Southeast Coast Of China Research Articles

Projected Changes in Precipitation Extremes Over Jiulongjiang River Basin in Coastal Southeast China

The southeast coastal region of China is susceptible to challenges related to extreme precipitation events; hence, projection of future climate extremes changes is crucial for sustainable development in the region. Using the Regional Climate Model Version 4 (RegCM4), the future changes of summer precipitation extremes have been investigated over the Jiulongjiang River Basin (JRB), a coastal watershed in Southeast China. Comparison between the RegCM4 simulated and observed rainy season precipitation over JRB suggests that the RegCM4 can reasonably reproduce the seasonal precipitation cycle, the frequency distribution of precipitation intensity, and the 50-year return levels of precipitation extremes over JRB. Furthermore, the model projects an increase in daily maximum rainfall (RX1day) mostly over the northern part of the basin and a decrease over other parts of the basin, while projecting a widespread decrease for maximum consecutive 5-day precipitation amount (RX5day) relative to the present day. In terms of the 50-year return level of RX1day (RL50yr_RX1day), a general increase is projected over most parts of the basin in the near and far future of the 21st century, but a decrease can be found in the northeast and southwest parts of the JRB in the mid-21st century. The future change of the 50-year return level of RX5day (RL50yr_RX5day) shows a similar spatial pattern with that of RL50yr_RX1day in the near and mid-21st century, but with a larger magnitude. However, a remarkable decrease in RL50yr_RX5day is found in the south basin in the far future. Meanwhile, the projected changes in the 50-year return level for both RX1day and RX5day differ between the first and second rainy seasons in JRB. Specifically, the future increase in RL50yr_RX5day over the north basin is mainly contributed by the changes during the first-half rainy season, while the decrease of RL50yr_RX5day in the south is mostly ascribed to the future changes during the second-half rainy season. All above results indicate that the future changes of precipitation extremes in JRB are complicated, which might differ from extreme indices, seasons, and future projected periods. These will thus be of practical significance for flood risk management, mitigation, and adaptation measures in Jiulongjiang River Basin.

Response of methanotrophic activity and community structure to plant invasion in China’s coastal wetlands

Coastal wetlands are critical in the global carbon budget while vulnerable to plant invasion. Spartina alterniflora (S. alterniflora), a typical invasive plant species, has rapidly expanded in China’s coastal area since 1979, which disturbed the carbon cycle of the coastal wetland ecosystems. However, until now, the effect and underlying mechanisms of S. alterniflora invasion on methanotrophs are poorly known in coastal wetlands. Here, a large-scale investigation of the activity, abundance and community structure of methanotrophs was conducted in seven wetlands under both native (dominated by Phragmites australis, Kandelia candel or Avicennia marina) and invasive plants (dominated by S. alterniflora) across the southeast coast of China. Compared with the native community, S. alterniflora invasion led to a significant (p < 0.05) increase in activity and abundance of methanotrophs, which increased by 62.1% and 64.0% in average, respectively. The invasion of S. alterniflora did not greatly alter the methanotrophic community structure in most of the examined wetlands. However, the relative abundance of type I methanotrophs decreased under P. australis community, while type II methanotrophs (Methylocystis) increased after S. alterniflora invasion. In addition, the soil organic carbon content, ammonium content and salinity were identified as important environmental factors affecting the activity and community structure of methanotrophs. Overall, our results demonstrated that the activity and abundance of methanotrophs responded positively to S. alterniflora invasion, suggesting the important role of methanotrophs in reducing methane emissions from China’s coastal wetlands.

Typhoon hazard analysis based on the probability density evolution theory

In this article, a new typhoon hazard analysis method is presented by introducing the probability density evolution theory. In the suggested method, the randomness in the typhoon occurrence is represented by the combination of a homogeneous Poisson process and a joint probability density function for both the typhoon genesis time and the genesis position. Then a set of physical models, including a typhoon intensity model, a typhoon track model and a boundary layer wind field model, is introduced to describe the typhoon process. The typhoon intensity model with high efficiency is used to simulate the evolution of typhoon intensity given the environmental variables. The typhoon motion is simulated by the beta-advection model where the steering flow is the linear combination of the large-scale flows at 850 hPa and 250 hPa, and the beta drift is solved from the non-divergent barotropic vorticity equation. At last, the typhoon induced surface wind at the interested engineering site is calculated with the help of a three-dimensional non-linear boundary layer wind field model. On the basis of the above physical models, the generalized density evolution equation is adopted to solve the probability distribution of the annual maximum typhoon surface wind speeds. The typhoon surface wind speeds associated with specified recurrence intervals are estimated consequently. As an example, the typhoon hazard at ten selected cities on the southeast coast of China is assessed. The surface wind records from the observation stations are collected to estimate the cumulative distribution function of the annual maximum wind and are compared to the analyzed results. The good comparison between the historical records and the analyzed results demonstrates the adequacy of the proposed method.

