Modeling nighttime ecosystem respiration from measured CO2concentration and air temperature profiles using inverse methods

Aspects of carbon exchange were investigated in typical steppe east of Xilinhot city in Inner Mongolia. Four treatments with four replicates were imposed in a randomised block design: Control (C), warming (T), increased precipitation (P) and combined warming and increased precipitation (TP). Increased precipitation significantly increased both ecosystem respiration (ER) and soil respiration (SR) rates. Warming significantly reduced the ER rate but not the SR rate. The combination of increased precipitation and warming produced an intermediate response. The sensitivity of ER and SR to soil temperature and air temperature was assessed by calculating Q10 values: the increase in respiration for a 10°C increase in temperature. Q10 was lowest under T and TP, and highest under P. Both ER and SR all had significantly positive correlation with soil moisture. Increased precipitation increased net ecosystem exchange and gross ecosystem productivity, whereas warming reduced them. The combination of warming and increased precipitation had an intermediate effect. Both net ecosystem exchange and gross ecosystem productivity were positively related to soil moisture and negatively related to soil and air temperature. These findings suggest that predicted climate change in this region, involving both increased precipitation and warmer temperatures, will increase the net ecosystem exchange in the Stipa steppe meaning that the ecosystem will fix more carbon.

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A temperature threshold to identify the driving climate forces of the respiratory process in terrestrial ecosystems

10.5194/bg-2017-345 ◽

2017 ◽

Author(s):

Zhiyuan Zhang ◽

Renduo Zhang ◽

Yang Zhou ◽

Alessandro Cescatti ◽

Georg Wohlfahrt ◽

...

Keyword(s):

Air Temperature ◽

Driving Forces ◽

Ecosystem Respiration ◽

Large Fraction ◽

Terrestrial Ecosystem ◽

Terrestrial Ecosystems ◽

Co2 Concentration ◽

Temperature Threshold ◽

Current Scenario ◽

Ecosystem Flux

Abstract. Terrestrial ecosystem respiration (Re) is the major source of CO2 release and constitutes the second largest carbon flux between the biosphere and atmosphere. Therefore, climate-driven changes of Re may greatly impact on future atmospheric CO2 concentration. The aim of this study was to derive an air temperature threshold for identifying the driving climate forces of the respiratory process in terrestrial ecosystems within different temperature zones. For this purpose, a global dataset of 647 site-years of ecosystem flux data collected at 152 sites has been examined. Our analysis revealed an ecosystem threshold of mean annual air temperature (MAT) of 11 &pm; 2.3 °C. In ecosystems with the MAT below this threshold, the maximum Re rates were primarily dependent on temperature and respiration was mainly a temperature-driven process. On the contrary, in ecosystems with the MAT greater than 11 ± 2.3 °C, in addition to temperature, other driving forces, such as water availability and surface heat flux, became significant drivers of the maximum Re rates and respiration was a multi-factor-driven process. The information derived from this study highlight the key role of temperature as main controlling factor of the maximum Re rates on a large fraction of the terrestrial biosphere, while other driving forces reduce the maximum Re rates and temperature sensitivity of the respiratory process. These findings are particularly relevant under the current scenario of rapid global warming, given that the potential climate-induced changes in ecosystem respiration may lead to substantial anomalies in the seasonality and magnitude of the terrestrial carbon budget.

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96/06532 Slab heat loss calculation with non-uniform inside air temperature profiles

Fuel and Energy Abstracts ◽

10.1016/s0140-6701(97)83905-7 ◽

1996 ◽

Vol 37 (6) ◽

pp. 457

Keyword(s):

Heat Loss ◽

Air Temperature ◽

Temperature Profiles ◽

Loss Calculation

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Simulating carbon and water cycles of larch forests in East Asia by the BIOME-BGC model with AsiaFlux data

Biogeosciences ◽

10.5194/bg-7-959-2010 ◽

2010 ◽

Vol 7 (3) ◽

pp. 959-977 ◽

Cited By ~ 38

Author(s):

M. Ueyama ◽

K. Ichii ◽

R. Hirata ◽

K. Takagi ◽

J. Asanuma ◽

...

Keyword(s):

