Diurnal and Seasonal Variations of CO2Fluxes and Their Climate Controlling Factors for a Subtropical Forest in Ningxiang

In this study, the diurnal and seasonal variations of CO2 fluxes in a subtropical mixed evergreen forest in Ningxiang of Hunan Province, part of the East Asian monsoon region, were quantified for the first time. The fluxes were based on eddy covariance measurements from a newly initiated flux tower. The relationship between the CO2 fluxes and climate factors was also analyzed. The results showed that the target ecosystem appeared to be a clear carbon sink in 2013, with integrated net ecosystem CO2exchange（NEE）, ecosystem respiration（RE）, and gross ecosystem productivity（GEP） of-428.8, 1534.8 and1963.6 g C m^-2yr^-1, respectively. The net carbon uptake（i.e. the-NEE）, RE and GEP showed obvious seasonal variability,and were lower in winter and under drought conditions and higher in the growing season. The minimum NEE occurred on12 June（-7.4 g C m^-2d^-1）, due mainly to strong radiation, adequate moisture, and moderate temperature; while a very low net CO2 uptake occurred in August（9 g C m^-2month^-1）, attributable to extreme summer drought. In addition, the NEE and GEP showed obvious diurnal variability that changed with the seasons. In winter, solar radiation and temperature were the main controlling factors for GEP, while the soil water content and vapor pressure deficit were the controlling factors in summer. Furthermore, the daytime NEE was mainly limited by the water-stress effect under dry and warm atmospheric conditions, rather than by the direct temperature-stress effect.

Improving automatic climate control with decision support techniques to minimize disease effects in greenhouse tomatoes

Crop growth in greenhouses is basically determined by the climate variables in the environment and by the amounts of water and fertilizers supplied by irrigation.The management of these factors depends on the expertise of agricultural technicians and farmers,usually assisted by control systems installed within the greenhouse.In this context,decision support features enable us to incorporate invaluable human experience so thatwe can take quick and effective decisions to ensure efficient crop growth.This work describes a real-time decision support system for greenhouse tomatoes that supports decisions at three stages–the supervision stage identifies climate sensor faults,the control stage maintains climate variables at setpoints,and the strategic stage identifies diseases affecting the crop and changes climate variables accordingly to minimize damage.The DSS was implemented by integrating a real-time rule-based tool into the control system.Experimental results show that the system increases climate control effectiveness,while providing support in preventing diseaseswhich are difficult to eradicate.The system was tested by simulating the appearance of the disease and observing the real systemresponse.The main contribution has been to demonstrate that production rules,which aremature and well-known in the artificial intelligence domain,can act as a shared technology for the whole system.This means that fault detection,temperature control and disease monitoring features are not dealt with in isolation.

Reducing Electrical Consumption in Stationary Long-Haul Trucks

On average, long-haul trucks in the U.S. use approximately 667 million gallons of fuel each year just for idling. This idling primarily facilitates climate control operations during driver rest periods. To mitigate this, our study explored ways to diminish the electrical consumption of climate control systems in class 8 trucks through innovative load reduction technologies. We utilized the CoolCalc software, developed by the National Renewable Energy Laboratory (NREL), which integrates heat transfer principles with extensive weather data from across the U.S. to mimic the environmental conditions trucks face year-round. The analysis of the CoolCalc simulations was performed using MATLAB. We assessed the impact of various technologies, including white paint, advanced curtains, and Thinsulate insulation on reducing electrical demand compared to standard conditions. Our findings indicate that trucks operating in the eastern U.S. could see electrical load reductions of up to 40%, while those in the western regions could achieve reductions as high as 55%. Such significant decreases in energy consumption mean that a 10 kWh battery system could sufficiently manage the HVAC needs of these trucks throughout the year without idling. Given that many long-haul trucks are equipped with battery systems of around 800 Ah (9.6 kWh), implementing these advanced technologies could substantially curtail the necessity for idling to power air conditioning systems.

Potential control of climatic changes on flood events in the Yangtze Delta during1100-2002

Wide collection on the historic records of the climatic changes and flood events is performed in the Yangtze Delta. Man-Kendall (MK) method is applied to explore the changing trends of the time series of the flood discharge and the maximum high summer temperature. The research results indicate that the flood magnitudes increased during the transition from the medieval warm interval into the early Little Ice Age. Fluctuating climate changes of the Little Ice Age characterized by arid climate events followed by the humid and cold climate conditions give rise to the frequent flood hazards. Low-lying terrain made the study region prone to the flood hazards, storm tide and typhoon. MK analysis reveals that the jumping point of the time series of the flood discharge changes occurred in the mid-1960s, that of the maximum summer temperature changes in the mid-1990s, and the exact jump point in 1993. The flood discharge changes are on negative trend before the 1990s, they are on positive tendency after the 1990s; the maximum high summer temperature changes are on negative trend before the 1990s and on positive tendency after the 1990s. These results indicate that the trend of flood discharge matches that of the maximum high summer temperature in the Yangtze Delta. The occurrence probability of the maximum high summer temperature will be increasing under the climatic warming scenario and which will in turn increase the occurrence probability of the flood events. More active solar action epochs and the higher sea surface temperature index (SST index) of the south Pacific Ocean area lying between 4 o N-4 o S and 150 o W-90 o W correspond to increased annual precipitation, flood discharge and occurrence frequency of floods in the Yangtze Delta. This is partly because the intensified solar activities and the higher SST index give rise to accelerated hydrological circulation from ocean surface to the continent, resulting in increased precipitation on the continent.

