Subtropical Asia Research Articles

Local grasses for the control of the invasive vine Mikania micrantha

Abstract Mikania micrantha (Asteraceae) is an invasive vine found in tropical and southern subtropical Asian and the Pacific Islands. The current methods used to control this vine are inadequate, which warrants the development of ecologically sustainable methods. Therefore, we investigated the ability of four grass species to prevent the invasion of M. micrantha, with an ultimate goal of developing ecologically sustainable control methods for widespread application. The clumps of native grass species from China (Panicum incomtum, Pennisetum purpureum, Saccharum arundinaceum and Microstegium vagans) were established. We sowed M. micrantha seeds and transplanted the seedlings into the grass clumps to examine whether the clumps could eliminate the new M. micrantha plants. In addition, we transplanted M. micrantha into existing grass clumps to examine whether the grass clumps could prevent the re-invasion of M. micrantha. Furthermore, we grew M. micrantha with P. incomtum and P. purpureum in the field to examine whether the grasses could outcompete M. micrantha. Mikania micrantha seeds germinated hardly in the grass clumps, and all seedlings died within 3 months. It was difficult for the vine to survive in the grass clumps. Our field experiments showed that the coverage of M. micrantha was significantly lower than that of the grass species in the first year, and that the vine was outcompeted after 2 years. To the best of our knowledge, this study is the first to reveal that tall grasses, particularly P. incomtum and P. purpureum, have potential to serve as bio-control agents for M. micrantha.

The Zonal Wind Intraseasonal Oscillation in the Exit Region of the East Asian Subtropical Westerly Jet in Winter and Its Thermodynamic Mechanism

The six-hourly ERA-interim reanalysis data were used to analyze the intraseasonal oscillation (ISO) characteristics of the zonal wind in the exit region of the East Asian subtropical westerly jet (EAJ) during the winter (November to April). The results indicate that from East Asia to the North Pacific, the zonal wind in the upper troposphere shows significant 10–40-day oscillations, propagating eastward toward the jet exit region. The strength of the intraseasonal zonal wind anomaly increases from the lower troposphere to the upper troposphere, reaching a peak between 300 and 200 hPa. The zonal wind ISO in the jet exit area is closely related to the intraseasonal inverse temperature tendency between the north and south of the jet exit in the troposphere. In the acceleration (deceleration) phase of the intraseasonal west wind, the air temperature decreases (increases) in the north of the exit and increases (decreases) in the south of the exit. The intraseasonal temperature tendency is stronger in the north of the EAJ exit than that in the south. In the north of the EAJ exit, the intraseasonal temperature tendency is decided by the temperature advection, where the whole troposphere is controlled by the north wind in the west wind acceleration phase and controlled by the south wind in the west wind deceleration phase, so the intensity of temperature advection is strong. However, adiabatic heating plays a decisive role in affecting the temperature evolution in the south of the jet exit area, and the intraseasonal meridional wind is the opposite between the mid-upper troposphere and the lower troposphere, resulting in weak temperature advection and the weak temperature tendency. Therefore, although the zonal wind ISO in the jet exit area is the result of the joint action of the ISOs in different latitudes, the influence of mid-high latitudes is particularly important.

Venom of several Indian green pit vipers: Comparison of biochemical activities and cross-reactivity with antivenoms

Green pit vipers, a name that can refer to several unrelated species, comprise a large group of venomous snakes found across the humid areas of tropical and sub-tropical Asia, and are responsible for most of the bite cases across this region. In India, green pit vipers belonging to several genera are prevalent in the northern and north-eastern hilly region, unrelated to species present in the peninsular region. In the present study, crude venom of representative species of green pit vipers present in the north and north-eastern hilly region of India (Trimeresurus erythrurus, T. septentrionalis, Viridovipera medoensis, and Popiea popieorum) were characterized to elucidate venom composition and venom variation. Profiling of crude venoms using SDS-PAGE and RP-HPLC methods revealed quantitative differences among the species. Further, in vitro biochemical assays reveal variable levels of phospholipase activity, coagulation activity, thrombin-like activity, fibrinogenolytic and haemolytic activity. This correlates with the pseudo-procoagulant effects on the haemostatic system of victims, which causes consumptive coagulopathy, frequently observed in patients bitten by green pit vipers. The immunoreactivity of Indian polyvalent antivenom and Thai green pit viper antivenom towards crude venoms were also evaluated by western blotting and inhibition of biochemical activities. The results exhibited poor efficacy of Indian polyvalent antivenom in neutralizing the venom toxins of crude venoms; however, Thai green pit viper antivenin (raised against the venom of Trimeresurus allbolabris, not present in India) showed higher immunoreactivity towards congeneric venoms tested. Analysis of green pit viper bite patients records from a community health centre in Assam, India, further revealed the inability of Indian polyvalent antivenom to reverse the extended coagulopathy featured.