Genome-Wide Survey Reveals the Microsatellite Characteristics and Phylogenetic Relationships of Harpadon nehereus.

Harpadon nehereus forms one of the most important commercial fisheries along the Bay of Bengal and the southeast coast of China. In this study, the genome-wide survey dataset first produced using next-generation sequencing (NGS) was used to provide general information on the genome size, heterozygosity and repeat sequence ratio of H. nehereus. About 68.74 GB of high-quality sequence data were obtained in total and the genome size was estimated to be 1315 Mb with the 17-mer frequency distribution. The sequence repeat ratio and heterozygosity were calculated to be 52.49% and 0.67%, respectively. A total of 1,027,651 microsatellite motifs were identified and dinucleotide repeat was the most dominant simple sequence repeat (SSR) motif with a frequency of 54.35%. As a by-product of whole genome sequencing, the mitochondrial genome is a powerful tool to investigate the evolutionary relationships between H. nehereus and its relatives. The maximum likelihood (ML) phylogenetic tree was constructed according to the concatenated matrix of amino acids translated from the 13 protein-coding genes (PCGs). Monophyly of two species of the genus Harpadon was revealed in the present study and they formed a monophyletic clade with Saurida with a high bootstrap value of 100%. The results would help to push back the frontiers of genomics and open the doors of molecular diversity as well as conservation genetics studies on this species.

Jurassic to Early cretaceous sedimentary record: indications of Paleo-Pacific Plate subduction in Southeast China

ABSTRACT Plate subduction plays a decisive role in continental tectonics, and subduction history is closely connected to deformation and sedimentation in the overriding plate. When and how the Paleo-Pacific Plate subducted beneath Southeast China in the Mesozoic is debated. Here, we show that provenance data, including detrital composition point counts, palaeocurrent data, and detrital zircon U-Pb geochronology from basins in Southeast China, record the timing and process of Paleo-Pacific Plate subduction during the Jurassic and Earliest Cretaceous. The U-Pb dating of detrital zircons from Jurassic samples indicates that the sediments were transported from multiple sources, including intracratonic mountains, tectonic belts and the inferred active continental margin arc that resulted from Paleo-Pacific Plate subduction. The clastic composition and U-Pb dating of Early Cretaceous tuffs suggest that they were sourced from nearby magmatic rocks and the eastern inferred magmatic arc. Based on detrital zircon U-Pb dating, igneous rock isotope, sedimentary, and structural data, we infer that an active continental magmatic arc developed along the coast of Southeast China in the Early Jurassic to Early Cretaceous (~200 Ma-135 Ma). The westward subduction of the Paleo-Pacific Plate initiated in the Early Jurassic (~200 Ma) and continued to the Early Cretaceous (~135 Ma). Paleo-Pacific Plate subduction resulted in the uplift of the northern Wuyi Mountain region and eastern South China and controlled the provenance characteristics of the sedimentary basins in Southeast China during the Jurassic to Early Cretaceous.

Variability and profiles of lipophilic marine toxins in shellfish from southeastern China in 2017–2020

A total of 1338 samples were analyzed by ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to study the toxin profiles of lipophilic marine toxins in bivalve mollusks collected from the southeast coast of China from 2017 to 2020. The most abundant toxin was HomoYTX, followed progressively by YTX and PTX2. Low proportions of OA, DTX-1, and DTX-2 were found. No AZA1, AZA2, and AZA3 were quantified above limit of quantitation (LOQ). The highest concentrations of HomoYTX, YTX, PTX2, OA, DTX-1, and DTX-2 were 429, 98.0, 40.3, 33.0, 22.6, and 26.5 μg/kg, respectively. Mussels (Mytilus galloprovincialis, Perna viridis), scallop (Chlamys farreri) and clam (Atrina pectinate) accumulated higher toxin levels than clams (Sinonovaculla Constricta, Ruditapes philippinarum), oyster (Crassostrea gigas) and scallop (Arca granosa). Homo YTX and PTX2 levels reached the maximum in July and June, respectively, and the OA-group peaked in August. The results provide a reliable basis for monitoring marine toxins and protecting the health of aquatic consumers.

