Air-sea heat flux exchange over the South China Sea under different weather conditions before and after southwest monsoon onset in 2000

With the data observed from the Second SCS Air-Sea Flux Experiment on the Xisha air-sea flux research tower, the radiation budget, latent, sensible heat fluxes and net oceanic heat budgets were caculated before and after summer monsoon onset. It is discovered that, after summer monsoon onset, there are considerable changes in air-sea fluxes, especially in latent heat fluxes and net oceanic heat budget. Furthermore, the analyzed results of five synoptic stages are compared. And the characteristics of the flux transfer during different stages around onset of South China Sea monsoon are discussed. The flux change shows that there is an oceanic heat accumulating process during the pre-onset and the break period, as same as oceanic heat losing process during the onset period. Moreover, latent fluxes, the water vapor moving to the continent, even the rainfall appearance in Chinese Mainland also can be influenced by southwester. Comparing Xisha fluxes with those obtained from the Indian Ocean and the western Pacific Ocean, their differences may be observed. It is the reason why SSTs can keep stable over the South China Sea while they decrease quickly over the Arabian Sea and the Bay of Bengal after monsoon onset.

The Effect of Bioturbation Activity of the Ark Clam Scapharca subcrenata on the Fluxes of Nutrient Exchange at the Sediment–Water Interface

Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems.Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coastal areas owing to its tremendous economic value.However,there is little information regarding the effects of the bioturbation of S.subcrenata on the fluxes of nutrient exchange in the sediment-water interface(SWI).In this regard,S.subcrenata was sampled during October 2016 to determine the effects of its bioturbation activity on the nutrient exchange flux of the SWI.The results showed that the biological activity of S.subcrenata could increase the diffusion depth and the rate of the nutrients exchange in the sediments.The bioturbation of S.subcrenata could allow the nutrients to permeate into the surface sediments at 6-10cm and increase the release rate of nutrients at the SWI.The releasing fluxes of DIN and PO43−-P in the culture area were found to be around three times higher than that in the non-cultured region.The culture of S.subcrenata has been proved to be an important contributor to nutrient exchange across the SWI in the farming area of Haizhou Bay.Nutrients exchange in the SWI contributes a part of 86%DIN,71%PO43−-P and 18%SiO32−-Si for the aquaculture farm.

Response of IAP/LASG GOALS Model to the Coupling of Air-Sea Fresh Water Exchange

The process of air—sea fresh water exchange is included successfully in the Global— Ocean—Atmosphere Land—System model developed at the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG). The results of the coupled integration show that the climate drift has been controlled successfully. Analyses on the responses of ocean circulation to the changes of surface fresh water or salinity forcing show that the ocean spin-up stage under flux condition for salinity is the key to the implementation of air-sea fresh water flux coupling. This study also demonstrates that the Modified—Monthly—Flux—Anomaly coupling scheme (MMFA) brought forward by Yu and Zhang (1998) is suitable not only for daily air—sea heat flux coupling but also for daily fresh water flux coupling. Key words Fresh water flux - Air-sea coupling - Thermohaline circulation This work was co-supported by the National Key Project (Grant No.96-908-02-03), the Excellent National Key Laboratory Research Project (Grant No.49823002) and Chinese Academy of Sciences (CAS) under grant “ Bai Ren Ji Hua? for “Validation of Coupled Climate Models”.

Observing the air-sea turbulent heat flux on the trajectory of tropical storm Danas

Tropical cyclones constitute a major risk for coastal communities.To assess their damage potential,accurate predictions of their intensification are needed,which requires a detailed understanding of the evolution of turbulent heat flux(THF).By combining multiple buoy observations along the south north storm track,we investigated the THF anomalies associated with tropical storm Danas(2019)in the East China Sea(ECS)during its complete life cycle from the intensification stage to the mature stage and finally to its dissipation on land.The storm passage is characterized by strong winds of 10-20 m/s and a sea level pressure below 1000 hPa,resulting in a substantial enhancement of THF.Latent heat(LH)fluxes are most strongly affected by wind speed,with a gradually increasing contribution of humidity along the trajectory.The relative contributions of wind speed and temperature anomalies to sensible heat(SH)depend on the stability of the boundary layer.Under stable conditions,SH variations are driven by wind speed,while under near-neutral conditions,SH variations are driven by temperature.A comparison of the observed THF and associated variables with outputs from the ERA 5 and MERRA 2 reanalysis products reveals that the reanalysis products can reproduce the basic evolution and composition of the observed THF.However,under extreme weather conditions,temperature and humidity variations are poorly captured by ERA 5 and MERRA 2,leading to large LH and SH errors.The differences in the observed and reproduced LH and SH during the passage of Danas amount to 26.1 and 6.6 W/m^(2) for ERA 5,respectively,and to 39.4 and 12.5 W/m^(2) for MERRA 2,respectively.These results demonstrate the need to improve the representation of tropical cyclones in reanalysis products to better predict their intensification process and reduce their damage.

