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

Abstract

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.

Delay of the First Transition of Asian Summer Monsoon under Global Warming Condition

“…In observations, two stepwise expansions of onset (early June around 5°N, 125°E and middle July around 12.5°N, 135°E) are recognized, whereas the eastward expansions are contiguous rather than stepwise in w-MME. This tendency is similar to our previous study (Inoue and Ueda 2009) based on precipitation data. Figure 3 shows differences of ASM onset dates and their intermodel consistency between 20C3M (1981−99) and SRES-A1B (2081−99) based on w-MME.…”

“…This implies that, in the CGCMs, the monsoon onset over WNP is not directly influenced by the delay of the first transition in mid-May. In many CGCMs, however, convections over the WNP tend to start under a lower in situ SST than that in observations (Inoue and Ueda 2009), suggesting that the reproduction of the seasonal evolution of the WNP monsoon is still fundamental challenging topic in the state-of-theart CGCMs (Wang et al 2005). The delay of the onset over the Bay of Bengal and the South China Sea might be associated with change in large-scale circulations and thermal fields under global warming situations.…”

“…Reproducibility of seasonal evolution of ASM in the CMIP3 CGCMs is evaluated by some studies (e.g., Inoue and Ueda 2009;Li and Zhang 2009). On the future projections of the seasonal evolutions of ASM based on these CGCMs, Kitoh and Uchiyama (2006) examined the changes in onset and withdrawal of the monsoon based on precipitation data.…”

Seasonally asymmetric transition of the Asian monsoon in response to ice age boundary conditions

“…In addition to the changes of the mean-field, it has been reported that the seasonal excursion of rain band will also be modulated under the increase of CO 2 concentration that may affect the duration of the rainy season (e.g., Kitoh and Uchiyama 2006). The projected changes in the late onset and withdrawal of the Baiu rainfall may be associated with the slow establishment of the Asian monsoon and related air-sea interactions (Inoue and Ueda 2009). Despite this fact, our comprehension of the fundamental controlling mechanisms remains deficient.…”

Seasonal modulation of the Asian summer monsoon between the Medieval Warm Period and Little Ice Age: a multi model study

“…Ueda et al (2011) used this model to examine the seasonal transition of the Asian monsoon during the LGM. This model is capable of reproducing general features of the Asian summer monsoon including its seasonal transition (Inoue and Ueda 2009). Its atmospheric model is a spectral model with T42 spatial resolution (approximately 2.8°) that uses 30 vertical layers.…”