A chromosome-level genome assembly of the miiuy croaker (Miichthys miiuy) using nanopore sequencing and Hi-C

Miiuy croaker, Miichthys miiuy is an ecologically important teleost species which is widely distributed in southeast coast of China. In this study, we present a chromosomal-scale genome assembly of the miiuy croaker which is an important Sciaenidae fish and economical species. We adopted Oxford Nanopore and Hi-C sequencing techniques to achieve an assembly with high accuracy and completeness. The investigation of genome characteristic and functional features may provide insights into the study of phylogenetic diversity of miiuy croaker. This study can also be beneficial to improve molecular assisted breeding techniques. Moreover, it can be a great resource to better conduct further study of other sciaenids.

Modeling of the Ecological Carrying Index of reclaimed land in coastal city: A sustainable marine ecology perspective

In recent years, Wenzhou City located on the southeast coast of China has experienced the largest scale of land reclamation projects in China. However, the extent to which such projects still bring about the destruction of marine resources and the environment. So, in this study, a marine ecological development carrying capacity index model was established and analyzed the ecological carrying capacity index of the reclaimed sea area in Wenzhou with the detection and warning conditions to propose a marine ecological protection supervision mechanism. By the proposed mechanism, five primary-level indicators and 10 corresponding secondary-level indicators were established. The obtained results showed that the ecological carrying index of the reclaimed area in Wenzhou falls within the range, 2.35–5.45, which is indicative of small geographic differences. These results suggest that in future, a detection and early warning mechanism for the determination of the ecological carrying capacity of reclaimed sea areas should be established. Furthermore, the strict implementation of the reclamation project development evaluation management control system is recommended, and it is also necessary to reasonably adjust the planning and construction of the sea area.

Spatial distribution and source apportionment of peroxyacetyl nitrate (PAN) in a coastal region in southern China

Peroxyacetyl nitrate (PAN) is a typical secondary product of photochemical pollution and has attracted considerable attention because of its important role in atmospheric photochemical reactions and biotoxicity. Although existing studies have determined the dominant species of volatile organic compounds (VOCs) that can generate PAN, there are few studies including quantitative source analysis of PAN and precursor VOCs. In this study, PAN and precursor VOCs were measured at three sites in Shenzhen, a megacity on the southeast coast of China. The mean daytime (8:00–18:00) concentrations of PAN at the three sites during the sampling period were 0.70 ppbv (YMK, rural), 1.31 ppbv (DXC, residential) and 1.52 ppbv (FC, industrial), which had a different spatial distribution pattern compared to those of O3 and better reflect the degree of local anthropogenic emissions. Based on the steady-state model, the calculated PA radical formation rates cumulative contribution by six major carbonyl compounds at YMK and DXC were 4.4 × 106 molecules*cm−3*s−1 and 6.8 × 106 molecules*cm−3*s−1, respectively, and acetaldehyde contributed the highest percentage (44.4–54.3%) followed by acetone (15.1–25.6%), diacetyl (10.0–10.9%) and methylglyoxal (12.2–13.4%). Using an improved photochemical age-based parameterization method to analyze the daytime sources of PA radicals, the results show that biogenic sources were the most important source of PA radicals, accounting for 27.1% and 29.8% at YMK and DXC, respectively, and the contribution of anthropogenic secondary sources at DXC (25.8%) was significantly higher than at YMK (17.0%). The contribution of biomass burning at YMK reached 24.2%, emphasizing a critical role of biomass burning in atmospheric photochemical pollution in rural areas.