CO_2 exchange at air-sea interface in the Huanghai Sea

During the Huanghai Sea Circulation and Material Flux Expedition in Spring 1996, fco_2 in surface water and atmosphere was measured. The fco2 in surface water varied in a range from 220 to 360 uatm1) while atmospheric concentration was nearly constant at 360μatm, showing that the Huanghai Sea surface waters were undersaturated with respect to atmospheric Co during the time of investigation. A model was developed in this study in order to estimate the Co flux at the air-sea interface. The model incorporates the time-series variations of the distributions in SST (sea surface temperature), salinity, mixed-layer depth, atmospheric fco2, gas-transfer velocity, and CZCS chlorophyll concentration in the Huanghai Sea and was calibrated with the observed fco2 data. The primary parameter affecting fco2 in surface water is the variation of SST through time. The annual fluxes of Co are estimated as 0. 033 Gt C from the sea into the atmosphere and 0. 044 Gt C from the air into sea. The Huanghai Sea, thus behaves as a CO2 sink absorbing 0. 011 Gi C of CO2 a year. which.corresponds to about 0. 5 % of global oceanic absorption capacity.

Interannual variations of the air-sea carbon dioxide exchange in the different regions of the Pacific Ocean

Interannual variations of the air-sea CO2 exchange from 1965 to 2000 in the Pacific Ocean are studied with a Pacific Ocean model. Two numerical experiments are performed, including the control run that is forced by climatological monthly mean physical data and the climate-change run that is forced by interannually varying monthly mean physical data. Climatological monthly winds are used in both runs to calculate the coefficient of air-sea CO2 exchange. The analysis through the differences between the two runs shows that in the tropical Pacific the variation of export production induced by interannual variations of the physical fields is negatively correlated with that of the air-sea CO2 flux, while there is no correlation or a weak positive correlation in the subtropical North and South Pacific. It indicates that the variation of the physical fields can modulate the variation of the air-sea CO2 flux in converse ways in the tropical Pacific by changing the direct transport and biochemical process. Under the interannually varying monthly mean forcing, the simulated EOF 1 of the air-sea CO2 flux is basically consistent with that of sea surface temperature （SST） in the tropical Pacific, but contrary in the two subtropical Pacific Ocean. The correlation coefficient between the regionally integrated air-sea CO2 flux and area-mean SST shows that when the air-sea CO2 flux lags SST by about 5 months, the positive coefficient in the three regions is largest, indicating that in the tropical Pacific or on the longer time scale in the three regions, physical processes control the fiux-SST relationship.

A comparative study of the land-atmosphere energy and water exchanges over the Tibetan Plateau and the Yangtze River Region

正确认识不同区域能量和水分循环特征是研究局地地气相互作用及准确预测区域天气,气候变化的关键.为了研究属于干旱/半干旱气候的青藏高原(TP)和湿润/半湿润气候的长江流域(YRR)之间地表能量和水分交换的异同,本文对比分析了两个区域8个不同地表类型(包括高山荒漠,高山草地,(平原)城市和(平原)草地等)观测站点的地表辐射和能量通量数据.结果显示:(1)TP由于高原大气层稀薄且空气洁净,年平均入射短波辐射为251.3W m^(-2),是YRR的1.7倍.加之高原地表反照率高导致反射辐射(59.6 W m^(-2))是YRR的2.87倍.入射及出射的长波辐射为231.5和338.0 W m^(-2),分别为YRR的0.64和0.83.而两个区域的净辐射差异不大;(2)草地站更多的潜热释放使得地表总加热效率高于城市和高山荒漠,TP和YRR的草地站的年平均潜热分别为35.0和38.8 W m^(-2),而植被稀疏且土壤干燥的高山荒漠地区感热最大,年平均感热为42.1 W m^(-2);其次是城市下垫面,其年平均感热为37.7 W m^(-2).研究结果揭示了不同气候背景下典型下垫面地气相互作用特征,为地气相互作用过程深入分析奠定了基础.

