Satellite precipitation products such as IMERG exhibit biases that vary with terrain, season, and precipitation regime, leaving the applicability boundaries of machine learning correction unclear. This study proposes the Terrain-Moisture-Intensity (TMI) framework, centered on mechanism purity, extending the correction problem from purely algorithmic optimization to physical consistency diagnosis. A proof-of-concept study in Hunan Province employs IMERG V07, SRTM DEM, and ERA5 variables (tcwv, u10, v10). Ablation results indicate that, under the conditions of this study, terrain-moisture relationships are predominantly additive: RF-Full yields merely +0.001 R^2 gain over LR-Full, while bias rises to 1.282 mm d^-1; MAE decreases by approximately 14

Satellite precipitation products such as IMERG are widely used in hydrometeorological operations, yet their biases are jointly influenced by terrain, season, and precipitation regime, leaving the applicability boundaries of machine learning correction unclear. This study proposes the Terrain–Moisture–Intensity (TMI) framework, which centers on mechanism purity to extend the correction problem from purely algorithmic optimization to physical consistency diagnosis. Based on a proof-of-concept study in Hunan Province, IMERG V07, SRTM DEM, and ERA5 variables (tcwv, u10, v10) are employed for correction analysis. Ablation results indicate that, under the conditions of this study, terrain–moisture relationships are predominantly additive: RF-Full yields merely +0.001 R2 gain over LR-Full, while bias rises to 1.282 mm d-1; MAE decreases by approximately 14%, reflecting a trade-off between tail-fitting improvement and mean shift. SHAP diagnostics identify three categories of boundaries. Spatially, Central Hunan exhibits significant degradation (R2 = 0.133) despite strong variable activation, consistent with mechanism fragmentation induced by mixed terrain. Temporally, u10 undergoes directional reversal between summer and spring (+0.096 to −0.156), presenting "silent failure." In intensity, extreme precipitation (≥50 mm d-1) more closely approximates a mechanism saturation frontier than isolated out-ofdistribution samples, with SHAP disorder intensifying with strength and DEM showing the largest relative amplification (approximately +150%). The results demonstrate that machine learning correction performance is primarily constrained by mechanism purity. The framework can be applied to pre-operational boundary identification, adaptive model selection, and physics-constrained feature engineering. A pre-registered cross-regional test (Hunan, Guangxi, Guangdong) confirms this screening capability out of sample: a priori coherence proxies predict correction efficiency with a mean absolute error of 2.6 percentage points, while the transfer-versus-retraining contrast separates mechanismmismatch (coastal Guangdong) from portability (Guangxi), establishing the framework as a validated applicability screen.

Air-sea CO2 flux in marginal sea is an important component of the global ocean carbon cycle. Located between the East China Sea and the northern South China Sea shelves which are both CO2 sinks, the southeastern coast of Mainland China has large potential of CO2 sequestration, but studies on air-sea CO2 fluxes in this region are very limited. Surface water CO2 partial pressure (pCO2) and auxiliary parameters from 51 cruises conducted in 2001–2022 were integrated to estimate the air-sea CO2 fluxes. Surface water pCO2 exhibited conspicuous spatial and temporal variabilities. The lowest pCO2 occurred in winter (349 ± 20 μatm), gradually increased in spring (357 ± 21 μatm) and summer (371 ± 35 μatm), and reached a peak in fall (392 ± 27 μatm). Surface water pCO2 was primarily modulated by vertical mixing and cooling during cold seasons, and by coastal upwelling and biological CO2 uptake in warm seasons. Vertical water mixing and temperature effect induced highest pCO2 in fall. Air-sea CO2 fluxes also exhibited strong seasonal variations. The study area acts as a moderate to strong CO2 sinks of 9.4 ± 5.5 and 3.7 ± 3.9 mmol m−2 d-1 in winter and spring, respectively, and a CO2 source of 3.8 ± 7.0 mmol m−2 d-1 in fall. In summer, the surface water CO2 is near equilibrium with the atmosphere with an air-sea CO2 flux of −0.6 ± 2.8 mmol m−2 d-1. The annual average air-sea CO2 fluxes is −2.6 ± 6.8 mmol m−2 d-1, indicating the study area acting as a weak to moderate sink annually. pCO2 difference between the surface water and the atmosphere is the main factor regulating the seasonal variations of air-sea CO2 flux, and wind speed also played an important role, enhancing CO2 sink in winter.

