scholarly journals Optimal use of buffer volumes for the measurement of atmospheric gas concentration in multi-point systems

2016 ◽  
Author(s):  
Alessandro Cescatti ◽  
Barbara Marcolla ◽  
Ignacio Goded ◽  
Carsten Gruening
Keyword(s):  
Empirical Relationship ◽  
Concentration Field ◽  
Co2 Concentration ◽  
Surface Fluxes ◽  
Weighted Averaging ◽  
Atmospheric Measurements ◽  
Sampling System ◽  
Temporal Sampling ◽  
Technical Specifications ◽  
Volume Size

Abstract. Accurate multi-point monitoring systems are required to derive atmospheric measurements of greenhouse gas concentrations both for the calculation of surface fluxes with inversion transport models and for the estimation of non-turbulent components of the mass balance equation (i.e. advection and storage fluxes) at eddy covariance sites. When a single analyser is used to monitor multiple sampling points, the deployment of buffer volumes (BV) along sampling lines can reduce the uncertainty due to the discrete temporal sampling of the signal. In order to optimize the use of buffer volumes we explored various setups by simulating their effect on time series of high-frequency CO2 concentration collected at three Fluxnet sites. Besides, we proposed a novel scheme to calculate half hourly weighted averages from discrete point samples, accounting for the probabilistic fraction of the signal generated in the averaging period. Results show that the use of BV with the new averaging scheme reduces the mean absolute errors (MAE) up to 80 % compared to set-up without BV and up to 60 % compared to the case with BV and a standard, non-weighted averaging scheme. The MAE of CO2 concentration measurements was observed to depend on the variability of the concentration field and on the size of BV, which therefore have to be carefully dimensioned. The optimal volume size depends on two main features of the instrumental setup: the number of measurement points and the time needed to sample at one point (i.e. line purging plus sampling time). A linear and consistent relationship was observed at all sites between the sampling frequency, which summarizes the two features mentioned above, and the renewal frequency associated to the volume. Ultimately, this empirical relationship can be applied to estimate the optimal volume size according to the technical specifications of the sampling system.

scholarly journals Optimal use of buffer volumes for the measurement of atmospheric gas concentration in multi-point systems

2016 ◽  
Vol 9 (9) ◽  
pp. 4665-4672 ◽  
Author(s):  
Alessandro Cescatti ◽  
Barbara Marcolla ◽  
Ignacio Goded ◽  
Carsten Gruening
Keyword(s):  
Empirical Relationship ◽  
Concentration Field ◽  
Co2 Concentration ◽  
Surface Fluxes ◽  
Weighted Averaging ◽  
Atmospheric Measurements ◽  
Temporal Sampling ◽  
Technical Specifications ◽  
Set Up ◽  
Volume Size

Abstract. Accurate multi-point monitoring systems are required to derive atmospheric measurements of greenhouse gas concentrations both for the calculation of surface fluxes with inversion transport models and for the estimation of non-turbulent components of the mass balance equation (i.e. advection and storage fluxes) at eddy covariance sites. When a single analyser is used to monitor multiple sampling points, the deployment of buffer volumes (BVs) along sampling lines can reduce the uncertainty due to the discrete temporal sampling of the signal. In order to optimize the use of buffer volumes we explored various set-ups by simulating their effect on time series of high-frequency CO2 concentration collected at three Fluxnet sites. Besides, we proposed a novel scheme to calculate half-hourly weighted arithmetic means from discrete point samples, accounting for the probabilistic fraction of the signal generated in the averaging period. Results show that the use of BVs with the new averaging scheme reduces the mean absolute error (MAE) up to 80 % compared to a set-up without BVs and up to 60 % compared to the case with BVs and a standard, non-weighted averaging scheme. The MAE of CO2 concentration measurements was observed to depend on the variability of the concentration field and on the size of BVs, which therefore have to be carefully dimensioned. The optimal volume size depends on two main features of the instrumental set-up: the number of measurement points and the time needed to sample at one point (i.e. line purging plus sampling time). A linear and consistent relationship was observed at all sites between the sampling frequency, which summarizes the two features mentioned above, and the renewal frequency associated with the volume. Ultimately, this empirical relationship can be applied to estimate the optimal volume size according to the technical specifications of the sampling system.

