Observations of Longitudinal Rolls in a Near Neutral Atmosphere

Walter, Bernard A.; Overland, James E.

doi:10.1175/1520-0493(1984)112<0200:oolria>2.0.co;2

Cited by 53 publications

(29 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There are strong flux peaks at 23,97,157,191,222,287,308, and 38 1 s, averaging about 50 s or 5 km between points. The evidence of the 5-6 km wavelength with the 2.3 km roll-like structure found from the spectra suggest a hierarchy of roll structures as found by Walter and Overland (1984). It is also compatible with the nonlinear theory of Mourad (1987).…”

Section: Observational Flightssupporting

confidence: 88%

See 1 more Smart Citation

Observations of longitudinal roll vortices during arctic cold air outbreaks over open water

Hein

Brown

1988

Boundary-Layer Meteorol

View full text Add to dashboard Cite

An evolving convective Arctic planetary boundary layer (PBL) containing longitudinal roll vortices (rolls) was observed with aircraft data during the 1983 Marginal Ice Zone Experiment and the 1984 Arctic Cyclone Experiment.The PBL is observed to grow rapidly as the very cold and dry air flows off the ice over the relatively warm water. There is very large sensible heat flux, a result of the large surface-air temperature differences. Coherent structures were identified in these PBL's by use of power, coherence squared and phase spectra of the data. A systematic method of separating the rolls from organized thermal plumes was devised, based on theoretical characteristics for roll circulations and the resulting modified mean wind profile. The rapid mixing by the rolls aids in the establishment of equilibrium and an observed adiabatic modified mean Ekman layer. Rolls that form in a thermally neutral atmosphere over ice have different characteristics than those that appear in the unstable stratification over water. The rolls become increasingly more convective in character with distance from the ice edge. They have aspect ratios (wavelength/PBL height) that decrease with distance from the ice edge in agreement with linear theory. This is in contrast to the cloud street wavelength to inversion height ratio which is observed to increase downwind from the ice edge.

show abstract

Section: Observational Flightssupporting

confidence: 88%

“…The first flights were made in 1976 by the NCAR Electra during the Arctic Ice Dynamics Joint Experiment (Katz, 1979). Walter and Overland (1984) found roll motions in a near neutral atmosphere over pack ice. Cloud streets are commonly observed as air flows off the pack ice over warmer water (Walter, 1980).…”

Section: Introductionmentioning

confidence: 99%

Observations of longitudinal roll vortices during arctic cold air outbreaks over open water

Hein

Brown

1988

Boundary-Layer Meteorol

View full text Add to dashboard Cite

show abstract

“…and to thermal instability effected by atmospheric heating from the (water-) surface, or a combination of both mechanisms (LeMone 1973). Contrary to the above, some new observations by Walter and Overland (1984) under near neutral stratification over ice-covered Bering Sea, and by Mtiller et al (1985) over Northern Germany, have implied that inflectionpoint instability is the only cause, but in these cases, observed heat fluxes have been much smaller than during a typical CAO. The possible enhancement of dynamically initiated vortex rolls by buoyancy forces during boundary-layer modification over the arctic marginal ice zone has been pointed out by Hein and Brown (1988).…”

Section: Introductionmentioning

confidence: 75%

Numerical simulation of the development of the convective boundary layer during a cold air outbreak

Raasch

1990

Boundary-Layer Meteorol

View full text Add to dashboard Cite

During cold air outbreaks, cold and stably stratified air masses are advected from land or ice surfaces over a warmer sea surface. Due to the heating from below, a convective boundary layer develops. For small fetches, convection is organized in the form of horizontal roll vortices, which at greater distances join in a zone with open or closed cells. The formation of the convective boundary layer, and the associated roll vortices, is simulated with a numerical model and results are compared with observations obtained during the MASEX experiment off the east coast of the United States. To validate the model, a comparison with a one-dimensional mixed-layer model is also made. with special attention given to the exact representation of the observed initial and boundary conditions. Comparisons between model results and observations show good qualitative and quantitative correspondence in mean temperature and heat flux profiles respectively at different distances from the coast. Maximum values of vertical velocity are well reproduced. Turbulent kinetic energy is found to be concentrated in the small updraft regions of the rolls, which is in accordance with observations from the MASEX-experiment.

show abstract

“…The advantages of using the wind field for roll detection instead of visual satellite imagery is that it can be used even during cloud-free conditions. Moreover, it has been suggested that there can be several scales of roll motion, with a smaller convective scale and a larger cloud band scale [3,23,24]. By studying the wind field, the smaller scale would then be detected.…”

Section: Sar Imagesmentioning

confidence: 99%

A Case Study of Offshore Advection of Boundary Layer Rolls over a Stably Stratified Sea Surface

Svensson

Bergström

Nilsson

et al. 2017

Advances in Meteorology

View full text Add to dashboard Cite

Streaky structures of narrow (8-9 km) high wind belts have been observed from SAR images above the Baltic Sea during stably stratified conditions with offshore winds from the southern parts of Sweden. Case studies using the WRF model and in situ aircraft observations indicate that the streaks originate from boundary layer rolls generated over the convective air above Swedish mainland, also supported by visual satellite images showing the typical signature cloud streets. The simulations indicate that the rolls are advected and maintained at least 30-80 km off the coast, in agreement with the streaks observed by the SAR images. During evening when the convective conditions over land diminish, the streaky structures over the sea are still seen in the horizontal wind field; however, the vertical component is close to zero. Thus advected feature from a land surface can affect the wind field considerably for long times and over large areas in coastal regions. Although boundary layer rolls are a well-studied feature, no previous study has presented results concerning their persistence during situations with advection to a strongly stratified boundary layer. Such conditions are commonly encountered during spring in coastal regions at high latitudes.

show abstract

Observations of Longitudinal Rolls in a Near Neutral Atmosphere

Cited by 53 publications

References 0 publications

Observations of longitudinal roll vortices during arctic cold air outbreaks over open water

Observations of longitudinal roll vortices during arctic cold air outbreaks over open water

Numerical simulation of the development of the convective boundary layer during a cold air outbreak

A Case Study of Offshore Advection of Boundary Layer Rolls over a Stably Stratified Sea Surface

Contact Info

Product

Resources

About