Northwest Pacific Region Research Articles

Tempo-Spatial Distributions and Transport Characteristics of Two Dust Events over Northern China in March 2021

The Taklamakan Desert and the Gobi Desert in East Asia constitute the second-largest sources of dust in the world. In particular, dust originating from the Gobi Desert is more susceptible to long-range transport, with consequent impacts in downwind Asian countries and the Northwest Pacific region. Two intensive dust events (the 3·15 dust event and the 3·28 dust event) were experienced in North China in March 2021. The 3·15 dust process was rated as the most intensive dust process in China in the past 10 years. In this study, by using a combination of spaceborne remote sensing datasets from geostationary and polar-orbiting satellites, ground-based columnar observations of aerosol optical parameters, meteorological reanalysis data, and backward trajectory simulations of air masses, the transport pathways and the three-dimensional structure characteristics of dust aerosols during the transport of the two dust events in March 2021 were cross-validated. The results of the study indicated that the two dust events were induced by the Mongolian cyclone. Due to the different configurations of the ground meteorological system conditions, a backflow process occurred during the 3·15 dust event transmission process. After passing over North China and the Bohai Sea, the direction of transport of the dust plume was reversed. The wind deflected from northwest to northeast, and the dust reached the eastern coastal areas of China and was finally deposited on land. The 3·28 dust event exhibited aerosol stratification in the transport path, the higher pure dust layer reached up to 9 km height, and the lower layer underwent aerosol mixing and became a polluted dust aerosol. This study implies that the investigation of dust aerosol transport and the deposition processes, the impact on the ocean, and the impact of marine aerosols on land also needs to be taken into consideration; the integration of advanced satellites and ground-based remote sensing data, the meteorological reanalysis data and the backward trajectories simulation, which complemented and verified each other, can enhance the ability to delineate the transport pathways and the three-dimensional structural characteristics of dust events.

Typhoon Track Prediction Based on Deep Learning

China is located in the northwest Pacific region where typhoons occur frequently, and every year typhoons make landfall and cause large or small economic losses or even casualties. Therefore, how to predict typhoon paths more accurately has undoubtedly become an important research topic nowadays. Therefore, this paper predicts the path of typhoons formed in the South China Sea based on deep learning. This paper combines the CNN network and the LSTM network to build a C-LSTM typhoon path prediction model, using the typhoon paths and related meteorological variables formed in the South China Sea from 1949 to 2021 as the data set, and using the Granger causality test to select multiple features for the data set to achieve data dimensionality reduction. Finally, by comparing the experiments with the LSTM typhoon path prediction model, it is proved that the prediction results of the model have smaller errors.

Discovery of the Heteromorph Ammonoid Amapondella amapondense in the Middle Campanian of Hokkaido, Japan

The discovery of the heteromorph ammonoid Amapondella amapondense (van Hoepen) in the lower middle Campanian in the Urakawa, Biratori and Hidaka areas of Hokkaido, northern Japan, represents the first report of this taxon in the Northwest Pacific region. Because the species flourished in other regions during Santonian to early Campanian time, its final geographic occurrence in Hokkaido suggests that global environmental changes likely had a significant influence on ammonoid biogeography during early middle Campanian time.

Correlating atmospheric pressure and temperature with Meniere attack

ObjectiveThis paper correlated the Meniere attack with meteorological parameters i.e. atmospheric pressure, temperature, relative humidity and rainfall, to investigate which parameters that trigger the Meniere attack. MethodsDuring the past three years, totally 283 (2015), 351 (2016) and 319 (2017) patients with Meniere's disease (MD) were encountered at a clinic of the university hospital, accounting for 13%, 17% and 16% incidence in relation to overall annual neurotological cases, respectively. The onset of Meniere attack was then correlated with meteorological parameters. ResultsThe mean seasonal incidence of Meniere attack in relation to overall seasonal neurotological cases in 2015-2017 were 14.8 ± 2.8% (spring), 17.5 ± 2.2% (summer), 16.0 ± 1.8 % (autumn) and 12.8 ± 2.0% (winter), indicating that summer season had a higher incidence of Meniere attacks than winter season. Onset of Meniere attacks correlated significantly with the atmospheric pressure (r = -0.4484, p = 0.0061) and temperature (r = 0.4736, p = 0.0035), and the atmospheric pressure was highly negatively correlated with the temperature (r = -0.9421, p < 0.0001). In contrast, no correlation was identified between the onset of Meniere attacks and relative humidity or rainfall. The atmospheric pressure in the same month with typhoon compared with that without typhoon revealed a median reduction of 13.1 hectopascal. ConclusionAtmospheric pressure and temperature are correlated with the onset of Meniere attack. Summer season has a higher incidence of Meniere attack than winter season, likely because low atmospheric pressure in summer may aggravate endolymphatic hydrops, especially when accompanied by typhoons in the northwest Pacific region.

