# Presentation: 830601

## Winter Surface Temperature Anomalies in Japan and East Asian Atmospheric Circulation Patterns Associated with ENSO 

- Kiyoharu Takano, Chiaki Kobayashi
- Meteorological Research Institute /JMA
- Shuhei Maeda,Shoji Kusunoki
- Japan Meteorological Agency

## Objective

- To clarify the mechanism that brings warm winter in Japan during  ENSO warm episode
- (Halpert and Ropelewski, 1992).

- Winter(DJF) Surface  Temperature Tendency in Japan during Warm Episode of ENSO

## Northern Japan

**Northern Japan**

**Western**
**Japan**

- The Nansei Islands

- Eastern Japan

## Early Winter

- 3month mean
- (October,November, December)

- Late Winter
- 3-month mean
- (January, February, March

- Tmp850 correlation map with NINO3 SST
- (1960-1998) 39years

## Division of Winter into Early Winter and Late Winter

- Early Winter   October-December
- (Influence is over whole of Japan)
- Late Winter    January-March
- (Influence is only southern part of Japan)

## Data and Analysis Procedure

- Data : NCEP/NCAR Reanalysis
-            1979(59)-1993
-            CMAP
-           (Seasonal Predictability experiment
-           with Prescribed SSTs)
- Analysis: Correlation and Regression map
-                   from NINO3 SSTs
-                    Vorticity analysis at 200hpa

## Regression map with NINO3 SST

-  (Late Winter JFM)

- Precipitation

- Temperature
- at 850hPa

- Stream function
-  at 850hPa

- Stream function
- at 200hPa

## Western tropical Pacific pattern

-  ・ Negative precipitation anomalies
-  ・ Anti-cyclonic pattern at lower level
-  ・ Cyclonic pattern at upper level
- Matsuno-Gill Response to relative cooling (Bin Wang et al. 2000)

## Late Winter(JFM)

- Temperature Advection by Lower Circulation
- (Bin Wang et al. 2000, Yasutomi and Kimoto 1999)
-  Direct Effect :
-  Influence is restricted in Southern Japan

- Temperature
- at 850hPa

- Stream function
-  at 850hPa

## Temperature 

- Temperature
- at 850hPa
- (JFM)

- Advection by
- anomaly wind
- (JFM)

## Regression map with NINO3 SST (OND)

- Precipitation

- Temperature
- at 850hPa

- Stream function
-  at 850hPa

- Stream function
- at 200hPa

## Early Winter(OND)

- Warm surface temperature is brought by
- barotropic  circulation  near Japan
- which propagates from southern China.

- Stream function at 200hPa
- and Takaya-Nakamura(TN) Wave activity flux
- (TN  Flux shows Rossby wave propagation and activity   G.R.L. 1998)

## Warm(Cold) winter in Japan during warm(cold) episode of ENSO is brought by

- Late winter(JFM)
-       Temperature advection by low level  circulation over Western Pacific
-        This is direct influence of ENSO and the influence is restricted in the southern Japan.
- (b) Early winter(OND)
-       Barotoropic (positive) circulation which propagate from southern China.
-       This is indirect influence of ENSO and influence is over whole of Japan.
- Both effects originally come   from negative(positive) precipitation anomalies in the Western tropical pacific during warm(cold) episode.

## Discussion

- Why the mechanisms  in JFM and OND are different ?
- = Why Rossby wave propagates from southern China to Japan only in OND and not in JFM?
-  (a) Difference of Precipitation anomalies in the tropical western Pacific?
-            Not so different ?
-  (b) Difference of basic flow?
-           Not so different ?
- (c)  Other reason?

**Stream function at 200 and TN flux**

- JFM

- OND

## A Possibility

- Zonal component has large amplitude in JFM
- (Tropical Axisymmetric Mode (Watanabe et al.2002))

- Stream function at 200hPa OND

- Zonal mean component

- Ratio of zonal mean component
- to total amplitude

- Stream function at 200hPa JFM

- Zonal component of forcing is stronger in JFM than in OND.

## Vorticity equation liniarized around the climatorogical basic state at 200 hPa

- L: Liner operater
- ψc:Basic State(climatology)
- ψd   : perturbation
- Fd    : Perturbation forcing
- It can be solved symbolically,

## Note               has non-zonal component,

- Note               has non-zonal component,
- because basic state ψc  has non-zonal component.

- We consider to divide forcing into zonal component and non-zonal component.

## Late Winter (JFM)  case

- Liner solution  by non-zonal forcing

- Liner solution by zonal forcing

- Liner model by total forcing

- Regression from NINO3 SSTs

- Late Winter (JFM)  case

- Liner response by liner barotropic model

## Wave activity flux for response to total forcing

-  Wave activity flux for response to non-zonal forcing

## Early  Winter (OND)  case

- Liner model by Non zonal forcing

- Liner model by zonal forcing

- Liner model by total forcing

- Regression from NINO3 SSTs

- Early  Winter (OND)  case

- Liner response by liner barotropic model

## Hypothesis

- There is Rossby wave propagation from southern China to Japan both in early and late winter as a response to local (or non-zonal) forcing.
- However, in late winter, since zonal forcing is stronger, non-zonal response to zonal forcing covers this Rossby wave propagation, and then it can not be seen. On the other hand, in early winter since zonal forcing is weak, Rossby wave propagation can be seen.

## Conclusions

- Warm winter in Japan during warm episode of ENSO is brought by different two mechanisms depend on the period.
-      (1) In early winter(OND), barotropic Rossby wave propagating from southern China.
-      (2) In late winter(JFM), temperature advection by lower level anti-cyclones  flow in the tropical western Pacific.
- B.    The difference of these two mechanisms may be understood by considering the effect of non-zonal response to zonal forcing which is stronger in late winter.