Upload
grssieee
View
166
Download
1
Tags:
Embed Size (px)
Citation preview
1
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 ERDC2Mississippi State University
3NASA / GSFC
27 July 2011
2
Outline
• Motivation and Objective• Approach and Description of
the SRSS• Simulation Results• Future Work
3
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
4
Dry Conditions
5
Moist Conditions Flooded Conditions
6
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.
7
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.
8
Research Questions1. How do you simulate the forest
without explicitly simulating the forest?
2. During periods of high mass transfer, how much heat is transported by the fluid flow compared to conduction and radiative effects?
3. What is the effect of the root system on the spatial and temporal distributions of temperature and moisture content in the soil?
9
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.
10
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)
11
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
12
SRSS Component Verification
Radiative heat transferSky radiative heat transfer
Conduction in unsaturated porous media
Shortwave solar radiation
Convective heat transfer in porous media
13
SRSS Application to Historical Simulations
Herrington (1964)
0800
0900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
Figure 1.1 Temperature contours from the Derby and Gates pine log simulation. Time is in hours and temperature is deg C.
Derby and Gates (1965)
14
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
15
SRSS Application• Single tree in a mature
deciduous forest• Both winter and early summer
simulationTable 1.1 Simulation Matrix for the Temperate Forest
Name Seasonal Setting Fluid Flow Soil State Solar Conditions
Alpha Winter N Saturated Winter Canopy Bravo Winter N Unsaturated Winter Canopy Charlie Early Summer N Saturated Summer Canopy Delta Early Summer N Unsaturated Summer Canopy Echo Early Summer Y Saturated Summer Canopy
Foxtrot Early Summer Y Saturated Open Canopy
16
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
17
Mesh Development• Requirements
• Realistic trunk and root system• Allows anisotropic thermal and fluid properties• Hydraulically connected
18
19
20
21
22
LIDAR Scan of Root System
Raw Data
Centerline Selection
Solid Geometry
23
24
25
26
Stem Cross-Sections
-0.4m -0.3m -0.2m
0.0m 0.3m 0.6m
0.9m 1.3m 1.6m
27
28
29
30
Winter
31
Early Summer
32
Simulation Results
33
Early Summer Example
34
Surface Heat Flux
35
Growth of Unsaturated Soil Region
36
37
Simulation Analyses• Temperature profiles along
cardinal radius lines• Flow vs. no flow• Open vs. close canopy
Table 1.1 Simulation Matrix for the Temperate Forest
Name Seasonal Setting Fluid Flow Soil State Solar Conditions
Alpha Winter N Saturated Winter Canopy Bravo Winter N Unsaturated Winter Canopy Charlie Early Summer N Saturated Summer Canopy Delta Early Summer N Unsaturated Summer Canopy Echo Early Summer Y Saturated Summer Canopy
Foxtrot Early Summer Y Saturated Open Canopy
38
N
W E
S
0.8
12.5 3.4
0.6
4.8
8.3
12.7
0.6 4.8 9.6
0.6
5.5
9.4
Bark
Xylem1Xylem2Xylem3Heartwoo
d
39
Winter trunk temperatures
North radius at 0.6m
South radius at 0.6m
40
Winter thermal radiation
0.3m
0.6m
1.3m
41
Flow effect on Temperature
flow no flow
flow – no flow
Early summer
North radius at 0.6m
42
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
43
Research Answers1. The SRSS demonstrated the ability
to simulate accurately the physics of thermal radiation without explicitly modeling the entire forest.
2. During periods of moderate fluid flow, simulations showed up to a 2 deg C change in temperature accounting for conduction and radiative effects.
3. Fluid flow from the soil into the roots creates unsaturated soil regions that vary diurnally and changes the thermal properties of the soil.
44
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
45
Thank You
46
Inclusion of understory vegetation
47
48
Critical Time Steps