Trend and Variability of East-Asian Precipitation: Linkage to Sea Surface Temperatures

Fanglin Yang

Environmental Modeling CenterNational Centers for Environmental Prediction

NOAA 32nd Climate Diagnostic and Prediction WorkshopCOAPS/FSU, October 22-27, 2007

Acknowledgment: This work was support by the NASA Modeling, Analysis and Prediction program while the author worked with William Lau at GFSC/NASA.

Possible causes:

1. South Asian black carbon emission

2. Climate regime shift3. Global warming4. Shift of Africa-North China

teleconncection5. SST trend

South China

Central China

North China

Questions?

• To what extent can the observed precipitation variability can be explained by SST variability?

• Does the precip-SST relation at the interannual timescale differ from that at the inter-decadal timescale?

Interannual Variability

Single Value Decomposition (SVD) applied to 7-year high-pass filtered precipitation and SSTs

SST Precip

MAM

SST Precip

JJA

SSTVariance

PrecipitationVariance

SST-PrecipitationCo-Variance

Correlation (PC_sst,

PC_precip)

MAM

SVD 1 31% 27% 27% 0.57

SVD 2 11% 15% 14% 0.64

JJA

SVD 1 43% 10% 24% – 0.77

SVD 2 7% 17% 13% 0.76

SST_PC Precip_PC

JJA, Regressions of wind850 and Z700 to PCs

JJA Climate, 1951-1998, NCEP R1

SVD Modes

SST_PC Precip_PC

MAM

Decadal Variation and Trend

SSTInterannual Mode

RainfallInterannual Mode

Projection of Obs to SVD modeArea-Mean Rainfall

ConclusionInterannual Variability• Precipitation over South China

in MAM and North China in JJA ENSO mode of SSTs

• Precipitation over central China in both MAM and JJA season SST in warm pool and northern Indian ocean;

• Features of the anomalous 850-hPa winds and 700-hPa geopotential height corresponding to these modes support a physical mechanism that explains the causal links between the modal variations of precipitation and SSTs.

Trend and decadal variation

• Upward South China MAM precipitation and downward JJA North China precipitation warming trend of the ENSO-like mode.

• Upward JJA central China precipitation warming trend of SSTs over the warm pool and Indian Ocean.

• Downward MAM South China precipitation downward central North Pacific SSTs (less robust)