Daily Flux Research Articles

Predicting Solar Proton Events of Solar Cycles 22–24 Using GOES Proton and Soft-X-Ray Flux Features

Solar energetic particle (SEP) events and their major subclass, solar proton events (SPEs), can have unfavorable consequences on numerous aspects of life and technology, making them one of the most harmful effects of solar activity. Garnering knowledge preceding such events by studying operational data flows is essential for their forecasting. Considering only solar cycle (SC) 24 in our previous study, we found that it may be sufficient to only utilize proton and soft X-ray (SXR) parameters for SPE forecasts. Here, we report a catalog recording ≥10 MeV ≥10 particle flux unit SPEs with their properties, spanning SCs 22–24, using NOAA’s Geostationary Operational Environmental Satellite flux data. We report an additional catalog of daily proton and SXR flux statistics for this period, employing it to test the application of machine learning (ML) on the prediction of SPEs using a support vector machine (SVM) and extreme gradient boosting (XGBoost). We explore the effects of training models with data from one and two SCs, evaluating how transferable a model might be across different time periods. XGBoost proved to be more accurate than SVMs for almost every test considered, while also outperforming operational SWPC NOAA predictions and a persistence forecast. Interestingly, training done with SC 24 produces weaker true skill statistic and Heidke skill scores2, even when paired with SC 22 or SC 23, indicating transferability issues. This work contributes toward validating forecasts using long-spanning data—an understudied area in SEP research that should be considered to verify the cross cycle robustness of ML-driven forecasts.

Addition of biochar decreased soil respiration in a permanent no-till cover crop system for organic soybean production

The increase in soil carbon sequestration under long-term no-till (NT) and cover crop management has been shown to form part of a sustainable agricultural management practice system. Along with the increase in soil organic carbon (SOC), soil respiration in this system was also enhanced by the increased soil temperature through the decomposition that causes carbon loss from the soil. To overcome this issue, biochar can be applied. However, the addition of biochar into this system is not well studied. Therefore, the aim of this study was to investigate the effect of this system on soil respiration. The experiment was conducted at the Center for International Field Agriculture Research & Education, Ibaraki University. Long-term tillage practices, such as NT and moldboard plowing (MP), cover crops such as rye (RY) and fallow (FA), and biochar application such as with biochar (WB) and no biochar (NB) were applied to a split–split plot in a randomized complete block design with four replications. The daily CO2 flux was measured every week at 9:00–11:00 a.m. The daily soil respiration was affected by tillage and cover crop with NT practice had significantly higher daily CO2 flux than that of MP (23.8%–107.4% and 38.0%–107.8%), while RY had higher flux than that of FA (11.9%–81.2% and 34.9%–65.4%) in 2020 and 2021 soybean growing season, respectively. Additionally, in the 2020 cover crop growing season RY also increased daily CO2 flux approximately 41.8%–88.2% compared to FA. Biochar addition significantly reduced soil respiration in soybean and cover crop seasons compared to NB by 24.0%–50.7% and by 25.9%–48.3%, respectively. This reduction in soil respiration by the biochar decreased annual CO2 emissions by 17.6% and 13.0% in 2020 and 2021. The values of these emissions ranged from 9.6 Mg ha−1 for MP FA WB to 18.9 Mg ha−1 for MP RY NB in 2020 and from 7.5 Mg ha−1 for MP FA WB to 13.7 Mg ha−1 for NT FA NB in 2021. This study highlights the crucial role of biochar in reducing soil respiration and enhancing SOC sequestration. The addition of biochar into this system was able to reduce soil respiration by regulating the soil temperature, soil moisture, and protect the SOC from decomposition. Biochar addition also increased the SOC and decreased the soil bulk density, which improves soil porosity. Therefore, these findings would be very useful to be included within the global scenario of soil organic matter management.

Persistent Organic Pollutants and Suspended Particulate Matter in Snow of Eastern Siberia in 2009-2023: Temporal Trends and Effects of Meteorological Factors and Recultivation Activities at Former Industrial Area.