The densely populated East Asia is vulnerable to precipitation extremes. By utilizing a deep learning downscaled high-resolution (0.1°) dataset CLIMEA-BCUD (Climate Change for East Asia with Bias corrected UNet Dataset), changes in precipitation extremes over East Asia under different emission scenarios are investigated. Evaluation against observations from different sources (i.e., reanalysis-based, in situ-based and satellite-based) shows that CLIMEA-BCUD can reasonably reproduce the spatial patterns of the extreme precipitation indices, although it tends to overestimate CWD (consecutive wet days) in the Indo-China Peninsula. CLIMEA-BCUD exhibits good agreement with the magnitude of the observations and presents an obvious improvement in terms of bias, root mean square error, and correlation coefficient compared with the driving CMIP6 (Coupled Model Intercomparison Project Phase 6) models. The frequency and intensity of precipitation extremes are projected to increase in most parts of East Asia, especially over southern latitudes such as India and Indo-China. More pronounced increases in R10mm are also projected over the Tibetan Plateau. Record-breaking events, even those that break historical records by much higher magnitude, are becoming more frequent in a warmer climate. During 2071–2100, precipitation extremes that break the historical records by two or more standard deviations are three to five times more likely to occur somewhere in East Asia under SSP5-8.5 compared to those under SSP1-2.6. Potential hotspots of such record-breaking precipitation extremes are high-altitude areas such as the Tibetan Plateau, where the probability of experiencing record-breaking R95p, which breaks historical records by at least two standard deviations, is 40

The Northwestern Pacific Ocean is one of the most important carbon sink regions globally. However, spatial variability and seasonal amplitude of surface water CO2 partial pressure (pCO2) and air-sea CO2 fluxes remain unresolved. Surface seawater pCO2 and auxiliary parameters were investigated in the Northwestern Pacific (10–33°N, 120–158°E) during spring, summer and winter in 2019 and 2020. The air-sea CO2 fluxes exhibited pronounced seasonal variability, acting as a CO2 sink of 5.0 ± 4.1 mmol m−2 d−1 in winter and a CO2 source of 1.7 ± 1.6 mmol m−2 d−1 in summer. In summer, the CO2 source increased with latitude, with the 10–14°N sub-region near equilibrium with the atmosphere (0.6 ± 0.6 mmol m−2 d−1) and the 27–33°N sub-region displaying the strongest source (3.6 ± 2.1 mmol m−2 d−1). The air-sea CO2 flux is primarily driven by variability in surface water pCO2. During summer, surface water pCO2 increases with latitude (408.4 ± 5.1, 418.2 ± 9.0 and 455.5 ± 12.4 μatm in 10–14°N, 14–27°N and 27–33°N, respectively), showing a “strange” pattern inverse with sea surface temperature. Temperature normalized pCO2 (NpCO2) also increases with latitude. In winter, surface water pCO2 generally decreases with latitude (379.4 ± 3.8, 372.9 ± 9.1 and 354.5 ± 3.6 μatm in 10–14°N, 14–27°N and 27–33°N, respectively), but NpCO2 increased with latitude (356.7 ± 7.7, 387.2 ± 13.1 and 434.4 ± 4.4 μatm in 10–14°N, 14–27°N and 27–33°N, respectively). In addition to the dominating temperature effect, different sub-regions have their own unique processes that affect the pCO2 behavior which in turn influences the air-sea CO2 fluxes. In the western zone (west of 130°E) of the 10-14°N sub-region, precipitation reduces pCO2 by 12.4 ± 5.2 μatm in summer and 14.8 ± 4.4 μatm in winter. In the 14-27°N sub-region, the relatively high NpCO2 is primarily driven by evaporation, with elevated salinity increasing surface water NpCO2 by 11.1 ± 12.7 μatm in summer and 7.7 ± 15.3 μatm in winter. The 27–33°N sub-region is located in the Subtropical Mode Water and atmospheric CO2 intrusion (increasing pCO2 by 44.2 μatm) also have important contributions to the high NpCO2. Under the context of global warming, the regional changes, such as variations in evaporation and precipitation, have the potential to significantly alter global ocean CO2 sink/source patterns and weaken the surface ocean’s CO2 sequestration ability.

