Air-sea CO₂ exchange of beach and near-coastal waters of the Chukchi Sea near Barrow, Alaska     

Hiroki Ikawa  Walter C. Oechel 《Continental Shelf Research》2011,31(13):1357-1364

Partial pressure of CO₂ in equilibrium with sample water (pCO₂) for the coastal water in the Chukchi Sea was continuously observed in summer, 2008. Average daily CO₂ flux calculated from the pCO₂ and gas transfer coefficients ranged from −0.144 to −0.0701 g C m⁻² day⁻¹ depending on which gas transfer coefficient was used. The pCO₂ before the landfast ice sheets melted appeared to be highly biologically controlled based on the following information: (1) the diurnal pattern of pCO₂ was strongly correlated with Photosynthetic Photon Flux Density (PPFD); (2) high chlorophyll density was observed during periods of peak uptake; and (3) the day-to-day variation in the pCO₂ strongly correlated with the presence or absence of near-shore ice sheets. The lowest pCO₂ of 35 ppm together with the highest PPFD of 1362 μmol E m⁻² s⁻¹ were observed in the afternoon on June 28 in the presence of sea ice. The very low pCO₂ observed in late June was likely caused by high photosynthetic rates related to high phytoplankton densities typically observed from spring to early summer near the ice edge, and by water low in salinity and CO₂ released by melting sea ice early in the season.  相似文献   

新30号泉水流量观测资料的初步分析     

汪成国  赵刚  高守权  邹广  陈大柱  张新成  常想德 《山西地震》2011,(3)

在系统清理新疆温泉地震台新30号泉水流量20多年的观测资料的基础上,发现新30号泉在中强地震前泉水流量有明显的异常变化,对附近的小震以同震响应或震后效应为主。因此,深入研究泉水流量的动态类型,有效地排除各种干扰,包括人为因素等,将会显著地增强泉水流量动态监测的映震效能,有助于提高温泉地震台地震短临预测能力。  相似文献   

Temporal variation of suspended sediment load in the Pearl River due to human activities     

Wei ZHANG  Shousheng MU  Yanjing ZHANG  and Kaimin CHEN  Assoc.Prof.  State 《国际泥沙研究》2011,(4):487-497

Data on sediment flux at three hydrologic stations from the 1950s to 2006 are utilized to study the decadal,annual,and monthly variations in suspended sediment load delivered from the Pearl River to the ocean.Results show that variations in sediment flux from three main tributaries,including the West River,the North River and the East River,are spatially non-uniform.Since nearly 90%of the suspended sediment load comes from the West River,its variation has dominated the overall tendency of sediment flux in the entire Pearl River.Although a significant decreasing trend exists in the annual variation of the total sediment flux,the decadal change can be divided into an increasing phase and a decreasing phase,with the turning point between the two phases in the late 1980s.From the 1950s to the 1980s,the average annual river sediment flux increased by 30.43%.However,sediment flux has decreased significantly since the 1990s,with the average sediment flux being 38.60%less in the 2000s than that in the 1950s.The current sediment flux is also 52.93%less than its peak in the 1980s. The monthly variation pattern of the suspended sediment load transport to the sea is more interesting. For the West River,all months show a decreasing trend,and for most months the reduction values are significant.However,for the East River the sediment load shows a decrease trend in the dry season and an increase trend in the wet season.The method of regression analysis was used to study the influence of precipitation in the variation on the sediment flux.It was found that the climate change is not the main driving force behind the variation in suspended sediment load.Before the 1990s, intensive land use destroyed the vulnerable ecosystem of the upper Pearl River,and speeded up the process of rocky desertification.Consequently,aggravated soil erosion caused an increase in suspended sediment load.However,sediment retention within reservoirs had begun to play a dominant role after the massive construction of large dams after 1990,and resulted in a decrease in the suspended sediment load delivered to the ocean.  相似文献   

Soil Organic Carbon mapping of partially vegetated agricultural fields with imaging spectroscopy     

Harm Bartholomeus  Lammert Kooistra  Antoine Stevens  Martin van Leeuwen  Bas van Wesemael  Eyal Ben-Dor  Bernard Tychon 《International Journal of Applied Earth Observation and Geoinformation》2011

Soil Organic Carbon (SOC) is one of the key soil properties, but the large spatial variation makes continuous mapping a complex task. Imaging spectroscopy has proven to be an useful technique for mapping of soil properties, but the applicability decreases rapidly when fields are partially covered with vegetation. In this paper we show that with only a few percent fractional maize cover the accuracy of a Partial Least Square Regression (PLSR) based SOC prediction model drops dramatically. However, this problem can be solved with the use of spectral unmixing techniques. First, the fractional maize cover is determined with linear spectral unmixing, taking the illumination and observation angles into account. In a next step the influence of maize is filtered out from the spectral signal by a new procedure termed Residual Spectral Unmixing (RSU). The residual soil spectra resulting from this procedure are used for mapping of SOC using PLSR, which could be done with accuracies comparable to studies performed on bare soil surfaces (Root Mean Standard Error of Calibration = 1.34 g/kg and Root Mean Standard Error of Prediction = 1.65 g/kg). With the presented RSU approach it is possible to filter out the influence of maize from the mixed spectra, and the residual soil spectra contain enough information for mapping of the SOC distribution within agricultural fields. This can improve the applicability of airborne imaging spectroscopy for soil studies in temperate climates, since the use of the RSU approach can extend the flight-window which is often constrained by the presence of vegetation.  相似文献   

