Relationship between the Maximum Wind Speed and the Minimum Sea Level Pressure for Tropical Cyclones in the Western North Pacific

Abstract. The influence of environmental conditions on the intensity changes of tropical cyclones (TCs) over the western North Pacific (WNP) is investigated through examination of 37 TCs during 2000–2011 that interacted directly with the western North Pacific subtropical high (WNPSH). Comprehensive composite analysis of the environmental conditions is performed for two stages of storms: one is categorized as intensifying events (maximum wind speed increases by 15 kts over 48 h) and the other is categorized as weakening events (maximum wind speed decreases by 15 kts over 48 h). Comparison of the composite analysis of these two cases show that environmental conditions associated with the WNPSH play important roles in the intensity changes of TCs over the WNP. When a TC moves along the southern edge of the WNPSH, the relatively weaker easterly environmental vertical wind shear helps bring warm moist air from the south and southeast, which is favorable for the TC to intensify. On the other hand, when a TC moves along the western edge of the WNPSH, under the combined influences of the WNPSH and an upper-level westerly trough, a strong westerly vertical shear promotes the intrusion of dry environmental air associated with the WNPSH from the north and northwest, which may lead to the inhibition of moisture supply and convection over the west half of the TC and thus its weakening. The average sea surface temperature (SST) of 27.8 °C for the weakening events is also lower than an average of 28.9 °C for the strengthening events, but remains above the critical value of 27 °C for TC intensification, suggesting that the SST may be regarded as a less positive factor for the weakening events.

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Tropical cyclone simulations over Bangladesh at convection permitting 4.4 km & 1.5 km resolution

Scientific Data ◽

10.1038/s41597-021-00847-5 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Hamish Steptoe ◽

Nicholas Henry Savage ◽

Saeed Sadri ◽

Kate Salmon ◽

Zubair Maalick ◽

...

Keyword(s):

Wind Speed ◽

Tropical Cyclone ◽

Sea Level ◽

Tropical Cyclones ◽

Weather Forecasting ◽

Sea Level Pressure ◽

Mean Sea Level ◽

Level Pressure ◽

Medium Range ◽

Gust Speed

AbstractHigh resolution simulations at 4.4 km and 1.5 km resolution have been performed for 12 historical tropical cyclones impacting Bangladesh. We use the European Centre for Medium-Range Weather Forecasting 5th generation Re-Analysis (ERA5) to provide a 9-member ensemble of initial and boundary conditions for the regional configuration of the Met Office Unified Model. The simulations are compared to the original ERA5 data and the International Best Track Archive for Climate Stewardship (IBTrACS) tropical cyclone database for wind speed, gust speed and mean sea-level pressure. The 4.4 km simulations show a typical increase in peak gust speed of 41 to 118 knots relative to ERA5, and a deepening of minimum mean sea-level pressure of up to −27 hPa, relative to ERA5 and IBTrACS data. The downscaled simulations compare more favourably with IBTrACS data than the ERA5 data suggesting tropical cyclone hazards in the ERA5 deterministic output may be underestimated. The dataset is freely available from 10.5281/zenodo.3600201.

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Dropsonde Observations of Intense Typhoons in 2017 and 2018 in the T-PARCII Project

10.5194/egusphere-egu2020-12614 ◽

2020 ◽

Author(s):

Kazuhisa Tsuboki ◽

Hiroyuki Yamada ◽

Tadayasu Ohigashi ◽

Taro Shinoda ◽

Kosuke Ito ◽

...

Keyword(s):

Wind Speed ◽

Tropical Cyclone ◽

North Pacific ◽

Western North Pacific ◽

Maximum Wind Speed ◽

Central Pressure ◽

The South ◽

Main Island ◽

Maximum Wind ◽

Typhoon Intensity

Typhoon is a tropical cyclone in the western North Pacific and the South China Sea. It is the most devastating weather system in East Asia. Strong winds and heavy rainfalls associated with a typhoon often cause severe disasters in these regions. There are many cases of typhoon disasters even in the recent decades in these regions. Furthermore, future projections of typhoon activity in the western North Pacific show that its maximum intensity will increase with the climate change. However, the historical data of typhoon (best track data) include large uncertainty after the US aircraft reconnaissance of typhoon was terminated in 1987. Another problem is that prediction of typhoon intensity has not been improved for the last few decades. To improve these problems, in situ observations of typhoon using an aircraft are indispensable. The T-PARCII (Tropical cyclone-Pacific Asian Research Campaign for Improvement of Intensity estimations/forecasts) project is aiming to improve estimations and forecasts of typhoon intensity as well as storm track forecasts.In 2017, the T-PARCII team performed dropsonde observations of intense Typhoon Lan in collaboration with Taiwan DOTSTAR, which was the most intense typhoon in 2017 and caused huge disaster over the central Japan. It was categorized as a supertyphoon by JTWC and as a very intense and huge typhoon by JMA. Typhoon Lan moved northeastward to the east of the Okinawa main island and it was located around 23 N on 21 and 28 N on 22 October. In these two days, we made dropsonde observations at the center of the eye and in the surrounding area of the eyewall. The observations showed that the central pressure of Lan slightly increases from 926 hPa on 21 to 928 hPa on 22 October with the northward movement. On the other hand, The JMA best track data indicate that the central pressure decreases from 935 hPa on 21 to 915 hPa on 22 October. The observations also showed a significant double warm core structure in the eye and the maximum wind speed along the eyewall. The dropsonde data were used for forecast experiments. The result shows an improvement of typhoon track prediction.The T-PARCII team also made aircraft observations of Typhoon Trami during the period from 25 to 28 September 2018 in collaboration with the SATREPS ULAT group and DOTSTAR. Trami was almost stationary during the period to the south of the Okinawa main island. Then, it moved northward and finally made a landfall over the central part of Japan. This also caused a big disaster and electricity was shut down for several days in the central part of Japan. Typhoon Trami showed a drastic change of intensity from 25 to 26 September with a large change of eye size from about a diameter of 60 km to 200 km. Dropsonde observations showed the change of central pressure and maximum wind speed as well as the thermodynamic structure of the eye.