Suspended particulate matter (SPM), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCP) were studied in the snow cover at urban and suburban localities in the Irkutsk region, Eastern Siberia for their temporal variations in 2009-2023, daily deposition fluxes (DDFs), and effects of some meteorological factors, as well as the effects of different technogenic activities in the industrial area of the former organochlorine enterprises of Usol'ekhimprom. SPM loads at both stations were found to be at a low level of pollution. The levels of HCB, α + γ-HCH, and ∑p,p'-DDX were lower than Russian maximum permissible levels (MPLs) in drinking water, groundwater, and surface water for household drinking and cultural purposes. The sums of all organochlorine compounds studied in snow were higher than the MPL in freshwater water bodies for fishery purposes. The levels of the DDFs of HCHs, DDTs, and heptachlorinated PCB decreased, di- and trichlorinated PCB levels increased, and HCB levels changed at a polynomial line during 2009-2023. The change in the relative composition of PCBs was found as a result of recultivation activities at the industrial area of the former organochlorine enterprise of Usol'ekhimprom. The air humidity and temperature are the key meteorological factors affecting the DDFs of PCBs and OCPs.

A Simple and Easily Implementable Model for the Prediction of Solar Irradiance for All-Sky Conditions: Model Development, Preliminary Evaluation and Application

A simple and easily implementable model and the associated computer code for predicting the solar irradiance at the earth’s surface have been developed. The input requirements of the model include Julian day, time, geographical latitude, atmospheric pressure and cloud cover. If the latter is not available, then the program user has the option of entering either the daily global solar flux or the duration of sunshine, from which the average cloud cover is estimated. Preliminary model evaluation has been carried out using data from two meteorological stations situated in rural and semi-rural areas of the East Midlands, United Kingdom. The scatter plots of predicted versus observed solar irradiance gave correlation coefficients approximately equal to 0.6 and slopes in the range of 0.80–0.93. The model is being implemented as a submodule within an urban air quality model. This specific application of the solar radiation model is discussed as a typical implementation. This work shows that by adopting relatively simple ‘textbook’ material, i.e., basic theory/information, one can achieve reasonably good solar radiation modelling, with outcomes that can be used for applications where accuracy is not a major requirement.

Optimization of Photoautotrophic Growth Regimens of Scenedesmaceae alga: The Influence of Light Conditions and Carbon Dioxide Concentrations

Improving methods for landless production of bioproducts is considered an important stage in the development of the modern bioeconomy. In this context, microalgal biomass is one of the most promising sources of valuable substances due to its rich biochemical composition. Despite the high adaptability of microalgae to various environmental factors, the effectiveness of cultivation systems depends on precisely selected parameters. Both the light conditions and the supply of inorganic carbon sources are key in determining the efficiency of photoautotrophic cultivation. In this work, the effect of a high daily photosynthetic photon flux density (PPFD) ranging from 37.44 to 112.32 mol m−2 day−1 on the growth and productivity of a novel Scenedesmaceae alga, strain EZ-B1, was assessed. The next stage of cultivation consisted of selecting the optimal CO2 concentration. Improved performance of microalga during cultivation in a photobioreactor was achieved at 112.32 mol m−2 day−1 (24 h photoperiod) and by supplying 2% CO2, as evidenced by the high biomass productivity (0.69 g L−1 day−1), total biomass yield (5.23 g L−1), and ammonium nitrogen consumption rate. The data obtained suggest that a higher level of PPFD led to the highest growth rate of the novel strain and the highest biomass productivity, which, in practice, will increase production capacity.

