Multi-radar observations of polar mesosphere summer echoes during the PHOCUS campaign on 20–22 July 2011

• Time–altitude behaviour of PMSE is similar for three radars located 150–250 km apart.
• Cross-correlation coefficients between time variations in PMSE strength for each pair of radars are up to 0.6.
• The same wave with 6-h period was observed by all the three radars.
• Simultaneous values of PMSE spectral width for three radars can be different.

During the PHOCUS rocket campaign, on 20–22 July 2011, the observations of polar mesosphere summer echoes (PMSE) were made by three mesosphere–stratosphere–troposphere radars, operating at about 50 MHz. One radar, ESRAD is located at Esrange in Sweden, where the rocket was launched, two other radars, MAARSY and MORRO, are located 250 km north-west and 200 km north of the ESRAD, respectively, on the other side of the Scandinavian mountain ridge. We compared PMSE as measured by these three radars in terms of their strength, spectral width and wave modulation. Time–altitude maps of PMSE strength look very similar for all three radars. Cross-correlations with maximum values 0.5–0.6 were found between the signal powers over the three days of observations for each pair of radars. By using cross-spectrum analysis of PMSE signals, we show that some waves with periods of a few hours were observed by all three radars. Unlike the strengths, simultaneous values of PMSE spectral width, which is related to turbulence, sometimes differ significantly between the radars. For interpretation of the results we suggested that large-scale fields of neutral temperature, ice particles and electron density, which are more or less uniform over 150–250 km horizontal extent were ‘modulated’ by waves and smaller patches of turbulence.