Coupled tropical cyclone seasonal forecasting system over the Northwest Pacific Ocean in NMEFC

Author(s):  
Yunfei Zhang ◽  
Xiang Li ◽  
Tiejun Ling ◽  
Chenqi Wang ◽  
Hongyu Qu

<p>Tropical cyclone (TC) activity has significant seasonal, interannual and interdecadal variations. Accurate prediction of TC seasonal activities before the onset of the coming TC season (June-November) can provide sufficient time for the government and the public to prepare for tropical cyclone disasters and minimize risks and life losses.<br>Based on COAWST model, we developed a new regional coupled seasonal forecasting system for the Northwest Pacific Ocean including a series of technology improvements. The results of multi-year hindcast experiments show that the coupled seasonal forecasting system can effectively improve the tropical cyclone frequency and intensity forecast compared to the CFSv2 real-time seasonal forecast, especially the tropical cyclone frequency forecast of the TC exceeding the typhoon level, but there is still a certain gap between the results in the forecasting system and the observed TC frequency and intensity, which is mainly reflected in the fact that the forecasting season has a higher frequency of TCs and the peak of strong TCs is relatively weaker. This gap may be caused by the forecasting bias of the sea surface temperature.</p>

2021 ◽  
Vol 13 (4) ◽  
pp. 661
Author(s):  
Mohamed Freeshah ◽  
Xiaohong Zhang ◽  
Erman Şentürk ◽  
Muhammad Arqim Adil ◽  
B. G. Mousa ◽  
...  

The Northwest Pacific Ocean (NWP) is one of the most vulnerable regions that has been hit by typhoons. In September 2018, Mangkhut was the 22nd Tropical Cyclone (TC) over the NWP regions (so, the event was numbered as 1822). In this paper, we investigated the highest amplitude ionospheric variations, along with the atmospheric anomalies, such as the sea-level pressure, Mangkhut’s cloud system, and the meridional and zonal wind during the typhoon. Regional Ionosphere Maps (RIMs) were created through the Hong Kong Continuously Operating Reference Stations (HKCORS) and International GNSS Service (IGS) data around the area of Mangkhut typhoon. RIMs were utilized to analyze the ionospheric Total Electron Content (TEC) response over the maximum wind speed points (maximum spots) under the meticulous observations of the solar-terrestrial environment and geomagnetic storm indices. Ionospheric vertical TEC (VTEC) time sequences over the maximum spots are detected by three methods: interquartile range method (IQR), enhanced average difference (EAD), and range of ten days (RTD) during the super typhoon Mangkhut. The research findings indicated significant ionospheric variations over the maximum spots during this powerful tropical cyclone within a few hours before the extreme wind speed. Moreover, the ionosphere showed a positive response where the maximum VTEC amplitude variations coincided with the cyclone rainbands or typhoon edges rather than the center of the storm. The sea-level pressure tends to decrease around the typhoon periphery, and the highest ionospheric VTEC amplitude was observed when the low-pressure cell covers the largest area. The possible mechanism of the ionospheric response is based on strong convective cells that create the gravity waves over tropical cyclones. Moreover, the critical change state in the meridional wind happened on the same day of maximum ionospheric variations on the 256th day of the year (DOY 256). This comprehensive analysis suggests that the meridional winds and their resulting waves may contribute in one way or another to upper atmosphere-ionosphere coupling.


2015 ◽  
Vol 36 (4) ◽  
pp. 1700-1707 ◽  
Author(s):  
Xiping Yu ◽  
Xiaojing Niu ◽  
Haojie Zhou

2006 ◽  
Vol 7 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Clifton S. Buck ◽  
William M. Landing ◽  
Joseph A. Resing ◽  
Geoffrey T. Lebon

2008 ◽  
Vol 360 (2) ◽  
pp. 63-70 ◽  
Author(s):  
Maki Hayakawa ◽  
Koji Suzuki ◽  
Hiroaki Saito ◽  
Kazutaka Takahashi ◽  
Shin-ichi Ito

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