A Numerical Study on the Effects of a Mountain on the Land and Sea Breezes

Abstract

Thermal and dynamical effects of mountain on the land and sea breezes are studied numerically, by paying special attention to the growth and decay of the circulations and the extent of them. A two dimensional model in a vertical plane perpendicular to a seacoast line and a mo untain chain is used. The horizontal extent and the depth of the computational region are assumed to be 130km and 3km, respectively. The mountain is assumed to have a simple trapezoidal form with 8km in width and 450m in height, and is located at 18km from the coastal line. In order to estimate the thermal and dynamical effects of the mountain, numerical experiments are conducted for the following three cases: case (a) no mountain case (b) mountain with thermally insulated boundary condition (insulated mountain) case (c) mountain with the diurnal change of its surface potential temperature (heating mountain) Main conclusions are summarized as follows: (1) The sea breeze can not invade inland beyond the heating mountain, while the breeze invades inland beyond the insulated mountain faster and deeper than expected in case of no mountain. (2) The land breeze develops strong in case of the heating mountain. This is due to the down-slope winds. In case of the insulated mountain, this down-slope winds do not develop and the land breeze remains weaker than that of no mountain case. (3) The phase difference between the time of the maximum land-and-sea surface temperature contrast and that of the strongest induced circulation is much reduced, compared to the case of no mountain, regardless of the thermal boundary condition of the mountain surface.

Sea and Lake Breezes: A Review of Numerical Studies

“…These studies have found that on a heated slope of sufficiently low steepness (less than 2.29 • according to Asai and Mitsumoto 1978 or ≈0.8 • according to Porson et al 2007b), thermally-driven slope flows may couple with sea breezes and increase u, w, l, and h (Mahrer and Pielke 1977;Estoque and Gross 1981;Miao et al 2003). Combined sea-breeze and slope flows may also lead to an earlier inland sea-breeze frontal passage (Ookouchi et al 1978;Kikuchi et al 1981). A slope of sufficiently high steepness will act to block the inland penetration of the sea-breeze front and decrease u, w, l, and h (Asai and Mitsumoto 1978;Segal et al 1983;Neumann and Savijarvi 1986;Porson et al 2007b).…”

“…The earliest hydrostatic models used simple boundary-layer schemes and neglected moisture, latent heating, radiation, and land-surface parametrisations. Some later models included radiation, moisture and latent heating, with increasingly sophisticated schemes for surface heating and the turbulent Neumann andMahrer (1971, 1974) 5 , Pearson (1973) Pielke (1974a,b) 4 1975-1979 2D 2.5-8 9 Neumann and Mahrer (1975) 5 , Sheih and Moroz (1975) 1 , Estoque et al (1976) 1 , Pielke (1976, 1977) 3 , Physick (1976) 4 , Anthes (1978) 2 , Asai and Mitsumoto (1978) 1 , Ookouchi et al (1978) 3 1980-19842D 3-10 8 Physick (1980 4 , Estoque and Gross (1981) 1985-1989 2D 1-10 14 Garratt and Physick (1985) 2 , Mahrer and Segal (1985) 1 , Physick and Smith (1985) 3 , Neumann and Savijarvi (1986) 1 , Noonan and Smith (1986) 2 , Segal et al (1986) 3 , Arritt (1987Arritt ( , 1989 4 , Briere (1987) 1 , Anthes (1987, 1988) Freitas et al (2007) 8 , Srinivas et al (2007) 8 , Talbot et al (2007) 8 , Thompson et al (2007) 8 , Cheng and Byun (2008) transport of heat, moisture, and momentum. Through the 1970s, turbulence in the surface layer was generally treated using simple K-theory, assuming constant fluxes, and with empirical formulations for turbulent transport in the overlying transition layer.…”

“…The intensity of inland breeze circulations caused by the difference in land-surface sensible heat fluxes between two land-surface types is typically weaker than a sea breeze, in part due to the enhanced turbulent mixing on the "moist" land side compared to the negligible thermal plumes noted over water (Segal and Arritt 1992;Yan and Anthes 1988). Small water bodies Neumann and Mahrer (1975), Yan and Anthes (1988), Zhong et al (1991), Boybeyi and Raman (1992a), Shen (1998) Curvature Convex shoreline strengthens sea breezes Concave shoreline weakens sea breezes Mahrer and Segal (1985), McPherson (1970), Arritt (1989), Gilliam et al (2004), Boybeyi and Raman (1992a) Mahrer and Pielke (1977), Asai and Mitsumoto (1978), Ookouchi et al (1978), Estoque and Gross (1981), Kikuchi et al (1981), Segal et al (1983), Neumann and Savijarvi (1986), Ramis and Romero (1995), Miao et al (2003), Porson et al (2007b) Other Channeling of sea breezes may locally enhance u, w, and l Small mountains inland from coast can block inland penetration Mountain slope can produce "chimney effect" stalling sea-breeze front Ookouchi et al (1978), Segal et al (1983), Neumann and Savijarvi (1986), Lu and Turco (1994), Ramis and Romero (1995), Millán et al (2000), Darby et al (2002) likely have boundary layers that are a hybrid between large-scale sea breezes and moist land situations. Shoreline curvature (r) can strongly affect interactions between the prevailing winds and sea breezes.…”

The Effect of the Width of a Peninsula to the Sea-breeze

“…The first term in (2.2.7); the vertical shear of a zonal flow, is neglected as it is much smaller than the second stability term. We assume that l is constant in the atmosphere and is decided to 50m by the convective instability considerations (see Ookouchi et al, 1978). Thus, when the stratification becomes unstable, KM or KH in the transition layer above z=50m is shown as follows, using *a= 302*K as the representative potential temperature in the middle layer of the model:…”

“…From the computations for the horizontal orographic effect (McPherson, 1970;Pielke, 1974;Takano, 1976;etc. ) and for the vertical orographic effect (Asai et al, 1978;Ookouchi et al, 1978;Kikuchi et al, 1981;etc. ) to the land and sea breeze, it has been shown that there was the ascending flow region at 10km inland across the coast, and the head of this region is sometimes termed the sea-breeze front.…”