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2014-03-02, 10-11 UTC. Supercooled liquid water. Moments only from „ principal peak “; can change between liquid and ice peak depending on which one is stronger !.

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Supercooled liquid water
Supercooled liquid water


2014 03 02 10 11 utc
Moments onlyfrom „principalpeak“; canchangebetween liquid andicepeakdepending on whichoneisstronger!


2014 03 02 10 11 utc

Characteristicsofcloudwaterpeak: Ifturbulenceislow, peakisverynarrow (narrow PSD), closeto 0 m/s, oftenseparatedfromfasterfallingsmalliceandaggregates. Can beusedastracerforestimatingverticalairvelocity.


2014 03 02 10 11 utc
Thicknessofsupercooledlayer at cloud top (usethe MDV switchingartefact!) seemstobewellcorrelatedwith LWP curve.


2014 03 02 10 11 utc

The RS-RH profilesuggests a secondpossiblelayerofsupercooledwater at around 500m. Sinceturbulenceincreasesdrastically in thelowest 500m itis not easy to find a clear liquid peakhere. Maybethesizeandconcentrationofdropletsis just tosmall/lowtobedetected…



2014 03 02 10 11 utc

Starting at the liquid layerwealready find a peakbetween 0.5 and 1 m/s. This couldbe due tosmalliceandfirstaggregatesoralreadyrimedsinglecrystals (hardtosaywithoutotherparameters)


2014 03 02 10 11 utc

Just a fewhundredmetersbelow, the dominant peakisalreadybetween 1 and 1.7 m/s whilewe find a large areaof different icevelocities. Those large Doppler velocitiesindicate additional riminghashappenedduringthe last fewhundredmeters


2014 03 02 10 11 utc

Finally, at 500m, themainpeakspeedsupto 1.5 to 2 m/s, a clearrimingfeaturebecausevertical wind speedseemstobeingenerallow in thiscloud. Youcan also nicelyseethespeedingupofthespectra in therangespectrogram! Watch also thenicecorrelationbetween LWP maximaand MDV maxima!



2014 03 02 10 11 utc

At 400m thespectralpeaksare still clearlyseparatedandrelativelynarrow. Also the temporal variabilityofthe MDV isrelativelysmall.


2014 03 02 10 11 utc

A fewrangegatesbelow, theseparatedspectramoreandmoremergetoonepeak due toturbulencebroadening. The variations in MDV (see Time Spectrogram) are also muchstrongerandof larger „frequency“.


2014 03 02 10 11 utc
At 275m aboveground, wecanonlyidentifyonebroadpeakandthevariations in MDV stronglyincreased.



Cloud structure fallstreaks size sorting effects
Cloud Structure– Fallstreaks – Size SortingEffects


2014 03 02 10 11 utc

Unlikethecasebeforewe find forthiscloudtiltedfallstreaks. At cloud top the wind speedis larger than at e.g. 1km. Can thisexplainthetiltedfallstreaks?


For more details see my erad talk on tuesday
Formoredetails, seemy ERAD talk on Tuesday…

Fallstreaksfor:

Snowflake,vdop= 1 m/s

Rimedsnow, vdop = 2 m/s

Verticalprofileof horizontal wind u (unidirectional)

Note: The time fortheparticleto fall 600m (600s) is not neccesarilyequaltothe time onewouldderivefromthefallstreakstructure (300s) !


Background ice snow spectrum inbetween the fallstreaks
„Background“ ice/snowspectruminbetweenthefallstreaks


2014 03 02 10 11 utc

Movingtotheleft, weentertheleftsideofthestreakwhereweexpectthe fastest particlestoappear (notetherightpeak in thespectrum!)


2014 03 02 10 11 utc
Movingfurthertotheleft, the fastest particlesdisappear, andthe fast peakseemstomergewiththebackgroundspectrum


Super cooled liquid water
Super-cooled liquid water


2014 03 02 10 11 utc

RS indicatesthicklayer at cloud top with 100% RH. Withinthislayerwecanoftenseethenarrow liquid peak. LWP andplumestructureseemtobecorrelated.


2014 03 02 10 11 utc

The HSRL lidardatashowthat liquid wateralreadyexistswhenthe RS firstreaches 100% (2km). However, thedropletsizesand/orconcentrationsseemtobelowandthusthe liquid peakisveryweak.



At the top of the fallstreaks plumes the particles are already at least partly rimed
At the top ofthefallstreaks/plumestheparticlesarealready (at least partly) rimed


But also outside the fallstreaks the spectra reveal rimed particles below the thick liquid layer
But also outside thefallstreaks, thespectrarevealrimedparticlesbelowthethick liquid layer.


Multi peak spectra
Multi-peak Spectra


2014 03 02 10 11 utc

Itis not trivial tosaywherethe multiple peakscomefromsincetheyareinfluencedbydynamicaleffects (e.g. mergingoftwofallstreaks) aswellasbymicrophysicaleffects (e.g. riming).