Analysis on the Dynamics of a Wave-like Teleconnection Pattern along the Summertime Asian Jet Based on a Reanalysis Dataset and Climate Model Simulations

Self Cite

Accurate simulation of summertime convection associated with the Asian monsoon trough over the subtropical western Pacific is important but di‰cult to achieve in many general circulation models (GCMs). This study reports a case in which bias could be reduced by introducing a higher-resolution regional atmospheric model (RAM), two-way nested in an atmospheric GCM over the western Pacific. Additional partial-coupling experiments revealed that GCM bias correction was insensitive to the coupling domain. The two-way nesting e¤ect was similar to one phase of a leading mode of natural variability in the system. This is indicative that the twoway nesting model provides more realistic tropical heating that e¤ectively excites a correct phase of the intrinsic dynamical mode to reduce GCM bias.

Section: Gcm Bias Correctionsupporting

confidence: 68%

Section: Leading Dynamical Modesmentioning

confidence: 99%

GCM Bias of the Western Pacific Summer Monsoon and Its Correction by Two-Way Nesting System

Inatsu

Satake

Kimoto

et al. 2012

Self Cite

“…In the present study, we present another possible mechanism in the delay of the Baiu withdrawal from the viewpoint of CJ, one of the key phenomena of the termination of the Baiu (Ueda et al 1995). The withdrawal of Baiu and summertime climate around Japan is affected not only by the tropical and subtropical forcing examined in the present study, but also by multiple atmospheric teleconnection patterns (Wakabayashi and Kawamura 2004), including mid-latitude forcing such as the Silk Road pattern (Enomoto et al 2003;Kosaka et al 2009). …”

Section: Summary and Discussionmentioning

confidence: 68%

Delay of the Baiu Withdrawal in Japan under Global Warming Condition with Relevance to Warming Patterns of SST

Inoue

Ueda

2012

Climatologically, an abrupt enhancement of convection occurs in mid-July over the western North Pacific (WNP) around 20°N, 150°E known as a convection jump (CJ), which is associated with a rapid diminishment of the Baiu rainband over central Japan through excitation of stationary Rossby wave. In view of the subtropical-origin teleconnection, we examined a projected future delay of the Baiu withdrawal under global warming conditions with relevance to future changes in seasonal evolution over the WNP. Based on reproducibility evaluation of the Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model outputs with respect to seasonal evolution of summertime precipitation over central Japan, we computed weighted multi-model ensembles, which are used for diagnosis of the projected future CJ changes. The result shows that CJ under global warming will occur more southeastward. In the future projection, increases in sea surface temperature (SST) over the equatorial Pacific and subtropical North Pacific are larger than those in the adjacent regions. Sensitivity experiments with a general circulation model (MJ98 AGCM) utilizing these salient warm SST anomalies also show the southeastward shift of CJ in comparison with a control simulation. These results indicate that the change in the location of subtropical convections associated with the spatial distribution of warm SST anomalies could be an important factor for the late termination of the Baiu season over central Japan under global warming conditions.

“…The strength of the lower tropospheric wind over the WNP region is intimately connected with the latitudinal position of the NPSH ridge. Figure 2 shows an inter-model relationship between JJA mean 850 hPa zonal wind over (Wakabayashi and Kawamura 2004) including the Silk Road pattern (Enomoto et al 2003;Kosaka et al 2009), this inter-model relationship suggests that the climatological circulation in the CGCMs over the WNP-EA domain is at least partly influenced by the PJ (Pacific-Japan) teleconnection pattern (Nitta 1987). It should be emphasized here that the latitude of NPSH ridge in many CGCMs is higher than that in observation (denoted as a filled square in Fig.…”

Section: Datamentioning

confidence: 86%

Evaluation for the Seasonal Evolution of the Summer Monsoon over the Asian and Western North Pacific Sector in the WCRP CMIP3 Multi-model Experiments

Inoue

Ueda

2009

Based on the World Climate Research Programme's (WCRP's) Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model dataset, evaluation for the summer monsoon over the Asian and western North Pacific (WNP) sectors is made in terms of reproducibility of the seasonal mean structure. Also investigated is a stepwise eastward progress of convection center from the Indian Ocean toward the WNP in the course of the maturing process of the continental and oceanic monsoons.Most models roughly reproduce seasonal mean broad-scale features on the Asian summer monsoon (ASM), but lower-tropospheric circulation over East Asia (EA) through the WNP and the location and intensity of the North Pacific subtropical high exhibit large inter-model variability. Some of the models fail to reproduce a reversal of the upper-tropospheric meridional temperature gradient over the South Asia and the North Indian Ocean sector. Metrics on the reproducibility of lower-tropospheric circulation of the ASM are also presented, in order to evaluate the reproducibility of the ASM circulation quantitatively.The large inter-model variability over the EA-WNP domains could be attributed to insu‰cient reproducibility of the oceanic monsoon. In most of the models, the stepwise eastward progress of convection over the South China Sea and WNP commences in May almost concurrently with large-scale circulation, whereas the eastward progress of convection is faster in most of the models than in the observation over the WNP. It is suggested that a teleconnection pattern associated with an intensification of convective activity over the WNP in mid-July is one of the key phenomena in both the observation and the coupled models, given the withdrawal of the Baiu rainy season around Japan. The analysis based on metrics concerning the stepwise eastward progress of convection over the WNP and its vicinity suggests that these models still have some di‰culties in reproducing the stepwise eastward progress of convection accurately.