Experimental Evidence of Arctic Summer Mesospheric Upwelling and Its Connection to Cold Summer Mesopause

Common volume mesospheric meteor detections from two radar stations separated by about 130 km were used to retrieve horizontal wind fields between 82 and 96 km altitudes at high-latitudes, near 69° N. The horizontal wind divergence was estimated from the gradients of the wind fields. This determination is the first of its kind for the mesosphere. Twelve years of nearly continuous datasets reveal systematic summer signatures in the horizontal wind divergence field, namely, a transition from negative to positive with increasing altitude while moving across the mesopause. There are indications that the reversal altitude is also anti-correlated with the mesopause temperature in addition for a tendency for the altitude of the reversal to increase over the years. We show that the reversal in the horizontal wind divergence at the mesosphere is consistent with upward winds peaking near the mesopause. These winds indicate that adiabatic cooling was strongest at the region of the deep temperature minimum seen in the summer mesopause.