资源环境科技发展态势分析平台

The convectively coupled equatorial Rossby waves (ERWs) how to quantitatively modulate the western North Pacific (WNP) tropical cyclones (TCs) are investigated systematically from observations in this study. Our results show that ERWs can exert a distinct modulation on the WNP TC genesis by altering large-scale conditions and thus significantly impact on the TC tracks and basin-wide TC intensity. During the convectively active ERW phase, more TCs and larger daily genesis rate (DGR) can be observed, while fewer TCs and lower DGR are found during the convectively inactive ERW phase. Such changes are mainly attributed to changes of large-scale parameters modulated by ERWs over the WNP. Budget terms of the total anomalous observed genesis potential index (GPI) indicate that the mid-level relative humidity and low-level vorticity are the two largest contributors to ERWs-composited GPI anomalies. Similar results are further obtained by analyses of the pattern correlations between the total anomalous GPI associated with ERWs and the anomalous GPI with varying environmental factors. Moreover, more TCs with north-westward tracks and more intense TCs over the WNP can be generally found during the convectively active phases of ERWs in contrast to that during the convectively inactive phases. This study enhances our understanding of intra-seasonal variability of WNP TC activity and has a substantial implication for its sub-seasonal prediction.