Tropical and subtropical Asia's valued tree species under threat.

Tree diversity in Asia's tropical and subtropical forests is central to nature-based solutions. Species vulnerability to multiple threats, which affect provision of ecosystem services, is poorly understood. We conducted a region-wide, spatially explicit assessment of the vulnerability of 63 socioeconomically important tree species to overexploitation, fire, overgrazing, habitat conversion, and climate change. Trees were selected for assessment from national priority lists, and selections were validated by an expert network representing 20 countries. We used Maxent suitability modeling to predict species distribution ranges, freely accessible spatial data sets to map threat exposures, and functional traits to estimate threat sensitivities. Species-specific vulnerability maps were created as the product of exposure maps and sensitivity estimates. Based on vulnerability to current threats and climate change, we identified priority areas for conservation and restoration. Overall, 74% of the most important areas for conservation of these trees fell outside protected areas, and all species were severely threatened across an average of 47% of their native ranges. The most imminent threats were overexploitation and habitat conversion; populations were severely threatened by these factors in an average of 24% and 16% of their ranges, respectively. Our model predicted limited overall climate change impacts, although some study species were likely to lose over 15% of their habitat by 2050 due to climate change. We pinpointed specific natural areas in Borneo rain forests as hotspots for in situ conservation of forest genetic resources, more than 82% of which fell outside designated protected areas. We also identified degraded areas in Western Ghats, Indochina dry forests, and Sumatran rain forests as hotspots for restoration, where planting or assisted natural regeneration will help conserve these species, and croplands in southern India and Thailand as potentially important agroforestry options. Our results highlight the need for regionally coordinated action for effective conservation and restoration.

Orbital Forcing Strongly Influences the Poleward Shift of the Spring Himalayan Jet During the Past Millennium

AbstractThe latitudinal position of the subtropical jet over the Himalayas (Himalayan jet latitude or HJL) controls the region's climate during winter and spring by guiding moisture‐delivering storms. Here we use the Community Earth System Model‐Last Millennium Ensemble to diagnose forced trends in HJL during the past millennium. During 850–1849, there is a weak equatorward trend in winter HJL. In contrast, the spring HJL has a relatively larger poleward trend, and increases in both variance and frequency of poleward/equatorward excursions. We demonstrate changes in orbital precession reduced the thermal gradient between tropical and subtropical Asia, shifting the spring HJL poleward. During 1850–2005, the spring HJL exhibits no trend due to compensating influences from orbital and anthropogenic greenhouse gas forcings. These findings suggest it is essential climate models properly simulate the effects of and potential interactions between orbital forcing and anthropogenic factors to accurately project Himalayan jet variability and associated storm tracks.

Perceived heat impacts and adaptive behaviours in different socio-demographic groups in the subtropics

Extreme high temperature poses significant threats to public health. Its slow-onset nature allows people to perceive discomfort and protect themselves from negative health consequences, but higher risk perception does not necessarily lead to precautions. Our study understands this gap by arguing that subjective heat-health symptoms are more direct motivations for some heat adaptive behaviours. Through a survey into households (n = 2008) in Taiwan, we assess negative perception of heat impacts during hot days against demographic and socio-economic factors and their relationship with adaptive behaviours. The results show that the frequency of feeling moody and ill varies with age, gender, and health condition, which is also connected to the use of umbrellas and hats. Older people, diabetic patients, and men tend to be less sensitive to high temperature, leaving them with higher heat risk. A sign of biophysical acclimatisation and adaptation of behaviours was found with people frequently working outdoors. They do not necessarily experience discomfort more frequently, but are more likely to use umbrellas and hats. Also, electricity cost may outweigh cooling benefits from using air conditioning in low-income and ethnic minority groups. These results reflect the subtropical Asian context, reinforcing the importance of biophysical as well as socio-cultural components in shaping heat vulnerability of individuals and the need for comprehensive and targeted policy interventions.

