scholarly journals Recent Changes in Explosively Developing Extratropical Cyclones over the Winter Northwestern Pacific

2012 ◽  
Vol 25 (20) ◽  
pp. 7282-7296 ◽  
Author(s):  
Koki Iwao ◽  
Masaru Inatsu ◽  
Masahide Kimoto
Keyword(s):  
Reanalysis Data ◽  
Japan Meteorological Agency ◽  
Energy Budgets ◽  
Northwestern Pacific ◽  
Extratropical Cyclones ◽  
Pacific Region ◽  
Climate Data ◽  
Explosive Cyclones ◽  
Dynamical Features ◽  
Data Assimilation System

Abstract This study investigated recent changes in the characteristics of explosively developing extratropical cyclones over the northwestern Pacific region in winter from 1979/80 to 2010/11 by using reanalysis data from the Japanese 25-yr Reanalysis/Japan Meteorological Agency Climate Data Assimilation System (JRA-25/JCDAS). The results showed that the frequency of explosive cyclones increased in the northwestern Pacific region east of Japan. This increase was accompanied by a decrease in the number of slowly developing cyclones, indicating an increase in the cyclone growth rate. Moreover, most of the increased explosive cyclones east of Japan originated southwest of Japan. A comparison of the dynamical features and energy budgets of two composite cyclones in the earlier and later halves of the study period suggested that the increase was due to an enhancement of the low-level baroclinicity to the east of Japan and an increase in humidity associated with sea surface temperature warming and enhanced evaporation along the eastern shore of the Asian continent.

The quantification of development processes of explosive cyclones over Northwestern Pacific and Atlantic in boreal winter

2020 ◽  
Author(s):  
Joonsuk Kang ◽  
Seok-Woo Son
Keyword(s):  
Potential Vorticity ◽  
Geopotential Height ◽  
Reanalysis Data ◽  
Northwestern Pacific ◽  
Boreal Winter ◽  
Mean Flow ◽  
Explosive Cyclones ◽  
Development Processes ◽  
Zonal Advection ◽  
Negative Factors

<p>A method utilizing a prognostic potential vorticity (PV) inversion is designed and applied to quantify the processes that contribute to the explosive cyclone (EC) development over Northwestern Pacific and Atlantic in boreal winter. The ECs deepening in the two remarked regions are identified and tracked, by using the automated tracking method on ERA-Interim reanalysis data over the period of 1979–2017. The quantification process first involves time differentiation of linearized potential vorticity (PV), which results in a linear function of geopotential height tendency. It is then equated with the PV tendency equation that consists of mean and transient advection terms to represent dynamical processes that contribute to EC development. The quantification, finally, is performed through the inversion of PV tendency budgets, which yields corresponding geopotential height tendency. The results indicate that EC development is primarily caused by zonal advection of PV anomalies by mean flow (~65%) and diabatic production of PV (~40%), with some negative factors in both regions. The former contributes more for ECs deepening over Northwestern Atlantic (~71%) than Northwestern Pacific (~60%), whereas the latter contributes to a similar extent.</p>

scholarly journals Predictability of Explosive Cyclogenesis over the Northwestern Pacific Region Using Ensemble Reanalysis

2013 ◽  
Vol 141 (11) ◽  
pp. 3769-3785 ◽  
Author(s):  
Akira Kuwano-Yoshida ◽  
Takeshi Enomoto
Keyword(s):  
Heat Release ◽  
Sea Level ◽  
Northwestern Pacific ◽  
Pacific Region ◽  
Latent Heat Release ◽  
Sea Level Pressure ◽  
Cyclone Center ◽  
Explosive Cyclone ◽  
Level Pressure ◽  
Explosive Cyclones

Abstract The predictability of explosive cyclones over the northwestern Pacific region is investigated using an ensemble reanalysis dataset. Explosive cyclones are categorized into two types according to whether the region of the most rapid development is in the Sea of Okhotsk or Sea of Japan (OJ) or in the northwestern Pacific Ocean (PO). Cyclone-relative composite analyses are performed for analysis increments (the differences between the analysis and the 6-h forecast) and ensemble spreads (the standard deviations of ensemble members of the analysis or first guess) at the time of the maximum deepening rate. The increment composite shows that the OJ explosive cyclone center is forecast too far north compared to the analyzed center, whereas the PO explosive cyclone is forecast shallower than the analyzed center. To understand the cause of these biases, a diagnosis of the increment using the Zwack–Okossi (Z-O) development equation is conducted. The results suggest that the increment characteristics of both the OJ and PO explosive cyclones are associated with the most important cyclone development mechanisms. The OJ explosive cyclone forecast error is related to a deeper upper trough, whereas the PO explosive cyclone error is related to weaker latent heat release in the model. A diagnosis of the spread utilizing the Z-O development equation clarifies the mechanism underlying the uncertainty in the modeled sea level pressure. For OJ explosive cyclones, the spread of adiabatic warming causes substantial sea level pressure spreading southwest of the center of the cyclones. For PO explosive cyclones, the latent heat release causes substantial sea level pressure spreading around the cyclone center.