We examined the sub-seasonal to interannual variability and multi-year trend of sea surface CO2 partial pressure (pCO2) and air-sea CO2 flux at a coastal site of the East China Sea (31⁰N, 122.8⁰E) based on high-frequency time-series data collected by a buoy since 2013. Seasonal average sea surface pCO2 was highest in autumn, but the lowest value can appear in winter or spring, depending on the biological productivity in spring. The seasonal amplitude of pCO2 was up to 123 μatm. Based on property-property relationships and a simple mass budget model, we found that temperature change, biological activity, water mixing and air-sea CO2 exchange all made significant contributions to the seasonal variation of pCO2. From winter to summer, seasonal warming and atmospheric CO2 uptake elevated the pCO2, while net biological production, weakened vertical mixing and the retreat of the Yellow Sea Coastal Water (YSCW) lowered the pCO2. Conversely, from summer to winter, seasonal cooling and CO2 emission lowered the pCO2, while respiration, enhanced vertical mixing and the YSCW intrusion raised them up. Over short-term timescale, biological production and respiration frequently drew down or elevated the pCO2 by 150-400 μatm within 5-10 days during warm months. When biological activity was suppressed during cold months, such short-term variations were dominated by water mixing with a smaller pCO2 amplitude of 5-60 μatm within 2-6 days. This site was a sink of atmospheric CO2 in winter and spring, but a CO2 source in summer and autumn. Annually, it was a moderate CO2 source in 2014 (air-sea CO2 flux was 2.88 ± 11.02 mmol m−2 d−1), a weak CO2 sink in 2016 (-0.21 ± 12.23 mmol m−2 d−1), and a weak CO2 source in the combined year of the first half of 2017 and the second half of 2018 (0.40 ± 9.11 mmol m−2 d−1). The relatively high CO2 source in 2014 was likely due to the weaker biological production in spring and more typhoon passage in autumn. From 2013 to 2019, the wintertime sea surface pCO2 didn’t follow the increasing trend of the atmospheric pCO2, leading to an enhancing carbon sink in winter.

This study reports the surface water partial pressure of CO2 (pCO2) and air-sea CO2 fluxes on the East China Sea shelf off the Changjiang estuary in August 2023. Surface water pCO2 ranged from 110 μatm to 910 μatm with an average value of 427±154 μatm. Air-sea CO2 fluxes in the surveyed area ranged from −20.6 mmol m−2 d−1 to 35.9 mmol m−2 d−1 and averaged 3.0±8.9 mmol m−2 d−1 (a moderate source), which was contrary to this region generally being a CO2 sink during summer. Changjiang discharge played a key role in regulating surface water pCO2; the decreased Changjiang discharge in August 2023 increased surface water pCO2 on the adjacent inner shelf substantially, and the high sea surface temperature further elevated the surface water pCO2. The combined effect of drought and high temperatures in August 2023 turned the study area from a CO2 sink to a CO2 source. Under the context of global change, climate events such as floods, droughts and heatwaves occur more frequently, which will continue to add more complexity to CO2 sink/source evaluations in large river-dominated marginal seas and suggest further research is needed.