First report of the invasive crop pest Stenocranus pacificus (Hemiptera: Delphacidae) in temperate Asia

AbstractNumerous delphacid planthopper species are major pests of economically important and widely cultivated crops (i.e. rice, corn, and sugarcane). These insects have the potential to become serious crop pests in areas where they have either naturally migrated or been newly introduced. The white‐bellied planthopper, Stenocranus pacificus Kirkaldy, 1907, originally known from tropical South Pacific islands, appeared in tropical and subtropical Asia in the early years of the 21st century. Since then, S. pacificus has become a serious pest of corn in some Southeast Asian countries, although it also feeds on rice, sugarcane, sorghum, and other grasses. Here, we report the presence of S. pacificus in mainland Japan, representing the first record of this species in temperate Asia. Seven male and 17 female adult individuals collected in Kumamoto Prefecture in 2019 and 2020 were identified as S. pacificus based on their morphological characteristics and mitochondrial COI sequences. In addition, molecular phylogenetic analysis showed that S. pacificus formed a distinct clade from other Stenocranus species, indicating uncertainty in its generic assignment. Although crop damage by S. pacificus has not yet been reported from temperate regions, given its wide range of plant hosts and the potential for future range expansions, damaged crops in Asia, including in temperate regions, should be monitored for the presence of this species.

Intensified climate drying and cooling during the last glacial culmination (20.8–17.5 cal ka BP) in the south-eastern Asian monsoon domain inferred from a high-resolution pollen record

Recent global sea-level data indicate that a final growth of ice volume occurred towards the end of the Last Glacial Maximum (LGM). The LGM culmination, LGM-b, lasted from about 21 to 17 ka and was followed by rapid deglaciation. This finding suggests a millennial-scale state with extreme glacial conditions (at least regionally) that immediately preceded the onset of full deglaciation marked by Heinrich event 1. In order to check how regional climate and vegetation in subtropical East Asia responded to the global-scale LGM culmination and the deglaciation onset, a new high-resolution pollen record from the Lijiafang peatland (LJF: 26°36.849′N, 116°08.463′E, 270 m) in Southeast China was generated. This record demonstrates a massive expansion of herbs during LGM-b. The dominance of herbaceous pollen suggests sparse forest cover in the lowlands of the subtropical East Asian Summer Monsoon (EASM) region and indicates an approximately 3300-year-long interval of the driest climate conditions of the entire last glacial-interglacial cycle. The LJF pollen-based reconstruction is consistent with the other vegetation records from the larger region, suggesting the climate change during LGM-b significantly impacted terrestrial ecosystems. The environmental change in the EASM region is likely linked to the Sea Surface Temperatures (SSTs) decrease that weakened the Walker cell convection over the western Pacific Ocean and reduced convection and moisture content in the Intertropical Convergence Zone. The strengthened decrease in moisture supply during LGM-b seems to have resulted in extreme and widespread megadroughts in the EASM and Australian regions. Our data indicate that the cold SSTs may have also decreased air temperatures in the neighboring parts of the continents. We suggest that the widespread SSTs decline in the western Pacific may have been linked to the cooling of the Southern Ocean and the expansion of Antarctic sea ice during LGM-b.

Phytochemistry and Diverse Pharmacology of Genus Mimosa: A Review.

