1ST HEIGHT COMPARISON OF NOCTILUCENT CLOUDS AND SIMULTANEOUS PMSE

On the night of August 9-10, 1991, two rocket payloads were launched i nto simultaneously occurring noctilucent clouds (NLC) and polar mesosp heric summer echoes (PMSE) above Esrange, a third rocket payload was l aunched into a NLC where a PMSE was detected 5 minutes later above Esr ange, in Sweden as part of the NLC-91 campaign. An aim of this experim ent was to compare the vertical structures and locations of the NLC an d PMSE events. To this end, in situ optical photometers and particle i mpact sensors were used to measure the altitude and vertical structure of the NLC layer, while the Cornell University portable radar interfe rometer (CUPRI) was used to probe the PMSE. Although this comparison i s complicated by the horizontal separations between the in situ measur ements and the radar volume, and low electron densities which reduced the overall radar reflectivity, we conclude that the PMSE layer in the CUPRI radar volume remained above the NLC layer detected by the in si tu instruments by 300 to 2000 m throughout the experiment. We interpre t this result as supporting th view that PMSE are more likely to resul t from the presence of aerosols smaller than the ones optically detect able as NLCs.