Fluxes: measurements and modeling. Flux

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1 Fluxes: measurements and modeling Schlesinger and Bernhardt Pg Gustin flux paper Griffis, Timothy J paper Denmead 2008 Discussion 2 - Work in groups of 2 Papers due to Mae Sept 24 Pick one paper that compares satellite and field data, or modeled data versus observations, or that assesses a flux data collection method through comparison with another method to share in class briefly. Pick a graph or table or multiple that illustrates the major results. Summarize in a brief paper the data collected, how they integrate measurements made at multiple levels or how they assess the method, results and conclusions. Critique their work. Be prepared to present and discuss in class (10 minute presentations). Flux C time Amount of material transferred from one reservoir to the other Source Sink Budget-balance of sources and sinks 1

2 ENVE117 Biophysical Environments AIR- Introduction to the Atmosphere Transport phenomena Flux = amount of a given quantity that flows through a unit area per unit time (a vector). Examples: Heat flux (J m -2 s -1 ) Volumetric flux (m 3 m -2 s -1 ) Chemical flux (mol m -2 s -1 ) Mass flux (g m -2 s -1 ) source e.g. hydrologic cycle sink 2

3 Global water cycle Pools (km 3 ) Fluxes (km 3 yr -1 ) 373, ,000 26,350,000 New figure and numbers S and B Figure ENVE302 Applied Climatology Boundary Layer Climates & Air Pollution Meteorology Conservation of Mass Everything has to go somewhere Boundary A substance entering a defined region has three possible fates inputs Sinks Sources Accumulation outputs 1) It gets to leave unchanged 2) It may accumulate Accumulation = Input Output Sinks + Sources rate rate rate rate rate 3) It may change or be removed (sink) or some may be added (source) 3

4 Evaporation from the oceans ranges from 4 mm day -1 in the tropics to <1 mm d -1 at the poles. Runoff = ppt ET- groundwater The relative balance of ppt and evaporation differs between regions. Precipitation hard to model and predict Solid and dashed lines rain gauge Dots-models Chahine 4

5 Gimeno et al (2011) Understanding evaporation source regions and continental precipitation Satellite data Isotopes Flux analyses Humidity Climate change Intensified hydrologic cycle Changing circulation patterns It s more complicated than it seemed at first! We have to consider both temporal and spatial scale Satellite A train 5

6 Leaf Cells Individual plant Scales of fluxes Landscape Globe Approaches for scaling fluxes Bottom up- scaling with empirical data Bottom up-scaling with processes Top down-apply air concentrations and model to get at what is driving exchange Top down-remote sensing 6

7 Methods for quantifying fluxes Air approach but similar for water/ soil ( Baldocchi, 2012) 1. Deposition collectors (dry and wet) 2. Flux chambers (enclosures)-net flux Static (equilibrium) Dynamic (flow through) 3. MicroMet (tower) approach-net flux Gradient method (MBR) Eddy covariance Eddy accumulation (REA) Horizontal flux (MMB) Unidirectional Flux Deposition 7

8 Collectors Unidirectional or Net Flux chambers C out C in Flux C Q C A out in 8

9 ENVE302 Applied Climatology Boundary Layer Climates & Air Pollution Meteorology Mass Balance Tools & Applications for Air Pollution Where; C = pollutant concentration (g/m 3 ) C in = Pollutant concentration in incoming air ( g/m 3 ) q s = emission rate of pollutant or flux (g/m 2 s) H = Mixing height (m) L = Length of Box (m) W = Width of box (m) U = Average wind speed (m/s) C(0) = concentration in the box initially t = time Steady State At steady state dc/dt = 0 C = q s L/uH + C in Non Steady State C(t) = q s L/uH (1 e ut/l + C in ) + C(0) e ut/l Alert,NU ENVE302 Applied Climatology Boundary Layer Climates & Air Pollution Meteorology Field Set up continued Reno,NV 9

10 ENVE302 Applied Climatology Boundary Layer Climates & Air Pollution Meteorology Flow Through Chamber Flux= Q(Cout-Cin)/A ENVE302 Applied Climatology Boundary Layer Climates & Air Pollution Meteorology Mass Balance Static Chamber flux measurement Static Chambers mass Balance Flux= (ΔC/Δt ) V/A (ng/m2s) 10

11 Baldocchi (2012) Fast flux measurements isotopes C, O, carbonyl sulfide OCS to partition fluxes between plants and soil CH4 and N2O to assess microbial activity in the soil Hydrocarbons, ozone, nitrogen oxides to assess pollutant loads To interpret trace gas fluxes Need meteorology, land use and disturbance, state of vegetation and soil ENVE302 Applied Climatology Boundary Layer Climates & Air Pollution Meteorology Surface Layer Turbulence & Fluxes Reynolds averaging F ' ' F q w K F H E C ' ' c T w c K p ' ' w c K C Fluxes V p H q 2 ( w / m ) z C 2 ( ng / m s) z T 2 ( w / m ) z Deposition velocity = V d =F C /C L(m) is the Monin Obukov Length, ratio of mechanical to buoyancy forces 3 u* T C L kgh p z/l =0 neutral z/l>0 stable z/l<0 unstable (m/s) 11