The genus Mimosa belongs to the Fabaceae family and comprises almost 400 species of herbs, shrubs and ornamental trees. The genus Mimosa is found all over the tropics and subtropics of Asia, Africa, South America, North America and Australia. Traditionally, this genus has been popular for the treatment of jaundice, diarrhea, fever, toothache, wound healing, asthma, leprosy, vaginal and urinary complaints, skin diseases, piles, gastrointestinal disorders, small pox, hepatitis, tumor, HIV, ulcers and ringworm. The review covered literature available from 1959 to 2020 collected from books, scientific journals and electronic searches, such as Science Direct, Web of Science and Google scholar. Various keywords, such as Mimosa, secondary metabolites, medicines, phytochemicals and pharmacological values, were used for the data search. The Mimosa species are acknowledged to be an essential source of secondary metabolites with a wide-ranging biological functions, and up until now, 145 compounds have been isolated from this genus. Pharmacological studies showed that isolated compounds possess significant potential, such as antiprotozoal, antimicrobial, antiviral, antioxidant, and antiproliferative as well as cytotoxic activities. Alkaloids, chalcones, flavonoids, indoles, terpenes, terpenoids, saponins, steroids, amino acids, glycosides, flavanols, phenols, lignoids, polysaccharides, lignins, salts and fatty esters have been isolated from this genus. This review focused on the medicinal aspects of the Mimosa species and may provide a comprehensive understanding of the prospective of this genus as a foundation of medicine, supplement and nourishment. The plants of this genus could be a potential source of medicines in the near future.

Reconstruction of the evolutionary biogeography reveals the origins of Alpinia Roxb. (Zingiberaceae): A case of “out-of-Asia” migration to the Southern Hemisphere

Alpinia is considered the largest genus of Zingiberaceae with ca. 250 species occurring in tropical and subtropical Asia, Australia, and Pacific Islands. The historical biogeography of Alpinia was conducted to explain where Alpinia originated and how it migrated to other regions. The phylogeny, divergence times and ancestral area reconstruction of Alpinia were performed by using the molecular data based on the comprehensive taxon sampling. Our results provide an objective approach to understand the historical biogeography of Alpinia. The genus originated in Asia during the Late Cretaceous ca. 69 Ma and started to diverge after the K-Pg boundary during the early Paleocene with the presence and development of the tropical rainforest and a warm, moist climate. Alpinia migrated to Malesia and then dispersed to Australasia. The molecular analyses supported the diversification of Alpinia in Asia and Malesia. Additionally, the Indian Alpinia has likely a common ancestor with Renealmia and Aframomum, and it is possible that after originating in Asia, Alpinia migrated from Asia to India then to Africa during the early period of collision between the Indian subcontinent and Eurasia to form the common ancestor of Indian Alpinia, Renealmia, and Aframomum. Our phylogeny provides a framework for studies in biogeography, comparative ecology, and evolution.

History Does Not Repeat Itself; It Rhymes: Range Expansion and Outbreak of Plecia longiforceps (Diptera: Bibionidae) in East Asia

Abstract Plecia longiforceps Duda (Diptera: Bibionidae) is reported for the first time from Korea. P. longiforceps has been previously known from the East Asian subtropics, south of the 33rd parallel, including southeastern China, Taiwan, and the Ryukyu Islands of Japan. An integrative taxonomic approach based on morphological examination of male genitalia and molecular analysis of mitochondrial cytochrome c oxidase subunit I gene sequences confirms the species identification. The recent outbreak of P. longiforceps in the Seoul Metropolitan Area, Korea, documented herein represents the northernmost record of this species and suggests its possible range expansion into the temperate zone. Similar to the range expansion and outbreak history of Plecia nearctica Hardy (Diptera: Bibionidae) in North America around the Gulf of Mexico in the 1960–1970s, P. longiforceps may become a new invasive pest in temperate East Asia. Here, we evaluate range expansion and invasion potential of P. longiforceps through Ensemble species distribution modeling and show that a great portion of Northeast Asia and Japan will likely become habitable for P. longiforceps in the next 50 years.

A Narrative Review on the Phytochemistry, Pharmacology and Therapeutic Potentials of Clinacanthus nutans (Burm. f.) Lindau Leaves as an Alternative Source of Future Medicine.

