A"Comparison"of"X.band"Polariza4on"Parameters"with"In.Situ"Cloud"&"W.band"Radar"Measurements"in"the"Comma"Head"of"A"Winter"Cyclone"

Joseph"A."Finlon1,"David"M."Plummer1,"Robert"M."Rauber1,"Greg"M."McFarquhar1,"Brian"F."JeweN1,"Kevin"R."Knupp2,"David"Leon3"

1Department"of"Atmospheric"Sciences,"University"of"Illinois"at"Urbana.Champaign,"2Atmospheric"Science,"University"of"Alabama,"Huntsville,"3University"of"Wyoming"Atmospheric"Science""1.  Objec4ves"

• Analyze" the" ver4cal" change" of" dual.polariza4on"parameters"(from"ground.based"radar)"within"the"22"February"2010"cyclone"during"the"Profiling"of"Winter"Storms"(PLOWS)"field"campaign."• Relate" these" findings" to" coincident" in.situ" cloud"microphysical"measurements."

2.  Data"Both"the"Mobile"Alabama"X.band"(MAX)"Doppler"Radar"and"the"W.band"Wyoming"Cloud"Radar"(WCR)"profiled"the"comma"head"region"of"a"cyclone"as"the"NSF/NCAR"C.130"aircra\"made"ver4cally"stacked"passes"along"the"same"azimuthal"angle"as"the"MAX"RHI"radar"scans."

Fig." 1" The" MAX" radar" measured"reflec4vity" (Z)" and" radial" velocity,"a s" we l l" a s" the" co r re l a4on"coefficient" (ρhv)" and" differen4al"reflec4vity"(Zdr)."

Fig." 2" The" two.dimensional" cloud"(2D.C," above)" and" precipita4on"(2D.P)" probes" captured" par4cle"size" and" shape" along" with" other"variables."

Fig." 3" WSR.88D" regional" radar" for"0045" UTC" 22" February" 2010." The"MAX"radar"loca4on"(pink"triangle)"is"shown,"with" the"black" line"outlining"the" scanning" direc4on" and" flight"path" of" the" MAX" and" C.130,"respec4vely."

""

4."Dual.Polariza4on"Measurements"

S" N"

5(a)%

Fig."4"(a)"WCR"reflec4vity"cross"sec4on"for"the"same"path"as"(b.d)"MAX"RHI"variables."Pink"dot"in"RHI"scans"denote"the"loca4on"of"the"C.130"aircra\,"with"average"values"of"Z,"ρhv,"and"Zdr"as"the"aircra\"flew"toward/away"from"the"MAX"radar."Same"as"in"Fig."5 "but"at"a"different"aircra\"al4tude."

5."Microphysical"Measurements"

4"4.5"5"

5.5"6"

6.5"7"

7.5"8"

Al(tud

e%[km]%

Fig." 6" 2D.C" par4cle" images" taken" at" four"specified" al4tudes," with" a" notable" shi\" in"crystal"size"and"composi4on"at"lower"al4tudes."

1.6mm"

Z"[dBZ]"ρhv"

Zdr "[dB]"

Fig."7"Plots"of"(a)"size"distribu4ons,"(b)"concentra4on,"(c)"IWC,"(d)"median"mass"diameter,"and"(e)"mass.weighted"area"ra4o" for" four"different"al4tudes"within" the" cyclone." Increasing"par4cle" size"deeper"within" the" cloud" support"par4cle"growth"by"aggrega4on"as" in"Fig."6."Current"work" is"examining" linkage"between"area"ra4o"and"Zdr"data"on"a"point.by.point"basis."

3.  Methodology"• Reflec4vity" and" dual.polariza4on" variables" from" the"MAX"were"averaged"at"specific"C.130"al4tudes"during"4mes" when" the" aircra\" was" close" to" the" X.band"radar."•  2D.C" images," as" well" as" size" distribu4ons" and"corresponding" bulk" parameters" determined" from"2DC/2DP"probes,"were"used"when" the"C.130"was" in"the"view"sampled"by"the"MAX"RHI"scans."

6.  Conclusions"• Dual.pol" measurements" of""ρhv" and" Zdr" are" consistent"with" more" uniformity" in"par4cle" shape" and" larger"par4cle" size" deeper" within"the"cloud,"respec4vely."•  Corresponding" probe" data"suggests" that" growth" by"aggrega4on" is" occurring"during"the"par4cle’s"descent"(no"liquid"water"is"present"at"these" levels" for" riming" to"occur)."• Uniqueness" of" coincident"ground." and" a i r .based"measurements" of" the" same"cyclone" region" give" further"insight" into" the"MAX" radar’s"dual.pol"values."

Acknowledgements""

This" research" is" funded" by"grant" NSF.AGS.0833828."Thanks" to" the" University" of"Alabama"in"Huntsville"for"data"collec4on" through" the" use" of"the"MAX"radar."

Contact""

finlon2@illinois.edu"www.joefinlon.me"

Al4tud

e"[km]"

Time"[UTC]"

Distance"[km]"20" 40" 60" 80"

Sensi4vity"of"WCR"makes"it"beNer"able"to"detect"weak"echoes."C.130"flight"track"

Reflec4vity"[dBZe ]"

20" 40" 60" 80"Distance"[km]"

Time"[UTC]"

C.130" encountering" merging" of" ice"par4cles"deeper"within"the"cloud."

(b)%

(c)%

(d)%

Distance"from"Radar"[km]"

Al4tud

e"[km]"

Zavg"=".14.8"dBZ"

ρhv,avg="0.48"

Zdr,avg"="1.4"dB"

4(a)%

(b)%

(c)%

Zavg"=".3.9"dBZ"

ρhv,avg="0.86"

(d)%

Zdr,avg"="2.9"dB"

S" N"Distance"from"Radar"[km]"

Higher"values"indicate"par4cles"fairly"uniform"in"size"and"shape."

Higher"values"are"consistent"with"larger,"more"dense"crystals."

MAX Radar (01:05 UTC) MAX Radar (02:35 UTC)

Growing"size"suggests"aggrega4on"of"crystals"is"occurring."

LiNle"increase"in"par4cle"concentra4on"

Al4tud

e"[km]"

N"[#"liter.1]"

Increasing"IWC"

IWC"[g"m.3]"

Increasing"par4cle"size"

Al4tud

e"[km]"

Dmm"[μm]" Mass.weighted"Area"Ra4o"

General"trend"consistent"with"more"circular"

par4cles"(except"for"

lowest"al4tude)"

Higher"concentra4ons"of"

larger"par4cles"deeper"within"

cloud."

Dmax"[μm]"

N(D)"[cm

.4]"