TITLE:
A Case Study of Ocean-Atmosphere Interactions during the Passage of an Extra-Tropical Cyclone in the Vicinity of Cape Hatteras, North Carolina
AUTHORS:
Neil Jacobs, James Churchill, Leonard Pietrafesa, Shaowu Bao, Paul Gayes
KEYWORDS:
Mid-Latitude Cyclone, Extra-Tropical Cyclone, Cyclogenesis, Nor’easter Winter Storms, Latent and Sensible Heat Fluxes, Salt Flux
JOURNAL NAME:
International Journal of Geosciences,
Vol.14 No.9,
September
26,
2023
ABSTRACT: The authors document the interaction of the
atmosphere and ocean during the formation
and passage of an Extra-Tropical Cyclone, which is a Nor-Easter, winter
storm that formed in the southern apex of the Middle Atlantic Bight near Cape
Hatteras North Carolina, between February 15 and 18, 1996. While Nor-Easters per se, which have formed along the
Atlantic Eastern Seaboard of the United States have been studied for decades,
the actual atmospheric-oceanic mechanics and thermodynamics in the formation
of a Nor-Easter has never been documented. We report on having done so with
in-situ observations and data-based calculations and a numerical model. The
in-situ observations were made via a Control Volume consisting of an array of
Eulerian Oceanic-Atmospheric Moorings with current meters, temperature and
salinity sensors and meteorological towers. We find that Gulf Stream waters
were located surrounding the mooring array, and that with the invasion of cold
dry atmospheric air, there was a rapid loss of heat from the ocean to the
atmosphere via latent and sensible surface heat flux during the cyclogenesis
onset of the storm. A unique feature of this storm was that neither satellite
nor buoy data showed significant sea surface cooling
in the control volume. The findings indicate that storm winds drove warm saline
waters from the Gulf Stream across the continental shelf into the control
volume, accounting for a 51 cm rise in water level along the coast. This
lateral heat advection provided heat to the control volume of 3.4e+18 Joules.
On average, the heat loss at the surface of the control volume, via sensible
and latent heat fluxes and radiation, was 0.7e+18 Joules, corresponding to a surface heat flux of -600 Watts per
Meter2 (W/m2). However, the heat lost by the control volume as
latent and sensible heat fluxes was less than the heat it received via lateral
heat advection, resulting in the lack of an often-observed sea surface cooling
during other winter storms. The serendipitous and detailed observations and
calculations reveal a climatological flywheel in this region, documenting the
role of ETCs in the global heat balance.