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

Ocean observations in developing and mature TC’s based on a new airborne observing
strategy: 'Combo' deployments of AXBT’s and GPS dropsondes from long-endurance,
multi-altitude reconnaissance flights
P. G. Black 1 and J. D. Hawkins 2
(peter.black.ctr@nrlmry.navy.mil)
1 Science Applications International Corporation/Naval Research Laboratory; 2 Naval Research
Laboratory
The first ‘combo’ deployment of AXBTs and dropsondes into pre-genesis, and mature tropical
cyclones (TC’s) within the Western North Pacific (WPAC) basin was conducted during the
TPARC-Tropical Cyclone Structure (TPARC/TCS-08) field program. This strategy was repeated
again during the Interaction of Typhoons over the Pacific experiment (ITOP/TCS10) in 2010.
This sampling strategy enabled a unique view of the three- dimensional (3-D) oceanic thermal
and atmospheric environments in evolving tropical systems to be obtained. Coupled with the
low-level ocean buoy/float deployment capability of the AFRC WC-130J aircraft, its longendurance
in excess of 12-hours and high-altitude capabilities (300 mb) demonstrates a new era
in TC operational ocean feature observation capabilities for initialization and validation of new
coupled air-sea TC models such as the NRL coupled COAMPS-TC model, brought on line for
the first time during ITOP/TCS10.
Preliminary analysis of the TPARC and ITOP WC-130J AXBT data indicated that three of four
systems that developed into typhoons in 2008 and two of three systems in 2010 developed within
the WPAC oceanic region referred to as the ‘Southern Eddy Zone' between 16-24 N. In
TPARC/TCS08, AXBT data for one case (Jangmi) showed rapid intensification (RI) over a
warm eddy and subsequent rapid decay (RD) over a cold eddy while during ITOP/TCS10,
another case (Fanapi) showed rapid development over a warm eddy. While underlying ocean
conditions seemed not to be a factor in TC formation, or lack thereof, subsequent development
did appear to depend on subsurface ocean eddy conditions, a result that makes monitoring these
ocean conditions for coupled model use an important new consideration in TC observational
requirements.
We suggest that this sampling strategy may prove effective in meeting emerging observational
requirements for model initialization and validation in the Atlantic Basin as the use of coupled
TC prediction models grows. This strategy of flying high in weak systems rather than flying low
looking for closed circulations takes advantage of the high altitude and long range capability of
the WC-130J aircraft and provides the ability to simultaneously map vertical atmospheric
structure searching for signatures of mid-level as well as low-level spin-up at the earliest possible
time while also mapping the surface wind field through use of the new Stepped Frequency
Microwave Radiometer (SFMR), also flown on the WC-130J aircraft. Furthermore, simultaneous
ocean vertical structure profiles reveal signatures of ocean eddies that may impact TC
development and subsequent intensification. This type of strategy, especially in concert with G-
IV surveillance flights in the storm environment would bring a powerful new set of observations
into play that could be ideal not only for coupled model initialization and validation but for
forecaster diagnostics for subsequent TC intensification or decay.
Session 9 – Page 6