中国近海海面通量的气候平均和季节变化特征

该文依据英国南安普郭海洋中心气候学海面通量资料集,采用EOF及一般统计分析方法,分析和研究了中国近海热通量、淡水通量及由动量通量计算而得的风应力旋度场的气候平均和季节变化特征.并分别对日本海、渤黄东海及南海进行了讨论.结果显示,日本海与渤黄东海年平均海面净热通量为失热,日本海为-27Wm<'-2>,渤黄东海为-25Wm<'-2>.南海为海洋获得净热通量,量值为58Wm<'-2>.在黑潮流区存在最大的净热通量损失值区,在冬季12月份最大损失值可达-330Wm<'-2>.在日本海区对马暖流沿日本群岛西海岸在冬季12月也有最大损失值-270Wm<'-2>.日本海与东中国海净热通量变化趋势基本一致,而南海在4月达到净热通量的最大值.最后该文还对海表通量与海表温度场及风速场作了延迟相关分析.

Effect of pulse heating parameters on the microscale bubble dynamics at a microheater surface

We study the effects of pulse heating parameters on the micro bubble behavior of a platinum microheater (100 mu m x 20 mu m) immersed in a methanol pool. The experiment covers the heat fluxes of 10-37 MW/m(2) and pulse frequencies of 25-500 Hz. The boiling incipience is initiated at the superheat limit of methanol, corresponding to the homogeneous nucleation. Three types of micro boiling patterns are identified. The first type is named as the bubble explosion and regrowth, consisting of a violent explosive boiling and shrinking, followed by a slower bubble regrowth and subsequent shrinking, occurring at lower heat fluxes. The second type, named as the bubble breakup and attraction, consists of the violent explosive boiling, bubble breakup and emission, bubble attraction and coalescence process, occurring at higher heat fluxes than those of the first type. The third type, named as the bubble size oscillation and large bubble formation, involves the initial explosive boiling, followed by a short periodic bubble growth and shrinking. Then the bubble continues to increase its size, until a constant bubble size is reached which is larger than the microheater length. 

Validating MODIS-derived land surface evapotranspiration with in situ measurements at two AmeriFlux sites in a semiarid region

Reducing uncertainties in the estimation of land surface evapotranspiration (ET) from remote-sensing data is essential to better understand earth-atmosphere interactions. This paper demonstrates the applicability of temperature-vegetation index triangle (T-s-VI) method in estimating regional ET and evaporative fraction (EF, defined as the ratio of latent heat flux to surface available energy) from MODIS/Terra and MODIS/Aqua products in a semiarid region. We have compared the satellite-based estimates of ET and EF with eddy covariance measurements made over 4 years at two semiarid grassland sites: Audubon Ranch (AR) and Kendall Grassland (KG). The lack of closure in the eddy covariance measured surface energy components is shown to be more serious at MODIS/Aqua overpass time than that at MODIS/Terra overpass time for both AR and KG sites. The T-s-VI-derived EF could reproduce in situ EF reasonably well with BIAS and root-mean-square difference (RMSD) of less than 0.07 and 0.13, respectively. Surface net radiation has been shown to be systematically overestimated by as large as about 60 W/m(2). Satisfactory validation results of the T-s-VI-derived sensible and latent heat fluxes have been obtained with RMSD within 54 W/m(2). The simplicity and yet easy use of the T-s-VI triangle method show a great potential in estimating regional ET with highly acceptable accuracy that is of critical significance in better understanding water and energy budgets on the Earth. Nevertheless, more validation work should be carried out over various climatic regions and under other different land use/land cover conditions in the future.

Suspended particulate matter fluxes through the Straits of Dover, English Channel: observations and modelling

