Browsing by Author "Larsen, M.F."
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Item Restricted Frequency domain interferometry observations of tropo/stratospheric scattering layers using the MU radar: Description and first results(American Geophysical Union, 1990-11) Palmer, R.D.; Woodman Pollitt, Ronald Francisco; Fukao, S.; Larsen, M.F.; Yamamoto, M.; Tsuda, T.; Kato, S.This paper describes the first results of the implementation of frequency domain interferometry (FDI) using the Middle and Upper (MU) atmosphere radar. A new method of using this FDI data is introduced, which is shown to be useful in studying the dynamics of scattering layers in the troposphere and lower stratosphere. Using this method, the effective altitude resolution of the MU radar has been improved.Item Open Access Julia radar studies of electric fields in the equatorial electrojet(American Geophysical Union, 1997-07) Hysell, D.L.; Larsen, M.F.; Woodman Pollitt, Ronald FranciscoFirst results from the JULIA radar at Jicamarca are presented. These include coherent scatter observations of the equatorial electrojet and of 150-km echoes. Interferometry is used to measure the zonal drift rate of kilometer scale waves in the electrojet as functions of altitude. A technique for estimating the background zonal electric field from the interferometry data is described. The electric field estimates can be calibrated against the Doppler speed of the 150-km echoes when the latter are present. The kilometer-scale wave drifts sometimes exhibit large-amplitude, periodic height variations with vertical wavelengths of about 10 km. These signatures are reminiscent of the wind profiles measured with chemical release techniques in the lower thermosphere during the Guará campaign.Item Open Access Radar observations of the development of tropical thunderstorms and convection cells using the Arecibo radar(Instituto Geofísico del Perú, Radio Observatorio de Jicamarca, 1974) Larsen, M.F.; Swartz, W.E.; Woodman Pollitt, Ronald FranciscoIn the period from 13 Sept to 20 Sept 1979, the 430 MHz radar system at the Arecibo Observatory was used to study profiles of vertical velocity in developing and mature thunderstorms during the afternoon hours. During the eight day period, five days produced significant convective activity. The great sensitivity of the Arecibo radar facility allowed vertical velocities to be measured up to an altitude of 20 km. Since the tropopause over Puerto Rico is at an altitude of approximately 14 km at that time of year, the lower part of the stratosphere was also observed during the period of cloud development. Many studies have been carried out using Doppler radars to probe the interior of convective cells (see Wilson and Miller, 1972 for an excellent review and bibliography; also Battan, 1973). This is particularly true of radars operating at shorter wavelengths of 3 or 10 cm whích are more sensitive to reflections from precipitation within the clouds. The Arecibo radar, operating ata wavelength of 70 cm, receives echoes from variations in the index of refraction with a scale size of half the wavelength, or 35 cm. The fact that vertical velocities could be measured in both the troposphere and lower stratosphere is of particular interest.in view of the theory that the upward flux of mass in the tropical branch of the Hadley cell is concentrated in the cumulus towers (Riehl and Malkus, 1958; Reiter, 1975). Puerto Rico, at approximately 13°N latitude, is in this branch of the Hadley cell.