Impacts of tropical cyclones on the meridional movement of the western Pacific subtropical high

Abstract

Movements of the western Pacific subtropical high (WPSH) are an important factor dominating the synoptic weather and climate over East Asia. In this study, characteristics of the WPSH meridional movement are statistically analysed for the tropical cyclone (TC) peak months (July-September) from 2001 to 2010. The results show that the WPSH meridional movement is consistent overall, namely, its ridge line moves synchronously with its main body centroid, with a correlation coefficient of 0.70 between the ridge line and main body centroid. Moreover, the sensitivity experiment with the Weather Research and Forecasting Model (WRF) for super typhoon Megi (2010) demonstrates that TCs can affect the WPSH meridional movement by stimulating abnormal perturbations that disperse and propagate outwards. Specifically, the WPSH ridge line would shift northwards at an average of 0.64 latitude and a maximum of 1.44 latitude for the period when TC Megi moves to the south of the WPSH. In summary, the meridional movement of the WPSH ridge and centroid are well-correlated and are strongly influenced by TC activity. This study proposes a possible way by which TCs over western North Pacific could affect the weather and climate in East Asia.

The relationship of frequent tropical cyclone activities over the western North Pacific and hot summer days in central-eastern China

“…Therefore, the abnormal meridional circulation can influence the atmospheric circulation in the mid-latitudes (Yamada and Kawamura 2007;Kosaka and Nakamura 2010). In particular, strong convections including the contribution of TCs in the tropical WNP will lead to abnormal descending flows along the latitudes at southern Japan, which will intensify the pressure system there and cause a poleward shift of the WPSH as pointed out by Wang et al (2019). In other words, while TC activities can directly increase positive vorticity and intensify ascending motions in the middle and lower troposphere along their tracks, frequent TC activities can indirectly increase negative vorticity and intensify descending motions in the mid-latitudes from central-eastern China to the Pacific Ocean to the east of Japan.…”

Association between the Biophysical Environment in Coastal South China Sea and Large-Scale Synoptic Circulation Patterns: The Role of the Northwest Pacific Subtropical High and Typhoons

“…Due to the special geographic location and complex surrounding terrain of the SCS, the multiscale ocean dynamic processes of its upper circulation will be affected by various external factors [85][86][87]; one of the most important factors is typhoons. On average, 10.3 typhoons affect the SCS every year, occurring frequently from July to September, including typhoons moving westward from the Northwest Pacific and those generated in the southern part of the SCS [88][89][90].…”

“…Notably, Type 1 mainly appears in June, while Type 2, Type 3 and Type 4 mainly appear in July and August. This is because the NWSPH moves southwest mainly in June, and gradually moves northwards from July to August [66,85]. Secondly, using all sample days under each type minus the sample days without typhoon influence, and then dividing by the sample days without typhoon influence, the effect of typhoons on chl-a in the four LSCPs was obtained (Figure 12).…”

“…Notably, Type 1 mainly appears in June, while Type 2, Type 3 and Type 4 mainly appear in July and August. This is because the NWSPH moves southwest mainly in June, and gradually moves northwards from July to August[66,85].…”

Large-scale synoptic drivers of co-occurring summertime ozone and PM<sub>2.5</sub> pollution in eastern China

“…10 presents the daily variations of NO 2 and OX. As we can see, the daily variations of NO 2 showed two peaks during a day, including a first peak in the morning and a second peak associated with traffic emissions in the evening (Xie et al, 2016;Yu et al, 2020). As we found the lowest point of NO 2 at 15:00 BJT and since NO 2 can be photolyzed to produce O 3 during the day, we assumed that this particular time was the peak time for O 3 formation across the study areas.…”