Water, Energy, and Carbon with Artificial Neural Networks (WECANN): A statistically-based estimate of global surface turbulent fluxes and gross primary productivity using solar-induced fluorescence.

A new global estimate of surface turbulent fluxes, latent heat flux (LE) and sensible heat flux (H), and gross primary production (GPP) is developed using a machine learning approach informed by novel remotely sensed Solar-Induced Fluorescence (SIF) and other radiative and meteorological variables. This is the first study to jointly retrieve LE, H and GPP using SIF observations. The approach uses an artificial neural network (ANN) with a target dataset generated from three independent data sources, weighted based on triple collocation (TC) algorithm. The new retrieval, named Water, Energy, and Carbon with Artificial Neural Networks (WECANN), provides estimates of LE, H and GPP from 2007 to 2015 at 1° × 1° spatial resolution and on monthly time resolution. The quality of ANN training is assessed using the target data, and the WECANN retrievals are evaluated using eddy covariance tower estimates from FLUXNET network across various climates and conditions. When compared to eddy covariance estimates, WECANN typically outperforms other products, particularly for sensible and latent heat fluxes. Analysing WECANN retrievals across three extreme drought and heatwave events demonstrates the capability of the retrievals in capturing the extent of these events. Uncertainty estimates of the retrievals are analysed and the inter-annual variability in average global and regional fluxes show the impact of distinct climatic events - such as the 2015 El Niño - on surface turbulent fluxes and GPP.

[1]  N. Loeb,et al.  Surface Irradiances Consistent With CERES-Derived Top-of-Atmosphere Shortwave and Longwave Irradiances , 2013 .

[2]  Marc Aubinet,et al.  Annual net ecosystem carbon exchange by a sugar beet crop , 2006 .

[3]  Jonas Ardö,et al.  Seasonal variation of carbon fluxes in a sparse savanna in semi arid Sudan , 2008, Carbon balance and management.

[4]  S. Swenson,et al.  Post‐processing removal of correlated errors in GRACE data , 2006 .

[5]  D. Entekhabi,et al.  Characterization of precipitation product errors across the United States using multiplicative triple collocation , 2015 .

[6]  N. Verhoest,et al.  GLEAM v3: satellite-based land evaporation and root-zone soil moisture , 2016 .

[7]  B. Rudolf,et al.  Verification scores for the operational GPCP-1DD product over the European Alps , 2002 .

[8]  Maosheng Zhao,et al.  Development of a global evapotranspiration algorithm based on MODIS and global meteorology data , 2007 .

[9]  Damiano Gianelle,et al.  Climatic controls and ecosystem responses drive the inter-annual variability of the net ecosystem exchange of an alpine meadow , 2011 .

[10]  Andrew E. Suyker,et al.  Annual carbon dioxide exchange in irrigated and rainfed maize-based agroecosystems , 2005 .

[11]  Russell L. Scott,et al.  The carbon balance pivot point of southwestern U.S. semiarid ecosystems: Insights from the 21st century drought , 2015 .

[12]  C. Williams,et al.  Drivers of inter-annual variability in Net Ecosystem Exchange in a semi-arid savanna ecosystem, South Africa , 2008 .

[13]  J. Monteith.  Climate and the efficiency of crop production in Britain , 1977 .

[14]  N. Buchmann,et al.  Methodical study of nitrous oxide eddy covariance measurements using quantum cascade laser spectrometery over a Swiss forest , 2007 .

[15]  T. Holmes,et al.  Global land-surface evaporation estimated from satellite-based observations , 2010 .

[16]  M. Havaux,et al.  Chlorophyll fluorescence induction: A sensitive indicator of water stress in maize plants , 1983, Irrigation Science.

[17]  Filipe Aires,et al.  Soil moisture retrieval from multi‐instrument observations: Information content analysis and retrieval methodology , 2013 .

[18]  T. A. Black,et al.  Energy balance closure at the BERMS flux towers in relation to the water balance of the White Gull Creek watershed 1999–2009 , 2012 .

