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- Author or Editor: R. Gilmer x
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Abstract
A case-study comparison is made of simultaneous airborne gust probe and dual-Doppler radar measurements of motions associated with roll vortices in the optically clear planetary boundary layer. Inter-comparison of the cross-roll component of motion is emphasized. Some similarities and some differences in the data obtained with the two systems are discussed. Considering the differences in measurement techniques, agreement is good between the independent depictions of the roll structure and quantitative determinations of the intensities and predominant scales of eddy motion. The observed roll vortices fit descriptions and cause-effect relationships from certain models and other observations.
Abstract
A case-study comparison is made of simultaneous airborne gust probe and dual-Doppler radar measurements of motions associated with roll vortices in the optically clear planetary boundary layer. Inter-comparison of the cross-roll component of motion is emphasized. Some similarities and some differences in the data obtained with the two systems are discussed. Considering the differences in measurement techniques, agreement is good between the independent depictions of the roll structure and quantitative determinations of the intensities and predominant scales of eddy motion. The observed roll vortices fit descriptions and cause-effect relationships from certain models and other observations.
Abstract
The initial analysis of the water vapor flux measurements taken onboard a NOAA DC-6 during the Barbados Oceanographic and Meteorological Experiment (BOMEX) is presented. The flux of water vapor seems to be constant in the lower subcloud layer. Day-to-day variations, as well as variations within a day are apparent in the evaporation data. Spatial variations of evaporation also seem to be present. The average value of water vapor flux for the experimental period is ∼0.5 cm day−1. Spectra of the instantaneous flux reveal significant alongwind-crosswind differences. Height variation of the wavelength of maximum spectral density for crosswind runs is confirmed. The instantaneous flux is intermittent in nature. Consideration of the cross spectra and time series signatures allows some speculation upon models which may be responsible for a major portion of the water vapor transport in the lower subcloud layer during BOMEX.
Abstract
The initial analysis of the water vapor flux measurements taken onboard a NOAA DC-6 during the Barbados Oceanographic and Meteorological Experiment (BOMEX) is presented. The flux of water vapor seems to be constant in the lower subcloud layer. Day-to-day variations, as well as variations within a day are apparent in the evaporation data. Spatial variations of evaporation also seem to be present. The average value of water vapor flux for the experimental period is ∼0.5 cm day−1. Spectra of the instantaneous flux reveal significant alongwind-crosswind differences. Height variation of the wavelength of maximum spectral density for crosswind runs is confirmed. The instantaneous flux is intermittent in nature. Consideration of the cross spectra and time series signatures allows some speculation upon models which may be responsible for a major portion of the water vapor transport in the lower subcloud layer during BOMEX.
Abstract
During the 1972 IFYGL “alert” periods, the NOAA/RFF/DC-6 gust probe instrumented aircraft was used to record time series of wind, temperature and water vapor at heights ranging from 18 to 300 m above the surface of Lake Ontario. The time series records show great variability. This is especially the case for evaporation when, in the fall, polar continental outbreaks move across the lake. In particular, such an outbreak of cold dry air moved across the lake at 12–15 m s−1 on 9 October 1972. This resulted in a drop of the air temperature at 30 m above the take from 12 to 6°C while the evaporation rate increased to more than 1 cm day−1. This may be compared to the 0.5 cm day−1 typical evaporation rate observed in the tropics during BOMEX. Furthermore, IR lake surface temperatures show cold regions (∼5°C) along the north shore, presumably due to strong upwelling, while the center and south shore regions of the lake were of the order of 12–15°C. The turbulent flux quantities of momentum, heat and water vapor were obtained by the eddy correlation technique and their spectra were determined at severed locations over the lake surface for 3 min sampling lengths. At the aircraft speed of 92 m s−1 this represents a flight path of about 17 km. The spectra demonstrate the tendency for the peak value to march to longer wavelengths with increasing height.
Abstract
During the 1972 IFYGL “alert” periods, the NOAA/RFF/DC-6 gust probe instrumented aircraft was used to record time series of wind, temperature and water vapor at heights ranging from 18 to 300 m above the surface of Lake Ontario. The time series records show great variability. This is especially the case for evaporation when, in the fall, polar continental outbreaks move across the lake. In particular, such an outbreak of cold dry air moved across the lake at 12–15 m s−1 on 9 October 1972. This resulted in a drop of the air temperature at 30 m above the take from 12 to 6°C while the evaporation rate increased to more than 1 cm day−1. This may be compared to the 0.5 cm day−1 typical evaporation rate observed in the tropics during BOMEX. Furthermore, IR lake surface temperatures show cold regions (∼5°C) along the north shore, presumably due to strong upwelling, while the center and south shore regions of the lake were of the order of 12–15°C. The turbulent flux quantities of momentum, heat and water vapor were obtained by the eddy correlation technique and their spectra were determined at severed locations over the lake surface for 3 min sampling lengths. At the aircraft speed of 92 m s−1 this represents a flight path of about 17 km. The spectra demonstrate the tendency for the peak value to march to longer wavelengths with increasing height.