Land Cover Control on the Drivers of Evaporation and Sensible Heat Fluxes: An Observation‐Based Synthesis for the Netherlands

AbstractLand cover controls the land‐atmosphere exchange of water and energy through the partitioning of solar energy into latent and sensible heat. Observations over all land cover types at the regional scale are required to study these turbulent flux dynamics over a landscape. Here, we aim to study how the control of daily and midday latent and sensible heat fluxes over different land cover types is distributed along three axes: energy availability, water availability and exchange efficiency. To this end, observations from 19 eddy covariance flux tower sites in the Netherlands, covering six different land cover types located within the same climatic zone, were used in a regression analysis to explain the observed dynamics and find the principle drivers. The resulting relative position of these sites along the three axes suggests that land cover partly explains the variance of daily and midday turbulent fluxes. We found that evaporation dynamics from grassland, peatland swamp and cropland sites could mostly be explained by energy availability. Forest evaporation can mainly be explained by water availability, urban evaporation by water availability and exchange efficiency, and open water evaporation can almost entirely be explained by exchange efficiency. We found that the sensible heat flux is less sensitive to land cover type. This demonstrates that the land‐atmosphere interface plays an active role in the shedding of sensible heat. Our results contribute to a better understanding of the dynamics of evaporation over different land cover types and may help to optimize, and potentially simplify, models to predict evaporation.

Quantification of soil N2O and CH4 fluxes using the flux gradient method on a drainage water managed farm on the eastern shore of Maryland

Drainage water management (DWM) is an effective best management practice (BMP) to reduce hydrological nitrate export from croplands to surface and ground water by controlling the timing and the amount of ditch discharge and retaining water within ditches and adjacent fields using drainage control structures (DCS). While the intended consequences of maintaining higher water table levels are to increase denitrification and thereby decrease nitrate leaching, an unintended consequence is possible increased production of nitrous oxide (N2O) from denitrification and methane (CH4) from methanogenesis, both potent greenhouse gasses (GHGs). Hence, application of DWM may lead to a "pollution swapping" concern – i.e., does DWM trade reduction of nitrate concentrations in ditch water for increases in soil emissions of N2O and CH4 to the atmosphere?Here we employed the micrometeorological flux gradient (FG) technique to a corn-soybean rotation on an operational farm with DCS in eastern Maryland on the Delmarva Peninsula to answer this question. Soil N2O and CH4 fluxes were quantified under DWM and non-DWM management of a soybean crop without N fertilization (2018) and a corn crop with synthetic N fertilization (2019). To our knowledge, this is the first study employing a micrometeorological method to evaluate the effects of agricultural DWM on GHG emissions. No consistent or statistically significant differences in N2O and CH4 fluxes were observed between DWM and non-DWM fields, suggesting that DWM did not trade reduced nitrate leaching for increased soil GHG emissions. The FG measurements were also compared with chamber measurements, which revealed similar patterns, but chamber measurements had large spatial variability and overall higher daily mean flux estimates, while the tower measurements revealed more frequent, short-lived N2O pulses following fertilization and precipitation events. This research adds to the existing understanding of benefits and risks of DWM as a BMP.

Global terrestrial nitrogen uptake and nitrogen use efficiency

Abstract Plant biomass production (BP), nitrogen uptake (Nup) and their ratio, and nitrogen use efficiency (NUE) must be quantified to understand how nitrogen (N) cycling constrains terrestrial carbon (C) uptake. But the controls of key plant processes determining Nup and NUE, including BP, C and N allocation, tissue C:N ratios and N resorption efficiency (NRE), remain poorly known. We compiled measurements from 804 forest and grassland sites and derived regression models for each of these processes with growth temperature, vapour pressure deficit, stand age, soil C:N ratio, fAPAR (remotely sensed fraction of photosynthetically active radiation absorbed by green vegetation) and growing‐season average daily incident photosynthetic photon flux density (gPPFD; effectively the seasonal concentration of light availability, which increases polewards) as predictors. An empirical model for leaf N was based on optimal photosynthetic capacity (a function of gPPFD and climate) and observed leaf mass per area. The models were used to produce global maps of Nup and NUE. Global BP was estimated as 72 Pg C/year; Nup as 950 Tg N/year; and NUE as 76 g C/g N. Forest BP was found to increase with growth temperature and fAPAR and to decrease with stand age, soil C:N ratio and gPPFD. Forest NUE is controlled primarily by climate through its effect on C allocation—especially to leaves, being richer in N than other tissues. NUE is greater in colder climates, where N is less readily available, because below‐ground allocation is increased. NUE is also greater in drier climates because leaf allocation is reduced. NRE is enhanced (further promoting NUE) in both cold and dry climates. Synthesis. These findings can provide observationally based benchmarks for model representations of C–N cycle coupling. State‐of‐the‐art vegetation models in the TRENDY ensemble showed variable performance against these benchmarks, and models including coupled C–N cycling produced relatively poor simulations of Nup and NUE.

