Global atmospheric CO2 inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate
Gaubert, Benjamin ; Stephens, Britton B. ; Basu, Sourish ; Chevallier, Frédéric ; Deng, Feng ; Kort, Eric A. ; Patra, Prabir K. ; Peters, Wouter ; Rödenbeck, Christian ; Saeki, Tazu ; Schimel, David ; Laan-Luijkx, Ingrid van der; Wofsy, Steven ; Yin, Yi - \ 2019
Biogeosciences 16 (2019)1. - ISSN 1726-4170 - p. 117 - 134.
We have compared a suite of recent global CO2 atmospheric inversion results to independent airborne observations and to each other, to assess their dependence on differences in northern extratropical (NET) vertical transport and to identify some of the drivers of model spread. We evaluate posterior CO2 concentration profiles against observations from the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-To-Pole Observations (HIPPO) aircraft campaigns over the mid-Pacific in 2009-2011. Although the models differ in inverse approaches, assimilated observations, prior fluxes, and transport models, their broad latitudinal separation of land fluxes has converged significantly since the Atmospheric Carbon Cycle Inversion Intercomparison (TransCom 3) and the REgional Carbon Cycle Assessment and Processes (RECCAP) projects, with model spread reduced by 80% since TransCom 3 and 70% since RECCAP. Most modeled CO2 fields agree reasonably well with the HIPPO observations, specifically for the annual mean vertical gradients in the Northern Hemisphere. Northern Hemisphere vertical mixing no longer appears to be a dominant driver of northern versus tropical (T) annual flux differences. Our newer suite of models still gives northern extratropical land uptake that is modest relative to previous estimates (Gurney et al., 2002; Peylin et al., 2013) and near-neutral tropical land uptake for 2009- 2011. Given estimates of emissions from deforestation, this implies a continued uptake in intact tropical forests that is strong relative to historical estimates (Gurney et al., 2002; Peylin et al., 2013). The results from these models for other time periods (2004-2014, 2001-2004, 1992-1996) and reevaluation of the TransCom 3 Level 2 and RECCAP results confirm that tropical land carbon fluxes including deforestation have been near neutral for several decades. However, models still have large disagreements on ocean-land partitioning. The fossil fuel (FF) and the atmospheric growth rate terms have been thought to be the best-known terms in the global carbon budget, but we show that they currently limit our ability to assess regional-scale terrestrial fluxes and ocean-land partitioning from the model ensemble.
Canopy-scale biophysical controls of transpiration and evaporation in the Amazon Basin
Mallick, Kaniska ; Trebs, Ivonne ; Boegh, Eva ; Giustarini, Laura ; Schlerf, Martin ; Drewry, Darren T. ; Hoffmann, Lucien ; Randow, Celso Von; Kruijt, Bart ; Araùjo, Alessandro ; Saleska, Scott ; Ehleringer, James R. ; Domingues, Tomas F. ; Ometto, Jean Pierre H.B. ; Nobre, Antonio D. ; Luiz Leal De Moraes, Osvaldo ; Hayek, Matthew ; William Munger, J. ; Wofsy, Steven C. - \ 2016
Hydrology and Earth System Sciences 20 (2016)10. - ISSN 1027-5606 - p. 4237 - 4264.
Canopy and aerodynamic conductances (gC and gA) are two of the key land surface biophysical variables that control the land surface response of land surface schemes in climate models. Their representation is crucial for predicting transpiration (λET) and evaporation (λEE) flux components of the terrestrial latent heat flux (λE), which has important implications for global climate change and water resource management. By physical integration of radiometric surface temperature (TR) into an integrated framework of the Penman-Monteith and Shuttleworth-Wallace models, we present a novel approach to directly quantify the canopy-scale biophysical controls on λET and λEE over multiple plant functional types (PFTs) in the Amazon Basin. Combining data from six LBA (Large-scale Biosphere-Atmosphere Experiment in Amazonia) eddy covariance tower sites and a TR-driven physically based modeling approach, we identified the canopy-scale feedback-response mechanism between gC, λET, and atmospheric vapor pressure deficit (DA), without using any leaf-scale empirical parameterizations for the modeling. The TR-based model shows minor biophysical control on λET during the wet (rainy) seasons where λET becomes predominantly radiation driven and net radiation (RN) determines 75 to 80% of the variances of λET. However, biophysical control on λET is dramatically increased during the dry seasons, and particularly the 2005 drought year, explaining 50 to 65% of the variances of λET, and indicates λET to be substantially soil moisture driven during the rainfall deficit phase. Despite substantial differences in gA between forests and pastures, very similar canopy-atmosphere "coupling" was found in these two biomes due to soil moisture-induced decrease in gC in the pasture. This revealed the pragmatic aspect of the TR-driven model behavior that exhibits a high sensitivity of gC to per unit change in wetness as opposed to gA that is marginally sensitive to surface wetness variability. Our results reveal the occurrence of a significant hysteresis between λET and gC during the dry season for the pasture sites, which is attributed to relatively low soil water availability as compared to the rainforests, likely due to differences in rooting depth between the two systems. Evaporation was significantly influenced by gA for all the PFTs and across all wetness conditions. Our analytical framework logically captures the responses of gC and gA to changes in atmospheric radiation, DA, and surface radiometric temperature, and thus appears to be promising for the improvement of existing land-surface-atmosphere exchange parameterizations across a range of spatial scales.