Suspended Particulate Matter (SPM) concentrations at various levels within the water column, together with salinity and temperature, were measured using water samples collected from six stations across the Straits of Dover. The sampling programme covered a 16-month period, undertaken during 23 cruises. On the basis of the spatial variability in the concentrations, the water bodies are divided by several boundaries, controlled by tidal and wind conditions. Within the water column, SPM concentrations were higher near the sea bed than in the surface waters. Throughout the cross-section, maximum concentrations occurred adjacent to the coastlines. Temporal variability in the SPM concentration exists on daily and seasonal scales within the coastal waters (4.2 to 74.5 mg L-1): resuspension processes, in response to semi-diurnal tidal cycles (with a period of around 12.4 h) and spring-neap cycles (with a period of 15 days) make significant contributions. Distinctive seasonal/annual concentration changes have also been observed. In the offshore waters, such variability is much less significant (0.9 to 6.0 mg L-1). In the summer the English Coastal Zone is associated with relatively high SPM concentrations: the Central Zone has a low and stable SPM concentration between these zones, there is a Transitional Zone, where there is a rapid response of SPM concentration to wind forcing. Finally, the French Coastal Zone is characterized by variable (sometimes high) SPM concentrations. Because of the zonation, SPM fluxes within the Dover Strait are controlled by different transport mechanisms. Within the Central Zone, the flux can be represented by the product of mean water discharges and SPM concentrations. However, within the coastal zones fluctuations in SPM concentrations on various time-scales must be considered. In order to calculate the maximum and minimum SPM fluxes, 10 cells were divided in the strait. A simple modelling calculation has been proposed for this complex area. The effect of spring-neap tidal cycles and seasonal changes can contribute significantly to the overall flux, which is of the order of 20 x 10(6) t.yr(-1) (through the Dover Strait, towards the North Sea). Such an estimate is higher than most obtained previously. (C) 2000 Ifremer/CNRS/IRD/Editions scientifiques et medicales Elsevier SAS.

Response of coastal marine eco-environment to river fluxes into the sea: A case study of the Huanghe (Yellow) River mouth and adjacent waters

The impact of the Huanghe (Yellow) River outflows on its estuary was investigated with river gauging and shipboard hydrographic observations. The river flux has been decreasing dramatically; the discharges of water and sediment in the 1990s dropped to 27.4% and 31.9% of those in the 1950s, respectively, resulting in frequent and lengthy events of downstream channel dry-up since the 1970s. There were accumulatively 897 zero-flow days during the 1990s in the river course below the Lijin Hydrological Station, 100 km upstream from the river mouth, which is 82.4% of that in 1972. As freshwater input decreases, river-borne nutrients to the estuarine increased significantly. Concentration of dissolved inorganic nitrogen (DIN) in the 1990s was four times of that in 1950s. Changes in amount and content of the riverine inputs have greatly affected the estuarine ecosystem. Over the past several decades, sea surface temperature and salinity in the estuary and its adjacent waters increased and their distribution pattern altered in response to the reduction of freshwater inflow. The distribution of and seasonal succession in nutrient concentrations in the surface layer have also changed with a shift of river outlet and the decrease in riverine nutrient loads. Furthermore, deterioration of estuarine ecosystem by less river input has decreased primary productivity in the deltaic region waters, and in turn depressed the fishery. (C) 2008 Published by Elsevier Ltd.

Neural network retrieval of ocean surface parameters from SSM/I data

A new algorithm based on the multiparameter neural network is proposed to retrieve wind speed (WS), sea surface temperature (SST), sea surface air temperature, and relative humidity ( RH) simultaneously over the global oceans from Special Sensor Microwave Imager (SSM/I) observations. The retrieved geophysical parameters are used to estimate the surface latent heat flux and sensible heat flux using a bulk method over the global oceans. The neural network is trained and validated with the matchups of SSM/I overpasses and National Data Buoy Center buoys under both clear and cloudy weather conditions. In addition, the data acquired by the 85.5-GHz channels of SSM/I are used as the input variables of the neural network to improve its performance. The root-mean-square (rms) errors between the estimated WS, SST, sea surface air temperature, and RH from SSM/I observations and the buoy measurements are 1.48 m s(-1), 1.54 degrees C, 1.47 degrees C, and 7.85, respectively. The rms errors between the estimated latent and sensible heat fluxes from SSM/I observations and the Xisha Island ( in the South China Sea) measurements are 3.21 and 30.54 W m(-2), whereas those between the SSM/ I estimates and the buoy data are 4.9 and 37.85 W m(-2), respectively. Both of these errors ( those for WS, SST, and sea surface air temperature, in particular) are smaller than those by previous retrieval algorithms of SSM/ I observations over the global oceans. Unlike previous methods, the present algorithm is capable of producing near-real-time estimates of surface latent and sensible heat fluxes for the global oceans from SSM/I data.