[19]  W. Wagner,et al.  Fusion of active and passive microwave observations to create an Essential Climate Variable data record on soil moisture , 2012 .

[20]  Maosheng Zhao,et al.  A Continuous Satellite-Derived Measure of Global Terrestrial Primary Production , 2004 .

[21]  L. Guanter,et al.  Model-based analysis of the relationship between sun-induced chlorophyll fluorescence and gross primary production for remote sensing applications , 2016 .

[22]  Matthew F. McCabe,et al.  The WACMOS-ET project – Part 1: Tower-scale evaluation of four remote-sensing-based evapotranspiration algorithms , 2015 .

[23]  S. Wofsy,et al.  What drives the seasonality of photosynthesis across the Amazon basin? A cross-site analysis of eddy flux tower measurements from the Brasil flux network , 2013 .

[24]  Wout Verhoef,et al.  The FLuorescence EXplorer Mission Concept—ESA’s Earth Explorer 8 , 2017, IEEE Transactions on Geoscience and Remote Sensing.

[25]  Xin Pan,et al.  Comparative Assessment of Satellite-Retrieved Surface Net Radiation: An Examination on CERES and SRB Datasets in China , 2015, Remote. Sens..

[26]  P. Cook,et al.  Dynamics of component carbon fluxes in a semi‐arid Acacia woodland, central Australia , 2013 .

[27]  M. Pihlatie,et al.  Responses of N2O fluxes to temperature, water table and N deposition in a northern boreal fen , 2010 .

[28]  F. Landerer,et al.  Accuracy of scaled GRACE terrestrial water storage estimates , 2012 .

[29]  Ge Sun,et al.  Response of carbon fluxes to drought in a coastal plain loblolly pine forest , 2010 .

[30]  Maosheng Zhao,et al.  Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009 , 2010, Science.

[31]  L. Guanter,et al.  The seasonal cycle of satellite chlorophyll fluorescence observations and its relationship to vegetation phenology and ecosystem atmosphere carbon exchange , 2014 .

[32]  S. Seneviratne,et al.  Recent decline in the global land evapotranspiration trend due to limited moisture supply , 2010, Nature.

[33]  Alexandre Roy,et al.  Triple collocation for binary and categorical variables: Application to validating landscape freeze/thaw retrievals , 2016 .

[34]  Serge Rambal,et al.  The growth respiration component in eddy CO2 flux from a Quercus ilex mediterranean forest , 2004 .

[35]  Corinna Rebmann,et al.  Spruce forests (Norway and Sitka spruce, including Douglas fir): Carbon and water fluxes, Balances, Ecological and ecophysiological determinants , 2003 .

[36]  A. Arneth,et al.  Global patterns of land-atmosphere fluxes of carbon dioxide, latent heat, and sensible heat derived from eddy covariance, satellite, and meteorological observations , 2011 .

[37]  Diego G. Miralles,et al.  Reconciling spatial and temporal soil moisture effects on afternoon rainfall , 2015, Nature Communications.

[38]  Marcy E. Litvak,et al.  Differential responses of production and respiration to temperature and moisture drive the carbon balance across a climatic gradient in New Mexico , 2011 .

[39]  C. Frankenberg,et al.  Simulations of chlorophyll fluorescence incorporated into the Community Land Model version 4 , 2015, Global change biology.

[40]  A. Noormets,et al.  Response of carbon fluxes to drought in a coastal plain loblolly pine forest , 2010 .

[41]  Youngryel Ryu,et al.  Multi-scale evaluation of global gross primary productivity and evapotranspiration products derived from Breathing Earth System Simulator (BESS) , 2016 .

[42]  L. Guanter,et al.  Satellite chlorophyll fluorescence measurements reveal large‐scale decoupling of photosynthesis and greenness dynamics in boreal evergreen forests , 2016, Global change biology.

[43]  A. Stoffelen.  Toward the true near-surface wind speed: Error modeling and calibration using triple collocation , 1998 .

