brief notes on airs may 9, 2007 group meeting. atmospheric infrared sounders (airs) 650 – 2670 cm...
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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.
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