Analysis of the air-sea heat exchange during the El Nino event in 1983

In this paper,by using the ECMWF objective analysed data as well as CAC and NOAA grid point data of 1981 and 1983,the sensible and latent heat fluxes at the air and sea boundary surface within the range of 45°E-75°W, 35°N-35°S over the Pacific and the Indian Ocean are calculated. The purpose is to analyse the different revealing features during the mature stage and at the end of the 1982 -1983 El Nino event and to compare the difference of the features between thd El Nino and the normal. The result shows that the air and sea heat exchange west of the dateline over the central tropical Pacific during the EJ Nino period is more intense than that of the normal. However,the fluxes of the sensible and latent heat on the sea surface with strong warming of SSTneat by and on the south side of the equator east of 170°W are low and even negative,and the patterns of the sensible and latent heat fluxes over the Indian Ocean during the year of 1983 are similer to that of normal. Spatial patterns of the sensible heat ,the latent heat,SST,OLR and the wind speed exhibit large anomalies during the El Nino event. The corresponding relationships of the spatial distribution of the streng exchange of heat fluxes with regions of high SST and action convection or negative anomalies of OLR are relatively complicated. But the region of maximum air and sea heat exchange is in good coincidence with that of high value of the Vs. The strong heat exchange is weakened with the declining and the finishing of the El Nino event in the central tropical Pacific.

Laminar Heat Transfer Modeling and Investigation of Thermal Dispersion in a Flat Plate Heat Exchanger： Estimating Heat Transfer Coefficient, Heat Flux and Nusselt Number

PHEs （plate heat exchangers） are among the most common thermal equipments in diverse industries particularly in oil and gas companies. This wide usage is obviously due to significant benefits of these heat exchangers over other types. In this article, a behavioral analysis of heat transfer in fiat plates of these heat exchangers in laminar flow situation through CFD （computational fluid dynamics） simulation using FLUENT 6.3.26 software is done. The study reveals results graphically based on fluid＇s behavior in co-current and counter current flows and discusses thermal indexes consisting of heat transfer coefficient, Nusslet and total heat flux in both conditions. Eventually, a comparison via the graphical results is presented between the two types of flow directions.

Role of Kuroshio frontal eddy in exchange between shelf water and Kuroshio water in East China Sea

Basic patterns of the reversal of the Kuroshio water toward the shelf, intrusion of the shelf mixed water into the Kuroshio and uplifting of the near-bottom nutrient-rich water into the upper layer by the pumping of the frontal eddy are analyzed on the basis of satellite infrared images and hydrologic, chemical and biological observations. Results show that the Kuroshio frontal eddies play a very important role in the exchange between the shelf water and the Kuroshio water. The estimation of the average volume transports for three frontal eddy events indicates that the shelf mixed water entrained by an eddy into Kuroshio is 0.44×10~6 m3/s and the reversal Kuroshio water onto the shelf region only 0.04×10~6 m3/s. Along the whole shelf edge, the volume transport of the shelf mixed water entrained by the eddies into the Kuroshio is 1.8×10~6 m3/s. The nutrient (NO3-N) flux pumped to the euphotic zone and input to the continental shelf through a column with 1 m wide is 974 μmol/(s·m) when there is frontal eddy and only 79 μmol/(s·m) in the case of no frontal eddy. Yearly nutrient (NO3-N) flux input to the shelf area caused by the frontal eddy is 1.7×10~5 t/a.

Modelling Air-Sea Fluxes during a Western Pacific Typhoon:Role of Sea Spray

It has long been recognized that the evolution of marine storms may be strongly affected by the flux transfer processes over the ocean. High winds in a storm can generate large amounts of spray, which can modify the transfer of momentum, heat, and moisture across the air-sea interface. However, the role of sea spray and air-sea processes in western Pacific typhoons has remained elusive. In this study, the impact of sea spray on air-sea fluxes and the evolution of a typhoon over the western Pacific is investigated using a coupled atmosphere-sea-spray modeling system. Through the case study of the recent Typhoon Fengshen from 2002, we found that: (1) Sea spray can cause a significant latent heat flux increase of up to 40% of the interfacial fluxes in the typhoon; (2) Taking into account the effects of sea spray, the intensity of the modeled typhoon can be increased by 30% in the 10-m wind speed, which may greatly improve estimates of storm maximum intensity and, to some extent, improve the simulations of overall storm structure in the atmospheric model; (3) The effects of sea spray are mainly focused over the high wind regions around the storm center and are mainly felt in the lower part of the troposphere.