Review of Ophioplinthaca Verrill, 1899 (Echinodermata, Ophiuroidea, Ophiacanthidae), description of new species in Ophioplinthaca and Ophiophthalmus, and new records from the Northwest Pacific and the South China Sea.

The ophiuroid genus Ophioplinthaca is well characterized by the deep incisions in the disc. Prior to this study, it contained 32 accepted species, but species limits and geographic distributions were not well understood. The manned submersible vehicle 'Shenhaiyongshi' was used to collect ophiuroid specimens from the deep-sea seamounts and cold seeps in the South China Sea and Northwest Pacific at 602-3600 m depth, during 2018 to 2020. The genus Ophioplinthaca was reviewed using both morphological data and a phylogenetic analysis, based on COI sequences. The taxonomic status of the genus Ophiophthalmus Matsumoto, 1917, a junior homonym of Ophiophthalmus Fitzinger, 1843 (a reptile) was clarified by proving prevailing usage of the ophiuroid name. A total of eight species were identified, including two new species, described asOphioplinthacabrachispina sp. nov. and Ophiophthalmusserratus sp. nov., and two new records. The new species are characterized by unique features of the arm skeletons. Tabular keys to all Ophioplinthaca and Ophiophthalmus species are provided. Interspecific and intraspecific genetic distance of Ophioplinthaca species ranged from 2.32% to 19.72%, and from 0.26% to 0.90%, respectively. The data suggest that species of the genus Ophioplinthaca are more widely spread around the Northwest Pacific region deep-sea seamounts than previously known.

Research on marine plastic garbage governance in Northwest Pacific Region from the perspective of cooperative game

With the frequent coastal activities of human beings, tens of thousands of tons of floating marine plastics pose a serious threat to marine ecosystems and human survival. This paper studies the feasibility of regional marine plastic garbage management, taking the Northwest Pacific as the research object. According to the Cobb-Douglas utility function of the costs and benefits of plastic processing in China, Japan and South Korea, the Shapley value method was used to analyze it. The study found that the data were substituted into the Shapley value model of cooperative game for calculation, and the results showed that any country joining the triple alliance U would create greater benefits, and obtain higher benefits than the sub alliance. It is a triple win situation for China, Japan and the South Korea to jointly manage marine plastic in the Northwest Pacific. The results of the model confirm that the three countries are willing to maintain long-term cooperation on marine plastic governance, this method can be used to solve the trans-national marine governance innovatively and promote regional ocean cooperation governance. At the same time, by comparing the Northwest Pacific Plan with other action plans, China, Japan and South Korea should abandon political controversy, seeking common ground while putting aside differences, to cooperate fully to curb the growing trend of plastic waste problem in the Northwest Pacific, and contribute to the sustainable development of regional marine.

Order Euryalida (Echinodermata, Ophiuroidea), new species and new records from the South China Sea and the Northwest Pacific seamounts.

Ophiuroids were collected by the manned submersible ‘Shenhaiyongshi’ from the deep-sea seamounts in the South China Sea and Northwest Pacific regions at 602–1920 m depth, during 2018 to 2020. A total of nine species was identified, including two new species and seven new records from the South China Sea and one new record from the Northwest Pacific region. Two new species are described as Asteroschemashenhaiyongshiisp. nov. and Asteroschemadomogranulatumsp. nov. The seven new records included five species from the genus Asteroschema, and one species each from the genera Asterostegus and Astrodendrum. Comprehensive descriptions of morphological features are provided, including characteristics of the arm skeleton, as well as a phylogenetic analysis based on 16S and COI sequences. Intraspecific genetic distance ranges of Euryalida species from the present study were 0.34% to 1.38%, which was relatively low compared to other orders in the class Ophiuroidea. The present study suggests a high probability that species of the order Euryalida are more widely spread around the Indo-Pacific region than previously expected.