Atmospheric CH4 in the first decade of the 21st century: Inverse modeling analysis using SCIAMACHY satellite retrievals and NOAA surface measurements
Bergamaschi, P. ; Houweling, S. ; Segers, A. ; Krol, M.C. ; Frankenberg, C. ; Scheepmaker, R.A. ; Dlugokencky, E. ; Wofsy, S.C. ; Kort, E.A. ; Sweeney, C. ; Schuck, T. ; Brenninkmeijer, C. ; Chen, H. ; Beck, V. ; Gerbig, C. - \ 2013
Journal of Geophysical Research: Atmospheres 118 (2013)13. - ISSN 2169-897X - p. 7350 - 7369.
growth-rate - methane emissions - carbon-dioxide - northern-hemisphere - data assimilation - transport model - variability - chemistry - climate - troposphere
The causes of renewed growth in the atmospheric CH4 burden since 2007 are still poorly understood and subject of intensive scientific discussion. We present a reanalysis of global CH4 emissions during the 2000s, based on the TM5-4DVAR inverse modeling system. The model is optimized using high-accuracy surface observations from NOAA ESRL's global air sampling network for 2000-2010 combined with retrievals of column-averaged CH4 mole fractions from SCIAMACHY onboard ENVISAT (starting 2003). Using climatological OH fields, derived global total emissions for 2007-2010 are 16-20 Tg CH4/yr higher compared to 2003-2005. Most of the inferred emission increase was located in the tropics (9-14 Tg CH4/yr) and mid- latitudes of the northern hemisphere (6-8 Tg CH4/yr), while no significant trend was derived for Arctic latitudes. The atmospheric increase can be attributed mainly to increased anthropogenic emissions, but the derived trend is significantly smaller than estimated in the EDGARv4.2 emission inventory. Superimposed on the increasing trend in anthropogenic CH4 emissions are significant inter-annual variations (IAV) of emissions from wetlands (up to +/- 10 Tg CH4/yr), and biomass burning (up to +/- 7 Tg CH4/yr). Sensitivity experiments, which investigated the impact of the SCIAMACHY observations (versus inversions using only surface observations), of the OH fields used, and of a priori emission inventories, resulted in differences in the detailed latitudinal attribution of CH4 emissions, but the IAV and trends aggregated over larger latitude bands were reasonably robust. All sensitivity experiments show similar performance against independent shipboard and airborne observations used for validation, except over Amazonia where satellite retrievals improved agreement with observations in the free troposphere.
Patterns of water and heat flux across a biome gradient from tropical forest to savanna in Brazil
Rocha, H.R. da; Manzi, A.O. ; Cabral, O.M. ; Miller, S.D. ; Goulden, M.L. ; Saleska, S.R. ; Coupe, N.R. ; Wofsy, S.C. ; Borma, L.S. ; Artaxo, P. ; Vourlitis, G. ; Nogueira, J.S. ; Cardoso, F.L. ; Nobre, A.D. ; Kruijt, B. ; Freitas, H.C. ; Randow, C. von; Aguiar, R.G. ; Maia, J.F. - \ 2009
Journal of Geophysical Research: Biogeosciences 114 (2009). - ISSN 2169-8953 - 8 p.
