Variability in the mesosphere observed by the Nimbus 6 pressure modulator radiometer

Abstract

The pressure modulator radiometer flew aboard Nimbus 6, collecting radiance data from June 1975 until June 1978. These data have been processed to yield daily temperatures, geopotential heights, and balance wind estimates from the stratosphere and mesosphere (30-85 km) for the entire period. We use these data to examine the variability of both the zonal-mean and the nonzonal disturbances present in the data. In terms of the zonal-mean, we show that the COSPAR International Reference Atmosphere (1986), developed from these data, can be misleading in the mesosphere due to the underlying interannual variability and the merging with other data sets. Daily variability of the zonal-mean flow is examined, and these data show strong evidence of coupling between the stratosphere and mesosphere for such variations. We also find evidence for significant coupling of wave-like events in the stratosphere and the mesosphere but that not all such disturbances seen in the mesosphere are due to simple propagation from below. Space-time spectral analysis is used to search for traveling planetary waves: Results show a weak 5-day normal mode present in the equinox seasons, which appears to correspond to the first symmetric mode predicted by theory. These data also show clear evidence of the 4-day wave in all three southern winters examined and are consistent with the hypothesis that this mode grows due to instability of the background zonal flow.

Wave activity (planetary, tidal) throughout the middle atmosphere (20-100km) over the CUJO network: Satellite (TOMS) and Medium Frequency (MF) radar observations

“…These are likely to be the "normal" mode features, usually considered to dominate the MLT region. It was noted by Lawrence and Randel (1996) that the energy associated with these normal modes is small compared with other stratospheric and tropospheric features. There is also considerable spectral activity in the eastward wave number sectors, with m=−1, −2, and −3 and periods of 10-20 days, which could be associated with the jet stream's variability, fluctuations of the zonal vortex, and PW associated with instability processes.…”

“…A more recent study worthy of note is that by Lawrence and Randel (1996), who used Nimbus 6 satellite data (PMR) to demonstrate stratospheric-mesospheric coupling in three distinctive ways: the variance of the geopotential height around latitude circles • N) showed strong correlation throughout the atmosphere (35-83 km); and episodic wave-like events, in particular westward propagating "normal" PW modes (periods, 5 to 10-d band) having near global coherence, and eastward propagating PWs (4-d period) in southern winters (hereafter SH, Southern Hemisphere) associated with an instability process, were identified throughout the atmosphere.…”

Transient eastward-propagating long-period waves observed over the South Pole

“…One can argue that the gradients used to compute " q y from these data will be underestimated due to the smoothed nature of the climatology. More realistic estimates of " q y were made by Lawrence and Randel (1996) for June 1975 to June 1978 using the Nimbus-6 PMR data. These results are consistent with our results and indicate a region of negative " q y present poleward of 70 S present during the winter months at 48, 65 and 81 km (other altitudes are not shown).…”

Interhemispheric structure and variability of the 5-day planetary wave from meteor radar wind measurements

“…These include sea-surface pressure (Madden and Jullian, 1972), temperature (Mechoso and Hartmann, 1982;Prata, 1989;Rogers, 1976), stratospheric height and thickness (Hirota and Hirooka, 1984), geopotential height (Lawrence and Randel, 1996), mesospheric airglow (Sivjee et al, 1994), and winds in the mesosphere and lower-thermosphere (MLT) (Clark et al, 2002;Jiang et al, 2008;Wu et al, 1994). 5DW influences have also been observed in stratospheric ozone (Belova et al, 2008a(Belova et al, , b, 2009Rosenlof and Thomas, 1990), water vapor mixing ratio (Sonnermann et al, 2008), chemical species (Pendlebury et al, 2008), polar mesosphere summer echoes (PMSEs) , mesospheric temperature (von Savigny et al, 2007), noctilucent clouds (NLCs) or polar mesospheric clouds (PMCs) (Merkel et al, 2003(Merkel et al, , 2008Nielsen et al, 2010), and ionospheric parameters (Fraser, 1977;Kokourov et al, 2009;Takahashi et al, 2006).…”