[44]  D. Hollinger,et al.  Refining light-use efficiency calculations for a deciduous forest canopy using simultaneous tower-based carbon flux and radiometric measurements , 2007 .

[45]  Wade T. Crow,et al.  An intercomparison of available soil moisture estimates from thermal infrared and passive microwave remote sensing and land surface modeling , 2011 .

[46]  Nathaniel A. Brunsell,et al.  Assessing the multi-resolution information content of remotely sensed variables and elevation for evapotranspiration in a tall-grass prairie environment , 2008 .

[47]  P. Cox,et al.  Observing terrestrial ecosystems and the carbon cycle from space , 2015, Global change biology.

[48]  M. Aubinet,et al.  Long term carbon dioxide exchange above a mixed forest in the Belgian Ardennes , 2001 .

[49]  R. Dickinson,et al.  Evidence for decadal variation in global terrestrial evapotranspiration between 1982 and 2002: 1. Model development , 2010 .

[50]  W. Crow,et al.  Estimating Spatial Sampling Errors in Coarse-Scale Soil Moisture Estimates Derived from Point-Scale Observations , 2010 .

[51]  G. Krause,et al.  Chlorophyll Fluorescence and Photosynthesis: The Basics , 1991 .

[52]  Jouni Pulliainen,et al.  Mapping of snow water equivalent and snow depth in boreal and sub-arctic zones by assimilating space-borne microwave radiometer data and ground-based observations , 2006 .

[53]  Filipe Aires,et al.  Toward an estimation of global land surface heat fluxes from multisatellite observations , 2009 .

[54]  Govindjee,et al.  Chlorophyll A fluorescence transient as an indicator of water potential of leaves , 1981 .

[55]  W. Meyer,et al.  Evaporation of perennial semi‐arid woodland in southeastern Australia is adapted for irregular but common dry periods , 2015 .

[56]  D. Baldocchi,et al.  Global estimates of the land–atmosphere water flux based on monthly AVHRR and ISLSCP-II data, validated at 16 FLUXNET sites , 2008 .

[57]  Analyzing the major drivers of NEE in a Mediterranean alpine shrubland , 2010 .

[58]  Hervé Cochard,et al.  An overview of models of stomatal conductance at the leaf level. , 2010, Plant, cell & environment.

[59]  Wade T. Crow,et al.  The Impact of Local Acquisition Time on the Accuracy of Microwave Surface Soil Moisture Retrievals over the Contiguous United States , 2015, Remote. Sens..

[60]  Philippe Richaume,et al.  Soil Moisture Retrieval Using Neural Networks: Application to SMOS , 2015, IEEE Transactions on Geoscience and Remote Sensing.

[61]  T. Kolb,et al.  Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand‐replacing fire , 2012, Global change biology.

[62]  W. Massman.  A simple method for estimating frequency response corrections for eddy covariance systems , 2000 .

[63]  Yi Y. Liu,et al.  ESA CCI Soil Moisture for improved Earth system understanding : State-of-the art and future directions , 2017 .

[64]  Markus Reichstein,et al.  Predicting carbon dioxide and energy fluxes across global FLUXNET sites with regression algorithms , 2016 .

[65]  A. C. Pandey,et al.  Validation of TMPA and GPCP 1DD against the ground truth rain‐gauge data for Indian region , 2013 .

[66]  M. Mauder,et al.  Mesoscale Eddies Affect Near-Surface Turbulent Exchange: Evidence from Lidar and Tower Measurements , 2015 .

[67]  Diego G. Miralles,et al.  Magnitude and variability of land evaporation and its components at the global scale , 2011 .

[68]  David P. Billesbach,et al.  Spatiotemporal Variations in Growing Season Exchanges of CO2, H2O, and Sensible Heat in Agricultural Fields of the Southern Great Plains , 2007 .

[69]  N. Coops,et al.  Intercomparison of fraction of absorbed photosynthetically active radiation products derived from satellite data over Europe , 2014 .