The application of natural products and supplements has expanded tremendously over the past few decades. Clinacanthus nutans (C. nutans), which is affiliated to the Acanthaceae family, has recently caught the interest of researchers from the countries of subtropical Asia due to its medicinal uses in alternative treatment for skin infection conditions due to insect bites, microorganism infections and cancer, as well as for health well-being. A number of bioactive compounds from this plant’s extract, namely phenolic compounds, sulphur containing compounds, sulphur containing glycosides compounds, terpens-tripenoids, terpens-phytosterols and chlorophyll-related compounds possess high antioxidant activities. This literature search yielded about one hundred articles which were then further documented, including the valuable data and findings obtained from all accessible electronic searches and library databases. The promising pharmacological activities from C. nutans leaves extract, including antioxidant, anti-cancer, anti-viral, anti-bacterial, anti-fungal, anti-venom, analgesic and anti-nociceptive properties were meticulously dissected. Moreover, the authors also discuss a few of the pharmacological aspect of C. nutans leaves extracts against anti-hyperlipidemia, vasorelaxation and renoprotective activities, which are seldom available from the previously discussed review papers. From the aspect of toxicological studies, controversial findings have been reported in both in-vitro and in-vivo experiments. Thus, further investigations on their phytochemical compounds and their mode of action showing pharmacological activities are required to fully grasp both traditional usage and their suitability for future drugs development. Data related to therapeutic activity and the constituents of C. nutans leaves were searched by using the search engines Google scholar, PubMed, Scopus and Science Direct, and accepting literature reported between 2010 to present. On the whole, this review paper compiles all the available contemporary data from this subtropical herb on its phytochemistry and pharmacological activities with a view towards garnering further interest in exploring its use in cardiovascular and renal diseases.

Chemical constituents and biological activities of essential oils of Amomum genus (Zingiberaceae)

Amomum Roxb. includes the aromatic and medicinal plants native to tropical and subtropical Asia belonging to the family Zingiberaceae. Members of Amomum genus have been used for a long time in traditional medicine for the treatment of throat trouble, congestion of lungs, inflammation of eyelids, and digestive disorders, etc. Amomum essential oils have been studied for their chemical profiles in which limonene, allo-aromadendrene, 1,8-cineole, camphor, farnesyl acetate, α-pinene, β-pinene, caryophyllene, camphene, D-camphor, santolina triene, methyl chavicol, bornyl acetate, β-elemene, δ-3-carene, etc. were the major compounds. Furthermore, the oils extracted from Amomum plants have been reported to possess antimicrobial, antioxidant, insecticidal, larvicidal, cytotoxic, anti-scabies, and anti-inflammatory activities. This review focuses on the chemical constituents and biological activities of the essential oils isolated from the different plant parts of Amomum plants. The objective of the present review is to highlight therapeutic potentials and provide evidence for future medicinal applications of these species of genus Amomum.

Distribution and biodiversity of rhizobia nodulating Chamaecrista mimosoides in the Shandong peninsula of china

Chamaecrista mimosoides is an annual herb legume widely distributed in tropical and subtropical Asia and Africa. It may have primitive and independently-evolved root nodule types but its rhizobia have not been systematically studied. Therefore, in order to learn the diversity and species affinity of its rhizobia, root nodules were sampled from C. mimosoides plants growing in seven geographical sites along the coast line of Shandong Peninsula, China. A total of 422 rhizobial isolates were obtained from nodules, and they were classified into 28 recA haplotypes. By using multilocus sequence analysis of the concatenated housekeeping genes dnaK, glnII, gyrB, recA and rpoB, the representative strains for these haplotypes were designated as eight defined and five candidate novel genospecies in the genus Bradyrhizobium. Bradyrhizobium elkanii and Bradyrhizobium ferriligni were predominant and universally distributed. The symbiotic genes nodC and nifH of the representative strains showed very similar topology in their phylogenetic trees indicating their co-evolution history. All the representative strains formed effective root nodules in nodulation tests. The correlation between genospecies and soil characteristics analyzed by CANOCO software indicated that available potassium (AK), organic carbon (OC) and available nitrogen (AN) in the soil samples were the main factors affecting the distribution of the symbionts involved in this current study. The study is the first systematic survey of Chamaecrista mimosoides-nodulating rhizobia, and it showed that Chamaecrista spp. were nodulated by bradyrhizobia in natural environments. In addition, the host spectrum of the corresponding rhizobial species was extended, and the study provided novel information on the biodiversity and biogeography of rhizobia.

GC-MS Analysis of Bioactive Compounds in Ethanolic Leaf Extract of Hellenia speciosa (J.Koenig) S.R. Dutta.