scholarly journals A new model of the global biogeochemical cycle of carbonyl sulfide – Part 2: Use of ocs to constrain gross primary productivity of current vegetation models

2014 ◽  
Vol 14 (20) ◽  
pp. 27663-27729 ◽  
Author(s):  
T. Launois ◽  
P. Peylin ◽  
S. Belviso ◽  
B. Poulter
Keyword(s):  
Northern Hemisphere ◽  
Seasonal Variations ◽  
Gross Primary Production ◽  
Experimental Studies ◽  
Carbonyl Sulfide ◽  
Surface Fluxes ◽  
Atmospheric Measurements ◽  
Mixing Ratios ◽  
Co2 Diffusion ◽  
Vegetation Models

Abstract. Clear analogies between carbonyl sulfide (OCS) and carbon dioxide (CO2) diffusion pathways through leaves have been revealed by experimental studies with plant uptake playing an important role for the atmospheric budget of both species. Here we use atmospheric OCS to evaluate the gross primary production (GPP) of three dynamic global vegetation models (LPJ, NCAR-CLM4 and ORCHIDEE). Vegetation uptake of OCS is modeled as a linear function of GPP and LRU, the ratio of OCS to CO2 deposition velocities to plants. New parameterizations for the non-photosynthetic sinks (oxic soils, atmospheric oxidation) and biogenic sources (oceans and anoxic soils) of OCS are also provided. Despite new large oceanic emissions, global OCS budgets created with each vegetation model show exceeding sinks by several hundreds of Gg S yr−1. An inversion of the surface fluxes (optimization of a global scalar which accounts for flux uncertainties) led to balanced OCS global budgets, as atmospheric measurements suggest, mainly by drastic reduction (−30%) of soil and vegetation uptakes. The amplitude of variations in atmospheric OCS mixing ratios is mainly dictated by the vegetation sink over the Northern Hemisphere. This allows for bias recognition in the GPP representations of the three selected models. Main bias patterns are (i) the terrestrial GPP of ORCHIDEE at high Northern latitudes is currently over-estimated, (ii) the seasonal variations of the GPP are out of phase in the NCAR-CLM4 model, showing a maximum carbon uptake too early in spring in the northernmost ecosystems, (iii) the overall amplitude of the seasonal variations of GPP in NCAR-CLM4 is too small, and (iv) for the LPJ model, the GPP is slightly out of phase for northernmost ecosystems and the respiration fluxes might be too large in summer in the Northern Hemisphere.

scholarly journals Can the Impact of Aerosols on Deep Convection be Isolated from Meteorological Effects in Atmospheric Observations?

2018 ◽  
Vol 75 (10) ◽  
pp. 3347-3363 ◽  
Author(s):  
Wojciech W. Grabowski
Keyword(s):  
Numerical Simulations ◽  
Large Scale ◽  
Cloud Condensation Nuclei ◽  
Deep Convection ◽  
Surface Fluxes ◽  
Phase Iii ◽  
Moist Convection ◽  
Atmospheric Measurements ◽  
The Impact ◽  
Meteorological Effects

Influence of pollution on dynamics of deep convection continues to be a controversial topic. Arguably, only carefully designed numerical simulations can clearly separate the impact of aerosols from the effects of meteorological factors that affect moist convection. This paper argues that such a separation is virtually impossible using observations because of the insufficient accuracy of atmospheric measurements and the fundamental nature of the interaction between deep convection and its environment. To support this conjecture, results from numerical simulations are presented that apply modeling methodology previously developed by the author. The simulations consider small modifications, difficult to detect in observations, of the initial sounding, surface fluxes, and large-scale forcing tendencies. All these represent variations of meteorological conditions that affect deep convective dynamics independently of aerosols. The setup follows the case of daytime convective development over land based on observations during the Large-Scale Biosphere–Atmosphere (LBA) field project in Amazonia. The simulated observable macroscopic changes of convection, such as the surface precipitation and upper-tropospheric cloudiness, are similar to or larger than those resulting from changes of cloud condensation nuclei from pristine to polluted conditions studied previously using the same modeling case. Observations from Phase III of the Global Atmospheric Research Program Atlantic Tropical Experiment (GATE) are also used to support the argument concerning the impact of the large-scale forcing. The simulations suggest that the aerosol impacts on dynamics of deep convection cannot be isolated from meteorological effects, at least for the daytime development of unorganized deep convection considered in this study.