[70]  Robert M. Parinussa,et al.  Error Estimates for Near-Real-Time Satellite Soil Moisture as Derived From the Land Parameter Retrieval Model , 2011, IEEE Geoscience and Remote Sensing Letters.

[71]  C. Prigent,et al.  Synergistic multi‐wavelength remote sensing versus a posteriori combination of retrieved products: Application for the retrieval of atmospheric profiles using MetOp‐A , 2012 .

[72]  Maosheng Zhao,et al.  Improvements of the MODIS terrestrial gross and net primary production global data set , 2005 .

[73]  Henry L. Gholz,et al.  Energy exchange across a chronosequence of slash pine forests in Florida , 2002 .

[74]  Alfredo Huete,et al.  Dry-season greening of Amazon forests , 2016, Nature.

[75]  C. Frankenberg,et al.  Prospects for Chlorophyll Fluorescence Remote Sensing from the Orbiting Carbon Observatory-2 , 2014 .

[76]  E C WASSINK,et al.  Chlorophyll fluorescence and photosynthesis. , 1951, Advances in enzymology and related subjects of biochemistry.

[77]  S. Seneviratne,et al.  Global intercomparison of 12 land surface heat flux estimates , 2011 .

[78]  A. Sobel,et al.  Fog and rain in the Amazon , 2015, Proceedings of the National Academy of Sciences.

[79]  B. Hurk,et al.  A Revised Hydrology for the ECMWF Model: Verification from Field Site to Terrestrial Water Storage and Impact in the Integrated Forecast System , 2009 .

[80]  W. Oechel,et al.  FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities , 2001 .

[81]  Steven A. Margulis,et al.  Validation and Error Characterization of the GPCP-1DD Precipitation Product over the Contiguous United States , 2004 .

[82]  L. Guanter,et al.  New methods for the retrieval of chlorophyll red fluorescence from hyperspectral satellite instruments: simulations andapplication to GOME-2 and SCIAMACHY , 2016 .

[83]  Laura S. Borma,et al.  Patterns of water and heat flux across a biome gradient from tropical forest to savanna in Brazil , 2009 .

[84]  M. Palecki,et al.  THE DROUGHT MONITOR , 2002 .

[85]  Wade T. Crow,et al.  Recent advances in (soil moisture) triple collocation analysis , 2016, Int. J. Appl. Earth Obs. Geoinformation.

[86]  Dario Papale,et al.  Observational Data Patterns for Time Series Data Quality Assessment , 2014, 2014 IEEE 10th International Conference on e-Science.

[87]  G. D. Jenerette,et al.  Effects of seasonal drought on net carbon dioxide exchange from a woody-plant-encroached semiarid grassland , 2009 .

[88]  Jean-Philippe Gastellu-Etchegorry,et al.  Amazon forest structure generates diurnal and seasonal variability in light utilization , 2015 .

[89]  P. Toivonen,et al.  Variable Chlorophyll a Fluorescence and CO(2) Uptake in Water-Stressed White Spruce Seedlings. , 1988, Plant physiology.

[90]  Yi Y. Liu,et al.  Developing an improved soil moisture dataset by blending passive and active microwave satellite-based retrievals , 2011 .

[91]  Yi Y. Liu,et al.  Multi-decadal trends in global terrestrial evapotranspiration and its components , 2016, Scientific Reports.

[92]  C. Frankenberg,et al.  Remote sensing of near-infrared chlorophyll fluorescence from space in scattering atmospheres: implications for its retrieval and interferences with atmospheric CO 2 retrievals , 2012 .

[93]  Rafael Rosolem,et al.  Measurements of CO2 exchange over a woodland savanna (Cerrado Sensu stricto) in southeast Brasil , 2002 .

[94]  Miikka Dal Maso,et al.  Long-term measurements of surface fluxes above a Scots pine forest in Hyytiälä, southern Finland, 1996-2001 , 2003 .

[95]  L. Luo,et al.  Did we see the 2011 summer heat wave coming? , 2012 .

