Kelvin Waves and the QBO

1. Kelvin Waves and the QBO Rolando Garcia 1 2 Colorado Research Associates, Boulder, CO

2. Synoptic mapping of long asynoptic data sequences • Example using TIMED/SABER temperature data • Salby’s Fast-Fourier Synoptic Mapping • Extension to arbitrarily long data sequences Compare with models • WACCM3 with different convective parameterizations • Compare wave forcing in model vs. observational estimates HIRDLS data • Higher vertical resolution • Ozone and water vapor (?) HIRDLS JAN 08

3. SABER observations are asynoptic: • Salby (1982) has shown that one can obtain a synoptic spectrum from the spectra of asynoptic observations referred to an “s-coordinate”: • (which is a hybrid of longitude and UT) • Salby’s technique requires a regular observation sequence (which SABER–and HIRDLS–can provide) • Fourier analysis of asynoptic data yields an asynoptic spectrum that corresponds closely to the synoptic one • The technique has usually been applied to observations made in a single satellite “yaw cycle” • But the technique can be extended to data sequences of arbitrary length HIRDLS JAN 08

4. absolute values of s common sasc sasc common sdesc yaw maneuver sdesc s relative to common sasc common sasc sasc this shows the common s-cordinates for an entire year’s sequence (>5000 orbits), referred to common sasc so the entire sequence can be viewed clearly common sdesc sdesc Interpolation to common s-coordinates • At yaw maneuvers, the value of the s-coordinate shifts slightly, as shown on the right • To analyze data sequences longer than one yaw cycle, the observations are interpolated to common ascending and descending s-coordinates • The data are interpolated across gaps associated with yaw maneuvers • The analysis then proceeds as usual; but it can be extended to arbitrarily long sequences of data. Here we will show results for 1-year sequences. HIRDLS JAN 08

5. stratosphere stratosphere and mesosphere 1 4 3 2 Equatorial waves: Equatorial Spectra(z,) for m = 1 2 high-frequency Kevin waves low-frequency Kelvin waves diurnal tide non-sun-synchronous tide • Notesign convention: • positive frequencies <=> westward • negative frequencies <=> eastward • frequencies are given in cycles/day (cpd) HIRDLS JAN 08

6. 1. m=1 Kelvin wave structure, t~12 d 2. m=1 Kelvin wave structure, t~3 d 2.5 K 0.5 K Examples of Kelvin wave structures These waves are presumed to play a role in forcing the QBO These wave structures are obtained via Hayashi (1971) coherence analysis. Only locations with significance level > 1  are plotted. Note different latitude scales. HIRDLS JAN 08

7. 2002 02 04 06 03 05 2003 s ~ 0.05 cpd => t ~ 20 d i.e., c ~ 20 ms-1 for m=1 Spectra (z,), m=1, Equator Low-frequency m=1 Kelvin waves (t ~ 20 days) and the QBO HIRDLS JAN 08

8. QBO West QBO East 2002 2003 2004 2005 Amplitude(t,z) of m=1 Kelvin waves at the Equator amplitude in frequency range –0.08 to –0.025 cpd, or t ~ 12–40 days eastward note the clear relationship between wave amplitude and QBO phase at z ~ 2 – 5.5 s.h. HIRDLS JAN 08

9. Work with WACCM highlights the importance of the parameterization of convection HIRDLS JAN 08

10. Model calculations vs. SABER observations of temperature at 10 mb in the Tropics WACCM + Tietdke • Spectra in WACCM and SABER observations are remarkably similar overall • But relative amplitude of east- vs. west-propagating (arrows) waves appears smaller in SABER compared to WACCM • Vertical resolution too coarse in SABER? Can HIRDLS data help here? HIRDLS JAN 08

11. Possible Applications of HIRDLS data • Confirm SABER results for equatorial waves • Does higher vertical resolution in SABER enhance the detectability of westward-propagating waves (inertia-gravity, Rossby gravity)? • Use HIRDLS and SABER data to quantify wave driving; compare with model results • Can ozone and water vapor data be used to look for the signature of the QBO in minor constituents? HIRDLS JAN 08