Temporal Structures in Positron Spectra and Charge-Sign Effects in Galactic Cosmic Rays.

We present the precision measurements of 11years of daily cosmic positron fluxes in the rigidity range from 1.00 to 41.9GV based on 3.4×10^{6} positrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The positron fluxes show distinctly different time variations from the electron fluxes at short and long timescales. A hysteresis between the electron fluxes and the positron fluxes is observed with a significance greater than 5σ at rigidities below 8.5GV. On the contrary, the positron fluxes and the proton fluxes show similar time variation. Remarkably, we found that positron fluxes are modulated more than proton fluxes with a significance greater than 5σ for rigidities below 7GV. These continuous daily positron fluxes, together with AMS daily electron, proton, and helium fluxes over an 11-year solar cycle, provide unique input to the understanding of both the charge-sign and mass dependencies of cosmic rays in the heliosphere.

The Response of Daily Carbon Dioxide and Water Vapor Fluxes to Temperature and Precipitation Extremes in Temperate and Boreal Forests

Forest ecosystems in the mid-latitudes of the Northern Hemisphere are significantly affected by frequent extreme weather events. How different forest ecosystems respond to these changes is a major challenge. This study aims to assess differences in the response of daily net ecosystem exchange (NEE) of CO2 and latent heat flux (LE) between different boreal and temperate ecosystems and the atmosphere to extreme weather events (e.g., anomalous temperature and precipitation). In order to achieve the main objective of our study, we used available reanalysis data and existing information on turbulent atmospheric fluxes and meteorological parameters from the global and regional FLUXNET databases. The analysis of NEE and LE responses to high/low temperature and precipitation revealed a large diversity of flux responses in temperate and boreal forests, mainly related to forest type, geographic location, regional climate conditions, and plant species composition. During the warm and cold seasons, the extremely high temperatures usually lead to increased CO2 release in all forest types, with the largest response in coniferous forests. The decreasing air temperatures that occur during the warm season mostly lead to higher CO2 uptake, indicating more favorable conditions for photosynthesis at relatively low summer temperatures. The extremely low temperatures in the cold season are not accompanied by significant NEE anomalies. The response of LE to temperature variations does not change significantly throughout the year, with higher temperatures leading to LE increases and lower temperatures leading to LE reductions. The immediate response to heavy precipitation is an increase in CO2 release and a decrease in evaporation. The cumulative effect of heavy precipitations is opposite to the immediate effect in the warm season and results in increased CO2 uptake due to intensified photosynthesis in living plants under sufficient soil moisture conditions.

Твердый сток реки Дон и поступление взвеси в дельту при нагонах: статистическое моделирование и сопоставление в период маловодья

Statistical modeling of the Don River solid runoff based on water discharge and turbidity measurements obtained at the hydrological station in the village of Razdorskaya for the twelve-year period 2009–2020 was carried out. The WRTDS (Weighted Regressions on Time, Discharge, and Season) and WRTDSKalman (WRTDS with Kalman filtering) methods were applied. The developed statistical model is aimed at solving the problem of the imbalance between the regularity of collecting data on water discharge and data on the concentration of suspended matter by “restoring” the concentration values on days without measurements based on data on the most “similar” days with measurements in terms of time, discharge and season and does not claim to describe a relationship between the concentration of the constituent of interest and discharge. The quality of the developed statistical model and its modification were checked. The average daily concentrations and fluxes of suspended matter were compared with estimates of the volumes of suspended material deposited during periods of recurring strong surge phenomena. A comparative assessment of sea and river factors contributions to the transport and sedimentation of suspended matter in the Don River delta was fulfilled.

Optimizing Moss and Lichen Transplants as Biomonitors of Airborne Anthropogenic Microfibers.