A chromosome-level genome assembly of the blackspotted croaker (Protonibea diacanthus)

The blackspotted croaker (Protonibea diacanthus) is an endangered coastal marine fish. It is also a valuable species that is cultured on the southeast coast of China. While some genetic studies have been conducted to protect this species, genomic resources are lacking. Here, we report a chromosome-scale assembly of P. diacanthus genome by high-depth genome sequencing, assembly, and annotation. The genome scale was 635.69 Mb with contig and scaffold N50 length of 3.33 Mb and 25.60 Mb, respectively. Hi-C scaffolding of the genome resulted in 24 chromosomes of 94.15% total genome. We predicted 23,971 protein-coding genes. In addition, we constructed a phylogenetic tree using 2755 single-copy gene families and identified 462 unique gene families in P. diacanthus genome compared to three other sciaenids. What's more, from the analysis of gene families, we found that several gene families related to innate immunity were significantly expanded in the blackspotted croaker genome compared to other teleost genomes. The high-quality genome can improve our understanding of the molecular mechanisms behind economically valuable traits and provide insights into characteristics of the immune system.

Prey decline leads to diet shift in the largest population of Indo-Pacific humpback dolphins?

The Pearl River Delta (PRD) region on the southeast coast of China has long been known as a highly productive fishing ground. Since the late 1980s, fishing pressure in the PRD has been intense, which warrants concerns of potential fishery-related impacts on the food resources and foraging ecology of apex marine predators in this region, such as the Indo-Pacific humpback dolphin (Sousa chinensis). In this study, we examined 54 stomachs with food remains, collected from beached carcasses of humpback dolphins recovered during fifteen years between 2003 and 2017. The 6043 identified prey items represent 62 teleost taxa, primarily small estuarine fish, but also larger reef fish. The dolphins appear to be opportunistic foragers, hunting across the water-column, with preference for shoaling and meaty fishes (e.g. Collichthys lucidus IRI% = 38.6%, Johnius belangerii IRI% = 23.1%, Mugil cephalus IRI% = 14.0%). Our findings suggest a dietary shift in recent years, from primarily demersal (as previously reported) to greater intake of neritic and pelagic fish. Dolphin foraging group size has decreased in recent years, which corresponds with declining size and numbers of prey items retrieved from dolphin stomachs. We suggest that these are indicators of declining food resources. Faced with a shortage of preferred prey, humpback dolphins may have broadened their dietary spectrum to maintain their daily energy intake, while their foraging group size decreased in response to the altered tradeoff between the costs and benefits of group foraging.

Simulation of storm surge and wave due to Typhoon Lekima in 2019

Zhejiang province is located at the southeast coast of China and vulnerable to typhoons generated in the northwest Pacific Ocean. An integrally coupled surge-wave model is developed and applied to the simulation of storm surge and wave induced by typhoon Lekima occurred in 2019. When considering wave-induced forces and using identical unstructured grid in coupled model, the model shows high accuracy and reproduces the typhoon process well. The distribution of maximum surge level shows great spatial differences along Zhejiang coast. Due to shelf geometry and shallow water effect, peak surge level rises significantly near Zhejiang coast. In addition, the peak surge levels on the right side of typhoon track are much higher than that on the left side. Contrary to characteristics of storm surge levels, significant wave height decreases rapidly near the Zhejiang coast due to shoaling, blocking of islands, and wave breaking.

Origin and Paleoenvironmental Significance of the Old Red Sand Along the Southeast Coast of China

The “Old Red Sand” (ORS) along the southeast coast of China is of significant paleoclimatic and paleoenvironmental significance. However, its provenance remains controversial. In this study, grain size characteristics and quartz grain surface microtextures were analyzed to study the origin and paleoenvironmental significance of the ORS, the results show that the grain size of the ORS show typical aeolian features, the quartz grain surface microtextures of the ORS show both aeolian features and subaqueous environments characteristics. Combined with the latest OSL dating data, we suggest that the ORS was coastal aeolian sand dunes developed since the last interglacial period. The formation of the ORS was restricted jointly by climate changes of the coastal area and the distance from the shoreline that resulted from sea level changes.