hydrologic-cycle - amazon forests - carbon - dynamics
We investigated the seasonal patterns of water vapor and sensible heat flux along a tropical biome gradient from forest to savanna. We analyzed data from a network of flux towers in Brazil that were operated within the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA). These tower sites included tropical humid and semideciduous forest, transitional forest, floodplain (with physiognomies of cerrado), and cerrado sensu stricto. The mean annual sensible heat flux at all sites ranged from 20 to 38 Wm-2, and was generally reduced in the wet season and increased in the late dry season, coincident with seasonal variations of net radiation and soil moisture. The sites were easily divisible into two functional groups based on the seasonality of evaporation: tropical forest and savanna. At sites with an annual precipitation above 1900 mm and a dry season length less than 4 months (Manaus, Santarem and Rondonia), evaporation rates increased in the dry season, coincident with increased radiation. Evaporation rates were as high as 4.0 mm d-1 in these evergreen or semidecidous forests. In contrast, ecosystems with precipitation less than 1700 mm and a longer dry season (Mato Grosso, Tocantins and São Paulo) showed clear evidence of reduced evaporation in the dry season. Evaporation rates were as low as 2.5 mm d-1 in the transitional forests and 1 mm d-1 in the cerrado. The controls on evapotranspiration seasonality changed along the biome gradient, with evaporative demand (especially net radiation) playing a more important role in the wetter forests, and soil moisture playing a more important role in the drier savannah sites
Latitudinal patterns of magnitude and interannual variability in net ecosystem exchange regulated by biological and environmental variables
Yuan, W.P. ; Luo, Y.Q. ; Richardson, A.D. ; Oren, R. ; Luyssaert, S. ; Janssens, I.A. ; Ceulemans, R. ; Zhou, X.H. ; Grunwald, T. ; Aubinet, M. ; Berhofer, C. ; Baldocchi, D.D. ; Chen, J.Q. ; Dunn, A.L. ; Deforest, J.L. ; Dragoni, D. ; Goldstein, A.H. ; Moors, E.J. ; Munger, J.W. ; Monson, R.K. ; Suyker, A.E. ; Star, G. ; Scott, R.L. ; Tenhunen, J. ; Verma, S.B. ; Vesala, T. ; Wofsy, S. - \ 2009
Global Change Biology 15 (2009)12. - ISSN 1354-1013 - p. 2905 - 2920.
netto ecosysteem uitwisseling - kooldioxide - eddy-covariantie - patronen - ruimtelijke variatie - variatie in de tijd - net ecosystem exchange - carbon dioxide - eddy covariance - patterns - spatial variation - temporal variation - water-vapor exchange - northern temperate grassland - native tallgrass prairie - carbon-dioxide exchange - long-term measurements - plant functional-type - eddy covariance data - deciduous forest - european forests - co2 exchange
Over the last two and half decades, strong evidence showed that the terrestrial ecosystems are acting as a net sink for atmospheric carbon. However the spatial and temporal patterns of variation in the sink are not well known. In this study, we examined latitudinal patterns of interannual variability (IAV) in net ecosystem exchange (NEE) of CO2 based on 163 site-years of eddy covariance data, from 39 northern-hemisphere research sites located at latitudes ranging from ~29°N to ~64°N. We computed the standard deviation of annual NEE integrals at individual sites to represent absolute interannual variability (AIAV), and the corresponding coefficient of variation as a measure of relative interannual variability (RIAV). Our results showed decreased trends of annual NEE with increasing latitude for both deciduous broadleaf forests and evergreen needleleaf forests. Gross primary production (GPP) explained a significant proportion of the spatial variation of NEE across evergreen needleleaf forests, whereas, across deciduous broadleaf forests, it is ecosystem respiration (Re). In addition, AIAV in GPP and Re increased significantly with latitude in deciduous broadleaf forests, but AIAV in GPP decreased significantly with latitude in evergreen needleleaf forests. Furthermore, RIAV in NEE, GPP, and Re appeared to increase significantly with latitude in deciduous broadleaf forests, but not in evergreen needleleaf forests. Correlation analyses showed air temperature was the primary environmental factor that determined RIAV of NEE in deciduous broadleaf forest across the North American sites, and none of the chosen climatic factors could explain RIAV of NEE in evergreen needleleaf forests. Mean annual NEE significantly increased with latitude in grasslands. Precipitation was dominant environmental factor for the spatial variation of magnitude and IAV in GPP and Re in grasslands.
