1. Jennifer C. DeHart, Robert A. Houze, Jr., and Robert F. Rogers
Quadrant distribution of tropical cyclone inner-core kinematics in relation to environmental shear
This research was supported by NASA grants NNX12AJ82G and NNX13AG71G and NSF grant ATM
Jennifer C. DeHart, Robert A. Houze, Jr., and Robert F. Rogers
AMS Tropical • April 4th, 2014

2. Prior Composite Studies
Big Takeaways
General downshear-upshear convective pattern
No analysis of vertical dimension
Horizontal Composites
Rainfall (Chen et al. 2006)
Lightning (Corbosiero and Molinari 2002, 2003)
interaction between environmental shear and tropical cyclones has been studied in case studies to modeling studies and large sample size compositing studies, such as the rainfall and lightning ones mentioned here. They all found a downshear-upshear convective pattern, where convection more frequent downshear and less frequent upshear. However, in the case of these compositing studies of convective proxies, there was a lack of analysis of the vertical dimension.
TRANSITION: include analysis of vertical dimension.

3. Vertical Structure Hence and Houze (2011) Reasor et al. (2013)
TRMM PR
convective evolution
BUT: lack velocity
Reasor et al. (2013)
vertical motion consistent with previous studies
BUT: only examine mean
Hence and Houze included the vertical dimension using data from the TRMM PR. From their distribution analysis of these storms, they found that convection initiated DR, matured DL before dying out upshear. However, they lacked vertical velocity data.
Reasor et al took advantage of kinematic information from airborne doppler radar data and through examining quadrant cross-sections, found that vertical motion was consistent with previous studies. However, in analyzing only the mean quadrant structure, information about variability within the quadrant is lost.
Transition: where do we go from here?

4. Objective
Examine the PDF of vertical velocity to determine if it is consistent with the eyewall convective evolution implied by the radar reflectivity statistics
Transition: In order to accomplish this, we will utilize airborne dual-doppler radar data.

5. Dataset NOAA WP-3D Tail Radar Automated variational algorithm
125 eyewall crossings, 39 flights, 12 hurricanes
SHIPS deep-layer shear ( hPa)
> 2 kts
NOAA WP-3D Tail Radar
Automated variational algorithm
Gamache 1997
Normalize horizontal dimension by RMW2km

6. Eyewall Radar-derived Vertical Velocity CFAD
contours: 5%
: 50%
Here’s the total eyewall w CFAD. Only analyzing w data below 10km due to loss of data quality above that altitude. CFAD is normalized by the maximum count, corresponding to a frequency of 100%. The most frequent vertical velocities, signified by frequencies larger than 50%, encompass velocities between -1 and 1.5 m/s. However, 5% contour lines extend out to strong vertical motion (-3 and 6 m/s). Strong vertical velocities occur more frequently at upper levels, consistent with previous radar studies and likely related to latent heat of fusion and precipitation unloading.
TRANSITION: This is nice, but again, we want to see structural differences due to shear. Here, I’m going to switch directly to the anomaly CFADs as they are more informative.

7. Eyewall Vertical Velocity -- Anomalies+%
contours: 2%
Anomaly CFADs for w. DR is primarily updrafts, moreover, the frequency anomalies are centered on weak to moderate upward motion. DL has a broad distribution: reduction in weak velocity occurrence. Downdrafts begin to develop from DR to DL. Additionally, updrafts present in this quadrant tend to be stronger. This combination of strong upward motion and downdraft development show that convection within this quadrant is more mature. Additionally, Reasor et al noted that composite ascent is stronger DR, the usage of the mean means that you lose this variability information. Downdrafts are prevalent UL: convection begins to die out here. UR motion is weak (both updrafts and downdrafts).
TRANSITION: this is all for middle of the road velocities, what about outliers? -%

8. Conclusion #1: Confirmation of convective evolution hypothesis

9. What about outlier velocities?
Recent studies have analyzed strong updrafts in relation to intensity changes
how do they behave in relation to shear?
Isolate data points where:
w >= 5 m s-1
w <= -4 m s-1
Investigate radial-height structure
Set thresholds and require 5 contiguous pixels. Velocity magnitudes weaker than some seen in higher-resolution datasets, but these numbers correspond to ~95% outliers. Want to study radial-height structure. Similar to CFAD, but more like a cross-section. Recent focus has placed emphasis on strong updrafts in relation to intensity changes. Want to see how these vary.
say that I did same thresholds for -3 m/s, get same pattern

10. Intense Updrafts -- Shear
Here, plots have been normalized by maximum occurrence in any quadrant. As expected, strong downshear dominance. Segregating by high/low shear makes this more apparent. Appear to be slightly more DL, again consistent with what was shown in CFADs. Mature convection in this quadrant = more of these here.
TRANSITION: Downdrafts
contours: 5%
: 50%

11. Intense Downdrafts -- Shear
Similar, normalized by maximum in any quadrant. Really impressive dominance by UL quadrant. Very few DR. DL they hug eyewall, again, likely in response buoyant updrafts in this quadrant. Perhaps there is a different reason for the UL distribution.
ADD IN summary box
TRANSITION: What is the context for these drafts? Any different behavior between updrafts and downdrafts?
contours: 5%
: 50%

12. Intense drafts follow same pattern in relation to shear:
Conclusion #2
Intense drafts follow same pattern in relation to shear:
Strong updrafts occur more often downshear.
Strong downdrafts are highly concentrated in the UL quadrant.

13. Frame drafts in context of w, vr
Identify azimuth of strong drafts
Isolate sector +/- 2 degrees from azimuth
Composite cross-sections
Only unique data points used
sectors of adjacent drafts used only once
Go through methodology.
TRANSITION: Start with updrafts.

14. Total Eyewall Intense Updrafts Intense Downdrafts w vr w vr
Only looking at vertical and radial velocity as reflectivity and tangential velocity weren’t very different for updrafts and downdrafts.
Let’s compare the different flow structures. Very different structures. Is this a difference in behavior associated with these types of drafts? Or is it a result of sampling.
TRANSITION: Split by shear.

15. Radial Flow in left of shear quadrants
Intense Updrafts
Intense Downdrafts
Relationship between radial and vertical flow:
is vertical motion amplified by radial flow?
does vertical motion induce radial flow?
do they arise from a common cause
Radial flow pattern suggest a possible dynamic forcing in addition to convective lifecycle for downdraft maximum there (either from the relative flow pattern, or through entrainment of dry air). However, without thermodynamic information, it’s not possible to fully evaluate that.
TRANSITION: In summary, …

16. Conclusion #3
Radial flow suggests different dynamical behavior when intense updrafts and downdrafts present