Presence of quasi 27-day oscillations in the atmosphere

Mao-Chang Liang (Academia Sinica and NCU)

K. Fai Li, and Yuk L. Yung (Caltech)

European Geosciences Union General Assembly 2009 Vienna, Austria, 19 – 24 April 2009

27-day solar cycle

11-year solar insolation: 0.1%

11-year Lyman-: 50%

27-day UV (200-300 nm): 0.23%

27-day Lyman-: 5%

COSMIC occultations in 24 hrs

(Illustration by Bill Schreiner, UCAR.)

FORMOSAT-3/COSMIC mission

Launch on April 14, 2006 6 satellites orbiting at ~800 km 3 instruments

GPS radio occultation receiver Tiny ionospheric photometer Triband beacon

1.7M (neutral) and 1.9M (ionized) soundings (2008.114) ~1500 soundings per day

Liang et al. (2008)

Daily mean5-day running mean15-day running mean

27-day FFT54-day FFT10.7-cmLyman-alpha

13.5-day FFTLyman-alpha

355 kmTropics

Methods

Daily and zonally averaged in 36 latitude bins 30 layers from 1-1000 mbar Traditional Fourier transform, with Hanning

window of 20-25 (10-20) days and 35-40 (40-50) days

Empirical mode decomposition 27-day mainly in mode #4, sometime leak to

mode #3 13.5-day mainly in model #3

EMD to remove long periods followed by FFT Running mean window of 60 days CMD & Wavelet

Methods

Daily and zonally averaged in 36 latitude bins 30 layers from 1-1000 mbar Traditional Fourier transform, with Hanning

window of 20-25 (10-20) days and 35-40 (40-50) days

Empirical mode decomposition 27-day mainly in mode #4, sometime leak to

mode #3 13.5-day mainly in model #3

EMD to remove long periods followed by FFT Running mean window of 60 days CMD & Wavelet

FFT of atmospheric temperature35 mbar22.5N

281 mbartropics

Lyman-

F10.7 cm

Liang et al. (submitted)

Liang et al. (submitted)

Latitudinal profiles

35 mbar

281 mbar

Liang et al. (submitted)

Vertical profile at low latitudes

Liang et al. (submitted)

Further verification

NCEP2COSMIC+FFTCOSMIC+EMDAIRS+FFT

Liang et al. (submitted)

CMD of COSMIC and MLS data

Li et al. (submitted)

MLS

COSMIC

Summary and Future work

Presence of quasi 27-day signals in the atmosphere is established

A likely source is solar forcing A potentially useful tool for calibrating climate

models

Analyzing WACCM3 (0-150 km)

Thanks you!

Comments?

Solar forcing

>>10 kyr of precession, obliquity, eccentricity 70-2300 years cycle 22-year magnetic field cycle 11-year sunspot cycle Annual cycle 27-day cycle Diurnal cycle