2008, Nilsson, H., Kirkwood, S., Morris, R.J., Latteck, R., Klekociuk, A.R., Murphy, D.J., Zecha, M., Belova, E.

Simultaneous observations of Polar Mesosphere Summer Echoes (PMSE) at Wasa and Davis in Antarctica have been compared. Data with simultaneous observations were obtained for 16 days between 18 January and 5 February 2007. Wasa is at a higher geographic latitude than Davis, but at lower geomagnetic latitude. PMSE strength and occurrence frequency were significantly higher at Wasa. The variation of daily PMSE occurrence over the measurement period was in agreement with temperature and frost-point estimates from the Microwave Limb Sounder on the Aura spacecraft for both Wasa and Davis. The diurnal variation of PMSE strength and occurrence frequency as well as the shape of the altitude profiles of average PMSE strength and occurrence frequency were similar for the two sites. The deepest part of the evening minimum in PMSE occurrence frequency occurred for the same magnetic local time at the two sites rather than for the same local solar time. The study indicates that PMSE strength and occurrence increase between 68.6° and 73° geographic latitude, consistent with observed differences in mesospheric temperatures and water vapor content. The average altitude distribution of PMSE varies relatively little with latitude in the same hemisphere.

2008, Sica, R.J., Izawa, M.R.M., Walker, K.A., Boone, C., Petelina, S.V., Argall, P.S., Bernath, P., Burns, G.B., Catoire, V., Collins, R.L., Daffer, W.H., De Clercq, C., Fan, Z.Y., Firanski, B.J., French, W.J.R., Gerard, P., Gerding, M., Granville, J., Innis, J.L., Keckhut, P., Kerzenmacher, T., Klekociuk, A.R., Kyrö, E., Lambert, J.C., Llewellyn, E.J., Manney, G.L., McDermid, I.S., Mizutani, K., Murayama, Y., Piccolo, C., Raspollini, P., Ridolfi, M., Robert, C., Steinbrecht, W., Strawbridge, K.B., Strong, K., Stübi, R., Thurairajah, B.

An ensemble of space-borne and ground-based instruments has been used to evaluate the quality of the version 2.2 temperature retrievals from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The agreement of ACE-FTS temperatures with other sensors is typically better than 2 K in the stratosphere and upper troposphere and 5 K in the lower mesosphere. There is evidence of a systematic high bias (roughly 3–6 K) in the ACE-FTS temperatures in the mesosphere, and a possible systematic low bias (roughly 2 K) in ACE-FTS temperatures near 23 km. Some ACE-FTS temperature profiles exhibit unphysical oscillations, a problem fixed in preliminary comparisons with temperatures derived using the next version of the ACE-FTS retrieval software. Though these relatively large oscillations in temperature can be on the order of 10 K in the mesosphere, retrieved volume mixing ratio profiles typically vary by less than a percent or so. Statistical comparisons suggest these oscillations occur in about 10% of the retrieved profiles. Analysis from a set of coincident lidar measurements suggests that the random error in ACE-FTS version 2.2 temperatures has a lower limit of about ±2 K.