Effect of industrial crop Jerusalem artichoke on the micro-ecological rhizosphere environment in saline soil

Salinity is not only a threat to organisms and ecosystems, but also a major factor restricting the development of agricultural production. This study aimed to explore the modification effect of in-situ Jerusalem artichoke (genotype NY-1) cultivation on the rhizosphere micro-ecological environment in the saline-alkali region along the southeast coast of China. We analyzed the change of carbon and nitrogen in the saline soil from a microbial perspective, through the quantification of the area of root channels, rhizosphere secretions and soil microbiome (cbbL, cbbM and nifH). The root channels of NY-1 not only improved the physical structure of saline soil, but also provided a living space for microorganisms, afforded basic conditions for the optimization of the soil micro-ecological environment. In addition, rhizosphere secretions (from roots of NY-1 as well as microorganisms), such as carbohydrates, hydrocarbons, acids, etc., could be considered as a way to improve the saline-alkali soil habitat. NY-1 increased the diversity and abundance of autotrophic and nitrogen-fixing bacteria in saline soil (rhizosphere > bulk soils), which should be a biological way to increase the amount of carbon and nitrogen fixation in soil. Moreover, some of the detected genera (Sideroxydans, Thiobacillus, Sulfuritalea, Desulfuromonas, etc.) participate in the carbon and nitrogen cycles, and in the biogeochemical cycle of other elements. In short, Jerusalem artichoke can improve not only the physical and chemical properties of saline-alkali soil, but also promote material circulation and energy flow in the micro-ecological rhizosphere environment of saline soils.

Source or sink? A study on the methane flux from mangroves stems in Zhangjiang estuary, southeast coast of China

Mangrove ecosystems are an important component of “blue carbon”. However, it is not clear whether the stems play roles in the CH4 budget of mangrove ecosystems. This study investigated the CH4 emission from mangrove stems and its potential driving factors. We set up six sample plots in the Zhangjiang Estuary National Mangrove Nature Reserve, where Kandelia obovata, Avicennia marina and Aegiceras corniculata are the main mangrove tree species. Soil properties such as total carbon content, redox potential and salinity were determined in each plot. The dynamic chamber method was used to measure mangrove stems and soil CH4 fluxes. Combined field survey results with Principal Component Analysis (PCA) of soil properties, we divided the six plots into two sites (S1 and S2) to perform statistical analyses of stem CH4 fluxes. Then the CH4 fluxes from mangrove tree stems and soil were further scaled up to the ecosystem level through the mapping model. Under different backgrounds of soil properties, salinity and microbial biomass carbon were the main factors modified soil CH4 fluxes in the two sites, and further affected the stem CH4 fluxes of mangroves. The soil of both sites are sources of CH4, and the soil CH4 emission of S2 was about twice higher than that of S1. Results of upscaling model showed that mangrove stems in S1 were CH4 sinks with −105.65 g d−1. But stems in S2 were CH4 sources around 1448.24 g d−1. Taken together, our results suggested that CH4 emission from mangrove soils closely depends on soils properties. And mangrove stems were found to act as both CH4 sources and CH4 sinks depend on soil CH4 production. Therefore, when calculating the CH4 budget of the mangrove ecosystem, the contribution of mangrove plant stems cannot be ignored.

Two new species of Amphinemura (Plecoptera: Nemouridae) from Taiwan Province on the southeast coast of China.

Two new species of Amphinemura were described and illustrated from Taiwan Province of China: Amphinemura reni Du Zhao, sp. nov. and Amphinemura triquetra Zhao Du, sp. nov. The morphological characteristics of the new species were compared to related taxa. Additionally, a key to the adult males of Amphinemura known from Taiwan Province of China was given in this paper.

Spatial variations in CO2 fluxes in a subtropical coastal reservoir of Southeast China were related to urbanization and land-use types

Carbon dioxide (CO2) emissions from aquatic ecosystems are important components of the global carbon cycle, yet the CO2 emissions from coastal reservoirs, especially in developing countries where urbanization and rapid land use change occur, are still poorly understood. In this study, the spatiotemporal variations in CO2 concentrations and fluxes were investigated in Wenwusha Reservoir located in the southeast coast of China. Overall, the mean CO2 concentration and flux across the whole reservoir were 41.85 ± 2.03 µmol/L and 2.87 ± 0.29 mmol/m2/h, respectively, and the reservoir was a consistent net CO2 source over the entire year. The land use types and urbanization levels in the reservoir catchment significantly affected the input of exogenous carbon to water. The mean CO2 flux was much higher from waters adjacent to the urban land (5.05 ± 0.87 mmol/m2/hr) than other land use types. Sites with larger input of exogenous substance via sewage discharge and upstream runoff were often the hotspots of CO2 emission in the reservoir. Our results suggested that urbanization process, agricultural activities, and large input of exogenous carbon could result in large spatial heterogeneity of CO2 emissions and alter the CO2 biogeochemical cycling in coastal reservoirs. Further studies should characterize the diurnal variations, microbial mechanisms, and impact of meteorological conditions on reservoir CO2 emissions to expand our understanding of the carbon cycle in aquatic ecosystems.

