1. Investigation of an Unusual Winter Time Rossby Wave Event over Antarctica
Yucheng Zhao, M. J. Taylor, P.-D. Pautet,
W. R. Pendleton Jr., T. Moffat-Griffin,
D. Murphy, M. E. Hervig, J. M. Russell, III and MLS Team

2. Introduction
Advanced Mesospheric Temperature Mapper (AMTM) at South Pole station as part of the ANGWIN program (2010-to date)
Infrared OH (3,1) band intensity and rotational temperature ~87 km)
Temporal resolution: 30 sec.
Continues measurements each winter during the “dark time” (April-August)
Zenith temperature from ,
SOFIE/AIM temperature
MLS temperature at hpa (~83 km)

3. Sample of OH (3,1) Band Intensity and Temperature

4. Observed Planetary Wave Over South Pole
18 day
45 day
5 day
28 day
Rich spectrum of planetary waves
5, 18, 28, 45 days
Year to year variability

5. South Pole: 2014 Daily Mean Temperature
Large amplitude oscillation starting in June
Max amplitude ~12K
28 day dominant the spectrum

6. Band Pass (24-30 day) Filtering
Strong 28 day oscillation in 2011 and 2013, amplitude 4-7 K
Weaker in 2012, amplitude ~2K
Amplitude growth 2014, reaching ~12K by the end of the winter season

7. Temperature Comparison with Davis
Davis: 69S, 78 E

8. OH Temperatures: Rothera and Southpole
Lat. 67°35'S, Long. 68°8’W, BAS
OH (3,1) temperature using Bomem spectrometer

9. Wavelet Results: Rothera
Strong wave activity during the later part of the winter season.
Very broad spectrum: period between days.

10. Daily Averaged SOFIE/AIM Temperature 2014
SOFIE v1.2 temperature in the southern hemisphere
15 measurements each hemisphere
Latitude coverage: 48S to 71 S

11. 25-30 Day Oscillation in SOFIE Temperature
Big oscillation in the SOFIE temperature in the southern hemisphere in the later part of the winter season
FFT: Strong peak at ~25-30 day

12. The Zonal Structure SOFIE temperature binned to 30 longitude bin
Filtered results: 85 km
Localized in longitude: [-90,0]
No zonal propagation

13. SOFIE, AMTM and Bomen
The 28 day oscillation amplitudes of SOFIE are comparable to the amplitude at the Pole, or even bigger.
Mostly in phase between the SP AMTM and SOFIE

14. The Vertical Structure
Filtered SOFIE temperatures from the longitude bin.
Amplitude increases with height
Vertical wavelength ~60-70 km.

15. Latitudinal Extension (MLS Temperature)
EOS Aura MLS temperature
within longitude bin
At hpa (~83 km)
Winter/spring time high latitude (>60) in the southern hemisphere.

16. MLS bandpass filtered Temperature @ ~83 km, day 247

17. Orographic Forcing?
Davis (68S): Highly calibrated OH Spectrometer
Localized winter/spring oscillation over the peninsula at mesopause altitudes

18. MLS filtered Temperature: Day 247, 10 mb
Southern hemisphere high latitudes,
Wave #1, with amplitude larger between E.

19. SOFIE: Height vs Longitude
Day 223
Day 236
Below 80 km: wave #1
km: localized

20. SOFIE: Day 247, Altitude vs Longitude

21. propagation? SOFIE temperature binned to 30 longitude bin 85 km
Localized in longitudes: [-90,0]
No zonal propagation
30 km
Extended to all longitudes
Apparent Eastward propagation

22. Rossby Waves Madden (2007): s=1, l-s=4, period 28.08 day
Sassi et al., (2012): 25 day (1,4) Rossby mode during the northern hemispheric winters using NOGAPS- ALPHA.
The 28 day (1,4) Rossby mode
(Madden, 2007)

23. Solar Effect on Temperature
Thomas et al., 2015
The amplitude of the observed 28 day oscillation is much larger than the solar driven temperature response- “small signal”

24. Summary
Strong (~12 K amplitude), persistent (5 months) 28 day oscillation in temperature during 2014 winter/early spring over Antarctica
The 28 day oscillation is evident in OH temperature (2 sites), SOFIE and MLS temperature data.
OH temperatures at South Pole and Rothera, SOFIE temperatures at 85 km are in phase.
SOFIE results show amplitude increase with altitude.
MLS data indicate the oscillation is limited to southern hemisphere high latitudes (>50S) in both mesosphere and stratosphere.
Strong longitudinal localization (peninsula) at mesopause heights.
Satellite data suggest wave #1 planetary wave in the stratosphere and lower mesosphere.