Air Temperature ◽

Ecosystem Respiration ◽

Spatial Scales ◽

Model Performance ◽

Limiting Factors ◽

Model Parameters ◽

Total Precipitation ◽

Water Conditions ◽

Larch Forests ◽

Water Cycles

Abstract. Larch forests are widely distributed across many cool-temperate and boreal regions, and they are expected to play an important role in global carbon and water cycles. Model parameterizations for larch forests still contain large uncertainties owing to a lack of validation. In this study, a process-based terrestrial biosphere model, BIOME-BGC, was tested for larch forests at six AsiaFlux sites and used to identify important environmental factors that affect the carbon and water cycles at both temporal and spatial scales. The model simulation performed with the default deciduous conifer parameters produced results that had large differences from the observed net ecosystem exchange (NEE), gross primary productivity (GPP), ecosystem respiration (RE), and evapotranspiration (ET). Therefore, we adjusted several model parameters in order to reproduce the observed rates of carbon and water cycle processes. This model calibration, performed using the AsiaFlux data, substantially improved the model performance. The simulated annual GPP, RE, NEE, and ET from the calibrated model were highly consistent with observed values. The observed and simulated GPP and RE across the six sites were positively correlated with the annual mean air temperature and annual total precipitation. On the other hand, the simulated carbon budget was partly explained by the stand disturbance history in addition to the climate. The sensitivity study indicated that spring warming enhanced the carbon sink, whereas summer warming decreased it across the larch forests. The summer radiation was the most important factor that controlled the carbon fluxes in the temperate site, but the VPD and water conditions were the limiting factors in the boreal sites. One model parameter, the allocation ratio of carbon between belowground and aboveground, was site-specific, and it was negatively correlated with the annual climate of annual mean air temperature and total precipitation. Although this study substantially improved the model performance, the uncertainties that remained in terms of the sensitivity to water conditions should be examined in ongoing and long-term observations.

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Forecasting of vertical temperature profiles in the atmosphere during nocturnal radiation inversions from air temperature trend at screen height

Quarterly Journal of the Royal Meteorological Society ◽

10.1002/qj.49710243114 ◽

1976 ◽

Vol 102 (431) ◽

pp. 173-180 ◽

Cited By ~ 32

Author(s):

D. Anfossi ◽

P. Bacci ◽

A. Longhetto

Keyword(s):

Air Temperature ◽

Temperature Trend ◽

Temperature Profiles ◽

Vertical Temperature ◽

Screen Height

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Finite difference analysis of respiratory heat transfer

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.6.2252 ◽

1986 ◽

Vol 61 (6) ◽

pp. 2252-2259 ◽

Cited By ~ 27

Author(s):

E. P. Ingenito ◽

J. Solway ◽

E. R. McFadden ◽

B. M. Pichurko ◽

E. G. Cravalho ◽

...

Keyword(s):

Heat Transfer ◽

Heat Loss ◽

Air Temperature ◽

Breathing Pattern ◽

Human Subjects ◽

Minute Ventilation ◽

Tracheobronchial Tree ◽

Temperature Profiles ◽

Opposite Pattern ◽

Normal Human

A numerical computer model of heat and water transfer within the tracheobronchial tree of humans was developed based on an integral formulation of the first law of thermodynamics. Simulation results were compared with directly measured intraluminal airway temperature profiles previously obtained in normal human subjects, and a good correlation was demonstrated. The model was used to study aspects of regional pulmonary heat transfer and to predict the outcomes of experiments not yet performed. The results of these simulations show that a decrease in inspired air temperature and water content at fixed minute ventilation produces a proportionately larger increase in heat loss from extrathoracic airways relative to intrathoracic, whereas an increase in minute ventilation at fixed inspired air conditions produces the opposite pattern, with cold dry air penetrating further into the lung, and that changes in breathing pattern (tidal volume and frequency) at fixed minute ventilation and fixed inspiratory-to-expiratory (I/E) ratio do not affect local air temperature profiles and heat loss, whereas changes in I/E ratio at fixed minute ventilation do cause a significant change.

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Moist moss tundra on Kapp Linne, Svalbard is a net source of CO<sub>2</sub> and CH<sub>4</sub> to the atmosphere

10.5194/bg-2021-308 ◽

2021 ◽

Author(s):

Anders Lindroth ◽

Norbert Pirk ◽

Ingibjörg S. Jónsdóttir ◽

Christian Stiegler ◽

Leif Klemedtsson ◽

...

Keyword(s):

Soil Moisture ◽

Air Temperature ◽

Ecosystem Respiration ◽

Net Ecosystem Exchange ◽

Growing Season ◽

Mean Value ◽

The Arctic ◽

Spatial And Temporal Variability ◽

Annual Nee ◽

Greenness Index

Abstract. We measured CO2 and CH4 fluxes using chambers and eddy covariance (only CO2) from a moist moss tundra in Svalbard. The average net ecosystem exchange (NEE) during the summer (June–August) was −0.40 g C m−2 day−1 or −37 g C m−2 for the whole summer. Including spring and autumn periods the NEE was reduced to −6.8 g C m−2 and the annual NEE became positive, 24.7 gC m−2 due to the losses during the winter. The CH4 flux during the summer period showed a large spatial and temporal variability. The mean value of all 214 samples was 0.000511 ± 0.000315 µmol m−2s−1 which corresponds to a growing season estimate of 0.04 to 0.16 g CH4 m−2. We find that this moss tundra emits about 94–100 g CO2-equivalents m−2 yr−1 of which CH4 is responsible for 3.5–9.3 % using GWP100 of 27.9 respectively GWP20. Air temperature, soil moisture and greenness index contributed significantly to explain the variation in ecosystem respiration (Reco) while active layer depth, soil moisture and greenness index were the variables that best explained CH4 emissions. Estimate of temperature sensitivity of Reco and gross primary productivity showed that a modest increase in air temperature of 1 degree did not significantly change the NEE during the growing season but that the annual NEE would be even more positive adding another 8.5 g C m−2 to the atmosphere. We tentatively suggest that the warming of the Arctic that has already taken place is partly responsible for the fact that the moist moss tundra now is a source of CO2 to the atmosphere.

