The Structure and Dynamics of Horizontal Roll Vortices in the Planetary Boundary Layer

LeMone, Margaret A.

doi:10.1175/1520-0469(1973)030<1077:tsadoh>2.0.co;2

Cited by 364 publications

(222 citation statements)

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“…LeMone, 1973;Atkinson and Zhang, 1996;Weckwerth et al, 1997Weckwerth et al, , 1999Bennett et al, 2010). Weckwerth et al (1999) stressed that well-defined horizontal convective rolls occur only while the ratio-z i /L is less than ∼ 25, where z i is the CBL height and L is the Monin-Obukhov length, and that cellular cells are the dominant convection as −z i /L increases.…”

Section: Characteristics Of Convective Cellsmentioning

confidence: 99%

Daytime urban breeze circulation and its interaction with convective cells

Ryu

Baik

Han

2012

Quart J Royal Meteoro Soc

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The structure and evolution of daytime urban breeze circulation (UBC) and its interaction with convective cells in two dimensions are examined through highresolution numerical model simulation. The UBC is the thermally forced, solenoidal circulation that results from the difference in surface energy balance between the urban and rural areas. As the temperature excess in the urban area increases, the UBC becomes larger and stronger with time and the two urban-breeze fronts (the leading edges of the UBC) that initially form at the urban-rural boundaries in the morning move toward the urban centre. Meanwhile, due to strong surface heating in the daytime, a number of convective cells form in both the rural and urban areas and the different characteristics between rural and urban convective cells are identified. The aspect ratio of the urban cells is smaller than that of the rural cells, which is partly attributed to the deeper urban boundary layer. The cell updrafts originating from the urban area are stronger, warmer and drier than those from the rural area. As the UBC develops, the convective cells that form in the rural area are advected toward the urban area by the UBC. Under the influence of the UBC, the cell updrafts originating from the rural area weaken and the water vapour mixing ratio in the updrafts decreases. As the cell updrafts originating from both the rural and urban areas merge with the urban-breeze front, the front intensity increases and the water vapour mixing ratio at the front is modulated.

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Section: Characteristics Of Convective Cellsmentioning

confidence: 99%

Daytime urban breeze circulation and its interaction with convective cells

Ryu

Baik

Han

2012

Quart J Royal Meteoro Soc

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“…Many observational and theoretical studies concerning the cloud bands have been conducted (e.g., Angell et al, 1968;Asai, 1970;Kuettner, 1971;Brown, 1970Brown, , 1972Brown, , 1980Kelly, 1982Kelly, , 1984LeMone, 1973;LeMone and Pennell, 1976;Miura, 1986). The necessary condition for the formation of cloud bands has been identified as a convectively unstable layer having significant vertical wind shear.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Radar Echo Structure of a Snow Band Formed on the Lee Side of a Mountain

Fujiyoshi

Tsuboki

Satoh

et al. 1992

Journal of the Meteorological Society of Japan

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A snow band, formed on the lee side of Mt. Akaiwa at Takashima Peninsula, Hokkaido, was observed by a three-dimensional scanning Doppler radar. The snow band was composed of meso-* scale (*20 km) radar echoes, whose interval of appearance was about 40 minutes. Inside the meso-* scale echoes, were two or three convective echoes with 10 km in size. Further, each convective echo was composed of several convective cells 1-2 km in size. The snow band elongated from west to north and convective cells existing along the southern part of the snow band always appeared the most active and the highest. The convective cells successively formed only along the northern part of the snow band. The width of the snow band was dependent on the number of convective cells which composed the convective clouds. Thus, the snow band was asymmetrical in shape in the vertical plane, perpendicular to its elongated direction.on an average, the band width increased proportional to (distance)1/3. The band thickness linearly increased with increase in band width, and the ratio between them increased, that is, the snow band flattened as distance increased. Averaged snow water content continued to increase over the ocean, for the convective clouds which continued to grow. But it decreased near the sea coast. This can be explained as follows: When a cloud approaches land, snow particles which are sustained in the air over the sea begin to fall near the sea coast because the averaged speed of updraft in a cloud decreases there. After landfall, the convective clouds regenerated, owing to horizontal wind convergence created by Mt. Asoiwa and weakened rapidly on its lee side.

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“…Indeed, careful analysis of roll+cell radar signatures by Weckwerth et al (1997) indicate strong two-dimensional signatures, justifying this characterization. The structure could be verified with a combination of cross-wind aircraft legs and legs at a small angle to the expected roll direction, the latter revealing either longwavelength variation in wind direction (as in pure rolls), or, more likely, superposed long wavelengths (rolls) and short wavelengths (cells), as described for such structures being advected past a tower in LeMone (1973). As shown by the running spectra (Figure 3), there is another segment with possible occurrence of rolls located around 44.75 • N. However, we focus on the current segment because of the clearest roll-like signatures.…”

Section: Discussionmentioning

confidence: 99%

“…Horizontal rolls are elongated quasi-two-dimensional vortices appearing in the convective atmospheric boundary layer (ABL) (e.g., LeMone, 1973). While they are usually recognized as cloud streets, particularly in satellite imagery (e.g., Young et al, 2002), they have been observed in clear air as well (e.g., Konrad, 1970;Kelly, 1984).…”

Section: Introductionmentioning

confidence: 99%