scholarly journals First direct observation of the atmospheric CO<sub>2</sub> year-to-year increase from space

2007 ◽  
Vol 7 (16) ◽  
pp. 4249-4256 ◽  
Author(s):  
M. Buchwitz ◽  
O. Schneising ◽  
J. P. Burrows ◽  
H. Bovensmann ◽  
M. Reuter ◽  
...  
Keyword(s):  
Seasonal Cycle ◽  
Current Knowledge ◽  
Surface Fluxes ◽  
Atmospheric Co2 ◽  
Surface Measurement ◽  
Spectral Radiance ◽  
Satellite Measurements ◽  
Temporal Sampling ◽  
Northern Hemispheric ◽  
Total Column

Abstract. The reliable prediction of future atmospheric CO2 concentrations and associated global climate change requires an adequate understanding of the CO2 sources and sinks. The sparseness of the existing surface measurement network limits current knowledge about the global distribution of CO2 surface fluxes. The retrieval of CO2 total vertical columns from satellite observations is predicted to improve this situation. Such an application however requires very high accuracy and precision. We report on retrievals of the column-averaged CO2 dry air mole fraction, denoted XCO2, from the near-infrared nadir spectral radiance and solar irradiance measurements of the SCIAMACHY satellite instrument between 2003 and 2005. We focus on northern hemispheric large scale CO2 features such as the CO2 seasonal cycle and show - for the first time - that the atmospheric annual increase of CO2 can be directly observed using satellite measurements of the CO2 total column. The satellite retrievals are compared with global XCO2 obtained from NOAA's CO2 assimilation system CarbonTracker taking into account the spatio-temporal sampling and altitude sensitivity of the satellite data. We show that the measured CO2 year-to-year increase agrees within about 1 ppm/year with CarbonTracker. We also show that the latitude dependent amplitude of the northern hemispheric CO2 seasonal cycle agrees with CarbonTracker within about 2 ppm with the retrieved amplitude being systematically larger. The analysis demonstrates that it is possible using satellite measurements of the CO2 total column to retrieve information on the atmospheric CO2 on the level of a few parts per million.

scholarly journals Assessing the regional surface influence through Backward Lagrangian Dispersion Models for aircraft CO<sub>2</sub> vertical profiles observations in NE Spain

2011 ◽  
Vol 11 (4) ◽  
pp. 1659-1670 ◽  
Author(s):  
A. Font ◽  
J.-A. Morguí ◽  
X. Rodó
Keyword(s):  
Potential Surface ◽  
Regional Scale ◽  
Co2 Concentration ◽  
Surface Fluxes ◽  
Background Concentration ◽  
Aircraft Measurements ◽  
Influence Area ◽  
Lagrangian Dispersion ◽  
Atmospheric Sampling ◽  
Ne Spain

Abstract. In this study the differences in the measured atmospheric CO2 mixing ratio at three aircraft profiling sites in NE Spain separated by 60 km are analyzed in regard to the variability of the surface fluxes in the regional surface influence area. First, the Regional Potential Surface Influence (RPSI) for fifty-one days in 2006 is calculated to assess the vertical, horizontal and temporal extent of the surface influence for the three sites at the regional scale (104 km2) at different altitudes of the profile (600, 1200, 2500 and 4000 meters above the sea level, m a.s.l.). Second, three flights carried out in 2006 (7 February, 24 August and 29 November) following the Crown Atmospheric Sampling (CAS) design are presented to study the relation between the measured CO2 variability and the Potential Surface Influence (PSI) and RPSI concepts. At 600 and 1200 m a.s.l. the regional signal is confined up to 50 h before the measurements whereas at higher altitudes (2500 and 4000 m a.s.l.) the regional surface influence is only recovered during spring and summer months. The RPSI from sites separated by 60 km overlap by up to 70% of the regional surface influence at 600 and 1200 m a.s.l., while the overlap decreases to 10–40% at higher altitudes (2500 and 4000 m a.s.l.). The scale of the RPSI area is suitable to understand the differences in the measured CO2 concentration in the three vertices of the CAS, as CO2 differences are attributed to local surrounding fluxes (February) or to the variability of regional surface influence as for the August and November flights. For these two flights, the variability in the regional scale influences the variability measured in the local scale. The CAS sampling design for aircraft measurements appears to be a suitable method to cope with the variability of a typical grid for inversion models as measurements are intensified within the PBL and the background concentration is measured every ~102 km.