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Controls on winter ecosystem respiration at mid- and high-latitudes

Biogeosciences Discussions ◽

10.5194/bgd-7-6997-2010 ◽

2010 ◽

Vol 7 (5) ◽

pp. 6997-7027 ◽

Cited By ~ 4

Author(s):

T. Wang ◽

P. Ciais ◽

S. Piao ◽

C. Ottle ◽

P. Brender ◽

...

Keyword(s):

Soil Temperature ◽

Air Temperature ◽

Ecosystem Respiration ◽

Energy Parameter ◽

Satellite Observation ◽

Temporal Analysis ◽

Data Sets ◽

Area Index ◽

Wetland Ecosystems ◽

The Impact

Abstract. Winter CO2 fluxes represent an important component of the annual carbon budget in northern ecosystems. Understanding winter respiration processes and their responses to climate change is also central to our ability to assess terrestrial carbon cycle and climate feedbacks in the future. The factors influencing the spatial and temporal pattern of winter respiration (RECO) of northern ecosystems are poorly understood. For this reason, we analyzed eddy covariance flux data sets from 57 ecosystem sites ranging from ~35° N to ~70° N. Deciduous forests carry the highest winter RECO ratios (9.7–10.5 g C m−2 d−1), when winter is defined as the period during which air temperature remained below 0 °C. By contrast, wetland ecosystems had the lowest winter RECO (2.1–2.3 g C m−2 d−1). Evergreen needle-leaved forests, grasslands and croplands were characterized by intermediate winter RECO values of 7.4–7.9 g C m−2 d−1, 5.8–6.0 g C m−2 d−1, and 5.2–5.3 g C m−2 d−1, respectively. Cross site analysis showed that winter air or soil temperature, and the seasonal amplitude of the leaf area index inferred from satellite observation, which is a proxy for the amount of litter available for RECO in the subsequent winter, are the two main factors determining spatial pattern of daily mean winter RECO. Together, these two factors can explain 71% (Tair, ΔLAI) or 69% (Tsoil, ΔLAI) of the spatial variance of winter RECO across the 57 sites. The spatial temperature sensitivity of daily winter RECO was determined empirically by fitting an Arrhenius relationship to the data. The activation energy parameter of this relationship was found to decrease at increasing soil temperature at a rate of 83.1 KJ ° C-1 (r = −0.32, p < 0.05), which implies a possible dampening of the increase in winter RECO due to global warming. The interannual variability of winter RECO is better explained by soil temperature than by air temperature, likely due to the insulating effects of snow cover. The increase in winter RECO with a 1 °C warming based calculated from the spatial analysis was almost that double that calculated from the temporal analysis. Thus, models that calculate the effects of warming on RECO based only on spatial analyses could be over-estimating the impact.

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Vertical Temperature Profiles and Cooling Load in Large Spaces Ventilated by Stratified Air-Conditioning Systems: Scale-Model Experiment and Nodal Modeling

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4046214 ◽

2020 ◽

Vol 12 (5) ◽

Author(s):

Yukun Xu ◽

Xin Wang ◽

Chenlu Shi ◽

Xiaoqiang Huai ◽

Fei Wang

Keyword(s):

Heat Transfer ◽

Air Temperature ◽

Air Conditioning ◽

Heat Transfer Process ◽

Scale Model ◽

Temperature Profiles ◽

Model Experiments ◽

Thermal Environments ◽

Load Calculation ◽

Nodal Model

Abstract An improved heat balance nodal model is proposed to predict the inner wall temperature profiles and calculate the stratified air-conditioning load in large spaces. The model aims to weaken the correlation between load calculation methods and indoor airflow patterns, and to ensure the synchronization of each heat transfer process, so as to be closer to actual situations. The scale-model experiments were conducted in an enthalpy different laboratory in University of Shanghai for Science and Technology (USST) in Shanghai, China. This paper took the air distribution of nozzle air supply system as an example to calculate the inner wall temperatures and the stratified air-conditioning load by the nodal model and verified by the scale-model experiments. The results showed the maximum deviations of the experimental and theoretical values for the inner wall temperatures, the heat transfer load from the nonair-conditioned (NAC) area and the stratified air-conditioning load were all within 5%. The effects of the air temperature in the NAC area on the heat transfer load from the NAC area and the stratified air-conditioning load were analyzed, and the load nomogram was produced. It was found the heat transfer load from the NAC area accounted for 10–30% of the stratified air-conditioning load. The load nomogram compared two methods for determining the air temperature in the NAC area and gave the recommended one. The findings in this paper can be used to further develop load calculation models for non-uniform thermal environments.

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