Abstract
Using a combination of NOAA P-3 aircraft tail Doppler radar, NOAA and NASA dropsondes, and buoyand drifter-based sea surface temperature data, different types of downdrafts and their influence on boundary layer (BL) thermodynamics are examined in Hurricane Earl (2010) during periods prior to rapid intensification [RI; a 30-kt (15.4ms -1 ) increase in intensity over 24 h] and during RI. Before RI, the BL was generally warm and moist. The largest hindrances for intensification are convectively driven downdrafts inside the radius of maximum winds (RMW) and upshear-right quadrant, and vortex-tilt-induced downdrafts outside the RMWin the upshear-left quadrant. Possible mechanisms for overcoming the low entropy (θe) air induced by these downdrafts are BL recovery through air-sea enthalpy fluxes and turbulent mixing by atmospheric eddies. During RI, convective downdrafts of varying strengths in the upshear-left quadrant had differing effects on the low-level entropy and surface heat fluxes. Interestingly, the stronger downdrafts corresponded with maximums in 10-m θe. It is hypothesized that the large amount of evaporation in a strong (>2ms -1 ) downdraft underneath a precipitation core can lead to high amounts of near-surface specific humidity. By contrast, weaker downdrafts corresponded with minimums in 10-m θe, likely because they contained lower evaporation rates. Since weak and dry downdrafts require more surface fluxes to recover the low entropy air than strong and moist downdrafts, they are greater hindrances to storm intensification. This study emphasizes how different types of downdrafts are tied to hurricane intensity change through their modification of BL thermodynamics.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3545-3565 |
| Number of pages | 21 |
| Journal | Monthly Weather Review |
| Volume | 146 |
| Issue number | 11 |
| DOIs | |
| State | Published - Jan 1 2018 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Atmospheric Science
Cite this
Downdrafts and the evolution of boundary layer thermodynamics in hurricane earl (2010) before and during rapid intensification. / Wadler, Joshua B.; Zhang, Jun A.; Jaimes, Benjamin; Shay, Lynn K.
In: Monthly Weather Review, Vol. 146, No. 11, 01.01.2018, p. 3545-3565.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Downdrafts and the evolution of boundary layer thermodynamics in hurricane earl (2010) before and during rapid intensification
AU - Wadler, Joshua B.
AU - Zhang, Jun A.
AU - Jaimes, Benjamin
AU - Shay, Lynn K
PY - 2018/1/1
Y1 - 2018/1/1
N2 - Using a combination of NOAA P-3 aircraft tail Doppler radar, NOAA and NASA dropsondes, and buoyand drifter-based sea surface temperature data, different types of downdrafts and their influence on boundary layer (BL) thermodynamics are examined in Hurricane Earl (2010) during periods prior to rapid intensification [RI; a 30-kt (15.4ms -1 ) increase in intensity over 24 h] and during RI. Before RI, the BL was generally warm and moist. The largest hindrances for intensification are convectively driven downdrafts inside the radius of maximum winds (RMW) and upshear-right quadrant, and vortex-tilt-induced downdrafts outside the RMWin the upshear-left quadrant. Possible mechanisms for overcoming the low entropy (θe) air induced by these downdrafts are BL recovery through air-sea enthalpy fluxes and turbulent mixing by atmospheric eddies. During RI, convective downdrafts of varying strengths in the upshear-left quadrant had differing effects on the low-level entropy and surface heat fluxes. Interestingly, the stronger downdrafts corresponded with maximums in 10-m θe. It is hypothesized that the large amount of evaporation in a strong (>2ms -1 ) downdraft underneath a precipitation core can lead to high amounts of near-surface specific humidity. By contrast, weaker downdrafts corresponded with minimums in 10-m θe, likely because they contained lower evaporation rates. Since weak and dry downdrafts require more surface fluxes to recover the low entropy air than strong and moist downdrafts, they are greater hindrances to storm intensification. This study emphasizes how different types of downdrafts are tied to hurricane intensity change through their modification of BL thermodynamics.
AB - Using a combination of NOAA P-3 aircraft tail Doppler radar, NOAA and NASA dropsondes, and buoyand drifter-based sea surface temperature data, different types of downdrafts and their influence on boundary layer (BL) thermodynamics are examined in Hurricane Earl (2010) during periods prior to rapid intensification [RI; a 30-kt (15.4ms -1 ) increase in intensity over 24 h] and during RI. Before RI, the BL was generally warm and moist. The largest hindrances for intensification are convectively driven downdrafts inside the radius of maximum winds (RMW) and upshear-right quadrant, and vortex-tilt-induced downdrafts outside the RMWin the upshear-left quadrant. Possible mechanisms for overcoming the low entropy (θe) air induced by these downdrafts are BL recovery through air-sea enthalpy fluxes and turbulent mixing by atmospheric eddies. During RI, convective downdrafts of varying strengths in the upshear-left quadrant had differing effects on the low-level entropy and surface heat fluxes. Interestingly, the stronger downdrafts corresponded with maximums in 10-m θe. It is hypothesized that the large amount of evaporation in a strong (>2ms -1 ) downdraft underneath a precipitation core can lead to high amounts of near-surface specific humidity. By contrast, weaker downdrafts corresponded with minimums in 10-m θe, likely because they contained lower evaporation rates. Since weak and dry downdrafts require more surface fluxes to recover the low entropy air than strong and moist downdrafts, they are greater hindrances to storm intensification. This study emphasizes how different types of downdrafts are tied to hurricane intensity change through their modification of BL thermodynamics.
UR - http://www.scopus.com/inward/record.url?scp=85062442792&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85062442792&partnerID=8YFLogxK
U2 - 10.1175/MWR-D-18-0090.1
DO - 10.1175/MWR-D-18-0090.1
M3 - Article
VL - 146
SP - 3545
EP - 3565
JO - Monthly Weather Review
JF - Monthly Weather Review
SN - 0027-0644
IS - 11
ER -