scholarly journals Detecting regional variability in sources and sinks of carbon dioxide: a synthesis

2009 ◽  
Vol 6 (1) ◽  
pp. 2331-2355 ◽  
Author(s):  
A. J. Dolman ◽  
C. Gerbig ◽  
J. Noilhan ◽  
C. Sarrat ◽  
F. Miglieta
Keyword(s):  
Carbon Balance ◽  
Regional Scale ◽  
Concentration Field ◽  
Co2 Concentration ◽  
Future Research ◽  
Model Errors ◽  
Regional Variability ◽  
Sources And Sinks ◽  
Induced Flow ◽  
Made In

Abstract. The papers of this special issue are put into the context of progress made in experiments and modelling aimed at understanding the carbon balance at regional scale. Mesoscale meteorological effects such as seas breezes and topographically induced flow have the potential to generate significant heterogeneities in the CO2 concentration fields. This has consequences for the interpretation or inverse modelling, of sources and sinks from these concentrations. Results of experiments executed in South West France in 2005 and 2007 are described and subsequent analysis of modelling results. Overall we conclude that we now have capability to model with mesoscale models realistic CO2 concentration fields, within the constraint of other model errors, such as in boundary layer characteristics. We show that progress has been made in inverting concentration field at regional scale and indicate the direction of future research efforts.

scholarly journals Spatially varying relevance of hydrometeorological hazards for vegetation productivity extremes

2021 ◽  
Author(s):  
Josephin Kroll ◽  
Jasper M. C. Denissen ◽  
Mirco Migliavacca ◽  
Wantong Li ◽  
Anke Hildebrandt ◽  
...  
Keyword(s):  
Crop Yields ◽  
Heat Waves ◽  
Co2 Concentration ◽  
Reanalysis Data ◽  
Vital Role ◽  
Surface Fluxes ◽  
Water Control ◽  
Vegetation Productivity ◽  
Near Surface ◽  
Temperature And Precipitation

Abstract. Vegetation plays a vital role in the Earth system by sequestering carbon, producing food and oxygen, and providing evaporative cooling. Vegetation productivity extremes have multi-faceted implications, for example on crop yields or the atmospheric CO2 concentration. Here, we focus on productivity extremes as possible impacts of coinciding, potentially extreme hydrometeorological anomalies. Using monthly global satellite-based Sun-induced chlorophyll fluorescence data as a proxy for vegetation productivity from 2007–2015, we show that vegetation productivity extremes are related to hydrometeorological hazards as characterized through ERA5-Land reanalysis data in approximately 50 % of our global study area. For the latter, we are considering sufficiently vegetated and cloud-free regions; and we refer to hydrometeorological hazards as water or energy related extremes inducing productivity extremes. The relevance of the different hazard types varies in space; temperature-related hazards dominate at higher latitudes with cold spells contributing to productivity minima and heat waves supporting productivity maxima, while water-related hazards are relevant in the (sub)tropics with droughts being associated with productivity minima and wet spells with the maxima. Next to single hazards also compound events such as joint droughts and heat waves or joint wet and cold spells play a role, particularly in dry and hot regions. Further, we detect regions where energy control transitions to water control between maxima and minima of vegetation productivity. Therefore, these areas represent hot spots of land-atmosphere coupling where vegetation efficiently translates soil moisture dynamics into surface fluxes such that the land affects near-surface weather. Overall, our results contribute to pinpoint how potential future changes in temperature and precipitation could propagate to shifting vegetation productivity extremes and related ecosystem services.

scholarly journals Thermal-based modeling of coupled carbon, water, and energy fluxes using nominal light use efficiencies constrained by leaf chlorophyll observations

