|
|
 |
|
|
Ann. Geophys., 15, 1099-1110, 1997
www.ann-geophys.net/15/1099/1997/
© European Geosciences Union 1997
Comparisons between Canadian prairie MF radars, FPI (green and OH lines) and UARS HRDI systems
C. E. Meek1, A. H. Manson1, M. D. Burrage2, G. Garbe3, and L. L. Cogger3
1Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Canada S7N 5E2
2Space Physics Research Lab., University of Michigan, Ann Arbor, MI 41809, USA
3Department of Physics and Astronomy, University of Calgary, Calgary, Canada T2N 1N4
Abstract. Detailed comparisons have been completed
between the MF radars (MFR) in the Canadian prairies and three other systems:
two ground-based Fabry-Perot interferometers (FPI) and the UARS high resolution
Doppler imager (HRDI) system. The radars were at Sylvan Lake (52°N,
114°W), Robsart
(49°N, 109°W)
and the main continuing facility is at Saskatoon (52°N,
107°W). Statistical comparisons of hourly mean
winds (1988-1992) for the Saskatoon MFR and FPI (557.7 nm green line) using
scatter plots, wind speed-ratios, and direction-difference histograms show
excellent agreement for Saskatoon. No serious biases in speeds or directions
occur at the height of best agreement, 98 km. If anything, the MFR speeds appear
bigger. The same applies to the Sylvan Lake MFR and Calgary FPI, where the best
height is 88 km. In both cases these are close to the preferred heights for the
emission layers. Differences between measurements seen on individual days are
likely related to the influence of gravity waves (GW) upon the optical and radar
systems, each of which have inherent spatial averaging (350, 50 km
respectively), as well as the spatial difference between the nominal measurement
locations. For HRDI, similar statistical comparisons are made, using
single-overpass satellite winds and hourly means (to improve data quality) from
MFR. Heights of best agreement, based upon direction-difference histograms, are
shown; there is a tendency, beginning near 87 km, for these MFR heights to be 2
or 3 km greater than the HRDI heights. Speeds at these heights are typically
larger for the satellite (MFR/HRDI = 0.7–0.8). Reasons for the differences are
investigated. It is shown that the estimated errors and short-term (90 min)
differences are larger for HRDI than for the MFR, indicating more noise or GW
contamination. This leads to modest but significant differences in median
speed-ratio (MFR/HRDI < 1). Also, comparison of the two systems is made under
conditions when they agree best and when they show large disagreement. For the
latter cases both systems show higher relative errors, and the HRDI vectors are
frequently small. It is suggested that spatial or temporal GW wind fluctuations
are the likely cause of the larger HRDI-MFR disagreement when wind speeds are
small. No satisfactory explanation exists for the overall discrepancy in speeds
between the MFR and HRDI.
Full Article in PDF (1305 KB) |
|
|