[96]  Natascha Kljun,et al.  Determining carbon isotope signatures from micrometeorological measurements: Implications for studying biosphere–atmosphere exchange processes , 2007 .

[97]  N. Buchmann,et al.  Link between continuous stem radius changes and net ecosystem productivity of a subalpine Norway spruce forest in the Swiss Alps. , 2010, The New phytologist.

[98]  J. Flexas,et al.  Steady-state chlorophyll fluorescence (Fs) measurements as a tool to follow variations of net CO2 assimilation and stomatal conductance during water-stress in C3 plants. , 2002, Physiologia plantarum.

[99]  David R. Doelling,et al.  Toward Optimal Closure of the Earth's Top-of-Atmosphere Radiation Budget , 2009 .

[100]  Nathaniel A. Brunsell,et al.  Impacts of seasonality and surface heterogeneity on water‐use efficiency in mesic grasslands , 2013 .

[101]  B. Barkstrom,et al.  Clouds and the Earth's Radiant Energy System (CERES): An Earth Observing System Experiment , 1996 .

[102]  Ad Stoffelen,et al.  Extended triple collocation: Estimating errors and correlation coefficients with respect to an unknown target , 2014 .

[103]  A. Bondeau,et al.  Towards global empirical upscaling of FLUXNET eddy covariance observations: validation of a model tree ensemble approach using a biosphere model , 2009 .

[104]  S. J. Birks,et al.  Terrestrial water fluxes dominated by transpiration , 2013, Nature.

[105]  B. Law,et al.  The influence of hydrological variability on inherent water use efficiency in forests of contrasting composition, age, and precipitation regimes in the Pacific Northwest , 2018 .

[106]  Wout Verhoef,et al.  A model for chlorophyll fluorescence and photosynthesis at leaf scale , 2009 .

[107]  F. Aires,et al.  Sensitivity of satellite microwave and infrared observations to soil moisture at a global scale: 2. Global statistical relationships , 2005 .

[108]  C. Frankenberg,et al.  Global monitoring of terrestrial chlorophyll fluorescence from moderate-spectral-resolution near-infrared satellite measurements: methodology, simulations, and application to GOME-2 , 2013 .

[109]  F. Aires,et al.  A new global method of satellite dataset merging and quality characterization constrained by the terrestrial water budget , 2018 .

[110]  N. Boulain,et al.  Carbon and water fluxes in an arid-zone acacia savanna woodland: An analyses of seasonal patterns and responses to rainfall events , 2013 .

[111]  Nicholas Skowronski,et al.  Invasive insects impact forest carbon dynamics , 2010 .

[112]  Diego G. Miralles,et al.  Mega-heatwave temperatures due to combined soil desiccation and atmospheric heat accumulation , 2014 .

[113]  S. Wofsy,et al.  Factors controlling CO2 exchange on timescales from hourly to decadal at Harvard Forest , 2007 .

[114]  T. Riutta,et al.  Carbon dioxide exchange on a northern boreal fen , 2009 .

[115]  F. Aires,et al.  A joint analysis of modeled soil moisture fields and satellite observations , 2013 .

[116]  R. Dewar.  The Ball–Berry–Leuning and Tardieu–Davies stomatal models: synthesis and extension within a spatially aggregated picture of guard cell function , 2002 .

[117]  Hans Peter Schmid,et al.  Measurements of CO2 and energy fluxes over a mixed hardwood forest in the mid-western United States , 2000 .

[118]  R. Scholes,et al.  The environment and vegetation of the flux measurement site near Skukuza, Kruger National Park , 2001 .

[119]  Bruce K. Wylie,et al.  Integration of CO 2 flux and remotely-sensed data for primary production and ecosystem respiration analyses in the Northern Great Plains: potential for quantitative spatial extrapolation , 2005 .

[120]  F. Beyrich,et al.  Energy balance closure for the LITFASS-2003 experiment , 2010 .

