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5.32 Estimating regions of tropopause folding and clear-air
turbulence with the GOES water vapor channel
Tony Wimmers, Wayne FeltzCooperative Institute for
Meteorological Satellite Studies (CIMSS), UW-Madison
World Weather Research Symposium on Nowcasting and Very Short
Range ForecastingToulouse, France, 5-9 Sept, 2005
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141210864150200300400500600700(~100 km)subtropicalair masspolar
air massstratospherePressure (hPa)Height (km)tropopauseCAT and
tropopause foldsUpper-air frontAbstract: Clear-air turbulence
remains a significant aviation hazard, yet by its nature it is very
difficult to detect. One of the sources of clear-air turbulence is
the dynamic instability associated with tropopause folding, which
describes the entrainment of stratospheric air into tropospheric
levels at upper-level fronts. We describe a near real-time
satellite product that estimates areas of tropopause folding in
regions of strong humidity gradients in the GOES midwave infrared
(water vapor) channel. Using an empirical relationship between
upper tropospheric humidity gradients and tropopause breaks, the
algorithm estimates that turbulence-generating tropopause folds
protrude from some of these tropopause breaks. This product is
validated over the United States with manual pilot reports as well
as newer automated aircraft reports of turbulence.
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Vertical component of the fold
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Web product: Real-time pirep validation Pirep data is provided
courtesy of NCAR Aviation Digital Data Service (ADDS)
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Web product: Real-time TAMDAR validation TAMDAR (Tropospheric
Airborne Meteorological Data Report) is part of the Great Lakes
Field Experiment Unfortunately, it is mostly lower and
midtroposphere
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http://cimss.ssec.wisc.edu/asap/exper/tfoldsVer2/pirepSep.htmlhttp://cimss.ssec.wisc.edu/asap/exper/tfoldsVer2/tamdarDisplay.html
Web pages:
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April 8-30, 2005 1500-2300 UTC (peak time) Eastern U.S. (away
from mountain wave turbulence) Above 15,000 feet (mid- and upper
troposphere) Areas of strong convection are filtered out (no
C.A.T.) If the pirep is in a modeled fold and reports turbulence,
then this is a correctly classified Yes report. If the pirep is
outside a modeled fold and reports no turbulence, this is a
correctly classified No report. 2,293 pirep observations, 62% of
ALL observations are turbulent.Validation: Details
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Find the models Probability of Detection for turbulence Next,
search for any further constraints on the model that improve the
Probability of DetectionValidation: Method
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* Does not purport to classify all negative reportsStatistics
for tropopause fold turbulence prediction (N=2293, background rate
of success=0.64)
Number of Yes reportsProportion of Yes reports correctly
classifiedProportion of No reports mis-classified*
1. Initial model2960.770.632. Revised model: Longer
folds2400.780.633. Revised model (#2): Longer folds, higher
gradients1380.820.63
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The tropopause folding model shows significant skill at
predicting upper-tropospheric turbulence The model increases in
accuracy significantly as it is made more selective (Prob of
Detection = 82%) Predicted turbulence is predominantly light or
moderatePreliminary conclusions: Trop folding + CATsubtropicalair
masspolar air massstratosphereUpper-air front
My title and objective is
Saves lives, prevents damage and injury for anyone who gets on a
plane. Basically, theres a lot of time and money that goes into
this kind of safety.
The tie-in to multispectral will be evident later
Those of you who do midwave IR water vapor applications should
be particularly interested in this. The rest of you, I dont
know.Although this graph shows the chemical mixing, it was
coincident with CATSo we need a tool to estimate tropopause
heightMajor issues for multispectral sounding: What position do we
assign to the fold? Can we obtain a tropopause height? Can we make
out multiple layers? ***Notes:This latest version, which uses RUC
grids to assign a height to the folds, was completed last
Friday.The base image is the specific humidity product blue and
purple are dry, polar subsiding air, yellow and orange are moist,
subtropical air, and convectionGray are the foldsTurbulent pireps
are red, non-turbulent pireps are in blueRed dots increase in size
with the severity of the turbulenceLabels are in hundreds of feet,
but reports that are in, above or below the folds show the
difference in potential temperature between the pirep and the
fold
Notes:
Now, I only have conclusions I can draw from an inspection of
the performance of the model so far, but since were just here to
share ideas, why dont I jump the gun and run these by you, and take
questions anyway?Now, I only have conclusions I can draw from an
inspection of the performance of the model so far, but since were
just here to share ideas, why dont I jump the gun and run these by
you, and take questions anyway?Now, I only have conclusions I can
draw from an inspection of the performance of the model so far, but
since were just here to share ideas, why dont I jump the gun and
run these by you, and take questions anyway?