SIMULATED SEASONAL SPATIO-TEMPORAL PATTERNS OF SOIL MOISTURE, TEMPERATURE, AND NET RADIATION IN A DECIDUOUS FOREST.pptx
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SIMULATED SEASONAL SPATIO-TEMPORAL PATTERNS OF SOIL MOISTURE, TEMPERATURE, AND NET RADIATION IN A DECIDUOUS FOREST.pptx

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SIMULATED SEASONAL SPATIO-TEMPORAL PATTERNS OF SOIL MOISTURE, TEMPERATURE, AND NET RADIATION IN A DECIDUOUS FOREST.pptx SIMULATED SEASONAL SPATIO-TEMPORAL PATTERNS OF SOIL MOISTURE, TEMPERATURE, AND NET RADIATION IN A DECIDUOUS FOREST.pptx Presentation Transcript

  • Simulated Seasonal Spatio-temporal Patterns of Soil Moisture, Temperature, and Net Radiation in a Deciduous Forest
    Jerry Ballard1, Stacy Howington1, Pasquale Cinella2, and Jim Smith3
    1US Army ERDC
    2Mississippi State University
    3NASA / GSFC
    27 July 2011
  • Outline
    Motivation and Objective
    Approach and Description of the SRSS
    Simulation Results
    Future Work
  • Introduction
    Both the temperature and moisture regimes in the forest are some of the most important components in forest ecosystem dynamics
    Affects:
    Tree growth and development
    Onset and cessation of cambial activity
    Nesting success of avian species (tree cavities)
    Uptake and metabolism of pollutants from the soil
    Growth and treeline elevation limitation
    Influences forest fire intensity and tree survivability
  • Dry Conditions
  • Moist Conditions
    Flooded Conditions
  • Motivation
    Both heat and fluid processes are well studied in trees, but little is known of the interactions of the processes temporally or spatially.
    Some work exists for coupled 1- or 2-D heat and fluid flow in trees, but rarely in three dimensions.
  • Objectives
    Develop a three-dimensional computational tool that simulates the radiative energy, conductive heat, and mass transfer interaction in a soil-root-stem system (SRSS).
    Verify process components of the SRSS and apply to a seasonally varying deciduous forest in a temperate environment.
  • Research Questions
    How do you simulate the forest without explicitly simulating the forest?
    During periods of high mass transfer, how much heat is transported by the fluid flow compared to conduction and radiative effects?
    What is the effect of the root system on the spatial and temporal distributions of temperature and moisture content in the soil?
  • Research Approach
    If we treat the behavior of water in the soil and xylem similarly, it should be possible to model the xylem as a porous medium
    Develop radiative transfer model that estimates infrared contribution from the surrounding environment using form factors derived from hemispherical images
    Construct a macro-scale model of a tree-root-soil system and simulate different seasonal time periods.
  • SRSS Components
    Radiative Heat Transfer
    Simulates radiative energy in the domain
    Simulates solar energy into the domain
    Monte Carlo multiprocessor C code
    Heat and Mass Transfer in Porous Media
    Simulates time varying thermal and fluid material properties
    Mass and momentum based on Richards’ equation
    Multiprocessor C code (ADH)
  • Simulation Assumptions
    Fluid in the system is constant viscosity and density
    All fluid movement occurs in a porous medium
    Fluid velocities constitute a creeping flow (Re < 10)
    Air is always at atmospheric pressure
    No radiative heat transfer occurs in the pore space in the solids
    Within a volume of porous media, the temperatures of water and air are the same
    All surfaces are diffuse and are treated as grey black bodies
    The air gap between surfaces neither attenuates or emits thermal radiation
  • SRSS Component Verification
    Conduction in unsaturated porous media
    Radiative heat transfer
    Sky radiative heat transfer
    Shortwave solar radiation
    Convective heat transfer in porous media
  • SRSS Application to Historical Simulations
    Derby and Gates (1965)
    Herrington (1964)
  • SRSS Application for a Tree within a Forest
    Simulate a single mature tree
    Located in a temperate deciduous forest
    Seasonally and diurnally varying
    Time-lapse thermal imagery movie
  • SRSS Application
    Single tree in a mature deciduous forest
    Both winter and early summer simulation
  • Computational Domain
    12x15x8 m domain
    2-m above soil, 6-m below the soil
    Top stem exiting fluid flow driven by time-varying flow
    Bottom of domain
    Saturated soil condition
    Constant temperature
    Surface of domain
    Modified by diurnal varying solar radiation
  • Mesh Development
    Requirements
    Realistic trunk and root system
    Allows anisotropic thermal and fluid properties
    Hydraulically connected
  • LIDAR Scan of Root System
    Raw Data
    Centerline Selection
    Solid Geometry
  • Stem Cross-Sections
  • Winter
  • Early Summer
  • Simulation Results
  • Early Summer Example
  • Surface Heat Flux
  • Growth of Unsaturated Soil Region
  • Simulation Analyses
    Temperature profiles along cardinal radius lines
    Flow vs. no flow
    Open vs. close canopy
  • N
    W
    E
    S
    0.6
    Bark
    Xylem1
    5.5
    Xylem2
    Xylem3
    9.4
    Heartwood
    0.6
    9.6
    4.8
    12.5
    3.4
    0.8
    12.7
    8.3
    4.8
    0.6
  • Winter trunk temperatures
    North radius at 0.6m
    South radius at 0.6m
  • Winter thermal radiation
    1.3m
    0.6m
    0.3m
  • Flow effect on Temperature
    flow
    no flow
    flow – no flow
    Early summer
    North radius at 0.6m
  • Analyses Summary
    Winter simulations agree with observations showing that the primary influence of temperature in the trunk is solar driven.
    Flow in summer simulations show up to a 2 deg C change in internal temperature due to fluid flow
    Both winter and summer simulations show internal temperatures affected by surrounding forest radiation and soil conduction
  • Research Answers
    The SRSS demonstrated the ability to simulate accurately the physics of thermal radiation without explicitly modeling the entire forest.
    During periods of moderate fluid flow, simulations showed up to a 2 deg C change in temperature accounting for conduction and radiative effects.
    Fluid flow from the soil into the roots creates unsaturated soil regions that vary diurnally and changes the thermal properties of the soil.
  • Future Work
    Inclusion of dense understory vegetation
    Long-term full season simulations
    Drought simulations
    Additional validation studies
    Macro vs. micro scale root fluid uptake analysis needed
  • Thank You
  • Inclusion of understory vegetation
  • Critical Time Steps