Using wind measurements from the recently installed Nippon/Norway Svalbard Meteor Radar, (NSMR) at 78¿N, 16¿E, we have derived wind shears, and, combining these with model Brunt-V¿is¿l¿ frequencies, have determined estimates of the gradient Richardson Number. These Richardson Number estimates parameterise the degree of stability of the upper mesosphere at a height of around 90 km. We find indications of dynamic instability in spring and autumn, with greater stability in summer.