The partial pressure of carbon dioxide and air-sea fluxes in the Changjiang River Estuary and adjacent Hangzhou Bay

The distributions of partial pressure of carbon dioxide （pCO2） in the surface waters of the Changjiang River Estuary and adjacent Hangzhou Bay were examined in the summer of 2010. Surface water pCO2 ranged from 751-2 095/zatm （1 atm=101 325 Pa） in the inner estuary, 177-1 036/zatm in the outer estuary, and 498-1 166 μatm in Hangzhou Bay. Overall, surface pCO2 behaved conservatively during the estuary mixing. In the inner estuary, surface pCO2 was relatively high due to urbanized pollution and a high respiration rate. The lowest pCO2 was observed in the outer estuary, which was apparently induced by a phytoplankton bloom because the dissolved oxygen and chlorophyll a were very high. The Changjiang River Estuary was a significant source of atmospheric CO2 and the degassing fluxes were estimated as 0-230 mmol/（m2.d） [61 mmol/（m2.d） on average] in the inner estuary. In contrast, the outer estuary acted as a CO2 sink.

A primary study of the correlation between the net air-sea heat flux and the interannual variation of western North Pacific tropical cyclone track and intensity

A singular value decomposition （SVD） analysis is carried out to reveal the relationship between the interannual variation of track and intensity of the western North Pacific tropical cyclones （WNPTCs） in the tropical cyclone （TC） active season （July–November） and the global net air-sea heat flux （Q net ） in the preceding season （April–June）. For this purpose, a tropical cyclone track and intensity function （TIF） is defined by a combination of accumulated cyclone energy （ACE） index and a cyclone track density function. The SVD analysis reveals that the first mode is responsible for the positive correlation between the upward heat flux in the tropical central Pacific and the increased activity of western North Pacific （WNP） TIF, the second mode for the positive correlation between the upward heat flux in the North Indian Ocean and the northeastward track shift of WNPTCs and the third mode for the negative correlation between the upward heat flux in mid-latitude central Pacific and the northwest displacement of the WNP TC-active center. This suggests that Q net anomalies in some key regions have a substantial remote impact on the WNP TC activity.

Numerical Study of Water and Suspended Matter Exchange Between the Yellow Sea and the East China Sea

POM was used to study the monthly mean circulation in the Yellow Sea and East China Sea. The calculated results showed almost all major characteristics of the circulation system. The calculated circulation system and observational data were used to determine the sediment concentration, volume transport, heat flux and suspended matter flux between the Yellow Sea and the East China Sea. The conclusions obtained were that the volume and heat are transported northward through the 32°N section during each season; that in winter and autumn, total suspended matter is transported southward, and is larger in winter than in autumn. The reason is that the Yellow Sea Coastal Current is strong and always contains more suspend matter in winter and autumn. The seasonal suspended matter exchange between the Yellow Sea and the East China Sea are 0.58×10 7 tons in spring, 2.81×10 7 tons in summer, -2.60×10 7 tons in autumn and -3.40×10 7 tons in winter. Net flux of suspended matter from the Yellow Sea to the East China Sea is 2.61×10 7 tons every year.

Cholangiocyte anion exchange and biliary bicarbonate excretion

Primary canalicular bile undergoes a process of fluidization and alkalinization along the biliary tract that is influenced by several factors including hormones, innervation/neuropeptides, and biliary constituents. The excretion of bicarbonate at both the canaliculi and the bile ducts is an important contributor to the generation of the so-called bile-salt independent flow. Bicarbonate is secreted from hepatocytes and cholangiocytes through parallel mechanisms which involve chloride efflux through activation of Cl- channels, and further bicarbonate secretion via AE2/SLC4A2-mediated Cl-/HCO3- exchange. Glucagon and secretin are two relevant hormones which seem to act very similarly in their target cells （hepatocytes for the former and cholangiocytes for the latter）. These hormones interact with their specific G protein-coupled receptors, causing increases in intracellular levels of cAMP and activation of cAMP-dependent Cl- and HCO3- secretory mechanisms. Both hepatocytes and cholangiocytes appear to have cAMP-responsive intracellular vesicles in which AE2/SLC4A2 colocalizes with cell specific Cl- channels （CFTR in cholangiocytes and not yet determined in hepatocytes） and aquaporins （AQP8 in hepatocytes and AQP1 in cholangiocytes）, cAMP-induced coordinated trafficking of these vesicles to either canalicular or cholangiocyte lumenal membranes and further exocytosis results in increased osmotic forces and passive movement of water with net bicarbonate-rich hydrocholeresis.

