Dynamical processes at the storm top PAO K. WANG DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES UNIVERSITY OF WISCONSIN-MADISON MADISON, WISCONSIN, USA RESEARCH CENTER FOR ENVIRONMENTAL CHANGES ACADEMIA SINICA TAIPEI, TAIWAN EUMETSAT CWG WORKSHOP, ZAGREB, CROATIA

collaborators  Kai-Yuan Cheng  Tempei Hashino  Martin Setvak  Maria Putsay  Zdenek Charvat

Satellite observed features of storm tops The features shown at the top of a storm is the combined result of many different physical processes If we can explain the formation of these features, we can understand better the development of thunderstorms We can also use such knowledge to nowcast the storm behavior

Some storm top features recently examined Above anvil cirrus plumes Cold-U(V) Cold area (CA) Closed-in warm area (CWA) Warm-cold couplet Cold rings Warm trenches Ship waves

Basic dynamic processes of deep convection Air parcel rapidly rises from the boundary layer to the tropopause level, and often overshoot, to release the instability Part of the KE carried by the parcel is used to excite internal gravity waves (IGW) near the storm top when the parcel encounters the stable stratosphere The interaction among updraft, ambient wind, and IGW is largely responsible for most storm top features as observed by meteorological satellites. 

Cold-V, CWA, warm-cold couplet, distant warm area

Interaction between ambient wind and updraft

Weak wind shear – cold ring

Something is going on… warmer doesn't necessarily mean lower 1500 sec

If we set U = 0 a symmetric cold ring appears

HIGHER BUT WARMER ?! Wave breaking and mixing 1800 sec

Masking effect of plumes

Above anvil cirrus plumes plume Anvil Storms over Balearic Islands

Above anvil cirrus plumes Instability and Wave Breaking  Convection-induced instability and gravity wave breaking at the storm top send H 2 O through the tropopause to enter the stratosphere. Overshooting top plumes Anvil wave breaking Wang (2007)

Wang et al. (2011)

Courtesy of Zdenek Charvat

Ship waves obstacle effect of storms

Latest example of storm top ship waves from Suomi NPP image Courtesy of Kris Bedka

Radial cirrus features Setvak et al., 2013

Putsay et al., 2009

Courtesy of Maria Putsay

Wave in a moving fluid wind

Courtesy of Martin Setvak

Interference of waves same phase, frequency, amplitude, no wind

Same phase, frequency, amplitude, constant wind 2 point sources. D = 3.5 lambda

D = 1.5 lambdaD = 2 lambda D = 3.5 lambda D = 4 lambda

3 sources (i.e., 3 Ots)

Implications  Cbs with radial cirrus features possibly have two or more overshooting tops  The IGW caused by different OTs interfere which causes the quasi-radial pattern  Interference enhances wave amplitude, hence stronger CAT above the storm may be expected  Above storm layer is possibly more humid than previously thought  Do the presence of multiple OTs indicate a more intense storm?