Abstract
Abstract. MF radar wind measurements in the mesosphere and lower thermosphere over Poker Flat, Alaska (65.1° N, 147.5° W) are used to study the features of mean winds and solar tides. Continuous observation with the newly installed radar is in progress and in the present study we have analyzed a database of the first 27 months (October 1998–December 2000) of observation. The observed mean wind climatology has been compared with previous measurements and the latest empirical model values (HWM93 model). Similarly, the tidal characteristics are described and compared with the Global Scale Wave Model (GSWM00). The mean wind characteristics observed are fairly consistent with previous wind measurements by the Poker Flat MST radar. The main feature of the zonal circulation is the annual variation with summer westward flow and winter eastward flow. The annual mean zonal wind has a west-ward motion at altitudes below 90 km. The annual mean meridional circulation has mainly southward motion at 70–100 km. There is very good agreement between the radar zonal winds and the HWM93 model winds. Comparison of the meridional winds shows some discrepancy. Analysis of two years of data indicated that the year-to-year consistency is preserved in the mean circulation in the mesosphere. Tidal characteristics observed are also consistent with previous measurements. Semidiurnal tides have the largest amplitudes in summer while the weakest amplitude is observed during the winter months. The vertical wavelength is longer during the summer season compared to the winter season. Comparison with the GSWM00 produces mixed results. There is reasonable agreement between the observed and modeled phases. Diurnal tide amplitudes are comparable in magnitude with that of the semidiurnal tide. Seasonal variation is less evident in the amplitudes. Comparison of the observed tidal parameters with the GSWM00 reveals some agreement and discrepancies.Key words. Meteorology and atmospheric dynamics (climatology; middle atmosphere dynamics; waves and tides)
Highlights
Studies of the arctic middle atmosphere over Poker Flat, Alaska, took a new dimension with the joint research project recently launched by the Communications Research Laboratory of Japan and the Geophysical Institute of University of Alaska, USA
We present an analysis of the wind field over Poker Flat for the first 27 months (October 1998–December 2000) of medium frequency (MF) radar observation
We have used two years of data collected by a new MF radar, which is installed as part of a collaborative research project
Summary
It is expected that the combined use of the data based on these collocated instruments will be able to address a number of issues of the dynamics of the high-latitude middle atmosphere. Information on high-latitude middle atmosphere dynamics is documented through observations at a number of stations in the northern and southern hemispheres. At Poker Flat, previous observations using the MST radar during 1980 s were useful to describe various features of the dynamics of the middle atmosphere. P. Kishore et al.: MF radar observations of mean winds and tides over Poker Flat, Alaska. We present an analysis of the wind field over Poker Flat for the first 27 months (October 1998–December 2000) of MF radar observation. The summary of the analysis is presented in the last section
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