Net water vapour exchange over a mixed needle and broad-leaved forest in Changbai Mountain during autumn

Water vapour and CO2 fluxes were measured by the eddy-covariance technique above a mixed needle and broad-leaved forest with affiliated meteorological measurements in Changbai Mountain as part of China's FLUX projects since late August in 2002. Net water vapour exchange and environmental control over the forest were examined from September 1 to October 31 in 2002. To quantify the seasonal dynamics, the transition period was separated into leafed, leaf falling and leafless stages according to the development of leaf area. The results showed that (a) seasonal variation of water vapour exchange was mainly controlled by net radiation (Rn) which could account for 78.5%, 63.4% and 56.6% for leafed, leaf falling and leafless stages, respectively, while other environmental factors' effects varied evidently; (b) magnitude of water vapour flux decreased remarkably during autumn and daily mean of water vapour exchange was 24.2 mg m-2 s-1 (100%), 14.8 mg m-2 s-1 (61.2%) and 10.3 mg m-2 s-1 (42.6%) for leafed, leaf falling and leafless stage, respectively; and (c) the budget of water vapour exchange during autumn was estimated to be 87.1 kg H2O m-2, with a mean of 1427.2 g H2O d-1' varying markedly from 3104.0 to 227.5 g H2O m-2d-1.

Application of ESMD Method to Air-Sea Flux Investigation

The ESMD method can be seen as a new alternate of the well-known Hilbert-Huang transform (HHT) for non-steady data processing. It is good at finding the optimal adaptive global mean fitting curve, which is superior to the common least-square method and running-mean approach. Take the air-sea momentum flux investigation as an example, only when the non-turbulent wind components is well extracted, can the remainder signal be seen as actual oscillations caused by turbulence. With the aid of —5/3 power law for the turbulence, a mode-filtering approach based on ESMD decomposition is developed here. The test on observational data indicates that this approach is very feasible and it may greatly reduce the error caused by the non-turbulent components.

A motion correction on direct estimations of air-sea fluxes from a buoy

A flux system deployed on a moored buoy has been described, which is capable of directly estimating the airsea fluxes after removing the contamination in the signal due to buoy motion. A triple loop fitting method has been demonstrated for determining the three angular offsets between measurement axes of the sonic anemometer and motion pack. The data collected in an experiment in the Northern Huanghai Sea is used to correct the three sonic anemometer measurements of turbulent wind for buoy motion. The effective removal of wave-scale motion from the spectra and cospectra are demonstrated. Estimates of along-wind momentum flux, sensible heat flux and latent heat flux calculated by the eddy correlation method based on data obtained by sonic anemometer 81000V are shown to be in the same trend and scale with those determined by the bulk aerodynamic method after motion correction. The motion correction not only greatly improve the estimation of the momentum flux but also has a great impact on the calculated sensible heat flux.

Distributions and air-sea fluxes of CO_2 in the summer Bering Sea

The 3rd Chinese National Arctic Research Expedition （CHINARE-Arctic III） was carried out from July to September in 2008. The partial pressure of CO2 （pCO2） in the atmosphere and in surface seawater were determined in the Bering Sea during luly 11-27, 2008, and a large number of seawater samples were taken for total alkalinity （TA） and total dissolved inorganic carbon （DIC） analysis. The distributions of CO2 parameters in the Bering Sea and their controlling factors were discussed. The pCO2 values in surface seawater presented a drastic variation from 148 to 563 laatm （1 μatm = 1.013 25× 10-1Pa）. The lowest pCOz values were observed near the Bering Sea shelf break while the highest pCO2 existed at the western Bering Strait. The Bering Sea generally acts as a net sink for atmospheric CO2 in summer. The air-sea CO2 fluxes in the Bering Sea shelf, slope, and basin were estimated at -9.4, -16.3, and -5.1 mmol/（m2.d）, respectively. The annual uptake of CO2 was about 34 Tg C in the Bering Sea.

Response of the South China Sea summer monsoon onset to air-sea heat fluxes over the Indian Ocean

We objectively define the onset date of the South China Sea (SCS) summer monsoon, after having evaluated previous studies and considered various factors. Then, interannual and interdecadal characteristics of the SCS summer monsoon onset are analyzed. In addition, we calculate air-sea heat fluxes over the Indian Ocean using the advanced method of CORARE3.0, based on satellite remote sensing data. The onset variation cycle has remarkable interdecadal variability with cycles of 16 a and 28 a. Correlation analysis between air-sea heat fluxes in the Indian Ocean and the SCS summer monsoon indicates that there is a remarkable lag correlation between them. This result has important implications for prediction of the SCS summer monsoon, and provides a scientific basis for further study of the onset process of this monsoon and its prediction. Based on these results, a linear regression equation is obtained to predict the onset date of the monsoon in 2011 and 2012. The forecast is that the onset date of 2011 will be normal or 1 pentad earlier than the normal year, while the onset date in 2012 will be 1-2 pentads later.