Strengthened influence of the East Asian trough on spring extreme precipitation variability over eastern Southwest China after the late 1980s

The relationship between variations in the East Asian trough (EAT) intensity and spring extreme precipitation over Southwest China (SWC) during 1961–2020 is investigated. The results indicate that there is an interdecadal increase in the relationship between the EAT and spring extreme precipitation over eastern SWC around the late 1980s. During the latter period, the weak (strong) EAT corresponds to a strong and large-scale anomalous anticyclone (cyclone) over the East Asia–Northwest Pacific region. The EAT-related anomalous southerlies (northerlies) dominate eastern SWC, leading to significant upward (downward) motion and moisture convergence (divergence) over the region, providing favorable (unfavorable) dynamic and moisture conditions for extreme precipitation over eastern SWC. In contrast, during the former period, the EAT-related circulation anomalies are weak and cover a relatively smaller region, which cannot significantly affect the moisture and dynamic conditions over eastern SWC; therefore, the response in extreme precipitation over eastern SWC to EAT is weak over the period. The interdecadal change in the relationship between eastern SWC spring extreme precipitation and the EAT could be related to the interdecadal change in the EAT variability. The large (small) variability of the EAT is associated with significant (insignificant) changes in spring extreme precipitation over eastern SWC during the latter (former) period.摘要本文研究表明东亚大槽强度与中国西南地区东部春季极端降水的关系在20世纪80年代末后显著增强, 这可能与东亚大槽自身变率的年代际变化有关. 在80年代末之后, 东亚大槽的变率显著增强, 其对应的大气环流异常也偏强, 范围偏大, 可以显著影响西南地区东部的水汽和动力条件, 从而引起该地区春季极端降水的显著变化. 而在80年代末之前, 东亚大槽的变率偏弱, 其对应的大气环流异常也偏弱, 范围偏小, 因此不能对西南地区东部春季极端降水的变化产生显著影响.

Molecular and microscopic identification of Eomarteilia granula infection in Manila clam Ruditapes philippinarum off the south coast of Korea.

A report on the new species Eomarteilia (=Marteilia) granula infecting Manila clam Ruditapes philippinarum from Japan in 2014 suggests the possibility of E. granula infecting other Manila clam populations in the Northwest Pacific region, including Korea. In this study, we report the first infections by E. granula in Manila clams off the south coast of Korea. Histology revealed Marteilia-like plasmodia in the digestive tubule epithelia. Tissue imprints demonstrated that each parasite sporangium enclosed 4 spores and transmission electron microscopy (TEM) revealed ultrastructure of primary cells enclosing secondary cells, which contained spores. Mature spores consisted of 3 sporoplasms: outermost, intermediate, and innermost. The outermost sporoplasm showed a peripheral electron-dense monolayer characteristic of E. granula. The 18S rDNA amplified from the Marteilia-like parasite yielded 1784-bp PCR amplicon sequences which were 99.8% similar to that of E. granula previously reported (as M. granula) from Japan. In the molecular phylogenetic analysis, the novel Marteilia-like organism formed a well-supported clade with E. granula. Accordingly, we concluded that the novel Marteilia-like parasite that we found infecting some Korean Manila clams is Eomarteilia granula. Field surveys revealed that the infection was limited to clams of the south coast of Korea, with the prevalence ranging from 3.3 to 5.0%.