Ship-board measurements and estimations of air-sea fluxes in the western tropical Pacific during TOGA COARE

Direct air-sea flux measurements were made on RN Kexue #1 at 40 degrees S, 156 degrees E during the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean-Atmospheric Response Experiment (COARE) Intensive Observation Period (IOP). An array of six accelerometers was used to measure the motion of the anchored ship, and a sonic anemometer and Lyman-alpha hygrometer were used to measure the turbulent wind vector and specific humidity. The contamination of the turbulent wind components by ship motion was largely removed by an improvement of a procedure due to Shao based on the acceleration signals. The scheme of the wind correction for ship motion is briefly outlined. Results are presented from data for the best wind direction relative to the ship to minimize flow distortion effects. Both the time series and the power spectra of the sonic-measured wind components show swell-induced ship motion contamination, which is largely removed by the accelerometer correction scheme, There was less contamination in the longitudinal wind component than in the vertical and transverse components. The spectral characteristics of the surface-layer turbulence properties are compared with those from previous land and ocean results, Momentum and latent heat fluxes were calculated by eddy correlation and compared to those estimated by the inertial dissipation method and the TOGA COARE bulk formula. The estimations of wind stress determined by eddy correlation are smaller than those from the TOGA COARE bulk formula, especially for higher wind speeds, while those from the bulk formula and inertial dissipation technique are generally in agreement. The estimations of latent heal flux from the three different methods are in reasonable agreement. The effect of the correction for ship motion on latent heat fluxes is not as large as on momentum fluxes.

Intraseasonal variability of Indian Ocean sea surface temperature during boreal winter: Madden-Julian Oscillation versus submonthly forcing and processes

[ 1] Intraseasonal variability of Indian Ocean sea surface temperature (SST) during boreal winter is investigated by analyzing available data and a suite of solutions to an ocean general circulation model for 1998 - 2004. This period covers the QuikSCAT and Tropical Rainfall Measuring Mission (TRMM) observations. Impacts of the 30 - 90 day and 10 - 30 day atmospheric intraseasonal oscillations (ISOs) are examined separately, with the former dominated by the Madden-Julian Oscillation (MJO) and the latter dominated by convectively coupled Rossby and Kelvin waves. The maximum variation of intraseasonal SST occurs at 10 degrees S - 2 degrees S in the wintertime Intertropical Convergence Zone (ITCZ), where the mixed layer is thin and intraseasonal wind speed reaches its maximum. The observed maximum warming ( cooling) averaged over ( 60 degrees E - 85 degrees E, 10 degrees S - 3 degrees S) is 1.13 degrees C ( - 0.97 degrees C) for the period of interest, with a standard deviation of 0.39 degrees C in winter. This SST change is forced predominantly by the MJO. While the MJO causes a basin-wide cooling ( warming) in the ITCZ region, submonthly ISOs cause a more complex SST structure that propagates southwestward in the western-central basin and southeastward in the eastern ocean. On both the MJO and submonthly timescales, winds are the deterministic factor for the SST variability. Short-wave radiation generally plays a secondary role, and effects of precipitation are negligible. The dominant role of winds results roughly equally from wind speed and stress forcing. Wind speed affects SST by altering turbulent heat fluxes and entrainment cooling. Wind stress affects SST via several local and remote oceanic processes.

Geochemical characteristics of nitrogen in the southern Yellow Sea surface sediments

Roles and distributions of various forms of nitrogen in biogeochemical cycling in the southern Yellow Sea surface sediments were investigated. The southern Yellow Sea could be divided into three regions (I, II and III) according to the proportion of fine-grained sediment in > 65%, 35-65% and < 35%, respectively. The ratios of different forms of nitrogen contents between each two of the three regions indicated that the nitrogen contents increased with the proportion of fine-grained sediment increasing. The quanta of exchangeable forms of nitrogen were similar in the three regions, while their releasing time increased from regions I to III, indicating that the cycle of nitrogen in fine-grained sediments was shorter than that in coarse-grained sediments. Nitrogen burial fluxes were also similar in these regions, while the burial efficiency increased from regions I to III. The highest burial efficiency was 30.21% in region III, indicating that more than 70% of nitrogen in the southern Yellow Sea surface sediments could be released to take part in biogeochemical recycling. When all the four forms of exchangeable nitrogen (nitrogen in ion exchangeable form (IEF-N), nitrogen in weak acid extractable form (WAEF-N), nitrogen in strong alkali extractable form (SAEF-N) and nitrogen in strong oxidant extractable form (SOEF-N)) were released to take part in recycling, their potential contributions were 80% (SOEF-N), 11% (IEF-N), 6% (SAEF-N), 3% (WAEF-N) respectively, which showed that SOEF-N was the predominant one, and its contribution to biogeochemical cycling was the highest. (c) 2004 Elsevier B.V. All rights reserved.