Mangrove and salt-marsh wetlands are important coastal carbon sinks. In order to quantify carbon export via pore water exchange and to evaluate subsequent fate of the exported carbon, we carried out continuous observations in a mangrove-Spartina alterniflora ecozone in the Zhangjiang River Estuary, China. The carbon fluxes via pore water exchange were estimated using 222Rn and 228Ra as tracers to be (2.15 ± 0.63) mol/(m2·d) for dissolved inorganic carbon (DIC) and (-0.008 ± 0.07) mol/(m2·d) for dissolved organic carbon (DOC) in the wet season and (3.02 ± 0.65) mol/(m2·d) for DIC and (-0.15 ± 0.007) mol/(m2·d) for DOC in the dry season in the mangrove-dominated creek (M-creek), while (2.52 ± 0.82) mol/(m2·d) for DIC and (0.02 ± 0.09) mol/(m2·d) for DOC in the dry season in the S. alterniflora-dominated creek (SA-creek). The negative value means that pore water was a sink of DOC in the creek. The total carbon via pore water exchange in the tidal creeks in the mangroves accounted for 41

This study examined carbonate dynamics in the northwestern South China Sea (NWSCS), an area jointly influenced by upwelling, river plumes and submarine groundwater discharge. Data were obtained from two cruises conducted in summer 2009 and 2012. In 2009, a high salinity-low temperature water mass occurred nearshore off northeastern Hainan Island, indicative of upwelling, commonly referred to as HNEU. A river plume fueled primarily by local rivers and characterized by low salinity and high temperature was observed in the NWSCS off the mainland roughly along the 30 m isobath. In 2012, coastal upwelling off northeastern Hainan Island was not detectable at the surface, but was observed at a different location off eastern Hainan Island (HEU). River plume waters in 2012 were patchily distributed, with a low salinity zone further westerly than that in 2009 and another on the mid-shelf of the NWSCS sourced from the Pearl River which reached out ∼250 km from the mouth of the Pearl River Estuary. In 2009, elevated dissolved inorganic carbon (DIC) and total alkalinity (TA) occurred in the coastal plume, where submarine groundwater discharge contributed DIC and TA additions of 38.9±20.5 and 42.5±22.3 µmol kg −1 , respectively, with a DIC/TA ratio of ∼0.92, which made a minor contribution to the variation of seawater partial pressure of CO 2 ( p CO 2 ), pH and the aragonite saturation state index (Ω arag ). Additionally, high surface phytoplankton production consumed DIC of 10.0±10.4 µmol kg −1 but did not significantly affect TA, which dominated p CO 2 drawdown in the coastal plume water and increased the pH and Ω arag at surface. Submarine groundwater discharge was also observed in the region influenced by upwelling, but to a lesser degree than that impacted by coastal plume. Lower pH and Ω arag and higher p CO 2 values than in offshore waters were observed downstream of the upwelling system, attributable largely to organic matter remineralization with a DIC addition of 23.8±8.4 µmol kg −1 . In 2012, submarine groundwater discharge was not detected but high phytoplankton production dominated carbonate dynamics in the coastal plume water with a net DIC consumption of 104.2 µmol kg −1 , which markedly drew down sea surface p CO 2 and increased pH and Ω arag . In the Pearl River Plume, the solubility-driven CO 2 sink exceeded biological CO 2 uptake, resulting in an additional decrease of pH and Ω arag and increase of seawater p CO 2 . Taken together, this study demonstrated complex spatial and year-to-year variability, and the controls of the carbonate system under the joint modulations of upwelling, river plumes and submarine groundwater discharge. A first order estimate that considered the rise of atmospheric CO 2 and seawater temperature further suggested a high risk of ocean acidification in this coastal area by the end of this century, which could be amplified under the stresses of river plumes, submarine groundwater discharge and organic matter remineralization.