Anthropogenic microfibers (mfs) are synthetic particles composed of cellulose (cotton, rayon, acetate, etc.) or petrochemical-based polymers (i.e., microplastics-MPs) that are less than 5 mm in length. The accumulation of mfs, including MPs, in the moss Hypnum cupressiforme and the lichen Pseudevernia furfuracea was compared in a transplant experiment lasting 6 weeks. We also tested the effects of the bag used for transplants on the accumulation of mfs. Anthropogenic particles trapped by both biomonitors were mostly filamentous (99% mfs), and their number was overall higher in the moss (mean ± s.d. 102 ± 24) than in the lichen (mean ± s.d. 87 ± 17), at parity of sample weight. On average, mfs found in lichen were significantly longer than those found in moss bags, suggesting that lichens are less efficient at retaining smaller mfs. Exposure without the net yielded a higher mfs number accumulation in both species, indicating that "naked" transplants provide greater sensitivity. The calculation of daily fluxes evidenced a loss of mfs in the lichen, suggesting the presence of more stable bonds between moss and mfs. Raman microspectroscopy carried out on about 100 debris confirms the anthropogenic nature of mfs, of which 20% were MPs. Overall results indicate that moss is preferable to lichen in the biomonitoring of airborne mfs especially when exposed naked.

Monitoring of carbon-water fluxes at Eurasian meteorological stations using random forest and remote sensing

Simulating the carbon-water fluxes at more widely distributed meteorological stations based on the sparsely and unevenly distributed eddy covariance flux stations is needed to accurately understand the carbon-water cycle of terrestrial ecosystems. We established a new framework consisting of machine learning, determination coefficient (R2), Euclidean distance, and remote sensing (RS), to simulate the daily net ecosystem carbon dioxide exchange (NEE) and water flux (WF) of the Eurasian meteorological stations using a random forest model or/and RS. The daily NEE and WF datasets with RS-based information (NEE-RS and WF-RS) for 3774 and 4427 meteorological stations during 2002–2020 were produced, respectively. And the daily NEE and WF datasets without RS-based information (NEE-WRS and WF-WRS) for 4667 and 6763 meteorological stations during 1983–2018 were generated, respectively. For each meteorological station, the carbon-water fluxes meet accuracy requirements and have quasi-observational properties. These four carbon-water flux datasets have great potential to improve the assessments of the ecosystem carbon-water dynamics.

A New Technique for the Passive Monitoring of Particulate Matter: Olive Pollen Grains as Bioindicators of Air Quality in Urban and Industrial Areas

A new technique for the passive monitoring of particulate matter was developed, exploiting olive pollen as a bioindicator. We tested the pollen bioaccumulation efficiency when exposed to atmospheric particulate at three different sites in the Umbria region (Central Italy). Pollen grains, placed into sampling holders, were exposed in Perugia, a polluted town impacted by traffic emissions; in Terni, an industrial hotspot; and at Monte Martano, a regional rural site. At the end of the exposure period, the daily deposition fluxes of the soluble and insoluble elements and soluble molecular ions present in particulate were determined, and the bioaccumulation factor (BAF) and bioaccumulation index over time (BAIt) were derived to validate the passive monitoring system, distinguish the deposition contribute from natural pollen composition, and interpret the temporal dependence of the pollen exposure to pollutants. We observed BAFs greater than 1, which means that bioaccumulation occurs, and pollen can be considered a good passive sampler for several crustal and anthropic ions and toxic elements at all sites. BAIt values greater than 1 were detected only for some of the ions and metals previously present in the pollen, like Ca, Cr, and Mn at Terni; and nitrate, Ca, and Mn at Monte Martano and Perugia.

