2004 LOM Workshop Wednesday 10:40 - 11:00 a.m.
A near real-time 1/12 degree Atlantic HYCOM nowcast/forecast system
Ole Martin Smedstad, Bruce Lunde, Harley E. Hurlburt, Alan Wallcraft, Eric Chassignet, Remy Baraille
Planning Systems, Inc., Stennis Space Center, MS 39259, USA
smedstad@nrlssc.navy.mil
ABSTRACT
A 1/12 degree Atlantic Ocean version of the HYbrid Coordinate Ocean Model (HYCOM) is used in a near real-time nowcast/forecast system. The model covers the region between 27S and 70N. The Modular Ocean Data Assimilation System (MODAS) sea surface height analysis of available satellite altimeter data is assimilated into the model. The surface information is projected in the vertical using the Cooper and Haines (JGR, 1996) technique. A relaxation to the MODAS SST analysis is also a part of the system. The model is currently run once a week to produce the nowcast. The run includes a 14 day forecast. The results from the system can be seen on the HYCOM Consortium web page at http://hycom.rsmas.miami.edu/. The results are compared to observations of frontal locations determined from independent MCSST observations. The frontal analysis is performed at the Naval Oceanographic Office. Independent observations from SeaWifs images are also used in the model-data comparisons. A series of images in the Gulf of Mexico in the summer and fall of 2003 show a very good agreement between the model sea surface height field and the pathway of the chlorophyll. The model results are also routinely compared to available profile data both from XBTs and the permanent PIRATA buoys in the equatorial Atlantic. This system is the first step toward a global 1/12 degree nowcast/forecast system based on HYCOM that is planned for transition to the Naval Oceanographic Office in 2006. The prediction system will provide boundary conditions for higher resolution coastal models. An accurate representation of the oceanographic fields at the open boundaries of a coastal model is important for a successful coastal ocean prediction system. More advanced assimilation techniques are in the process of being implemented/tested with HYCOM, e.g. a multivariate optimal interpolation scheme (MVOI) and the singular evolutive extended Kalman filter (SEEK).
LOM Users' Workshop, February 9-11, 2004