Characteristics of 3–4- and 6–8-Day Period Disturbances Observed over the Tropical Indian Ocean

2010 ◽  
Vol 138 (11) ◽  
pp. 4158-4174 ◽  
Author(s):  
Kazuaki Yasunaga ◽  
Kunio Yoneyama ◽  
Qoosaku Moteki ◽  
Mikiko Fujita ◽  
Yukari N. Takayabu ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Rossby Waves ◽  
Equatorial Indian Ocean ◽  
Tropical Indian Ocean ◽  
Meridional Wind ◽  
Reanalysis Data ◽  
Japan Meteorological Agency ◽  
Climate Data ◽  
Convectively Coupled Waves

Abstract A field observational campaign [i.e., the Mirai Indian Ocean cruise for the Study of the MJO-convection Onset (MISMO)] was conducted over the central equatorial Indian Ocean in October–December 2006. During MISMO, large-scale organized convection associated with a weak Madden–Julian oscillation (MJO) broke out, and some other notable variations were observed. Water vapor and precipitation data show a prominent 3–4-day-period cycle associated with meridional wind υ variations. Filtered υ anomalies at midlevels in reanalysis data [i.e., the Japan Meteorological Agency (JMA) Climate Data Assimilation System (JCDAS)] show westward phase velocities, and the structure is consistent with mixed Rossby–gravity waves. Estimated equivalent depths are a few tens of meters, typical of convectively coupled waves. In the more rainy part of MISMO (16–26 November), the 3–4-day waves were coherent through the lower and midtroposphere, while in the less active early November period midlevel υ fluctuations appear less connected to those at the surface. SST diurnal variations were enhanced in light-wind and clear conditions. These coincided with westerly anomalies in prominent 6–8-day zonal wind variations with a deep nearly barotropic structure through the troposphere. Westward propagation and structure of time-filtered winds suggest n = 1 equatorial Rossby waves, but with estimated equivalent depth greater than is common for convectively coupled waves, although sheared background flow complicates the estimation somewhat. An ensemble reanalysis [i.e., the AGCM for the Earth Simulator (AFES) Local Ensemble Transform Kalman Filter (LETKF) Experimental Reanalysis (ALERA)] shows enhanced spread among the ensemble members in the zonal confluence phase of these deep Rossby waves, suggesting that assimilating them excites rapidly growing differences among ensemble members.

scholarly journals Climatological features of strong winds caused by extratropical cyclones around Japan

2021 ◽  
Author(s):  
Hidetaka Hirata
Keyword(s):  
Seasonal Change ◽  
Japan Sea ◽  
Conveyor Belt ◽  
Reanalysis Data ◽  
Extratropical Cyclones ◽  
The Pacific ◽  
Explosive Cyclones ◽  
The Japan Sea ◽  
Horizontal Pressure ◽  
Strong Winds

AbstractWe examined the climatological features of strong winds associated with extratropical cyclones around Japan during 40 seasons between November-April from 1979/80 to 2018/19 using reanalysis data. Our assessments revealed that the extratropical cyclones caused most of the strong winds around Japan (80-90%). Notably, the contribution of explosively developing extratropical cyclones is larger (70-80%). The strong winds are mainly related to the warm conveyor belt (WCB) and cold conveyor belt (CCB) inside the explosive cyclones. Moreover, the strong winds tend to be distributed widely over the southwestern quadrant of the cyclones. This is due to the intensification of the horizontal pressure gradient between the mature cyclones and the Siberian high extending from the Eurasia continent to Japan. We investigated the regionality of strong winds by highlighting the three areas with high frequencies of strong winds: the area around Hokkaido (i.e., the northernmost island of Japan [area A]), and the areas around the Japan Sea side (area B) and the Pacific Ocean side (area C) of the main island of Japan. The features of the seasonal change in the frequency of the strong winds differ in each area, which reflects the seasonal change in the activities of the explosive cyclones. Moreover, the CCB, the head of the CCB and WCB, and the CCB and WCB bring the strong winds to areas A, B, and C, respectively. The timing of the appearance of these windstorms during the lifecycles of typical cases highlighted in this study is consistent with that observed in Europe.

scholarly journals An Improved Conversion Relationship between Tropical Cyclone Intensity Index and Maximum Wind Speed for the Advanced Dvorak Technique in the Northwestern Pacific Ocean Using SMAP Data

2020 ◽  
Vol 12 (16) ◽  
pp. 2580
Author(s):  
Sumin Ryu ◽  
Sung-Eun Hong ◽  
Jun-Dong Park ◽  
Sungwook Hong
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Surface Wind ◽  
Maximum Wind Speed ◽  
Japan Meteorological Agency ◽  
Northwestern Pacific ◽  
Pacific Region ◽  
Intensity Data ◽  
Maximum Wind ◽  
Intensity Index