Dissolved inorganic carbon and CO2 fluxes across Jiaozhou Bay air-water interface

On the basis of data collected in the Jiaozhou Bay in June and July 2003, the DIC distribution in seawater is studied, and an average air-sea flux of CO2 is estimated. The results show that the content of DIC inside the bay is markedly higher than outside the bay in June, but the content of DIC outside the bay is markedly higher than inside the bay in July. The trend of DIC distribution inside the bay is similar, viz. the content is the maximum in the northeast, then decreases gradually toward the west, and the content is the minimum in the west. The total trend of vertical distribution is to increase gradually from surface to bottom. This characteristic of DIC distribution is determined by Jiaozhou Bay hydrology and there is a close relation between DIC and particulate N,P. Average CO2 flux across the air-sea interface is 0.55 mol/(m(2.)a) in June and 0.72 mol/(m(2.)a) in July. Jiaozhou Bay is considered as a net annual source for atmospheric CO2 in June and July, and the total CO2 flux from seawater into atmosphere is about 740 t in June and 969 t in July.

pCO(2) and carbon fluxes across sea-air interface in the Changjiang Estuary and Hangzhou Bay

Partial pressure of CO2 (pCO(2)) was investigated in the Changjiang (Yangtze River) Estuary, Hangzhou Bay and their adjacent areas during a cruise in August 2004, China. The data show that pCO(2) in surface waters of the studied area was higher than that in the atmosphere with only exception of a patch east of Zhoushan Archipelago. The pCO(2) varied from 168 to 2 264 mu atm, which fell in the low range compared with those of other estuaries in the world. The calculated sea-air CO2 fluxes decreased offshore and varied from -10.0 to 88.1 mmol m(-2) d(-1) in average of 24.4 +/- 16.5 mmol m(-2) d(-1). Although the area studied was estimated only 2 x 10(4) km(2), it emitted (5.9 +/- 4.0) x 10(3) tons of carbon to the atmosphere every day. The estuaries and their plumes must be further studied for better understanding the role of coastal seas playing in the global oceanic carbon cycle.

Surface energy partitioning in alpine swamp meadow in the Qinghai Tibetan Plateau

Based on surface energy flux data measured by eddy covariance methods from China Flux in alpine swamp meadow of the Qinghai Tibetan Plateau in 2005, the daily and seasonal dynamic of surface energy fluxes and their partitioning, as well as abiotic factors effects were analyzed. The results suggested that LE （Latent heat flux） was the largest consumer of the incoming energy. Rn （Net radiation flux） and LE showed clear seasonal variations in sharp hump and up to their maximums in August and July, respectively. H （Sensible heat flux） increased to its peak in August whereafter declined slowly. Precipitation could reduce the components of surface energy. As to Rn and LE, their correlations with abiotic factors were evident while it was not significant in H. Average EBR （Energy balance ratio） was 50.7 %, which was much larger in growing season than non-growing season.

Monitoring and simulation of water, heat,and CO2 fluxes in terrestrial ecosystems based on the APEIS-FLUX system

The Integrated Environmental Monitoring (IEM) project, part of the Asia-Pacific Environmental Innovation Strategy (APEIS) project, developed an integrated environmental monitoring system that can be used to detect, monitor, and assess environmental disasters, degradation, and their impacts in the Asia-Pacific region. The system primarily employs data from the moderate resolution imaging spectrometer (MODIS) sensor on the Earth Observation System- (EOS-) Terra/Aqua satellite,as well as those from ground observations at five sites in different ecological systems in China. From the preliminary data analysis on both annual and daily variations of water, heat and CO2 fluxes, we can confirm that this system basically has been working well. The results show that both latent flux and CO2 flux are much greater in the crop field than those in the grassland and the saline desert, whereas the sensible heat flux shows the opposite trend. Different data products from MODIS have very different correspondence, e.g. MODIS-derived land surface temperature has a close correlation with measured ones, but LAI and NPP are quite different from ground measurements, which suggests that the algorithms used to process MODIS data need to be revised by using the local dataset. We are now using the APEIS-FLUX data to develop an integrated model, which can simulate the regional water,heat, and carbon fluxes. Finally, we are expected to use this model to develop more precise high-order MODIS products in Asia-Pacific region.