A simple model of drainage flow on a slope

Kondo, Junsei; Sato, Takeshi

doi:10.1007/bf00153975

Cited by 41 publications

(39 citation statements)

References 18 publications

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“…Notably, the depth of the KBL depends on the distance from the hill crest. Models describing the evolution of the velocity field in KBL flows were developed by Manins and Sawford (1979) and Kondo and Sato (1988). The latter predicted that the KBL depth (i.e., the height at which the minimum velocity is reached) would increase with distance from the crest at a rate depending mainly on the bulk heat exchange coefficient, and thus on momentum and heat roughness lengths (z o and z T , respectively).…”

Section: Horizontal Velocitiesmentioning

confidence: 99%

Comparing CO2 Storage and Advection Conditions at Night at Different Carboeuroflux Sites

Aubinet

Berbigier

Bernhofer

et al. 2005

Boundary-Layer Meteorol

172

146

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Abstract. Anemometer and CO 2 concentration data from temporary campaigns performed at six CARBOEUROFLUX forest sites were used to estimate the importance of non-turbulent fluxes in nighttime conditions. While storage was observed to be significant only during periods of both low turbulence and low advection, the advective fluxes strongly influence the nocturnal CO 2 balance, with the exception of almost flat and highly homogeneous sites. On the basis of the main factors determining the onset of advective fluxes, the 'advection velocity', which takes net radiation and local topography into account, was introduced as a criterion to characterise the conditions of storage enrichment/depletion. Comparative analyses of the six sites showed several common features of the advective fluxes but also some substantial differences. In particular, all sites where advection occurs show the onset of a boundary layer characterised by a downslope flow, negative vertical velocities and negative vertical CO 2 concentration gradients during nighttime. As a consequence, vertical advection was observed to be positive at all sites, which corresponds to a removal of CO 2 from the ecosystem. The main differences between sites are the distance from the ridge, which influences the boundarylayer depth, and the sign of the mean horizontal CO 2 concentration gradients, which is probably determined by the source/sink distribution. As a consequence, both positive and negative horizontal advective fluxes (corresponding respectively to CO 2 removal from the ecosystem and to CO 2 supply to the ecosystem) were observed. Conclusive results on the importance of non-turbulent components in the mass balance require, however, further experimental investigations at sites with different topographies, slopes, different land covers, which would allow a more comprehensive analysis of the processes underlying the occurrence of advective fluxes. The quantification of these processes would help to better quantify nocturnal CO 2 exchange rates.

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Section: Horizontal Velocitiesmentioning

confidence: 99%

Comparing CO2 Storage and Advection Conditions at Night at Different Carboeuroflux Sites

Aubinet

Berbigier

Bernhofer

et al. 2005

Boundary-Layer Meteorol

172

146

View full text Add to dashboard Cite

show abstract

“…Velocity and thickness of the drainage flow (a) The case of a slope Introducing the concept of cold air 'Parcel' and considering the momentum and sensible heat transport by the Parcel, Kondo and Sato (1988) have derived the characteristic velocity and thickness of a slope flow, u and h, as follows:…”

Section: Appendixmentioning

confidence: 99%

“…see the reviews by Atkinson, 1981 andBarry, 1981). Kondo and Sato (1988; hereafter referred to as KS) utilizing certain parameters proposed the Parcel Model of the drainage flow on a slope (slope flow) to describe its vertical extent or thickness and velocity. Recently, Sato and Kondo (1988; hereafter referred to as SK) presented a simple model for the drainage flow in a valley (valley drainage flow).…”

Section: Introductionmentioning

confidence: 99%

The Sensitivities of Nocturnal Cooling and Drainage Flow over an Inclined Topography to Meteorological, Ground Surface, and Topographic Conditions

Sato

1989

Journal of the Meteorological Society of Japan

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On the basis of results of slope and valley drainage flow models Sato and Kondo, 1988), a simple method is presented for the simultaneous evaluation of nocturnal cooling and drainage flow over slopes and in valleys under weak ambient wind conditions.Evaluations are made of the sensitivities of nocturnal cooling, drainage flow characteristics (velocity and thickness), and sensible heat transport by the drainage flow to the following conditions: meteorological conditions, thermal constant of the ground, surface aerodynamic properties and topographic features.Due to the enhancement of sensible heat transport by the drainage flow, surface cooling of an inclined topography is smaller than that of a horizontal plain. The velocity of the drainage flow is sensitive to the conditions mentioned above, but its thickness is dependent only on the surface aerodynamic properties and the topographic features. The side-slope flow plays an essential role in the energy exchange between the atmosphere and a valley.Available observations of nocturnal cooling and drainage flow support the present method.

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“…Researchers have examined relationships between wind speeds and thermal conditions for pure drainage flow with nearly no disturbance by shear flow. Consequently, relationships between pure drainage flow and thermal conditions above a slope have been understood and fairly well formulated (e.g., Kondo and Sato 1988;Heilman and Takle 1991;Papadopoulos et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Relationship between Nighttime Wind Speeds and Thermal Conditions above a Sloping Forest

Komatsu

Hotta

Kuraji

et al. 2008

Journal of the Meteorological Society of Japan

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Researchers have examined relationships between wind speeds and thermal conditions above a slope for pure drainage flow with nearly no disturbance by shear flow, though disturbances by shear flow are commonly present. This study examined the relationship between wind speeds and thermal conditions above a slope when wind speed is affected by shear as well as drainage flow. Data used in this study were obtained at a sloping forest site in Thailand, which had been also used in our previous studies . The canopy height (h) of the forest was approximately 30 m above ground level and wind speeds were measured at 34 m, 43 m, and 50 m (i.e., 1.13h, 1.43h, and 1.67h, respectively).After classifying measured wind speed data based on vertical air temperature differences, the mean and minimum wind speeds of each temperature-difference class were determined. Here, mean and minimum wind speeds refer to means and minimums among wind speeds for a specific temperature difference class. Regarding the 34-m wind speeds, mean wind speeds generally increased with increasing temperature difference and minimum wind speeds were non-zero, indicating the effect of drainage flow was generally dominant over the effect of shear flow at this height. Regarding the 50-m wind speeds, mean wind speeds decreased with increasing temperature difference and minimum wind speeds were nearly zero regardless of the temperature difference, indicating the effect of shear flow was dominant over the effect of drainage flow at this height. The 43-m wind speed data showed results that were intermediate to those of the 34-and 50-m wind speed data.Results of such analysis bring information on the significance of the drainage flow effect on wind speed data measured at different heights above a slope. Thus, such an analysis would be useful for examining vertical structures of wind flow above a slope when both drainage and shear flow effects are present.

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A simple model of drainage flow on a slope

Cited by 41 publications

References 18 publications

Comparing CO2 Storage and Advection Conditions at Night at Different Carboeuroflux Sites

Comparing CO2 Storage and Advection Conditions at Night at Different Carboeuroflux Sites

The Sensitivities of Nocturnal Cooling and Drainage Flow over an Inclined Topography to Meteorological, Ground Surface, and Topographic Conditions

Relationship between Nighttime Wind Speeds and Thermal Conditions above a Sloping Forest

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