Isotopic composition and emission characteristics of CO2 and CH4 in glacial lakes of the Tibetan Plateau

Carbon dioxide (CO2) and methane (CH4) emissions from freshwater ecosystems are predicted to increase under climate warming. However, freshwater ecosystems in glacierized regions differ critically from those in non-glacierized regions. The potential emissions of CO2 and CH4 from glacierized environments in the Tibetan Plateau (TP) were only recently recognized. Here, the first direct measurement of CO2 and CH4 emission fluxes and isotopic composition during the spring of 2022 in 13 glacial lakes of the TP revealed that glacial lakes were the previously overlooked CO2 sinks due to chemical weathering in glacierized regions. The daily average CO2 flux was −5.1 ± 4.4 mmol m−2 d−1, and the CO2 consumption could reach 38.9 Gg C-CO2 yr−1 by all glacial lakes in the TP. This consumption might be larger during summer when glaciers experience intensive melting, highlighting the importance of CO2 uptake by glacial lakes on the global carbon cycle. However, the studied glacial lakes were CH4 sources with total emission flux ranging from 4.4 ± 3.3 to 4082.5 ± 795.6 μmol m−2 d−1. The large CH4 range was attributed to ebullition found in three of the glacial lakes. Low dissolved organic carbon concentrations and CH4 oxidation might be responsible for the low CH4 diffusive fluxes of glacial lakes without ebullition. In addition, groundwater input could alter CO2 and CH4 emissions from glacial lakes. CH4 in glacial lakes probably had a thermogenic source; whereas CO2 was influenced mainly by atmospheric input, as well as organic matter remineralization and CH4 oxidation. Overall, glacial lakes in the TP play an important role in the global carbon cycle and budget, and more detailed isotopic and microbial studies are needed to constrain the contributions of different pathways to CO2 and CH4 production, consumption and emissions.

Evapotranspiration controls across spatial scales of heterogeneity

AbstractIn semi‐arid regions where irrigation causes thermal surface heterogeneities, evapotranspiration is controlled not only by the land surface but also by the interaction between the surface and the atmospheric boundary layer. The spatial scale of heterogeneity impacts the processes that drive the diurnal variability of evapotranspiration. In this study, we combine data with a conceptual, coupled land–atmosphere model to study the drivers of evapotranspiration across spatial scales of heterogeneity for the Land Interactions with the Atmosphere in the Iberian Semi‐arid Environment (LIAISE) field campaign. We use a latent heat tendency equation as a diagnostic tool to quantify the contributions of various surface‐ and boundary‐layer driven processes on surface latent heat flux. We define the following spatial scales based on surface characteristics: regional, landscape, and local. We find that, at the regional and landscape scales (1 km), the feedback mechanisms between the surface fluxes and the resulting boundary‐layer dynamics enhance the daily latent heat flux by 64% to 77%. Conversely, at the local scale (100 m), surface‐driven processes are most important for governing evapotranspiration. At the local scale, we find that the energy stored at the surface enhances evaporation in the late afternoon, which could explain the observed time lag between net radiation and latent heat flux. Furthermore, the combined effects of entrainment at the boundary‐layer top and advection of heat and moisture enhance daily latent heat by 27% at the regional scale to 43% at the local scale. This analysis also has implications for the land‐surface modelling community. It suggests that properly reproducing evapotranspiration to capture the relevant processes depends on capacity of the model to resolve the interaction of scales in surface heterogeneous conditions.

Application of Satellite‐Based Detections of Arctic Bromine Explosion Events Within GEOS‐Chem

AbstractDuring polar spring, periods of elevated tropospheric bromine drive near complete removal of surface ozone. These events impact the tropospheric oxidative capacity and are an area of active research with multiple approaches for representing the underlying processes in global models. We present a method for parameterizing emissions of molecular bromine (Br2) over the Arctic using satellite retrievals of bromine monoxide (BrO) from the Ozone Monitoring Instrument (OMI). OMI retrieves column BrO with daily near global coverage, and we use the GEOS‐Chem chemical mechanism, run online within the Goddard Earth Observing System Earth System Model to identify hotspots of BrO likely associated with polar processes. To account for uncertainties in modeling background BrO, hotspots are only identified where the difference between OMI and modeled columns exceeds a statistical threshold. The resulting hotspot columns are a lower‐limit for the portion of OMI BrO attributable to bromine explosion events. While these hotspots are correlated with BrO measured in the lower troposphere over the Arctic Ocean, a case study of missing detections of near‐surface BrO is identified. Daily flux of Br2 is estimated from hotspot columns of BrO using internal model parameters. When the emissions are applied, BrO hotspots are modeled with a 5% low bias. The sensitivity of the resulting ozone simulations to the treatment of background uncertainties in the BrO column is demonstrated. While periods of isolated, large (>50%) decreases in surface ozone are modeled, this technique does not simulate the low ozone observed at coastal stations and consistently underestimates ozone loss during March.

