[1] The sea breeze system (SBS) occurs at coastal locations throughout the world and consists of many spatially and temporally nested phenomena. Cool marine air propagates inland when a cross-shore mesoscale (2–2000 km) pressure gradient is created by daytime differential heating. The circulation is also characterized by rising currents at the sea breeze front and diffuse sinking currents well out to sea and is usually closed by seaward flow aloft. Coastal impacts include relief from oppressive hot weather, development of thunderstorms, and changes in air quality. This paper provides a review of SBS research extending back 2500 years but focuses primarily on recent discoveries. We address SBS forcing mechanisms, structure and related phenomena, life cycle, forecasting, and impacts on air quality.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2003RG000124

Sea breeze: Structure, forecasting, and impacts

Ramp patterns of temperature and humidity occur coherently at several levels within and above a deciduous forest as shown by data gathered with up to seven triaxial sonic anemometer/thermometers and three Lyman-alpha hygrometers at an experimental site in Ontario, Canada. The ramps appear most clearly in the middle and upper portion of the forest. Time/height cross-sections of scalar contours and velocity vectors, developed from both single events and ensemble averages of several events, portray details of the flow structures associated with the scalar ramps. Near the top of the forest they are composed of a weak ejecting motion transporting warm and/or moist air out of the forest followed by strong sweeps of cool and/or dry air penetrating into the canopy. The sweep is separated from the ejecting air by a sharp scalar microfront. At approximately twice the height of the forest, ejections and sweeps are of about equal strength.

Observation of organized structure in turbulent flow within and above a forest canopy

Gravity currents: In the environment and the laboratory

The earliest results concerning the turbulence structure in a turbulent boundary layer with very unstable thermal stratification are due to Prandtl (1932). These results were developed further and made more precise by Obukhov (1946, 1960), Monin & Obukhov (1954) and Priestley (1954, 1955, 1956, 1960). All of these authors dealt with a surface layer of the Earth's atmosphere on hot summer days. Such a layer is the most easily accessible example of an unstably stratified boundary layer and it will be the main concern in this paper too. The theoretical predictions by the above-mentioned authors seemed at first to be confirmed by the available experimental data but in the late 1960s it became clear that at least some of the predictions disagreed strongly with the experimental information.A more elaborate theory was proposed by Betchov & Yaglom (1971) who used a suggestion of Zilitinkevich (1971). According to this theory, within an unstably stratified boundary layer there are three special sublayers where turbulence structure is self-preserving and obeys rather simple power laws. The new theory explained the disagreement between some of the deductions from the old theory and the data. However, the data available in 1971 were insufficient for the confirmation of the new theory and it was even supposed by Betchov & Yaglom (1971) that their theory could not be applied to atmospheric surface layers on hot summer days.Much new experimental data concerning unstably stratified boundary layers has been obtained in recent years; in particular, extensive experimental information was collected during the summers of 1981–1987 at the Tsimlyansk Field Station of the Moscow Institute of Atmospheric Physics. This paper is a survey of the deductions from the theory by Betchov & Yaglom which concern the mean fields and the one-point fluctuation moments in unstably stratified boundary layers, and a comparison of these deductions with the data available in 1989. It is shown that the data agree more or less satisfactorily with the theoretical predictions and permit one to obtain estimates for a number of coefficients that enter the theoretical equations.

Mean fields and fluctuation moments in unstably stratified turbulent boundary layers

Much new experimental data concerning unstably stratified boundary layers has been obtained in recent years; in particular extensive experimental information was collected during the summers of 1981-87 at the Tsimlyansk Field Station of the Moscow Institute of Atmospheric Physics. This paper is a survey of the deductions from the theory by Betchov & Yaglom which concern the mean fields and the one-point fluctuation moments in unstably stratified boundary layers and a comparison of these deductions with the data available in 1989. It is shown that the data agree more or less satisfactorily with the theoretical predictions and permit one to obtain estimates for a number of coefficients that enter the theoretical equations.

Mean fields and fluctuation moment in unsteady stratified turbulent boundary layers

Because of interest in the relationship between vertical wind velocity skewness and the stability, considerable data of skewness observed by many workers are accumulated and an empirical formula about the relationship mentioned above is derived. It appears to be in considerable agreement with observed data.

Stability Dependence of the Vertical Wind Velocity Skewness in the Atmospheric Surface Layer

Tower measurements for the sea breeze front in the surface layer were carried out over the Kochi plain about 2 km inland from Tosa Bay in Shikoku, Japan during the period from August 1986 to October 1987. The study shows that the penetration time of the sea breeze has an annual variation, which is around 0830 JST in summer and 12 JST in winter, and that the width of the sea breeze front depends on the ratio of the sea breeze speed and the opposing flow speed. Moreover, the frontal width also shows a seasonal variation.

The turbulent characteristics in the lowest part of the sea breeze front in the atmospheric surface layer

Thermodynamical observations by a helicopter have been conducted to study the internal structure of the sea breeze blowing inland from Tosa Bay during three periods (September 1993, November 1994 and 1995). Inland-intrusion distances of the midday sea breeze observed at each flight leg were in the 10–25-km range, depending on the intensity of the ambient flow associated with the gradient wind, atmospheric stratification, and the geographical features of the observed area. The sea breeze observed over the sea had well-defined features, in particular a turbulent wake behind the head of the sea-breeze front and a closed sea-breeze circulation cell containing the subsidence of the return flow. In addition, a moist layer distributed around 15–20 km offshore forms because the land breeze moves in this region. Moreover, a calm condition exists from the coast to about 10 km offshore. Both phenomena are found before the onset of the sea breeze in the early morning. Such remarkable characteristics of the s...

Helicopter Observations of the Sea Breeze over a Coastal Area

Ensemble averages of temperature before and after step-like temperature fluctuations reveal the presence of inverted ramps in a stable surface layer. Normalized frequency of upward steps increases with increasing stability, whereas normalized magnitude of the temperature step decreases with stability and becomes constant at about R

 i
 = 1. These results suggest that the significance of temperature steps increases as stability increases. In moderate stability, the temperature pattern shows a gradual decrease after an upward step, which can be called a time-inverted ramp. Descending air and large downward heat flux are observed in a time-inverted ramp, suggesting a contribution from an ordered motion in wind. On the other hand, the temperature steps are related to gravity waves in strong stability.

Step-like temperature fluctuations associated with inverted ramps in a stable surface layer

Low-level katabatic wind profiles, which have shapes similar to those of the low-level jet (LLJ) wind profiles, are often observed during strong winds in the summer period at Mizuho Station, which is located at 70°42′ S, 44°20′ E in East Antarctica. The profiles may be classified according to the height of the maximum wind speed, z

 m
 , found below 30 m height. The behavior of z
m and of conditions in the layer above z
mare explained well by the normalized frequency, f
N = Nz/U at 30 m, whose value can be used to predict the existence of a LLJ wind profile. Subsidence and inertial oscillations above z
m are related closely to the height and time variations of z
m. Thus, not only effects emanating upward from surface but also momentum and heat transported downward from above are significant for the evolution of z
m.

Osamu Chiba

Papers

Stability Dependence of the Vertical Wind Velocity Skewness in the Atmospheric Surface Layer

The turbulent characteristics in the lowest part of the sea breeze front in the atmospheric surface layer

Helicopter Observations of the Sea Breeze over a Coastal Area

Step-like temperature fluctuations associated with inverted ramps in a stable surface layer

A study of the structure of low-level katabatic winds at Mizuho Station, East Antarctica