Hellenia speciosa (J.Koenig) S.R. Dutta is a plant species belonging to the family Costaceae. It is widely distributed in China, India, Malaysia, Indonesia, tropical, and subtropical Asia. In Ayurveda, the rhizome of this plant has been extensively used to treat fever, rash, asthma, bronchitis, and intestinal worms. The objective of the present study was to investigate the phytochemical constituents of the leaf of Hellenia speciosa using gas chromatography and mass spectroscopy analysis (GC-MS). The GC-MS analysis revealed the presence of 17 phytochemical components in the ethanolic leaf extract of Hellenia speciosa. The prevailing bioactive compounds present in Hellenia speciosa were thymol (RT-10.019; 3.59%), caryophyllene (RT-11.854; 0.62%), caryophyllene oxide (RT-13.919; 1.34%), artumerone (RT-14.795; 1.35%), hexadecanoic acid methyl ester (RT-17.536; 2.77%), 9,12-octadecanoic acid methyl ester (RT-19.163; 1.35%), squalene (RT-24.980; 1.19%), piperine (RT-25.745; 3.11%), beta tocopherol (RT-26.681; 2.88%), vitamin E (RT-27.290; 2.64%), progesterone (RT-29.608; 3.18%), caparratriene (RT-29.861; 9.72%), and testosterone (RT-30.73; 5.81%). The compounds were identified by comparing their retention time and peak area with that of the literature and by interpretation of mass spectra. The results and findings of the present study suggest that the plant leaf can be used as a valuable source in the field of herbal drug discovery. The presence of bioactive compounds justifies the use of plant leaves for treating various diseases with fewer side effects and recommended the plant of pharmaceutical importance. However, further studies are needed to undertake its bioactivity and toxicity profile.

Aerosol-boundary-layer-monsoon interactions amplify semi-direct effect of biomass smoke on low cloud formation in Southeast Asia

Low clouds play a key role in the Earth-atmosphere energy balance and influence agricultural production and solar-power generation. Smoke aloft has been found to enhance marine stratocumulus through aerosol-cloud interactions, but its role in regions with strong human activities and complex monsoon circulation remains unclear. Here we show that biomass burning aerosols aloft strongly increase the low cloud coverage over both land and ocean in subtropical southeastern Asia. The degree of this enhancement and its spatial extent are comparable to that in the Southeast Atlantic, even though the total biomass burning emissions in Southeast Asia are only one-fifth of those in Southern Africa. We find that a synergetic effect of aerosol-cloud-boundary layer interaction with the monsoon is the main reason for the strong semi-direct effect and enhanced low cloud formation in southeastern Asia.

Chromosome-scale genome assembly of Castanopsis tibetana provides a powerful comparative framework to study the evolution and adaptation of Fagaceae trees.

Fagaceae species are increasingly used as models to elucidate the process and mechanism of adaptation and speciation by integrating ecology, evolution and genomics. The genus Castanopsis belongs to the family Fagaceae and is mainly distributed across subtropical and tropical Asia. In the present study, we reported the first chromosome-scale genome assembly of Castanopsis tibetana, a common species of evergreen broadleaved forests in subtropical China. The combination of Nanopore sequencing and Hi-C technologies enabled a high-quality genome assembly. The final assembled genome size of C.tibetana was 878.6Mb (97.6% of the estimated genome size), consisting of 477 contigs with an N50length of 3.3Mb. The benchmarking universal single-copy orthologue (BUSCO) assessment indicated a completeness of 93.0%. Hi-C scaffolding generated 12pseudochromosomes, representing 98.7% of the assembled genome. Subsequently, 40,937 protein-coding genes were predicted and 90.04% of them were functionally annotated. More than 476.9Mb of repetitive sequences (54.3% of the genome) were identified, and the percentage of the genome covered by TE elements was 39.98%. Comparative genomics analysis revealed that C.tibetana was most closely related to Castanea mollissima and diverged at 18.48Ma, and that C.tibetana has undergone considerable gene family expansion and contraction. Evidence of positive selection was detected in 53genes, which showed different arrangement pattern compared to Quercus robur. The chromosome-scale genome assembly of C.tibetana will expand Fagaceae genome resources across the family and provide a powerful comparative framework to study the adaptation and evolution of Fagaceae trees.