The Advanced Dvorak Technique (ADT) uses geostationary satellite data to estimate tropical cyclone (TC) intensity owing to the difficulty in directly observing a TC’s internal structure. This study presents a new relationship (Hong and Ryu scale) between the current intensity (CI) number and estimated maximum wind speed (MWS) of TCs over the northwestern Pacific region; the CI number is the TC intensity index retrieved from the ADT. The Soil Moisture Active Passive (SMAP) with the L-band (1.4 GHz) microwave radiometer, is used to calibrate and produce the new Hong and Ryu scale for the ADT algorithm. Japan Meteorological Agency (JMA) best track MWS data, SMAP sea surface wind speed estimates, and ADT’s TC intensity data between 2015–2018 are spatiotemporally collocated for the calibration process. The CI number is derived from the Korea Meteorological Administration (KMA) operational ADT which uses the Koba scale to convert to the MWS for validation against the MWS of the best track. The conversion relationships between CI number and SMAP MWS, and between SMAP MWS and MWS of the best track a derived, and the MWS of two ADTs with the Koba and Hong and Ryu scales are then estimated using the same CI numbers with TC intensity data between 2015–2018. Finally, the MWS of the ADT with the Koba scale and the new ADT with the proposed Hong and Ryu scale are independently validated on best track data from 2013–2014. The MWS root mean square error (RMSE) is 4.39 m/s for the new ADT using the Hong and Ryu scale, which is lower than 4.77 m/s RMSE of the ADT using the Koba scale. Hence, the ADT using the Hong and Ryu scale can modestly improve the accuracy of TC intensity analysis in the northwestern Pacific region.

scholarly journals The concurrence of Atmospheric Rivers and explosive cyclogenesis in the North Atlantic and North Pacific basins

2017 ◽  
Author(s):  
Jorge Eiras-Barca ◽  
Alexandre M. Ramos ◽  
Joaquim G. Pinto ◽  
Ricardo M. Trigo ◽  
Margarida L. R. Liberato ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Reanalysis Data ◽  
Water Vapour Flux ◽  
Atmospheric Rivers ◽  
The North ◽  
Explosive Cyclones ◽  
The North Atlantic ◽  
Characteristic Features ◽  
Western Side

Abstract. The explosive cyclogenesis of extra-tropical cyclones and the occurrence of atmospheric rivers are characteristic features of baroclinic atmospheres, and are both closely related to extreme hydrometeorological events in the mid-latitudes, particularly on coastal areas on the western side of the continents. The potential role of atmospheric rivers in the explosive cyclone deepening has been previously analysed for selected case studies, but a general assessment from the climatological perspective is still missing. Using ERA-Interim reanalysis data for 1979–2011, we analyse the concurrence of atmospheric rivers and explosive cyclogenesis over the North Atlantic and North Pacific Basins for the extended winter months (ONDJFM). Atmospheric rivers are identified for almost 80 % of explosive deepening cyclones. For non-explosive cyclones, atmospheric rivers are found only in roughly 40 % of the cases. The analysis of the time evolution of the high values of water vapour flux associated with the atmospheric river during the cyclone development phase leads us to hypothesize that the identified relationship is the fingerprint of a mechanism that raises the odds of an explosive cyclogenesis occurrence and not merely a statistical relationship. This insight can be helpful for the predictability of high impact weather associated with explosive cyclones and atmospheric rivers.

Phylogeny and phylogeography of the land hermit crabCoenobita purpureus(Decapoda: Anomura: Coenobitidae) in the Northwestern Pacific Region

2017 ◽  
Vol 38 (1) ◽  
pp. e12369 ◽  
Author(s):  
Katsuyuki Hamasaki ◽  
Chikako Iizuka ◽  
Tetsuya Sanda ◽  
Hideyuki Imai ◽  
Shuichi Kitada
Keyword(s):  
Northwestern Pacific ◽  
Pacific Region

scholarly journals Monthly daily-mean rainfall forecast over Indonesia using machine learning and artificial intelligence ensemble

2021 ◽  
Vol 893 (1) ◽  
pp. 012030
Author(s):  
H Harsa ◽  
M N Habibie ◽  
A S Praja ◽  
S P Rahayu ◽  
T D Hutapea ◽  
...  
Keyword(s):  
Artificial Intelligence ◽  
Machine Learning ◽  
Southern Oscillation ◽  
Longwave Radiation ◽  
Reanalysis Data ◽  
Physical Models ◽  
Climate Data ◽  
Input Dataset ◽  
Forecast Models ◽  
Spatial Grid

Abstract A daily mean rainfall in a month forecast method is presented in this paper. The method provides spatial forecast over Indonesia and employs ensemble of Machine Learning and Artificial Intelligence algorithms as its forecast models. Each spatial grid in the forecast output is processed as an individual dataset. Therefore, each location in the forecast output has different stacked ensemble models as well as their model parameter settings. Furthermore, the best ensemble model is chosen for each spatial grid. The input dataset of the model consists of eight climate data (i.e., East and West Dipole Mode Index, Outgoing Longwave Radiation, Southern Oscillation Index, and Nino 1.2, 3, 4, 3.4) and monthly rainfall reanalysis data, ranging from January 1982 until December 2019. There are four assessment procedures performed on the models: daily mean rainfall establishment as a response function of climate patterns, and one-up to three-month lead forecast. The results show that, based on their performance, these non-Physical models are considerable to complement the existing forecast models.

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