Geographical variations in genetic group composition, life-history traits, and statolith shape for

Context Sepioteuthis cf. lessoniana is widely distributed in the coastal waters of the Indo-Pacific region and is a crucial fisheries resource along its distributional range. At least four lineages of Sepioteuthis have been identified in the western Pacific region; however, their biological information remains unclear. Aims In this study, the genetic groups of Sepioteuthis spp. in the southwestern Japan and northern Taiwan was examined using molecular markers, and the life-history traits and statolith morphology of the genetic groups were investigated. Methods A total of 137 and 205 squid individuals from Japan and Taiwan, respectively, were examined. Key results Three genetic groups of Sepioteuthis (S. sp. 1, sp. 2, and sp. 2A) were identified based on molecular evidence in both areas, among which Sepioteuthis sp. 2 was dominant in Japan (87%), whereas Sepioteuthis sp. 1 was dominant in Taiwan (70%). For the same genetic group, the mantle length, average growth rate, and size and age at maturity were greater for the squid in Japan than those in Taiwan. The statolith exhibited a wider lateral dome and longer rostrum for the squid in Taiwan than those in Japan. Conclusions This study indicated the variations in the life-history traits and statolith shapes of the squid were greater between geographic populations (Japan and Taiwan) than among the genetic groups, which suggested that environmental effects on life-history traits and statolith shape of squid were greater than genetic effects. Implications The results of this study provide insights into the population structure of Sepioteuthis spp. in the Northwest Pacific region, which is relevant for the sustainable management of the squid fisheries.

Influence of major typhoons on ocean, atmosphere and air quality of Northwest Pacific during August 2020

Tropical storms (TSs)/Typhoons (TYs) in the Northwest Pacific (NWP) region are one of the most devastating natural hazards, which cause large-scale impacts on human life and infrastructure. In August 2020, a total of 9 tropical storms were identified by International Best Track Archive for Climate Stewardship (IBTrACS) in the NWP region. These TSs/TYs made their landfall over the coastal parts of China, North Korea, and South Korea, while none of them made their landfall over Taiwan. These conditions were unique in recent years and induced drought conditions in Taiwan during 2020. We have carried out a three-dimensional analysis of oceanic, atmospheric, and meteorological parameters for the evaluation of changes associated with typhoons during August 2020. The model, satellite, and ground observations data have been used for the assessment of the impact of these TS/TYs on the ocean, atmosphere, and air quality. The rise in ocean temperature (1 °C–2 °C) was observed even at the depth of 100 m. Strong upwelling of the ocean water in the NWP originated a change in the mixed layer depth and also has affected the salinity in South China, East China, and the Philippines Sea. The strong convective forces during the storm conditions produced a prominent rise in CO and Ozone concentration. These typhoons also affected the air quality of Taiwan during August 2020. The transboundary air pollutants triggered the enhancement in particulate matter (PM1.0 and PM2.5) and surface ozone over Taiwan, which resulted in major health hazards to a large population.

Northeast China Cold Vortex Observed by FY‐3 MWTS‐2 and MetOp AMSU‐A

AbstractThe northeast China cold vortex (NCCV) refers to a closed low‐pressure system over northeast China extending from China‐Siberia to the northwest Pacific coast region. It is cut off from the westerly jet belt in the middle and upper troposphere, has a cold core, lasts several days, and could bring heavy rain events in late spring and summer that are of great challenge to weather forecasters. This study investigates the possibility of observing temperature structures of NCCVs by two microwave temperature sounders, that is, the Microwave Temperature Sounder‐2 (MWTS‐2) and the Advanced Microwave Sounding Unit‐A (AMSU‐A) onboard the two polar‐orbiting operational environmental satellites (POES) Fenyun‐3 satellite FY‐3D and Meteorological Operational satellite MetOp‐B, respectively. The MWTS‐2 and AMSU‐A together provide 3D atmospheric temperatures in the middle and upper troposphere, as well as the lower stratosphere four times daily. Both limb‐corrected direct observations of brightness temperature and retrievals of atmospheric temperature within NCCVs are characterized by cold and warm cores below and above the tropopause, respectively, comparing favorably with the European Centre for Medium‐Range Weather Forecasts ERA5 reanalysis. Compared with the ERA5 reanalysis in June 2019, the MWTS‐2 retrieved atmospheric temperatures have no scan‐dependent biases, the biases are smaller than ±0.2K, and root‐mean‐square errors (RMSEs) are smaller than and 2.0K at all altitudes. This study suggests the possibility of using multiple POES microwave‐temperature‐sounding observations for near‐real‐time monitoring of NCCVs' 3D temperature structures.

