dynamical processes at the storm top pao k. wang department of atmospheric and oceanic sciences...
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Dynamical processes at the storm top
PAO K. WANGDEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES
UNIVERSITY OF WISCONSIN-MADISONMADISON, WISCONSIN, USA
RESEARCH CENTER FOR ENVIRONMENTAL CHANGESACADEMIA SINICA
TAIPEI, TAIWAN
2014-04-08 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 = 0a 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 plumesInstability and Wave Breaking
Convection-induced instability and gravity wave breaking at the storm top send H2O through the tropopause to enter the stratosphere.
Overshooting top plumes Anvil wave breaking
Wang (2007)
Wang et al. (2011)
Courtesy of Zdenek Charvat
Ship wavesobstacle 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
Courtesy of Maria Putsay
Wave in a moving fluidwind
Courtesy of Martin Setvak
Interference of wavessame phase, frequency, amplitude, no wind
Same phase, frequency, amplitude, constant wind
2 point sources. D = 3.5 lambda
u
D = 1.5 lambda
D = 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?