Five-day Waves in Polar Stratosphere and Mesosphere Temperature and Mesospheric Ice Water Measured by SOFIE/AIM

Abstract:

The temperature and column ice water content (IWC) of polar mesospheric clouds (PMCs) have been simultaneously measured by the Solar Occultation for Ice Experiment (SOFIE) onboard NASA’s Aeronomy of Ice in the Mesosphere (AIM) satellite since April 2007. The 8-year (2007-2014) data of the temperature and IWC are used to extract the 5-day planetary waves (PWs) with zonal wavenumbers ranging from -1 to -3 (eastward propagating mode, E1-E3), 0 (stationary mode, W0), and 1 to 3 (westward propagating mode, W1-W3) in the polar stratosphere and mesosphere. The 5-day PWs in temperature are stronger in the polar winter stratosphere and mesosphere and exhibit substantial inter-hemispheric asymmetry. The date-height distributions of the 5-day waves coincide with those of the eastward jet in each hemisphere. This indicates that the 5-day PWs might be generated from barotropic/baroclinic instability in the polar stratosphere. The relative strengths of 5-day PWs decrease with increasing wavenumbers. The E1 (W1) 5-day PW is stronger than any other mode in the winter stratosphere and lower mesosphere (summer upper mesosphere). SOFIE temperature and IWC data are derived from simultaneous measurements in the same air column and thus provide a good opportunity to study the phase relationship between the 5-day PWs in temperature and IWC. Our analyses show that the phase shifts of W1 5-day PW in temperature relative to that in IWC have a mean of -2.0 h (0.3 h) with a standard deviation of 3.8 h (4.2 h) in the northern (southern) polar region. This indicates that the formation of the W1 5-day PW in PMCs is controlled mainly by the W1 5-day PW in temperature and influenced by other factors and is consistent with previous studies.