[121]  William L. Smith,et al.  AIRS/AMSU/HSB on the Aqua mission: design, science objectives, data products, and processing systems , 2003, IEEE Trans. Geosci. Remote. Sens..

[122]  Kyu-Myong Kim,et al.  The 2010 Pakistan Flood and Russian Heat Wave: Teleconnection of Hydrometeorological Extremes , 2012 .

[123]  F. Aires,et al.  Soil moisture retrieval from AMSR-E and ASCAT microwave observation synergy. Part 1: Satellite data analysis , 2016 .

[124]  Charles T. Garten,et al.  Temporal changes in C and N stocks of restored prairie: implications for C sequestration strategies. , 2008, Ecological applications : a publication of the Ecological Society of America.

[125]  M. Hodnett,et al.  Comparative measurements and seasonal variations in energy and carbon exchange over forest and pasture in South West Amazonia , 2004 .

[126]  Philip Lewis,et al.  Retrieval and global assessment of terrestrial chlorophyll fluorescence from GOSAT space measurements , 2012 .

[127]  Annette Freibauer,et al.  Winter wheat carbon exchange in Thuringia, Germany , 2004 .

[128]  N. Verhoest,et al.  El Niño-La Niña cycle and recent trends in continental evaporation , 2014 .

[129]  M. Bret-Harte,et al.  Seasonal patterns of carbon dioxide and water fluxes in three representative tundra ecosystems in northern Alaska , 2012 .

[130]  D. Baldocchi,et al.  Inter-annual variability in carbon dioxide exchange of an oak/grass savanna and open grassland in California , 2007 .

[131]  S. Ustin,et al.  Flux partitioning in an old-growth forest: seasonal and interannual dynamics. , 2008, Tree physiology.

[132]  F. Woodward,et al.  Terrestrial Gross Carbon Dioxide Uptake: Global Distribution and Covariation with Climate , 2010, Science.

[133]  T. A. Black,et al.  Gross and aboveground net primary production at Canadian forest carbon flux sites , 2013 .

[134]  A. Cescatti,et al.  Drag coefficient and turbulence intensity in conifer canopies , 2004 .

[135]  C. Frankenberg,et al.  New global observations of the terrestrial carbon cycle from GOSAT: Patterns of plant fluorescence with gross primary productivity , 2011, Geophysical Research Letters.

[136]  Matthew F. McCabe,et al.  The WACMOS-ET project – Part 2: Evaluation of global terrestrial evaporation data sets , 2015 .

[137]  M. Litvak,et al.  Grassland to shrubland state transitions enhance carbon sequestration in the northern Chihuahuan Desert , 2015, Global change biology.

[138]  C. Frankenberg,et al.  Satellite observation of tropical forest seasonality: spatial patterns of carbon exchange in Amazonia , 2015 .

[139]  M. Susan Moran,et al.  Carbon dioxide exchange in a semidesert grassland through drought‐induced vegetation change , 2010 .

[140]  Pavel Kabat,et al.  Comparative measurements of carbon dioxide fluxes from two nearby towers in a central Amazonian rainforest: the Manaus LBA site , 2002 .

[141]  Deborah P. Delmer,et al.  The U.S. drought of 2012 in perspective: A call to action , 2013 .

[142]  C. Frankenberg,et al.  Forest productivity and water stress in Amazonia: observations from GOSAT chlorophyll fluorescence , 2013, Proceedings of the Royal Society B: Biological Sciences.

[143]  Tao Zhang,et al.  Was there a basis for anticipating the 2010 Russian heat wave? , 2011 .

[144]  J. Beringer,et al.  Net ecosystem carbon exchange of a dry temperate eucalypt forest , 2016 .

[145]  Micrometeorological techniques to measure ecosystem-scale greenhouse gas fluxes for model validation and improvement , 2006 .

[146]  A. Westergaard‐Nielsen,et al.  Camera derived vegetation greenness index as proxy for gross primary production in a low Arctic wetland area , 2013 .

[147]  R D Jackson,et al.  Plant stress detection by remote measurement of fluorescence. , 1980, Applied optics.