Polyphenols separated from Enteromorpha clathrata by one-dimensional coupled with inner-recycling high-speed counter-current chromatography and their antioxidant activities

Algae polyphenols, derived from marine algae, have gained much attention in recent years for their diverse biological activities, such as antibacterial, antioxidant, anti-inflammatory, and cholesterol-lowering effects. Extraction, purification, and identification of individual compounds are difficult due to the broad range of molecular sizes and complex structures. In this paper, an efficient separation of polyphenols from Enteromorpha clathrata (E. clathrata), commonly found in the southeast coast of China, was achieved using ultrasonic-assisted extraction and multistage extraction followed by one-dimensional coupled with inner-recycling high-speed counter-current chromatography. The structure was identified by mass spectrometry and nuclear magnetic resonance spectra. Seven compounds with a purity of greater than 90% were separated from the ethyl acetate extract of E. clathrata, and identified as hydroquinone, gallic acid, (−)-epigallocatechin, caffeine, (−)-epicatechin, (−)-epigallocatechin-3-O-gallate, and epicatechin-3-O-gallate. These compounds were first separated and identified from E. clathrata. All of the six polyphenols exhibited potent antioxidant activity measured as 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, while (−)-epicatechin and epicatechin-3-O-gallate showed poor hydroxyl radical scavenging capacity, in comparison with Vitamin C (VC). The antioxidant activity of polyphenols with the same number of benzene rings was positively proportional to the number of phenolic hydroxyl groups. Esterification appeared to enhance the antioxidant activity of catechin and reduce the hydroxyl radical scavenging capacity of gallic acid. Our results about the separation, identification, and antioxidant activity of polyphenols from E. clathrata provide a basis for further elucidating the relationship between structure and antioxidant activity, which will promote the development and utilization of E. clathrata antioxidants.

Geology of the Macao Special Administrative Region (China)

ABSTRACT A 1:12,000 geological map of the Macao Special Administrative Region has been produced through detailed field work supported by petrographic, mineralogical, geochronological and geochemical data obtained in previous studies. This map aims to represent a reliable tool to understand the geological evolution of the region and for management of the territory. The geology of Macao is dominated by two groups of Jurassic granitic rocks belonging to an intrusive suite located along the coast of Southeast China: Macao Group I (MGI: 164.5 ± 0.6 to 162.9 ± 0.7 Ma) and Macao Group II (MGII: 156.6 ± 0.2 to 155.5 ± 0.8 Ma), including the associated microgranite, aplite and pegmatite dikes and quartz veins. Remnants of the metasedimentary wall-rock are present as Devonian xenoliths enclosed within the granites. Younger Jurassic to Cretaceous andesite to dacite dikes (150.6 ± 0.6 to <120 Ma) intrude the granitic rocks. Additionally, Quaternary sedimentary deposits cover the older lithologies.

Typhoon rainstorm simulations with radar data assimilation on the southeast coast of China

Abstract. As an effective technique to improve the rainfall forecast, data assimilation plays an important role in meteorology and hydrology. The aim of this study is to explore the reasonable use of Doppler radar data assimilation to correct the initial and lateral boundary conditions of the numerical weather prediction (NWP) systems. The Weather Research and Forecasting (WRF) model is applied to simulate three typhoon storm events on the southeast coast of China. Radar data from a Doppler radar station in Changle, China, are assimilated with three-dimensional variational data assimilation (3-DVar) model. Nine assimilation modes are designed by three kinds of radar data and at three assimilation time intervals. The rainfall simulations in a medium-scale catchment, Meixi, are evaluated by three indices, including relative error (RE), critical success index (CSI), and root mean square error (RMSE). Assimilating radial velocity at a time interval of 1 h can significantly improve the rainfall simulations, and it outperforms the other modes for all the three storm events. Shortening the assimilation time interval can improve the rainfall simulations in most cases, while assimilating radar reflectivity always leads to worse simulations as the time interval shortens. The rainfall simulations can be improved by data assimilation as a whole, especially for the heavy rainfall with strong convection. The findings provide references for improving the typhoon rainfall forecasts at catchment scale and have great significance on typhoon rainstorm warning.