We examined the diurnal to seasonal dynamics of the sea surface partial pressure of carbon dioxide (pCO(2)) in a subtropical nearshore estuarine system, Hangzhou Bay, adjacent to the Changjiang Estuary in the vicinity of the East China Sea, based on data collected between July 30, 2010 to September 20, 2011 by a surface buoy equipped with an autonomous pCO(2) system along with hydrological and other chemical sensors. The study site (122.37 degrees E, 30.55 degrees N) is influenced by the river plumes of both the Changjiang and Qiantang River and is characterized by strong tidal circulation and highly turbid waters. The amplitude of pCO(2) changes increased from winter to summer over both diurnal and spring-neap tidal cycle timescales. The average surface water pCO(2) was slightly undersaturated with respect to the atmosphere in winter (382 +/- 18 mu atm), but supersaturated in spring (500 +/- 56 mu atm) and summer (687 +/- 110 mu atm). Overall the study site was a source of atmospheric CO2 with an average sea to air flux of 14 +/- 9 mmol C m(-2) d(-1) from January to October 2011. We revealed factors controlling the pCO(2) dynamics at different timescales. Over seasonal timescales, temperature and estuarine mixing dominated the seawater pCO(2) variability. Over spring-neap tidal timescales in winter and spring, the major drivers were similarly water mass mixing and temperature. However, in summer, biological activity and air-sea exchange became the two principal factors controlling the variations in surface seawater pCO(2). Our mass balance models further suggested that biological processes impacted surface pCO2 differently during different tidal phases. Respiration was revealed to promote the increase in pCO(2) during spring tide in August, but in neap tides of the same month biological production was evident and resulted in the drawdown of pCO(2). This is because photosynthesis was generally limited by light in summer at the study site due to high turbidity, except during neap tides when turbidity was dramatically drawn down, triggering high biological productivity. At the diurnal timescale, sea surface pCO(2) was primarily controlled by tidal mixing, except during neap tides in summer when sea surface pCO(2) was greatly influenced by biological metabolism. This study also revealed significant inter-summer differences between 2010 and 2011, showing lower sea surface pCO(2) in August 2010 as compared to August 2011, which was likely due to the enhanced biological uptake as a result of the relatively low turbidity caused by weak tidal currents and enhanced river flow in August 2010. Our study highlights a highly dynamic system primarily driven by tidal mixing, which not only modulates water mass mixing but also affects turbidity, which subsequently controls biological production. These processes led to a synergy of CO2 dynamics in a tidally driven and highly turbid nearshore system, where high frequency time-series observations are essential to reveal the complex controls of CO2 dynamics.

In order to examine the sources of plutonium (Pu) and elaborate its scavenging and accumulation processes, 240Pu/239Pu atom ratios and 239+240Pu activities in the water column of the South China Sea (SCS) were determined and compared with our previously reported data for the sediments. Consistently high 240Pu/239Pu atom ratios that ranged from 0.184-0.250 (average=0.228±0.015), indicative of non-global fallout Pu sources were observed both in the surface water and at depth during 2012-2014. The spatial distribution of the 240Pu/239Pu atom ratio in the SCS showed a decreasing trend away from the Luzon Strait, which was very consistent with the introduction pathway of the Kuroshio Current. The Kuroshio had an even heavier Pu isotopic ratio ranging from 0.250-0.263 (average=0.255±0.006), traceable to the non-global fallout Pu signature from the Pacific Proving Grounds (PPG). Using a simple two end-member mixing model, we further revealed that this PPG source contributed 41±17% of the Pu in the SCS water column. The 239+240Pu activities in the SCS surface seawater varied from 1.59 to 2.94mBqm-3, with an average of 2.34±0.38mBqm-3. Such an activity level was ~40% higher than that in the Kuroshio. The distribution of 239+240Pu in the surface seawater further showed a general trend of increase from the Kuroshio to the SCS basin, suggesting significant accumulation of Pu within the SCS. The 239+240Pu inventory of the water column in the SCS basin at the SEATS station with a total depth of ~3840m was estimated to be ~29Bqm-2, which was substantially higher than the sediment core estimates made for the SCS basin (3.75Bqm-2) but much lower than the sediment core estimates made for the shelf of the northern SCS (365.6Bqm-2). Such differences were determined by the lower scavenging efficiency of Pu in the SCS basin compared to the northern SCS shelf.

