A Role of Zonal Gradient of SST between the Indian Ocean and the Western Pacific in Localized Convection around the Philippines

Abstract

Interannual fluctuations of the convective activity around the Philippines are highly correlated with the east-west gradient of SST between the North Indian Ocean (NIO) and the western North Pacific (WNP). We conducted a set of experiments by use of an atmospheric general circulation model (AGCM) to assess the relative importance of the remote (NIO) versus in situ (WNP) SST anomalies in determining the WNP monsoon rainfall as ocean-to-atmosphere feedback. The solutions indicate that both in situ and remote SST anomalies regulate precipitation around the Philippines in the early summer. This result implies that the WNP monsoon rainfall is sensitive to the spatial distribution of the NIO SST anomalies as well as the in situ anomalies. These physical interpretations suggest further increase of the predictability in the WNP monsoon.

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

“…The model experiment supports our hypotheses that circulation and rainfall anomalies over the southern Peninsular India and TIO in the summer 2010 are associated with the TIO warming during the decay phase of El Niño. Our regional model results are consistent with the previous atmospheric general circulation models (Ohba and Ueda 2006;Shen et al 1998) and linear baroclinic model experiments ) studies, suggesting that the importance of the TIO SST in summer rainfall over the Asian monsoon region.…”

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

“…Ueda et al (2009) evaluated the contribution rate of the seasonal SST warming for the commencement of ASM and determined that it amounted to about 20% of the total factors, demonstrating the importance of large-scale thermal contrast. The result obtained from the present study, together with that from the other simulation (Lindzen and Nigam 1987;Ohba and Ueda 2006), suggests that the convection over the ocean, which is particularly involved in the monsoon system, could be affected by the large-scale SST distributions rather than by the in situ SST. Wang et al (2005) showed that, once the summer monsoon begins, the subsequent SST drops sharply due to heat loss from the ocean surface (evaporative cooling/turbulent mixing of underlying water) as well as the cloud shielding effect of solar radiation.…”

“…As indicated in Lindzen and Nigam (1987) using the simple one-layer model of the cumulus boundary layer, the surface pressure gradients caused by the SST gradients contribute to the low-level convergence in the tropics. Ohba and Ueda (2006) provided evidence that the value of the SST gradient of about 0.5°C/3,000 km is sufficient for the acceleration of low-level convergence through the enhancement of the low-level pressure gradient. Ueda et al (2009) evaluated the contribution rate of the seasonal SST warming for the commencement of ASM and determined that it amounted to about 20% of the total factors, demonstrating the importance of large-scale thermal contrast.…”

Characteristics of the CMIP3 Models Simulating Realistic Response of Tropical Western Pacific Precipitation to Ninno3 SST Variability

“…The JJA2 northwestern Pacific SST anomaly correlated with the previous DJF Niñ o3-SST is pointed out as a possible direct forcing for the JJA2 TWP precipitation anomaly by Ueda et al (1995). Ohba and Ueda (2006) showed based on AGCM experiments that the precipitation and SST over the Arabian Sea can be the cause for the JJA2 TWP precipitation anomaly. They also showed in a figure of their experiments that the northwestern Pacific SST anomaly can create the precipitation anomaly east of the Philippines.…”