A dominant role of internal climate variability in controlling Atlantic multidecadal variability during the past 1200 years

Subject Code:D02With the support by the National Natural Science Foundation of China,a collaborative study by the research group led by Prof.Yang Bao(杨保)from the Key Laboratory of Desert and Desertification,Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences,and

A modeling framework for the integration of electrical and thermal energy systems in greenhouses

Greenhouse horticulture is associated to a significant energy consumption in temperate countries,mainly for lighting and for heating.Interestingly,the potential for energy optimization and energy savings is high but requires detailed models capable of considering various system configurations and control systems.This paper provides an open-source modeling framework capable of simulating and optimizing the design and the control of both the greenhouse and the generation systems covering all energy needs.The proposed model is composed of sub-models from different scientific fields:a greenhouse climate model,a crop yield model,a large number of energy generation and storage units models and different rule-based control strategies.The association of such state-of-the-art models in a single framework provides a powerful tool for optimization purposes and allows the definition of completely customized systems by means of an object-oriented interface.In this work,various control strategies are defined and simulated,thus demonstrating the capabilities of the proposed model.Results indicate that,by performing minor changes to the control of the thermal screen,heating consumption can be reduced by 3%without any loss in crop yield.The control of heat-generation units also has a significant impact on the operational costs,which vary by up to 17%when self-consumption levels are accounted for in the control strategy.

Biotic effects dominate the inter-annual variability in ecosystem carbon exchange in a Tibetan alpine meadow

The alpine meadow ecosystem in Tibet is fragile and sensitive,and its carbon sink function with respect to climate change has become a matter of widespread concern.Therefore,this study aims to clarify the inter-annual variations(IAVs)in the carbon fluxes in an alpine meadow and to further quantify the contributions of the driving factors to the IAVs.Based on 7 years of flux data(2012-2018)and the corresponding climatic and biotic data,a set of look-up tables was used to separate and quantify the IAV sources.Furthermore,linear perturbation analyses were employed to quantify the contributions of each key factor.During 2012-2018,the net ecosystem productivity(NEP),gross primary productivity(GPP)and ecosystem respiration(Re)of this alpine meadow were 3.31±26.90,210.18±48.35 and 206.88±28.45 g C m^(-2) y^(-1),respectively,which indicated relatively large IAVs.When the contributions of climatic and biotic effects were distinguished and quantified,the dominant effects of biotic factors emerged.Additionally,negative interactions between climatic and biotic effects were detected.Among the climatic factors,only soil water content contributed relatively more to the IAVs and played a role in regulating the interactions between climatic and biotic effects.These results suggest that biotic effects must be carefully considered to reduce the uncertainties associated with future carbon flux estimates.

Erosions on the southern Tibetan Plateau:Evidence from in-situ cosmogenic nuclides^(10)Be and^(26)Al in fluvial sediments

Investigating topographic and climatic controls on erosion at variable spatial and temporal scales is essential to our understanding of the topographic evolution of the orogen.In this work,we quantified millennial-scale erosion rates deduced from cosmogenic^(10)Be and^(26)Al concentrations in 15 fluvial sediments from the mainstream and major tributaries of the Yarlung Zangbo River draining the southern Tibetan Plateau(TP).The measured ratios of^(26)Al/^(10)Be range from 6.33±0.29 to 8.96±0.37,suggesting steady-state erosion processes.The resulted erosion rates vary from 20.60±1.79 to 154.00±13.60 m Myr-1,being spatially low in the upstream areas of the Gyaca knickpoint and high in the downstream areas.By examining the relationships between the erosion rate and topographic or climatic indices,we found that both topography and climate play significant roles in the erosion process for basins in the upstream areas of the Gyaca knickpoint.However,topography dominantly controls the erosion processes in the downstream areas of the Gyaca knickpoint,whereas variations in precipitation have only a second-order control.The marginal Himalayas and the Yarlung Zangbo River Basin(YZRB)yielded significantly higher erosion rates than the central plateau,which indicated that the landscape of the central plateau surface is remarkably stable and is being intensively consumed at its boundaries through river headward erosion.In addition,our^(10)Be erosion rates are comparable to present-day hydrologic erosion rates in most cases,suggesting either weak human activities or long-term steady-state erosion in this area.