The Impact of Soil Freezing/Thawing Processes on Water and Energy Balances     

ZHANG Xi  SUN Shufen 《大气科学进展》2011,28(1):169-177

A frozen soil parameterization coupling of thermal and hydrological processes is used to investigate how frozen soil processes affect water and energy balances in seasonal frozen soil. Simulation results of soil liquid water content and temperature using soil model with and without the inclusion of freezing and thawing processes are evaluated against observations at the Rosemount field station. By comparing the simulated water and heat fluxes of the two cases, the role of phase change processes in the water and energy balances is analyzed. Soil freezing induces upward water flow towards the freezing front and increases soil water content in the upper soil layer. In particular, soil ice obviously prevents and delays the infiltration during rain at Rosemount. In addition, soil freezingthawing processes alter the partitioning of surface energy fluxes and lead the soil to release more sensible heat into the atmosphere during freezing periods.  相似文献   

Characterizing the international carbon capture and storage community     

Jennie C. Stephens  Anders Hansson  Yue Liu 《Global Environmental Change》2011,21(2):379-390

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The social and political complexities of learning in carbon capture and storage demonstration projects     

Nils Markusson  Atsushi Ishii 《Global Environmental Change》2011,21(2):293-302

Demonstration of a fully integrated power plant with carbon capture and storage (CCS) at scale has not yet been achieved, despite growing international political interest in the potential of the technology to contribute to climate change mitigation and calls from multiple constituents for more demonstration projects. Acknowledging the scale of learning that still must occur for the technology to advance towards deployment, multiple CCS demonstration projects of various scales are emerging globally. Current plans for learning and knowledge sharing associated with demonstration projects, however, seem to be limited and narrowly conceived, raising questions about whether the projects will deliver on the expectations raised. Through a comparison of the structure, framing and socio-political context of three very different CCS demonstration projects in different places and contexts, this paper explores the complexity of social learning associated with demonstration projects. Variety in expectations of the demonstration projects’ objectives, learning processes, information sharing mechanisms, public engagement initiatives, financing and collaborative partnerships are highlighted. The comparison shows that multiple factors including the process of building support for the project, the governance context and the framing of the project matter for the learning in demonstration projects. This analysis supports a broader conceptualization of learning than that currently found in CCS demonstration plans - a result with implications for both future research and practice.  相似文献   

Toward policy integration: Assessing carbon capture and storage policies in Japan and Norway     

Atsushi Ishii  Oluf Langhelle 《Global Environmental Change》2011,21(2):358-367

The objective of this paper is to develop independent and systematic criteria for assessing CCS policy in terms of its level of policy integration. We believe that we should assess CCS policy in terms of the distance to an ideal integrated CCS policy in order to keep track of its trajectory toward sustainable development. After reviewing the existing literature of environmental policy integration, an assessment framework for integrated CCS policy is developed based on Arild Underdal's notion of ‘integrated policy’ then, its usefulness is demonstrated by applying it to CCS policies in Japan and Norway. In the final part, we summarize the findings of the cases and conclude with some observations regarding explanatory factors of the difference in terms of the achieved level of policy integration between Japan and Norway's CCS policies, and some policy implications derived from the analysis based on the framework.  相似文献   

IMPACT OF LATENT HEAT FLUX ON INDIAN SUMMER MONSOON DURING EL NI(N)O/LA NI(N)A YEARS     

M. V. Subrahmanyam  WANG Dong-xiao 《热带气象学报(英文版)》2011,17(4)

El Ni(n)o or La Ni(n)a manifest in December over the Pacific and will serve as an index for the forecasting of subsequent Indian summer monsoon,which occurs from June to mid-September.In the present article,an attempt is made to study the variation of latent heat flux (LHF) over the north Indian Ocean during strong El Ni(n)o and strong La Ni(n)a and relate it with Indian monsoon rainfall.During strong El Ni(n)o the LHF intensity is higher and associated with higher wind speed and lower cloud amount.During E1 Ni(n)o all India rainfall is having an inverse relation with LHF.Seasonal rainfall is higher in YY+1 (subsequent year) than YY (year of occurrence).However there is a lag in rainfall during El Ni(n)o YY+1 from June to July when compared with the monthly rainfall.  相似文献   

Characteristics of Quasi-Periodic Oscillations During Sea Fog Events   总被引：2，自引：2，他引：0  

沈忱  黄健  刘寿东  王鑫  吕卫华  周小云 《热带气象学报(英文版)》2011,17(1):50-57

Based on the high-resolution datasets collected in a sea fog field experiment at the northern coast of South China Sea, the variations of liquid water content (LWC) and net longwave radiation flux (NLRF) during two sea fog events on 16th-17th and 18th-19th March, 2008 are exaimeed by wavelet analysis, and the cooling mechanisms for fog formation and persistence are also investigated. The main results are shown as follows. (1) Sea fog may develop and persist whether it is cloudy or not aloft. However, when there is cloud aloft the LWC is less and wind speed in sea fog is higher than that in the clear sky. (2) The quasi-periodic oscillations (QPOs) of NLRF are observed in the formation stage of the two fogs. QPOs of LWC are only found in the developing stage no matter with cloudless or cloudy condition. (3) It is likely that sea fog forms by the cooling effects of longwave radiation and develops through the vertical mixing induced by the radiative cooling at the upper level. (4) During sea fog development and persistence, other mechanisms could also play important roles in fog-layer cooling, such as turbulent heat transport and radiation transport between air-sea interfaces.  相似文献