[148]  F. Aires,et al.  Combining data sets of satellite‐retrieved products for basin‐scale water balance study: 2. Evaluation on the Mississippi Basin and closure correction model , 2014 .

[149]  M. S. Moran,et al.  Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence , 2014, Proceedings of the National Academy of Sciences.

[150]  Witold F. Krajewski,et al.  A Detailed Evaluation of GPCP 1° Daily Rainfall Estimates over the Mississippi River Basin , 2005 .

[151]  S. Seneviratne,et al.  Evaluation of global observations‐based evapotranspiration datasets and IPCC AR4 simulations , 2011 .

[152]  Jonas Ardö,et al.  Precipitation as driver of carbon fluxes in 11 African ecosystems , 2008 .

[153]  Alessandro Cescatti,et al.  Importance of advection in the atmospheric CO2 exchanges of an alpine forest , 2005 .

[154]  P. Anthoni,et al.  Forest and agricultural land‐use‐dependent CO2 exchange in Thuringia, Germany , 2004 .

[155]  James R. Drummond,et al.  International Arctic Systems for Observing the Atmosphere: An International Polar Year Legacy Consortium , 2016 .

[156]  Giorgio Matteucci,et al.  Seasonal net carbon dioxide exchange of a beech forest with the atmosphere , 1996 .

[157]  J. Susskind,et al.  Global Precipitation at One-Degree Daily Resolution from Multisatellite Observations , 2001 .

[158]  R. Ceulemans,et al.  Scaling-Up Carbon Fluxes from Leaves to Stands in a Patchy Coniferous / Deciduous Forest , 1997 .

[159]  Mark Heuer,et al.  Direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning revealed by a prolonged drought at a temperate forest site , 2006 .

[160]  C. Frankenberg,et al.  Application of satellite solar-induced chlorophyll fluorescence to understanding large-scale variations in vegetation phenology and function over northern high latitude forests , 2017 .

[161]  Jonas Ardö,et al.  Dynamics in carbon exchange fluxes for a grazed semi-arid savanna ecosystem in West Africa , 2015 .

[162]  D. Billesbach,et al.  AmeriFlux US-AR1 ARM USDA UNL OSU Woodward Switchgrass 1 , 2016 .

[163]  D. Baldocchi,et al.  Scaling Properties of Biologically Active Scalar Concentration Fluctuations in the Atmospheric Surface Layer over a Managed Peatland , 2010 .

[164]  David J. Harding,et al.  Amazon forests maintain consistent canopy structure and greenness during the dry season , 2014, Nature.

[165]  Evan H. DeLucia,et al.  The effect of soil drought on water‐use efficiency in a contrasting Great Basin desert and Sierran montane species , 1989 .

[166]  T. A. Black,et al.  Comparison of carbon dioxide fluxes over three boreal black spruce forests in Canada , 2007 .

[167]  J. Snel,et al.  The use of chlorophyll fluorescence nomenclature in plant stress physiology , 1990, Photosynthesis Research.

[168]  Yi Y. Liu,et al.  Trend-preserving blending of passive and active microwave soil moisture retrievals , 2012 .

[169]  Pierre Gentine,et al.  Land-surface controls on afternoon precipitation diagnosed from observational data : uncertainties and confounding factors , 2014 .

[170]  F. Aires.  Combining Datasets of Satellite-Retrieved Products. Part I: Methodology and Water Budget Closure , 2014 .

[171]  R. Monson,et al.  Carbon sequestration in a high‐elevation, subalpine forest , 2001 .

[172]  Oliver Sonnentag,et al.  Greenhouse gas (CO2, CH4, H2O) fluxes from drained and flooded agricultural peatlands in the Sacramento-San Joaquin Delta , 2012 .

[173]  Jeffrey P. Walker,et al.  An introduction to the Australian and New Zealand flux tower network - OzFlux , 2016 .

[174]  Pete Smith,et al.  The net biome production of full crop rotations in Europe , 2010 .