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Environmental influences on the intensity changes of tropical cyclones over the western North Pacific

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-6329-2014 ◽

2014 ◽

Vol 14 (12) ◽

pp. 6329-6342 ◽

Cited By ~ 14

Author(s):

Shoujuan Shu ◽

Fuqing Zhang ◽

Jie Ming ◽

Yuan Wang

Keyword(s):

Wind Speed ◽

Tropical Cyclones ◽

Environmental Conditions ◽

North Pacific ◽

Wind Shear ◽

Western North Pacific ◽

Vertical Wind Shear ◽

Composite Analysis ◽

Maximum Wind ◽

Intensity Changes

Abstract. The influence of environmental conditions on the intensity changes of tropical cyclones (TCs) over the western North Pacific (WNP) is investigated through examination of 37 TCs during 2000–2011 that interacted directly with the western North Pacific subtropical high (WNPSH). Comprehensive composite analysis of the environmental conditions is performed for two stages of storms: one is categorized as intensifying events (maximum wind speed increases by 15 kn over 48 h) and the other is categorized as weakening events (maximum wind speed decreases by 15 kn over 48 h). Comparison of the composite analysis of these two cases show that environmental conditions associated with the WNPSH play important roles in the intensity changes of TCs over the WNP. When a TC moves along the southern periphery of the WNPSH, the relatively weaker easterly environmental vertical wind shear helps bring warm moist air from the south and southeast to its southeast quadrant within 500 km, which is favorable for the TC to intensify. However, when a TC moves along the western edge of the WNPSH, under the combined influences of the WNPSH and an upper-level westerly trough, a strong westerly vertical shear promotes the intrusion of dry environmental air associated with the WNPSH from the north and northwest, which may lead to the inhibition of moisture supply and convection over the western half of the TC and thus its weakening. These composite results are consistent with those with additional geographic restrictions, suggesting that the dry air intrusion and the vertical wind shear (VWS) associated with the WNPSH, indeed affect the intensity changes of TCs over the WNP beyond the difference related solely to variations in geographical locations. The average sea surface temperature (SST) of 27.6 °C for the weakening events is also lower than an average of 28.9 °C for the strengthening events, but remains above the critical value of 27 °C for TC intensification, suggesting that the SST may be regarded as a less positive factor for the weakening events.

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Complex network approach for detecting tropical cyclones

Climate Dynamics ◽

10.1007/s00382-021-05871-0 ◽

2021 ◽

Author(s):

Shraddha Gupta ◽

Niklas Boers ◽

Florian Pappenberger ◽

Jürgen Kurths

Keyword(s):

Sea Level ◽

Tropical Cyclones ◽

Complex Network ◽

Time Scales ◽

Southern Oscillation ◽

Volcanic Eruptions ◽

Network Approach ◽

Sea Level Pressure ◽

Level Pressure ◽

Climate Networks

AbstractTropical cyclones (TCs) are one of the most destructive natural hazards that pose a serious threat to society, particularly to those in the coastal regions. In this work, we study the temporal evolution of the regional weather conditions in relation to the occurrence of TCs using climate networks. Climate networks encode the interactions among climate variables at different locations on the Earth’s surface, and in particular, time-evolving climate networks have been successfully applied to study different climate phenomena at comparably long time scales, such as the El Niño Southern Oscillation, different monsoon systems, or the climatic impacts of volcanic eruptions. Here, we develop and apply a complex network approach suitable for the investigation of the relatively short-lived TCs. We show that our proposed methodology has the potential to identify TCs and their tracks from mean sea level pressure (MSLP) data. We use the ERA5 reanalysis MSLP data to construct successive networks of overlapping, short-length time windows for the regions under consideration, where we focus on the north Indian Ocean and the tropical north Atlantic Ocean. We compare the spatial features of various topological properties of the network, and the spatial scales involved, in the absence and presence of a cyclone. We find that network measures such as degree and clustering exhibit significant signatures of TCs and have striking similarities with their tracks. The study of the network topology over time scales relevant to TCs allows us to obtain crucial insights into the effects of TCs on the spatial connectivity structure of sea-level pressure fields.

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Analysis of Atmospheric and Ionospheric Variations Due to Impacts of Super Typhoon Mangkhut (1822) in the Northwest Pacific Ocean

Remote Sensing ◽

10.3390/rs13040661 ◽

2021 ◽

Vol 13 (4) ◽

pp. 661

Author(s):

Mohamed Freeshah ◽

Xiaohong Zhang ◽

Erman Şentürk ◽

Muhammad Arqim Adil ◽

B. G. Mousa ◽

...

Keyword(s):

Wind Speed ◽

Pacific Ocean ◽

Tropical Cyclone ◽

Sea Level ◽

Northwest Pacific ◽

Northwest Pacific Ocean ◽

Sea Level Pressure ◽

Level Pressure ◽

Super Typhoon ◽

The Northwest Pacific Ocean

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.

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