Estimating noctural ecosystem respiration from the vertical turbulent flux and change in storange of CO2
Gorsel, E. van; Delpierre, N. ; Leuning, R. ; Black, A. ; Munger, J.W. ; Wofsy, S. ; Aubinet, M. ; Feigenwinter, C. ; Beringer, J. ; Bonal, D. ; Chen, B. ; Chen, J. ; Clement, R. ; Davis, K.J. ; Desai, A.R. ; Dragoni, D. ; Etzold, S. ; Grünwald, T. ; Gu, L. ; Heinesch, B. ; Hutyra, L.R. ; Jans, W.W.P. ; Kutsch, W. ; Law, B.E. ; Leclerc, Y. ; Mammarella, I. ; Montagnani, L. ; Noormets, A. ; Rebmann, C. ; Wharton, S. - \ 2009
Agricultural and Forest Meteorology 149 (2009)11. - ISSN 0168-1923 - p. 1919 - 1930.
ecosystemen - ademhaling - meettechnieken - nacht - kooldioxide - eddy-covariantie - micrometeorologie - luchtstroming - netto ecosysteem koolstofbalans - ecosystems - respiration - measurement techniques - night - carbon dioxide - eddy covariance - micrometeorology - air flow - net ecosystem carbon balance - eddy covariance measurements - temperate deciduous forest - carbon-dioxide exchange - ponderosa pine forests - long-term measurements - douglas-fir stand - old-growth forest - soil respiration - pacific-northwest - difficult conditions
Micrometeorological measurements of nighttime ecosystem respiration can be systematically biased when stable atmospheric conditions lead to drainage flows associated with decoupling of air flow above and within plant canopies. The associated horizontal and vertical advective fluxes cannot be measured using instrumentation on the single towers typically used at micrometeorological sites. A common approach to minimize bias is to use a threshold in friction velocity, u*, to exclude periods when advection is assumed to be important, but this is problematic in situations when in-canopy flows are decoupled from the flow above. Using data from 25 flux stations in a wide variety of forest ecosystems globally, we examine the generality of a novel approach to estimating nocturnal respiration developed by van Gorsel et al. (van Gorsel, E., Leuning, R., Cleugh, H.A., Keith, H., Suni, T., 2007. Nocturnal carbon efflux: reconciliation of eddy covariance and chamber measurements using an alternative to the u*-threshold filtering technique. Tellus 59B, 397–403, Tellus, 59B, 307-403). The approach is based on the assumption that advection is small relative to the vertical turbulent flux (FC) and change in storage (FS) of CO2 in the few hours after sundown. The sum of FC and FS reach a maximum during this period which is used to derive a temperature response function for ecosystem respiration. Measured hourly soil temperatures are then used with this function to estimate respiration RRmax. The new approach yielded excellent agreement with (1) independent measurements using respiration chambers, (2) with estimates using ecosystem light-response curves of Fc + Fs extrapolated to zero light, RLRC, and (3) with a detailed process-based forest ecosystem model, Rcast. At most sites respiration rates estimated using the u*-filter, Rust, were smaller than RRmax and RLRC. Agreement of our approach with independent measurements indicates that RRmax provides an excellent estimate of nighttime ecosystem respiration.
|Patterns of CO2 and water fluxes measured by flux towers across tropical forest, ecotone and savanna ecosystems in Brazil
Rocha, H.R. da; Goulden, M. ; Miller, S. ; Manzi, A. ; Cabral, O. ; Freitas, H. ; Nobre, A. ; Saleska, S. ; Wofsy, S. ; Kruijt, B. ; Randow, C. von - \ 2006
In: Integrated land ecosystem-atmosphere processes study; proceedings of the 1st iLEAPS science conference. - Helsinki (Finland) : Yliopistopaino - ISBN 9789525027662 - p. 215 - 216.
|Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites
Wilson, K.B. ; Baldocchi, D.D. ; Aubinet, M. ; Berbigier, P. ; Bernhofer, C. ; Dolman, H. ; Falge, E. ; Field, C. ; Goldstein, A. ; Granier, A. ; Grelle, A. ; Halldor, T. ; Hollinger, D. ; Katul, G. ; Law, B.E. ; Lindroth, A. ; Meyers, T. ; Moncrieff, J. ; Monson, R. ; Oechel, W. ; Tenhunen, J. ; Valentini, R. ; Verma, S. ; Vesala, T. ; Wofsy, S. - \ 2002
Water Resources Research 38 (2002)12. - ISSN 0043-1397
atmosfeer - ecohydrologie - energiebalans - hydrologie - klimaat - vegetatie - verdamping - warmtestroming