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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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PowerPoint Slideshow about ' 2014-03-02, 10-11 UTC' - maggie-marquez


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Presentation Transcript
slide3
Moments onlyfrom „principalpeak“; canchangebetween liquid andicepeakdepending on whichoneisstronger!
slide4

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

slide5
Thicknessofsupercooledlayer at cloud top (usethe MDV switchingartefact!) seemstobewellcorrelatedwith LWP curve.
slide6

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…

slide8

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

slide9

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

slide10

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!

slide12

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

slide13

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

slide14
At 275m aboveground, wecanonlyidentifyonebroadpeakandthevariations in MDV stronglyincreased.
slide17

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) !

slide20

Movingtotheleft, weentertheleftsideofthestreakwhereweexpectthe fastest particlestoappear (notetherightpeak in thespectrum!)

slide21
Movingfurthertotheleft, the fastest particlesdisappear, andthe fast peakseemstomergewiththebackgroundspectrum
slide23

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

slide24

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

but also outside the fallstreaks the spectra reveal rimed particles below the thick liquid layer
But also outside thefallstreaks, thespectrarevealrimedparticlesbelowthethick liquid layer.
slide29

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

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