A comprehensive analysis of CO2 exchanges in agro-ecosystems based on a generic soil-crop model-derived methodology

Carbon emissions in agriculture play a major role in climate change. Modelling studies enable to investigate the impacts of climate change in crops, accounting for soil organic carbon feedbacks and CO2 concentrations. But it is primordial that crop models properly consider the CO2 exchanges at the level of crop rotations beyond the cycle of a single crop. With this goal in mind, we used the outputs of the soil-crop model STICS in its standard pre-parameterized version to model (i) the Gross Primary Productivity (GPP), derived from the autotrophic respiration and the Net Primary Productivity, which is computed through the daily change in plant carbon (C) pools; (ii) the Ecosystem Respiration (RECO), with the autotrophic component being derived from the plant biomass, plant nitrogen concentration and GPP, and the heterotrophic component from the mineralization of residues and organic matter; and (iii) the Net Ecosystem Exchange, equal to the sum of GPP and RECO. The comparison of simulations with field observations indicates that the model is able to simulate accurately daily CO2 fluxes originating from a long-term and diversified crop rotation (efficiency EF equal to 0.79 for GPP, 0.59 for RECO and 0.67 for NEE). Concerning the evaluation of the cumulated fluxes over the 16-year rotation, the model is able to evaluate it accurately for RECO, with a slight underestimation (normalized deviation ND = 15.7%), and very accurately for GPP (ND = 5.12%). But for NEE, the relative overestimation is higher (ND = 62.2%), indicating that a more precise estimation of HR is required to obtain reliable net C budgets. The model also succeeds to capture the trends in the influence of several environmental drivers on CO2 fluxes. It globally proves to be a valuable tool in the investigation of CO2 exchanges of crop rotations in historical and future climatic conditions.

An Investigation into Thermal Performance of Mist Water System and The Related Consumption Energy

Experimental tests were conducted to investigate the thermal performance (cooling effect) of water mist system consisting of 5μm volume median diameter droplets in reducing the heat gain entering a room through the roof and the west wall by reducing the outside surface temperature due to the evaporative cooling effect during the hot dry summer of Baghdad/Iraq. The test period was Fifty one days during the months May, June, and July 2012. The single test day consists of 16 test hours starting from 8:00 am to 12:00 pm. The results showed a reduction range of 1.71 to 15.5℃ of the roof outside surface temperature and 21.3 to 76.6% reduction in the daily heat flux entering the room through the roof compared with the case of not using water mist system. Also the results show a reduction range of 1.3 to 18.8℃ in the wall outside surface temperature. Finally numerical simulation with ANSYS-FLUENT.14 was conducted to compare its results with the experimental results of the roof and wall tests.

Marine Heatwaves Contribute More to Changing Air‐Water Exchange of Semi‐Volatile Organic Compounds Than Mean Sea Surface Temperature Rise

AbstractA consequence of global warming, marine heatwaves (MHWs), have destructive effects on local marine ecology. However, few studies have examined their influence on the biogeochemical carbon cycle. Here we show, global warming has changed the air‐water exchange of semi‐volatile organic compounds (SVOCs), and MHWs contribute more to changing air‐water exchange of SVOCs than increases in mean sea surface temperature (SST). Higher temperatures increased the flux of SVOCs exchange from water to air and suppressed the exchange from air to water. As a result, the MHWs lead to a 13.27% decrease for the daily flux of single SVOC and 0.05% decrease for annual flux of total SVOCs. In contrast, the raising of mean SST result of 0.14% decrease for the daily flux of single SVOC, and 0.01% decrease for annual flux of total SVOCs. Moreover, we observed inversion in the direction of SVOCs air‐water exchange during some MHWs.