65th IHC Booklet/Program (pdf - 4.9MB) - Office of the Federal ...

Real-Time Airborne Ocean Measurements and Predictions of Loop Current Eddy
Shedding During the Deepwater Horizon Oil Spill: Implications for Hurricane Intensity
Forecasting
Lynn K. Shay 1 , Benjamin Jaimes 1 , Jodi K. Brewster 1 , Patrick Meyers 1 , Claire McCaskill 1 ,
Steven Paul 2 , Eric W. Uhlhorn 3 , Frank D. Marks 3 , George R. Halliwell Jr. 4
(nshay@rsmas.miami.edu)
1 Division of Meteorology and Physical Oceanography, RSMAS, University of Miami; 2 Office of
Aircraft Operations, NOAA, MacDill AFB 3 Hurricane Research Division, NOAA, AOML
4 Physical Oceanography Division, NOAA, AOML
Several flights from NOAA WP-3D aircraft were conducted between 5 May and 9 July 2010 that
focused on temperature, currents and salinity in a geographical location to the southeast of the
Deepwater Horizon (DWH) rig, and over the Loop Current (LC) and associated eddies. These
flights provided the evolving oceanic variability of the LC, the shedding of warm core eddy
Franklin, and frontal eddies along its' periphery. Atmospheric dropsondes (for surface winds)
and airborne expendable ocean profilers sampling to as deep as 1500 m (from expendable current
profilers: AXCP) were deployed in a lawnmower pattern with essentially the drop points. Over
700 airborne ocean profilers were deployed that included AXBT, AXCP, and conductivitytemperature-depth
profilers (AXCTD). These data, acquired over a weekly basis over the LC,
were assimilated into operational ocean models (HYCOM) at NAVOCEANO to predict potential
pathways of the oil from the northern Gulf of Mexico. In addition, these measurements provided
data to vector ships to regions of mesoscale variability for detailed oil spill measurements, and
are being used to evaluate satellite-based products such as oceanic heat content from altimetry
and SMARTS climatology.
Surface currents derived from altimeter sea surface heights and direct current measurements
from AXCPs indicate that, from May to June, the circulation patterns between the DWH rig and
the northern boundary of the LC were dominated by nearly small-scale cyclones. Eddy Franklin
detached from the LC between 28 May and 18 June, where the 20 o C isotherm depth (h20)
reached maximum values of about 320 m at Franklin’s core, compared with values ranging from
280 to 300 m before the shedding event. During early July, Franklin experienced significant
erosion from several frontal eddies, where h20 values in Franklin’s core ranged from 260 to 280
m. Subsequently, Franklin began to move westward as expected with large warm core eddies.
Thus, the approach captured the complexities of the mesoscale LC-eddy shedding processes for
the first time over weekly time scales. The thermal structure data from all profilers were
assimilated into the operational HYCOM whereas the salinity and current data are being used to
evaluate model performance. Analyses of twin numerical experiments with and without data
assimilation clearly revealed the unprecedented importance of the real-time, 3-D measurements
in improving the trajectories to guide cleanup efforts. This approach needs to be applied to
oceanic and coupled model efforts and implemented for real-time ocean forecasting at the
National Centers for eventual use in coupled model forecasts.
Session 4 – Page 1