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- Author or Editor: R. L. PEACE JR. x
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Abstract
During the 1964–65 snow season, the Atmospheric Sciences Research Center, State University of New York (ASRC, SUNY), and the SUNY College at Oswego maintained a mesoscale network of surface pressure, temperature, and wind-recording stations around the eastern end of Lake Ontario to observe the conditions attendant upon lake effect storms on a scale commensurate with storm size. The Cornell Aeronautical Laboratory combined the SUNY data with conventional weather and radar data for the February 3 and 4, 1965 storm period to produce a combination of streamline, isotach, isobaric, and isallobaric analyses from which a number of interesting features became evident.
One important, storm characteristic is a narrow confluent-convergent wind shift zone (0.1 to 1.5 n.mi. wide) beneath the snow band. In the storm studied, the wind shift zone was evident beneath the full length of the overland portion of the storm, even when the west-to-east snow band migrated south of the lake. During a period in which two snow bands existed simultaneously, a wind shift line could be observed under each.
Also observed were lee shore pressure patterns that changed in a consistent manner with changes in location of the snow bands. Although lee shore convergence and cyclonic vorticity increases were in evidence throughout the period, these patterns did not appear to be directly related to the snow bands. The analyses strongly suggest that while the formation of the lake effect bands is caused by heating of the air by a warm lake, the location and movement of the bands are controlled by winds aloft, rather than by surface conditions.
Abstract
During the 1964–65 snow season, the Atmospheric Sciences Research Center, State University of New York (ASRC, SUNY), and the SUNY College at Oswego maintained a mesoscale network of surface pressure, temperature, and wind-recording stations around the eastern end of Lake Ontario to observe the conditions attendant upon lake effect storms on a scale commensurate with storm size. The Cornell Aeronautical Laboratory combined the SUNY data with conventional weather and radar data for the February 3 and 4, 1965 storm period to produce a combination of streamline, isotach, isobaric, and isallobaric analyses from which a number of interesting features became evident.
One important, storm characteristic is a narrow confluent-convergent wind shift zone (0.1 to 1.5 n.mi. wide) beneath the snow band. In the storm studied, the wind shift zone was evident beneath the full length of the overland portion of the storm, even when the west-to-east snow band migrated south of the lake. During a period in which two snow bands existed simultaneously, a wind shift line could be observed under each.
Also observed were lee shore pressure patterns that changed in a consistent manner with changes in location of the snow bands. Although lee shore convergence and cyclonic vorticity increases were in evidence throughout the period, these patterns did not appear to be directly related to the snow bands. The analyses strongly suggest that while the formation of the lake effect bands is caused by heating of the air by a warm lake, the location and movement of the bands are controlled by winds aloft, rather than by surface conditions.
Abstract
A generalized relationship is derived which relates an arbitrary horizontal wind field and the Doppler velocity field that results from its observation with a single horizontally directed radar. The relationship shows clearly how various elements of the horizontal wind field (velocity components and their space derivatives) combine to account for Doppler velocity variations with azimuth and range. The relationship also provides a basis for development of observational techniques for interpretation of the horizontal motion field from single pulse Doppler radar measurements.
Two sample techniques are presented for interpreting Doppler measurements in terms of horizontal motion in echoes located some distance from the radar. The underlying assumption upon which both techniques are based is the quasi-stationarity of the motion field relative to a reference frame moving with the observed echo. The practicality of one of these techniques is demonstrated for a model wind field by computer simulation of the Doppler velocity field that would be observed by a single radar with representative measurement accuracy, and computer reconstruction of the original motion field from these simulated Doppler measurements. Subject to the validity of the underlying assumption, the results demonstrate the feasibility of determining the horizontal motion field in a remote echo from the observations of a single pulse Doppler radar. Means of testing the basic assumption are presented.
Abstract
A generalized relationship is derived which relates an arbitrary horizontal wind field and the Doppler velocity field that results from its observation with a single horizontally directed radar. The relationship shows clearly how various elements of the horizontal wind field (velocity components and their space derivatives) combine to account for Doppler velocity variations with azimuth and range. The relationship also provides a basis for development of observational techniques for interpretation of the horizontal motion field from single pulse Doppler radar measurements.
Two sample techniques are presented for interpreting Doppler measurements in terms of horizontal motion in echoes located some distance from the radar. The underlying assumption upon which both techniques are based is the quasi-stationarity of the motion field relative to a reference frame moving with the observed echo. The practicality of one of these techniques is demonstrated for a model wind field by computer simulation of the Doppler velocity field that would be observed by a single radar with representative measurement accuracy, and computer reconstruction of the original motion field from these simulated Doppler measurements. Subject to the validity of the underlying assumption, the results demonstrate the feasibility of determining the horizontal motion field in a remote echo from the observations of a single pulse Doppler radar. Means of testing the basic assumption are presented.
