A VHF Windprofiler Network in Ontario and Quebec, Canada: Design Details and Capabilities

A new network of VHF windprofiler radars (40-55 MHz) is now under development in Ontario and Quebec, Canada. It will cover the latitude region 42N to 50N, and the longitude region from 74W to 85W. Three radars are currently complete. The network is unique in several ways. First, it is the first such network in Canada. Second, we concentrate on the VHF (Very High Frequency) band, using frequencies in the range 40 to 55 MHz. This will help avoid the problems related to signal contamination due to birds and insects, and will also reduce the contamination which can occur due to precipitation. In addition to supplying three components of the wind, the radars also present some new parameters. For example, we present scatterer anisotropy as a routine parameter. This parameter is a good indicator about the convective state of the atmosphere, and on some occasions has been correlated with precipitation. In addition, tropopause heights are reported on an hourly basis, and this has proved useful in studies of ozone exchange between the stratosphere and troposphere, and indeed for general studies of STE (stratosphere-troposphere exchange). Turbulence strengths are also reported as functions of height and time on at least an hourly basis, and this useful for aircraft safety as well as for studies of STE.

Traditionally frequencies around 50 MHz have been avoided for such networks due to the difficulties in obtaining low altitude winds (below 1.5 km), but recent developments by various groups have shown that with the right choice of antennas, and the correct method, measurements as low as 300 m altitude are possible. These new developments are integrated into our network. In additional a series of calibrations using balloons and instrumented aircraft are currently under way, and the radars are already participating in pollution transport studies in Canada.

The network is in a meteorologically interesting area, close to the Great Lakes. The Meteorological Research Branch (MRB) of the Meteorological Service of Canada plans to collaborate on applications Research and Development projects related to assimilation of the windprofiler data into NWP models, model validation, and severe weather studies.