Limitations of Seasonal Predictability for Summer Climate over East Asia and the Northwestern Pacific

Abstract

Predictability of summer climate anomalies over East Asia and the northwestern Pacific is investigated using observations and a multimodel hindcast ensemble initialized on 1 May for the recent 20-30 yr. Summertime East Asia is under the influence of the northwestern Pacific subtropical high (PASH). The Pacific-Japan (PJ) teleconnection pattern, a meridional dipole of sea level pressure variability, affects the northwestern PASH. The forecast models generally capture the association of the PJ pattern with the El Niñ o-Southern Oscillation (ENSO).The Silk Road pattern, a wave train along the summer Asian jet, is another dominant teleconnection that influences the northwestern PASH and East Asia. In contrast to the PJ pattern, observational analysis reveals a lack of correlations between the Silk Road pattern and ENSO. Coupled models cannot predict the temporal phase of the Silk Road pattern, despite their ability to reproduce its spatial structure as the leading mode of atmospheric internal variability. Thus, the pattern is rather unpredictable at monthly to seasonal lead, limiting the seasonal predictability for summer in East Asia.The anomalous summer of 2010 in East Asia is a case in point, illustrating the interference by the Silk Road pattern. Canonical anomalies associated with a decayed El Niñ o and developing La Niñ a would have the PJ pattern bring a cold summer to East Asia in 2010. In reality, the Silk Road pattern overwhelmed this tendency, bringing a record-breaking hot summer instead. A dynamical model experiment indicates that European blocking was instrumental in triggering the Silk Road pattern in the 2010 summer.

Seasonal Prediction of Distinct Climate Anomalies in Summer 2010 over the Tropical Indian Ocean and South Asia

“…Rainfall over northern Pakistan is positive, indicating influence of the TIO SST (Fig. 5) in addition to mid-latitude circulation (Kosaka et al 2012). Enhanced rainfall over the western TIO is consistent with low SLP anomalies and anomalous upper tropospheric circulation (Fig.…”

“…The pattern correlation between the observed and model's predicted precipitation anomaly is shown at the top of (b)-(g). (Hong et al 2011;Webster et al 2011;Lau and Kim 2012;Kosaka et al 2012). The MME shows reasonable skill in predicting the seasonal rainfall anomalies from north Arabian Sea to north Pakistan (Fig.…”

Linkages between the South and East Asian summer monsoons: a review and revisit

“…Because of the competitive mechanisms, it is very difficult to predict the linkage between the SAM and EAM at interannual and interdecadal timescales. The complex mechanisms have important implications for seasonal climate prediction of summer monsoon precipitation that remains very difficult Lee et al 2010;Kosaka et al 2012;Chowdary et al 2014 and many others). Although the CMIP5 models project an intensification of the negative SAM-EAM relationship in the future, the question of whether and to what extent the inter-connection would have changed under natural climate changes as opposed to anthropogenic climate changes remains a significant unsolved scientific issue.…”

Combined Effects of Synoptic-Scale Teleconnection Patterns on Summer Precipitation in Southern China

“…This implies that the combination of EAP and SR patterns may have a more effective contribution to precipitation in Southern China than the single events. The absence of intense precipitation during typical SR-S events suggests that the EAP pattern seems to be an essential factor for extreme precipitation in Southern China, and the SR pattern cannot cause extreme precipitation in Southern China directly [6,13,22]. However, the SR pattern may contribute to the development and preservation of the EAP pattern [21], and the combination of EAP and SR patterns may provide favorable conditions for persistent rainfall in Southern China, inducing PEP.…”

“…Circulation anomalies related to positive (negative) phases of the EAP pattern lead to summer floods (droughts) in Southern China [11,12]. Subsequently, various studies have considered the EAP pattern as an effective predictor of climate anomalies, focusing on its influence on the East Asian summer monsoon climate on inter-annual to inter-decadal timescales [12,13]. On the other hand, the SR pattern contributes to the formation of the Bonin high, the WPSH, and the Mei-Yu front, influencing the precipitation around the Asian jet regions [6,14,15].…”