Small-scale wind disturbances observed by the MU radar during the passage of typhoon Kelly

Journal Article · Sun Feb 14 00:00:00 EST 1993 · Journal of the Atmospheric Sciences; (United States)

DOI:https://doi.org/10.1175/1520-0469(1993)050<0518:SSWDOB>2.0.CO;2· OSTI ID:6779843

Sato, Kaoru ^[1]

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1. Kyoto Univ. (Japan)

This paper describes small-scale wind disturbances associated with Typhoon Kelly (October 1987) that were observed by the MU radar, one of the MST (mesosphere, stratosphere, and troposphere) radars, for about 60 hours with fine time and height resolution. To elucidate the background of small-scale disturbances, synoptic-scale variation in atmospheric stability related to the typhoon structure during the observation is examined. When the typhoon passed near the MU radar site, the structure was no longer axisymmetric. There is deep convection only in north-northeast side of the typhoon while convection behind it is suppressed by a synoptic-scale cold air mass moving eastward to the west of the typhoon. A change in atmospheric stability over the radar site as indicated by echo power profiles is likely due to the passage of the sharp transition zone of convection. Strong small-scale wind disturbances were observed around the typhoon passage. The statistical characteristics are different before (BT) and after (AT) the typhoon passage, especially in frequency spectra of vertical wind fluctuations. The spectra for BT are unique compared with earlier studies of vertical winds observed by VHF radars. Another difference is dominance of a horizontal wind component with a vertical wavelength of about 3 km, observed only in AT. Further analyses are made of characteristics and vertical momentum fluxes for dominant disturbances. Some disturbances are generated to remove the momentum of cyclonic wind rotation of the typhoon. Deep convection, topographic effects in strong winds, and strong vertical shear of horizontal winds around an inversion layer are possible sources of the disturbances. Two monochromatic disturbances lasting for more than 10 h in the lower stratosphere observed in BT and AT are identified as inertio-gravity waves, by obtaining wave parameters consistent with all observed quantities. Both of the inertio-gravity waves propagate energy away from the typhoon.

• OSTI ID: 6779843
• Journal Information: Journal of the Atmospheric Sciences; (United States), Vol. 50:4; ISSN 0022-4928
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
GRAVITY WAVES
MONITORING
HURRICANES
REMOTE SENSING
RADAR
DIAGNOSTIC USES
ATMOSPHERIC CIRCULATION
CONVECTION
MESOSPHERE
SHEAR
SPECTRA
STRATOSPHERE
TROPOSPHERE
WIND
DISASTERS
EARTH ATMOSPHERE
ENERGY TRANSFER
HEAT TRANSFER
MASS TRANSFER
MEASURING INSTRUMENTS
RANGE FINDERS
STORMS
USES
540110*