Paleo-Typhoon Events as Indicated by Coral Reef Boulder Deposits on the Southern Coast of Hainan Island, China

The southern coast of Hainan Island, China, is one of the most frequently hit areas of tropical cyclones in the Northwest Pacific regions. Although some of the extreme typhoon events were known in historical times, quantitative information on the timing and magnitude of paleo-typhoon events in this coastal area remains rare. In the present study, a large number of coral reef boulders were found on the Xiaodonghai reef platform, on the south coast of Hainan Island. Morphometric analysis of the boulders shows an exponentially fining landward trend, indicating a storm origin; a wave-induced current velocity of 2.41–5.71 m/s during the storm events is required to transport the boulders that were originally situated outside the reef edge. Based on the U/Th and 14C dating for the age-indicating samples taken from the boulders, seven major periods with intense typhoon activities were identified for the last 4,000 years, i.e., 1800–1500 BCE, 1200–900 BCE, 50–120 CE, 550–800 CE, 900–1000 CE, 1350–1900 CE, and 1910–2000 CE. A comparison with the regional typhoon records in terms of climatic parameters in the northwestern Pacific and the South China Sea regions indicates that the longitudinal variations of intense typhoon frequency were mainly controlled by El Niño-Southern Oscillation (ENSO), dominantly modulated by the Intertropical Convergence Zone. Because of the future warming climate, there will be a trend of enhanced typhoon risk for the southern Hainan Island coasts.

New and Poorly Known Species of Peniagone (Holothuroidea, Elpidiidae) from the Northwest Pacific Ocean with Discussion on Phylogeny of the Genus

The northwest Pacific fauna of Peniagone includes at least seven species. In the present study we considered the following six species: Peniagone dubia and P. mus are re-described, P. minuta and P. saveljevae are described as new to science, additional information is provided on P. vitrea and P. cf. purpurea. Peniagone japonica was not included in the analysis. A potentially new species Peniagone sp. “miniatura” was distinguished based on morphological and molecular data but not formally described due to insufficient material. In the northwest Pacific, the species of Peniagone are distributed from 2400 to 8200 m. The bathymetric range of most of the species is narrow except for P. mus being also one of the deepest representatives of the genus. Only one species, P. vitrea, is known outside the northwest Pacific region. Partial sequences of COI and 16S rDNA were obtained for provisionally ten species of the genus (four of them from the northwest Pacific) and two other species of Elpidiidae which were used as an outgroup in phylogenetic analyses. The phylogenetic analyses results suggest that the northwest Pacific species of Peniagone are not closely related.

Development of a Tsunami-tide Interaction Model with Simulation of Tsunami Wave Propagation to Korea Coasts

Kim, K.O.; Jung, K.T., and Ha, T.M., 2021. Development of a tsunami-tide interaction model with simulation of tsunami wave propagation to Korea coasts. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 91–95. Coconut Creek (Florida), ISSN 0749-0208. Simulation studies of historic and prognostic tsunamis have been performed with a focus on tsunami-tide interactions. A modeling system based on the 3D POM (Princeton Ocean Model) has been developed that is composed of a global tsunami model and a regional multinesting tide/tsunami/tsunami-tide interaction model covering the Northwest Pacific region. Propagations of two historic tsunamis, the 2010 Chilean and 2011 Tohoku tsunamis, were simulated to estimate the effects of tsunami-tide interactions by comparing the results from tsunami-only and tsunami simulations with tide simulations. Calculations show that tsunami waves are significantly transformed after traveling a long distance and subsequently affected by the tidal phase. As prognostic tsunami propagation, the Nankai Trough earthquake-induced tsunami wave in Japan was investigated. A series of calculations were performed with a systematic shift of the tsunami occurrence time. The effects of tsunami-tide interactions were examined in terms of local tidal phase changes, focusing on the changes in the first tsunami heights and occurrence times arriving at the selected tidal stations in Korea. The tsunami-tide interaction mostly results in a positive change in the tsunami first peak heights with a maximum change near low tide probably due to the interaction between the tsunami-induced current and tidal current. The water depth increase near high tide advances the arrival of the tsunami first peaks, whereas the water depth decrease near low tide delays the arrival of the tsunami first peaks.

