Brief Notes on Brief Notes on AIRSAIRS

May 9, 2007May 9, 2007

Group MeetingGroup Meeting

Atmospheric InfraRed Atmospheric InfraRed Sounders (AIRS)Sounders (AIRS)

• 650 – 2670 cm650 – 2670 cm-1-1

• 2378 channels2378 channels• Objectives:Objectives:

improve weather forecasting improve weather forecasting establish the connection establish the connection

between severe weather and between severe weather and climate change climate change

determine if the global water determine if the global water cycle is accelerating cycle is accelerating

detect the effects of greenhouse detect the effects of greenhouse gases gases

ReferenceReferenceStephens, GL. "Cloud feedbacks in Stephens, GL. "Cloud feedbacks in the climate system: A critical the climate system: A critical review." review." Journal of climate,Journal of climate, 1818(2), (2), 2005:237-273. 2005:237-273.

Huang et al, JGR, 110, D12102, 2005

Upper TroposphericMiddle Stratospheric

2005 July Global Average2005 July Global Average

Principal Component Analysis (PCA)Principal Component Analysis (PCA)

Data Matrix time steps stations

1Covariance Matrix entries

1T T

X N M

C X X E E M MN

EOFs eigenvectors of : Modes of Spatial Pattern

PCs : Time-dependent Amplitudes of EOFs

Eigenvalue: the fraction of variance captured by each EOF

The original data can be represented by

k

k k

e C

p X e

( ) ( , )Tk k

k

X p t e Spectral PCA: Replace time t by frequency

EOF Analysis – 2005 JulyEOF Analysis – 2005 July

EOF Analysis – 2005 July (Cloud-Cleared)EOF Analysis – 2005 July (Cloud-Cleared)

EOF Analysis – 2005 JanuaryEOF Analysis – 2005 January

EOF Analysis – 2005 January (Cloud-Cleared)EOF Analysis – 2005 January (Cloud-Cleared)