This study examined Pu source terms in the western North Pacific (WNP) based on data collected in 2014 and 2015. The basin wide Pu-240/Pu-239 atom ratios ranged from 0.227 to 0.263 with an average value of 0.244 +/- 0.011, consistently higher than that of global fallout (similar to 0.180). The spatial distribution of Pu-240/Pu-239 atom ratios showed higher values within the Kuroshio region, the main western ocean boundary current, as compared to the zone off of the Kuroshio. There was also an overall decreasing trend of Pu-240/Pu-239 along the Kuroshio path to its extensions. Pu239+240 activities in surface seawater exhibited a wide range from 1.15 to 4.30 mBqm(-3) and their spatial distribution showed an increasing trend with latitude. Unlike the Pu-240/Pu-239 atom ratios, which had heavier isotopic compositions in the Kuroshio mainstream compared to the zone off of the Kuroshio, the Pu239+240 activities were higher outside the Kuroshio than within the Kuroshio. These patterns in both Pu isotopic ratios and activities point towards a unique close-in fallout source, which levels down in its source term and has a high degree of scavenging during its transport along the Kuroshio, and can be traced back to a precursor, the North Equatorial Current, which originates near the Pacific Proving Grounds (PPG) with characteristically higher Pu-240/Pu-239 atom ratios. High Pu-240/Pu-239 atom ratios found in the zone outside the Kuroshio were transported from the Kuroshio via the formation and circulation of North Pacific Intermediate Water. We further revealed, using a simple two end-member mixing model, that the PPG source contributed 60 +/- 13% of the Pu in the Kuroshio zone and 45 +/- 10% in the zone off of the Kuroshio. Both the comparison of Pu isotopic composition in the WNP within a radius of 500 km or 1000 km off the Fukushima Daiichi Nuclear Power Plant (FDNPP) between prior to and post the accident and a simple first order mass balance calculation in terms of atmospheric deposition and release suggest that the Pu originating from the FDNPP accident, if any, was either negligible, or the input flux of Pu239+240 was too small to significantly alter the Pu isotopic composition in the ambient seawater. This article is part of a special issue entitled: "Cycles of trace elements and isotopes in the ocean - GEOTRACES and beyond" - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. Gonzalez.

The medium composition for poly-β-hydroxybutyrate(PHB) production by Ralstonia eutropha H16 was optimized in this paper.Based on the single factor experiments,two most significant factors(initial carbon source concentration and initial C/N ratio) on Ralstonia eutropha H16 growth and PHB accumulation were confirmed by the Plackett-Burman design.According to response surface analysis,the optimal fermentation medium was composed as following:glucose 28.8 g/L,yeast extract 0.2 g/L,C/N ratio 5,KH2PO4 1.0 g/L,Na2HPO4 0.3 g/L,MgSO4 1.0 g/L,CaCl2 0.1 g/L,ZnSO4 0.65 mg/L,FeSO4 0.1 mg/L,(NH4)6Mo7O24 0.3 mg/L,H3BO3 0.3 mg/L,and pH 7.0.Under this optimal conditions,the biomass and the PHB concentration reach 16.1 g/L and 7.9 g/L,respectively.Conversion of glucose is 64% and 32% based on cells and PHB,respectively.

目前,随着中资保险市场开放程度越来越高,外资保险企业开始掀起一场以抢占中国保险市场为目的的“圈地运动,”国内保险市场上的竞争悄然升级,外资保险企业的整体竞争实力开始凸显。中资保险企业应当如何面对这场“圈地运动”?本文通过资本运营、产品开发和创新、市场开发能力、品牌塑造等方面将中资保险企业和外资保险企业进行了一一比较,指出二者存在的差距,得出中资保险企业只有不断地提升自身的核心竞争力,才能在这场“圈地运动”中争取主动,扩大自身的市场份额,在与外资保险企业的竞争过程中立于不败之地。