Poleward migration of tropical cyclones and its related typological characteristics of seasonal maximum precipitation in China

AbstractTropical cyclones (TCs) influence extreme rainfall events. However, changes in TCs caused by their poleward migration and subsequent impacts on extreme rainfall are yet to be adequately explored. In this study, the long‐term trends of TCs and typological characteristics of TC‐induced rainfall were analysed. Daily rainfall data were obtained from 759 Chinese stations and TC data were obtained in the Northwest Pacific (NWP) regions from 1961 to 2017. From May to October of each year, the TC‐induced rainfall was separated from the total rainfall data and spatiotemporal distribution patterns of TC‐induced rainfall were identified. The amount and frequency of TC‐induced rainfall decrease from the coastal inland. The TCs migrate northward, leading to a decrease (increase) in their activities south (north) of 20°N, respectively. In the South China Sea, TC activity is decreasing. The number of TC landfall events is decreasing (increasing) in the Pearl River basin (Southeast River basin). Furthermore, nonstationary increasing trends in the Pearl River and Southeast basins account for 41.7 and 62.9%, respectively, whereas the decreasing trends account for 30.6 and 14.3%, respectively. The Southeast River basin may face more TC‐induced extreme rainfall in the future. The results can provide information for water resource management and flood disaster warning systems in China, especially in the southeast.

The level of oil spill risk in Northwest Pacific and regional cooperation activities of NOWPAP MERRAC on marine pollution preparedness and response.

1. ABSTRACT The Northwest Pacific region, covering the four member states namely, People's Republic of China, Japan, Republic of Korea and Russian Federation, has been severely exposed to oil and HNS spills due to its high shipping density and high levels of industrial and economic growth and became a hotspot worldwide. Since member states are geographically close to each other, it is possible to cause transboundary issue affecting neighboring countries when oil and HNS spill incidents occur. In accordance with the need, the NOWPAP member states adopted the Regional oil and HNS spill Contingency Plan (RCP) in 2008, which provides the technical and operational framework for regional cooperation on major spill accidents, is a major achievements among the various regional cooperation activities. This was the first agenda actually adopted in the NOWPAP region and shows a national level of cooperation to protect the marine and coastal environment of the region. Particularly, to enhance the response capacities under the RCP, since 2006, member states jointly conduct oil and HNS spill response exercises (DELTA exercise) biannually, mobilizing actual response resources from the member states in a rotational basis. The 7th NOWPAP DELTA exercise was organized by Japan and Russia in Maizuru city, Japan (Oct. 2018). In addition to this, 19 communication exercises (BRAVO exercise) have also been implemented to test joint operational response procedures and associated communication tools in case of major spills. To further facilitate the exchange of information on marine pollution and preparedness in the region, MERRAC developed and operates the online pollution reporting system (POLREP) since 2015, which enables real-time exchange of information not only with the emails and fax but also through personal mobile phones of competent national authorities of member states. During the Sanchi spill incident (Jan 2018), the member states and MERRAC exchanged almost 300 notifications through POLREP concerning the location and trajectory of the spill and response operations. Furthermore, Member states exchange information on their national policies and response resources and has been building regional cooperation to strengthen its capabilities. In order to establish and maintain such regional cooperation system, MERRAC has been holding Focal Points meetings every year and Expert meetings every two years to exchange information on oil and HNS spill preparedness and response and implement Specific projects for various purposes by the national experts from the member states. In this presentation, we will review the oil and HNS risk levels in the NOWPAP region and examine the various cooperative activities and achievements and discuss the future prospects which MERRAC should go in through.