Explosive range expansion of Eulophia graminea (Orchidaceae) in Puerto Ricio and the West Indies

Eulophia graminea Lindley (Orchidaceae), a native orchid of tropical and subtropical Asia, was first reported in the Western Hemisphere from populations in Miami, Florida, U.S.A. where it spread rapidly through the southern part of the state. Here we report the first record of this species for Puerto Rico and sightings in the Bahamas and Cuba, reflecting the rapid spread seen in southern Florida (U.S.A).

Dipole Mode of the Precipitation Anomaly Over the Tibetan Plateau in Mid‐Autumn Associated With Tropical Pacific‐Indian Ocean Sea Surface Temperature Anomaly: Role of Convection Over the Northern Maritime Continent

AbstractBased on observational data and numerical simulation results with the Community Atmosphere Model (CAM4), version 4 atmospheric general circulation model (AGCM), the influence of the sea surface temperature anomaly (SSTA) of the tropical Pacific–Indian Ocean mode (PIM) on the interannual variability of the Tibetan Plateau (TP) precipitation in mid‐autumn (October) is investigated. We find that the interannual variation of the mid‐autumn TP precipitation is characterized by a dipole mode with a southeast–northwest inverse pattern, which is influenced significantly by the large‐scale circulation anomalies induced by PIM. During a positive phase of PIM, that is, positive SSTA in both the tropical central‐eastern Pacific and western Indian Ocean accompanied by negative SSTA around the Maritime Continent, a robust lower‐level anticyclonic anomaly over the South Asia region (SAAC) and an upper‐level cyclonic anomaly over subtropical Asia are generated owing to the Rossby wave response to the suppressed convective heating over the northern Maritime Continent. As a result, the southerly (northerly) anomalies on the west (east) side of the SAAC can enhance (reduce) the transportation of moisture and the ascending motion over the northwestern (southeastern) TP. Meanwhile, the southward‐shifted East Asian westerly jet can further enhance the ascending motion over the northwestern TP by stimulating secondary circulation. Correspondingly, a positive (negative) precipitation anomaly appears over the northwestern (southeastern) TP. During a negative phase of PIM, the opposite case is also true. Therefore, the suppressed convective heating over the Maritime Continent serves as a pivotal medium by which PIM affects the TP precipitation in mid‐autumn.

Effect of the El Niño–Southern Oscillation (ENSO) Cycle on the Catches and Habitat Patterns of Three Swimming Crabs in the Taiwan Strait

The swimming crabs is a crucial predator species in benthic habitats and a high value in commercial fishery industries in subtropical and tropical Asia. The climate variability caused by El Niño–Southern Oscillation (ENSO) events has substantial impacts on the catch and habitat of this species. In this study, a weighted habitat suitability index (HSI) model was constructed using logbooks and voyage data records from Taiwanese crab vessels (2013–2019) with the addition of environmental variables to examine the influence of ENSO events on catch rates (CRs) and habitat suitability for Charybdis feriatus, Portunus pelagicus, and Portunus sanguinolentus in the Taiwan Strait (TS). The autumn (September–October) is the major fishing season for catching these three swimming crab species in the TS. A high CR of P. sanguinolentus was observed across the TS, whereas high CRs of P. pelagicus and C. feriatus were recorded in areas in the southern and northern TS, respectively, during autumn. Moreover, the CRs for C. feriatus and P. pelagicus were higher (>7.0 and >8.0 kg/h) during La Niña events, with the increase being more than 40.0% compared with the CRs under normal and El Niño events in autumn. For P. sanguinolentus, the CRs were higher during both La Niña and El Niño events (>8.0 kg/h) compared with normal years. The high CRs for C. feriatus and P. sanguinolentus during autumn in La Niña years co-occurred with high sea temperature and low salinity, whereas the high CR of P. pelagicus co-occurred with high sea temperature and high salinity. Furthermore, the high CRs for C. feriatus and P. pelagicus were observed in areas with high HSI in the La Niña years but were distributed more widely with a lower HSI during normal and El Niño years. The low CRs for C. feriatus and P. pelagicus during normal and El Niño years and the low CR for P. sanguinolentus in normal years during autumn were highly consistent with substantial shrinkage of suitable habitats. Our findings suggest that ENSO events strongly affected the catch and habitat suitability of C. feriatus, P. pelagicus, and P. sanguinolentus during autumn in the TS.