2015 ◽  
Vol 12 (5) ◽  
pp. 1511-1523 ◽  
Author(s):  
M. A. Schull ◽  
M. C. Anderson ◽  
R. Houborg ◽  
A. Gitelson ◽  
W. P. Kustas
Keyword(s):  
Land Surface ◽  
Empirical Relationship ◽  
Carbon Assimilation ◽  
Co2 Concentration ◽  
Energy Fluxes ◽  
Unit Leaf ◽  
Leaf Chlorophyll ◽  
Infrared Measurements ◽  
Vegetative Canopy

Abstract. Recent studies have shown that estimates of leaf chlorophyll content (Chl), defined as the combined mass of chlorophyll a and chlorophyll b per unit leaf area, can be useful for constraining estimates of canopy light use efficiency (LUE). Canopy LUE describes the amount of carbon assimilated by a vegetative canopy for a given amount of absorbed photosynthetically active radiation (APAR) and is a key parameter for modeling land-surface carbon fluxes. A carbon-enabled version of the remote-sensing-based two-source energy balance (TSEB) model simulates coupled canopy transpiration and carbon assimilation using an analytical sub-model of canopy resistance constrained by inputs of nominal LUE (βn), which is modulated within the model in response to varying conditions in light, humidity, ambient CO2 concentration, and temperature. Soil moisture constraints on water and carbon exchange are conveyed to the TSEB-LUE indirectly through thermal infrared measurements of land-surface temperature. We investigate the capability of using Chl estimates for capturing seasonal trends in the canopy βn from in situ measurements of Chl acquired in irrigated and rain-fed fields of soybean and maize near Mead, Nebraska. The results show that field-measured Chl is nonlinearly related to βn, with variability primarily related to phenological changes during early growth and senescence. Utilizing seasonally varying βn inputs based on an empirical relationship with in situ measured Chl resulted in improvements in carbon flux estimates from the TSEB model, while adjusting the partitioning of total water loss between plant transpiration and soil evaporation. The observed Chl–βn relationship provides a functional mechanism for integrating remotely sensed Chl into the TSEB model, with the potential for improved mapping of coupled carbon, water, and energy fluxes across vegetated landscapes.

GSWP-2: Multimodel Analysis and Implications for Our Perception of the Land Surface

2006 ◽  
Vol 87 (10) ◽  
pp. 1381-1398 ◽  
Author(s):  
Paul A. Dirmeyer ◽  
Xiang Gao ◽  
Mei Zhao ◽  
Zhichang Guo ◽  
Taikan Oki ◽  
...  
Keyword(s):  
Land Surface ◽  
Good Description ◽  
Regional Scale ◽  
Co2 Concentration ◽  
Atmospheric Measurements ◽  
Modeling Tools ◽  
Sources And Sinks ◽  
Spatial Gradients ◽  
Continental Scale ◽  
Regional Flow

Quantification of sources and sinks of carbon at global and regional scales requires not only a good description of the land sources and sinks of carbon, but also of the synoptic and mesoscale meteorology. An experiment was performed in Les Landes, southwest France, during May–June 2005, to determine the variability in concentration gradients and fluxes of CO2 The CarboEurope Regional Experiment Strategy (CERES; see also http://carboregional.mediasfrance.org/index) aimed to produce aggregated estimates of the carbon balance of a region that can be meaningfully compared to those obtained from the smallest downscaled information of atmospheric measurements and continental-scale inversions. We deployed several aircraft to sample the CO2 concentration and fluxes over the whole area, while fixed stations observed the fluxes and concentrations at high accuracy. Several (mesoscale) meteorological modeling tools were used to plan the experiment and flight patterns. Results show that at regional scale the relation between profiles and fluxes is not obvious, and is strongly influenced by airmass history and mesoscale flow patterns. In particular, we show from an analysis of data for a single day that taking either the concentration at several locations as representative of local fluxes or taking the flux measurements at those sites as representative of larger regions would lead to incorrect conclusions about the distribution of sources and sinks of carbon. Joint consideration of the synoptic and regional flow, fluxes, and land surface is required for a correct interpretation. This calls for an experimental and modeling strategy that takes into account the large spatial gradients in concentrations and the variability in sources and sinks that arise from different land use types. We briefly describe how such an analysis can be performed and evaluate the usefulness of the data for planning of future networks or longer campaigns with reduced experimental efforts.

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