Genetic Diversity and Population Genetic Structure of Korean Black Scraper Thamnaconus modestus in Korea and Japan Based on the mtDNA Marker

Thamnaconus modestus is a commercially important species that is widely distributed in the Northwest Pacific region. To investigate the genetic diversity, demographic history, and population structure, 84 individuals were collected from two locations in Korea (Geomundo and Jumunjin) and one location in Japan (Wakasa Bay). Analysis of the mitochondrial DNA control region sequence of 373 base pairs from the 84 individuals revealed 39 haplotypes with 50 polymorphic sites. The haplotype diversity and nucleotide diversity of different populations ranged from 0.973 (0.018) to 0.981 (0.013) and from 0.020 (0.011) to 0.021 (0.011), respectively. Phylogenetic analysis revealed three distinct clades of which two were large (clade 1 and clade 2) and one was small clade (clade 3). However, there was no significant geographical clustering of the haplotypes according to the sampling locality. Demographic analysis suggested that both clades experienced Late Pleistocene population expansion. The pairwise FST and AMOVA analysis were insignificant among the populations investigated. This indicated high gene flow among the populations of Korea and Japan. The dispersal capacity of the larvae and juveniles by ocean currents and migration of adult individuals could explain the genetic homogeneity. Insufficient time to accumulate genetic variation might be another reason for the lack of genetic structure.

Diurnal Variations in Rainfall and Precipitation Asymmetry of Tropical Cyclones in the Northwest Pacific Region

AbstractThis study investigates diurnal variations of tropical cyclone precipitation in the northwest Pacific (NWP) region, including the South China Sea (SCS) and adjacent landmasses. Diurnal cycles of TC rainfall show significant land-sea contrasts. The primary peak of (unconditional) mean TC rain rate occurs in the early morning (06 LT) and the afternoon (15 LT) over the ocean and land, respectively. Both the total and heavy TC precipitation extend further inland in the afternoon, while nocturnal heavy TC rain is more confined to the coast. A significant semidiurnal cycle of TC precipitation is observed over the ocean, i.e., a secondary peak near 18 LT. The diurnal cycle of TC rainfall also depends on precipitation frequency, intensity, and radial distance from the TC center. Over the ocean, though TC precipitation intensity shows a pronounced diurnal cycle, its precipitation frequency exhibits virtually no diurnal variation. Over land, TC precipitation frequency markedly peaks in the afternoon (15 LT), while its precipitation intensity interestingly maximizes in the early morning (03-06 LT). Diurnal variations of TC asymmetric rainfall structure are consistent with diurnal changes of vertical wind shear. Over the SCS, maximum precipitation located in the downshear-left quadrant and is the most extensive in the morning. However, this heavy rain area shrinks and shifts downshear-ward in the afternoon, consistent with changes of the magnitude (reduced) and direction (clockwise) of shear. In contrast, TCs over the open ocean of NWP (OWP) have little diurnal variability of precipitation asymmetry, due mainly to a diurnally invariant shear environment.

Future projections in tropical cyclone activity over multiple CORDEX domains from RegCM4 CORDEX-CORE simulations

The characteristics of tropical cyclone (TC) activity over five TC basins lying within four Coordinated Regional Downscaling Experiment (CORDEX) domains are examined for present and future climate conditions using a new ensemble of simulations completed as part of the CORDEX-CORE initiative with the regional climate model RegCM4. The simulations are conducted at a 25 km horizontal grid spacing and are driven by three CMIP5 general circulation models (GCMs) under two Representative Concentration Pathways (RCP2.6 and RCP8.5). The RegCM4 captures most features of the observed TC climatology, except for the TC intensity, which is thus statistically adjusted using a bias correction procedure to account for the effect of the coarse model resolution. The RegCM4 exhibits an improved simulation of several TC statistics compared to the driving GCMs, over most basins analyzed. In future climate conditions we find significant increases in TC frequency over the North Indian Ocean, the Northwest Pacific and Eastern Pacific regions, which are consistent with an increase in mid-tropospheric relative humidity. The North Atlantic and Australasia regions show a decrease in TC frequency, mostly associated with an increase in wind shear. We also find a consistent increase in future storm rainfall rates associated with TCs and in the frequency of the most intense TCs over most domains. Our study shows robust responses often, but not always, in line with previous studies, still implying the presence of significant uncertainties in the projection of TC characteristics, which need to be addressed using large ensembles of simulations with high-resolution models.