12 ENVE302 Applied Climatology Boundary Layer Climates & Air Pollution Meteorology Aerodynamic Gradient Method F K C Z C u* k( C2 C1) F K z ln( z d / z d) Stable Neutral H z d 4. 7 L H 0 Unstable 2 1 x H 2ln 2 3 u* T C L kgh p 2 1 h2 h1 1 z d x 15 L L(m) is the Monin Obukov Length where g = acceleration due to gravity (9.81 m/s 2 ) H = sensible heat flux (W/m 2 ) = air density (kg/m 3 ) T = temperature (K) Cp = specific heat at constant pressure (J/kg.K)

13 Net flux Gradient measurement (MBR) Net flux Eddy covariance/correlation Instantaneous change in vertical wind velocity and atmospheric gas concentration 13

14 Net flux?relaxed eddy accumulation Updraft Deadband Downdraft Micromet mass balance upwind mast downwind mast wind direction horizontal flux vertical flux surface x All require v specific ground characteristics 14

15 How can we possibly get at regional and global fluxes from a limited number of ground measurements? Multi-scale measurements 15

16 methodology page Mercury example Stamenkovic/Hartmann PhD 16

17 Do plants take up or emit mercury to the atmosphere? JStamenkovic - Dissertation Defense Is the exchange cuticular or stomatal? Species differences? Environmental controls? Measuring mercury (Hg) exchange C out C in Flux C Q C A out in 17

18 Four plant species: Andropogon gerardii Sorghastrum nutans Rudbeckia hirta Populus tremuloides RH: 25% Soil [Hg]: 0.02 / 0.90 g g -1 RH: 7-62% (avg. 25%) Light / Dark Ambient / Scrubbed air [CO 2 ]: 360, 613, 846 ppm [Hg]: 0, ambient, 2x, 5x (0-12 ng m -3 ) P. tremuloides 20 clean air ambient Hg exchange air Hg (ng m -3 ) Air Hg clean / ambient air Light / Dark Hg Flux (ng m -2 h -1 ) Stomatal movement and gas exchange Pnet ( mol m -2 s -1 )

19 Foliar Hg flux (ng m -2 h -1 ) air Hg concentration (ng m -3 ) EcoCELL- unfortunately blank too high to use data collected from this large chamber Ecologically Controlled Enclosed Lysimeter Laboratory Large flow-through gas-exchange chamber Flux ~ concentration differential, air flow, area 5.5 m 7.3 m Air intake 4.5 m EcoCELL 19

20 Components vs net flux Hg flux [ng m -2 hr -1 ] mesocosm 1 mesocosm 2 mesocosm 3 mesocosm 4-2 Bare soil Plant shoot Chamber net Components vs net flux Hg flux [ng m -2 hr -1 ] mesocosm 1 mesocosm 2 mesocosm 3 mesocosm 4? Litter correction 77% -2 Bare soil Plant shoot Chamber net Plant litter soil 20

21 Tallgrass prairie monoliths a net sink for atmospheric Hg g ha -1 yr g ha -1 yr g ha -1 yr -1 Litter-and-plant covered soil: g ha -1 yr g ha -1 Soil storage* Precipitation: g ha -1 yr -1 Uptake in vegetation (ephemeral storage): g ha -1 yr -1 litterfall 0.13 g ha -1 Root pool* Leaf Individual plant Role of vegetated systems in biogeochemical cycling of mercury Soil flux Landscape Biome Globe Continental / Global scale 21

22 Background biomes in the US GRASSLAND (Stamenkovic et al. in press) DESERT (Ericksen et al. 2006) DECIDUOUS FOREST (Kuiken et al. 2008) Classification and regression tree Rule-based model biome swc < 2 forest 0.2 ± ± ± 0.4 swc < ± ± 0.5 temperature irradiance % swc Hg flux 22

23 Spring Summer Fall Winter Hg flux rate (ng Hg m 2 h 1 ) NET ANNUAL EXCHANGE dry deposition of ~11 tons Hg g Hg m 2 JStamenkovic - Dissertation Defense max LAI leaf mass/area (100 g m -2 ) leaf [Hg] (25 ng g -1 ) 23

24 Vegetated systems are a net sink for atmospheric mercury 146 wet deposition fire, hydrothermal systems 5-7 Atmosphere Contiguous United States metric tonnes Hg per year 11 (?) Land storage Pacyna & Pacyna 2006, Brunke et al Engle et al Fluxes Measured in different ways Concentrations/time Concentration/area/ time A concentration does not give you a flux 24

25 Global carbon cycle Pools (10 15 g C) Fluxes (10 15 g C yr -1 ) Global nitrogen cycle Pools (10 15 g N) Fluxes (10 12 g N yr -1 ) 25

26 Global phosphorus cycle Pools (10 15 g P) Fluxes (10 12 g P yr -1 ) Global sulfur cycle Pools (10 15 g S) Fluxes (10 12 g S yr -1 ) 26