Upper Ocean Observations of Upwelling Processes During Tropical Storm/Hurricane Isaac

1
Upper Ocean Observations of Upwelling Processes
During Tropical Storm/Hurricane Isaac

• B. Jaimes, L. K. Shay, J. Brewster,
• R. Schuster (RSMAS/UM), M. D. Powell (HRD/NOAA)
• Acknowledge HRD (Frank Marks) and NCEP,
• J. McFadden and Steven Paul (NOAA-AOC)

2
Idealized ocean response carton that includes
upwelling due to the divergence of the
wind-driven current in the surface mixed layer,
current shear central for mixing, SST cooling
and, potential feedback to the storm.
Leaman (1976)
3
Key Air-Sea Parameter and Scales ( From Price ,
JPO, 1983)
Rmax (Km)
t is from the HRD Hwind Product (Powell
and Houston, MWR, 1996)
Uh (m s-1)
t (Pa)
4

• High levels of oceanic heat content (OHC) were
  measured 9 days before the arrival of tropical
  cyclone (TC) Isaac. Successful probes during the
  P3 flight 19 AXBT, 21 AXCTD, 5 AXCP, 8
  dropsondes.

Deploy Good Bad Success
AXBTs 20 19 1 95
AXCTDs 21 20 1 95
AXCPs 13 5 8 39
Overall 54 44 10 82

• Altimeter-based surface geostrophic currents
  during the day that Isaac moved into the Gulf of
  Mexico.

5
Expendable probes deployed during in-storm
flights in Isaac
6
In-storm flight (28 Aug, 4AM)
Deployed Good Bad Success
AXBTs 20 18 2 90
AXCTDs 11 10 1 91
AXCPs 8 5 3 63
Overall 39 33 6 85
7
Post-Isaac flight (30 Aug)
Isaac Flight Summary

• 58 AXBTs deployed in other 3 in-storm flights
  (97)
• 218 Ocean probes
• overall success 88 during six flights
• Below are the T/S curves from XCTDs prior, during
  and after Isaac.

Deployed Good Bad Success
AXBTs 23 20 3 87
AXCTDs 24 23 1 96
AXCPs 20 17 3 85
Overall 67 60 7 90
8
Intensification to hurricane status over OHC
gradients.
Stronger hurricane winds occurred across OHC
gradients.
9
Contrasting ocean response in oceanic geostrophic
features. Contrasting distribution of ?E as a
function of underlying oceanic features.
10
vectors Vg (altimeter-based)
h20pre (m)
Isaac moved over and intense geostrophic oceanic
eddy field in the eastern Gulf of Mexico.
During intensification to hurricane (28 Aug), the
cyclonic curl of the wind stress extended over a
region of more than 300 km in diameter (4Rmax to
5Rmax).
contours
h20pre (m)

• h20pre is from SMARTS (25 Aug)
• t is from Hwind (1030z, 28 Aug)

11
contours ? h20in - h20pre (m)
h20pre (m)
Contrasting upwelling (dashed contours) and
downwelling (solid contours) regimes developed
inside the region of cyclonic curl of the wind
stress.

• h20pre is from SMARTS (25 Aug)
• h20in is from in situ P-3 data (28 Aug)
• t is from Hwind (1030z, 28 Aug)

Vertical velocity associated with isopycnal
displacements are a function both the geostrophic
current vorticity and the wind stress (Stern,
1965 Jaimes nd Shay 2009)
h20pre (m)
(contours)
12
Contrasting upwelling and cooling inside the
region of cyclonic wind stress curl
Downwelling
Upwelling
In-storm data is from the 28 August morning
flight (during intensification to hurricane level)
13
Isaac Response Summary

• Isaac data set has both atmospheric and
  oceanographic measurements across the entire Gulf
  (GPS sonde, expendables, drifters, moorings).
• Complete post-processing of the Isaac data set
  and analyze results for the
• Upwelling (3-D) signals (Isaac slow mover over
  the shelf break)
• Upper ocean response relative to the storm
  forcing and
• Integrate the AXBT (from the Demo Project),
  drifters and subsurface mooring data from GoMRI
  projects.
• Provide a synthesized data set to carefully
  evaluate ocean component of the coupled system
  and OSSEs.
• Operational models need temperature, current and
  salinity to evaluate oceanic and air-sea
  parameterizations used in coupled system.