnac, plate-ike, dendeites, snowflakes, ginupel and
Troven deaps). Each type is described in teems of as size-cistitption fimetion eomisining
‘over 30 cateyories Chins). Nucleation (activation) processes atc based on tae size-disiibution
function far cloud condensatian nuclei (> 30 size categories), Dewsiled mierophysies
calculations are 9 useful tamework for evaluating and improving bulk microphysical
schomes. However, the numerous ineetaetions involved in bin.

cicrophysical

rootires CRM comains te small an! the ximations, esr

eo) Turbulence

While convective organization invotving mesoscale aud larger scale dynamics is rewlved by
CRMs, motion smaller than the grid-soale (sub-gtid scale SCS turbulence} have st be

pacomererized. An ensemble-macan tutuleuce modcl represents SIS effects. Typically, a

simple kyge (first-order) tarbolence closure i used a siugnense the k-cpelTcient of oben it
dem the turbulent kinviv onsrgy (TKT) equation (oneand-achatl onder}, fu the prognostic
IKK method, thermovmamie suhiliy, deformation, shear stability, diffesion, dissiparion,
moist processes and (rarspunt of sub-prid eneray’ are inclased, Ln the diagrossie enethod,
detocmation and seabitity are used to compute the k-cusilisiemt. The mpst epee
lwebulenoe parametelization used 8 CRMs 1s a third-order vlogure (Krueger 1988), The
peefoemance of thicd-eider mirbulence closure is similar to the one-und-a-hulé ondot TKE
appeoach for deep coavest.ve systems, ‘hind-order closure i+ neeesary for simulating

shallow cumuli aad boundary-layer cunnnlus (i.e, Cheng and Xu 2006; Cheng ot af 2004)

2 an inva viol Ainutbuion tt yng sosumel in Ln ota (1983)

nocspen

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