A Comparison between Observations and MM5 Simulations of the Marine Atmospheric Boundary Layer across a Temperature Front

Simulations, made with the fifth-generation Pennsylvania State University (PSU)–National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5), of the response of the marine atmospheric boundary layer (MABL) as air moves over a sharp SST front are compared with observations made during the Frontal Air–Sea Interaction Experiment (FASINEX) in the North Atlantic subtropical convergence zone. The purpose of undertaking these comparisons was to evaluate the performance of MM5 in the vicinity of an SST front and to determine which of the planetary boundary layer (PBL) parameterizations available best represents MABL processes. FASINEX provides an ideal dataset for this work in that it contains detailed measurements for scenarios at the two extremes: wind blowing from warm to cold water normal to a 2°C SST front and the converse, wind blowing from cold to warm water. For the wind blowing from warm to cold water, there is a pronounced modification of the near-surface wind field over the front, in both model results and aircraft observations. The decrease of near-surface wind speed and stress is due to a stable internal boundary layer (IBL) induced by the SST front, restricting exchange of mass and momentum between the surface and upper part of the MABL. For the cold-to-warm case, the relatively strong vertical mixing through the entire MABL over warm water dampens the response of the near-surface winds and surface stress to the SST front. The properties observed by the aircraft are simulated quite well in both cases, suggesting that MM5 captures the appropriate boundary layer physics at the mesoscale or regional scale

UNOLS Establishes SCOAR to Promote Research Aircraft Facilities for U.S. Ocean Sciences

Oceanography, Vol. 17, No. 4, pp. 176-185, December 2004

Wintertime boundary-layer structure and air-sea interaction over the Japan/East Sea

The article of record as published may be located at http://dx.doi.org/10.1016/j.dsr2.2004.04.005The wintertime meteorology over the Japan/East Sea (JES) is characterized by episodic strong northwesterly winds known as ‘‘cold-air outbreaks’’ resulting from the incursion of dry and cold air masses from the Eurasian continent. These were found by previous studies (mostly based on indirect methods) to greatly enhance the air–sea interaction and, in particular an area about 150km in diameter off Vladivostok was identified as the Flux Center. Aircraft in situ measurements of turbulent fluxes and mean meteorological variables were made during the winter 2000. The existence and location of the Flux Center were confirmed although the turbulent sensible and latent-heat fluxes were not as high as previously found due to the air temperature being several degrees warmer. However, the stress was found to be significantly larger as a result of higher wind speeds. The internal boundary layer was found to grow linearly with the square root of offshore fetch, with a growth rate of 2:49m1=2 for an intense cold-air outbreak and 2:06m1=2 for a moderate one. A persistent initialdecrease in the inversion height was observed at 41:86 N; 132:6 E and may be attributable to the fanning out of the jet flow out of the Vladivostok gap as it expands onto the open ocean. The radiometric skin sea-surface temperature in the Flux Center exhibited large variability in the 0–4 1C range and was positively correlated with the total turbulent ðlatent þ sensibleÞ heat loss. Meteorological variables and surface fluxes results from Naval Research Laboratory Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) model compared reasonably, while the predictions of the internal boundary layer height were markedly lower than the observations.This work was supported by the Office of Naval Research (ONR) with D.K. and C.A.F under Grant N00014-99-1-0205 and Q.W. under Grant N00014-00-WR20156 and N00014-01-WR20242

Observations of the Impact of Cloud Processing on Aerosol Light-Scattering Efficiency

Tellus 56B 285-293.Airborne data are presented on the impact of cloud processing on the aerosol mass light-scattering efficiency. The measurements, on marine stratocumulus, suggest that cloud processing significantly enhanced the mass light-scattering efficiency in three of the five cases analysed. Enhancements were of the order of 10% for air detraining from the cloud deck relative to non-detraining air. A diagnostic modelling analysis suggested that the observed enhancements were consistent with the previously proposed explanation of in-cloud sulfate production in the particle size range for efficient light scattering

UNOLS Establishes SCOAR to promote research aircraft facilities for U.S. ocean sciences

Oceanography, Vol. 17, No. 4, pp. 176-185, December 2004

A preliminary description of the CODE-1 field program

A Coastal Ocean Dynamics Experiment (CODE) has been undertaken to identify and study the important dynamical processes which govern the wind-driven motion of coastal water over the continental shelf. The initial effort in this four-year research program is to obtain high-quality data sets of all the relevant physical variables needed to construct accurate kinematic and dynamic descriptions of the response of shelf water to strong wind forcing in the 2 to 10-day band. A series of two small-scale, densely-instrumented field experiments of four-month duration (CODE-1 and CODE-2) is designed to explore and to determine the kinematics and momentum and heat balances of the local wind-driven flow over a region of the northern California shelf which is characterized by both relatively simple bottom topography and large wind stress events in both winter and summer. A more lightly-instrumented, long-term, large-scale component has been designed to help separate the local wind-driven response in the region of the small-scale experiments from motions generated either offshore by the California Current system or in some distant region along the coast, and also to help determine the seasonal cycles of the atmospheric forcing, water structure, and coastal currents over the northern California shelf. This report presents an overview of the CODE program and a preliminary description of the observational programs conducted during CODE-1. The various logical components of CODE are identified and described, and their relationship to the entire effort is discussed. The report itself represents a minor revision of the original cover proposal submitted to NSF in late 1979 by the principal investigators and is not a comprehensive guide nor does it contain any descriptions of the initial results from CODE-1. Scientific and engineering results will be presented elsewhere in individual technical and scientific reports. CODE has been jointly conceived by the following principal investigators (who collectively make up the CODE group): J. Allen , R. Beardsley, W. Brown, 0. Cacchione, R. Davis, D. Drake , C. Friehe, W. Grant, A. Huyer, J. Irish, M. Janopaul, A. Williams and C. Winant