4404138.pdf [Levina Tatyana Borisovna]
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- Bu sahifa navigatsiya:
- Air, canopy, and soil surface temperatures :: b.) Net
- Net longwave
- Sensible heat
- .-:." . . --.". c.) Soil moisture profiles
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Bare Soil R
Figure 3-2: An illustration of vegetation representation at the element scale. The area is divided into patches of bare soil, soil covered with herbaceous (grass) and woody vegetation. R is rainfall, I is infiltration, T is transpiration, and
is evaporation. (1995, 1996) provide typical values of leaf dimension for various plant types. The relative root abundance in each soil layer R,.oot [-] is calculated from an exponential root profile (J ackson et aI., 1996): (3.1) where
z [mm] is soil depth and TJ [mm- 1 ] is the decay rate of distribution of the root biornass with the soil depth. This formulation allows one to adjust the profile so that different vegetation types can have different distributions of the root biomass.
Two types of surfaces are considered within a computational element:
ground and canopy. The ground surface can be present as both bare soil and under-canopy soil. Ground albedos are parameterized based on the soil surface moisture content.
The 156
a.) b.) Figure 3-3: A schen1atic diagran1 of the a.) direct beal11 and b.) diffuse solar radiation absorbed, transl11itted, and reflected by vegetation and under-canopy ground.
They are used to calculate the Normalized Difference Vegetation Index (NDVI) for a given vegetation type:
=
The forn1ulation for the element-scale rnlT rVlS estin1ate of JV DV I is provided in Section 3.6.5. 3.6.1c Canopy fractions Canopy photosynthesis n10dels are generally formulated to describe the fluxes of both CO 2 and water vapor at the leaf level (Section 4.4.1). Some method is required to scale these quantities to the canopy level. Both multilayer and "big-leaf" approaches have been used for such scaling (Dai et al., 2004). A multilayer model integrates the fluxes frol11each canopy layer to give the total flux (e.g., Wang and Jarvis, 1990; Leuning et al., 1995); while the big-leaf approach maps properties of the whole canopy onto a single leaf to calculate the flux (e.g., Sellers et al., 1996a; Bonan, 1996; Oleson et al., 2004). The multilayer models can use parameters that are lneasured at the leaf level, however, such approaches are highly computationally delnanding. The big-leaf 1110delsrequire son1e plausible assumption about the vertical profile of leaf properties. 162
Figure 3-4: A schematic diagram of the longwave radiation absorbed, transnlitted, re-
flected, and emitted by vegetation and under-canopy ground.
1 is the downward atmospheric longwave radiation, L~eg 1 is the downward longwave radiation below
the vegetation canopy,
L;e g i is the upward longwave radiation from the ground, and L~eg i is the upward longwave radiation above the vegetation canopy. L~eg and L;e g are the net radiation fluxes (positive towards the atmosphere) for canopy and understory ground, respectively. 167 a.) Air, canopy, and soil surface temperatures ~::~~~
b.) Net downward radiative flux, Rn 600 E
~ 200
o 1000
C\/ E 500 ~ o d.) Net longwave radiation (positive towards the atmosphere), L D i~it! ~;'i~o~ e.) Ground heat flux (positive into the soil), G lwr~~~~~~~4~ N E 100 ._ .• __ .............•.......•.......•...............•......................•...... ~ 5~ : : : : : : '.' : ~ : . -50 / : : : : . f.) Sensible heat flux (positive towards the atmosphere), H N 400 r:.....•......•......•.....•.......•......•............•.......•....• / •
. . " . . . g.) Latent heat flux (positive towards the atmosphere), )"E
300 ~ : : : : : : : : : - AE - Canopy l~:
.••..•...•. ~••••.••.•.••••••••••..•• :•....•• ~, ••••.••. :•••....•.. E-Soil
... 10 20 30 40 50 60 70 80 90 100
110 120
Hour Figure 3-10: The simulated temperatures and components of canopy and ground surface energy budgets for an area vegetated with broadleaf deciduous trees: a.) air Tatm, canopy
Tv, and soil surface Tg temperatures; b.) net radiation
and
Rn g); c.) incoming global and absorbed shortwave radiation ((Satm 1~
1A) and
(Svveg and
Sgveg )); d.) net longwave radiation (L~.eg and
L;eg); e.) ground heat flux G; f.) sensible heat flux
and
Hgveg); g.) latent heat flux (AEvveg and
AEgveg). 197
a.) Sunlit and shaded canopy stomatal resistances 2000
1500 E en 1000 500
b.) Leaf boundary layer and aerodynamic resistances (above and within canopy) - A-dyn. within canopy - - A-dyn. above canopy
- Leaf boundary layer ..
'.' '.'
, ' . 120 100
80 ~ 60 ............ (/)
40 20
2000 ...
/' ... ': t . \ ' /' \: f .\ :. ,..\ .: ......
:/ \ , : .. \ . .I. ... t. \ , :,i::' ::, / .. ', .. :, - ARtmfosPhereh-:ehatm \ . f - e erence
elg t - es
/.: :., :I \ ' / \.: I' - - Stomatal- e*(Tv)
6000
5000 ~ 4000 3000 1000
d.) Soil surface resistance 2000
1500 ~ 1000 (/) 500
. o 10 20 30 40 50 60 70 Hour 80 90 100 110
120 Figure 3-11: Vapor pressures and the simulated resistances used to estimate canopy and ground surface energy fluxes for an area vegetated with broadleaf deciduous trees: a.) sunlit and shaded canopy stonlatal resistances (r;un and
r;hd); b.) leaf boundary layer
and aerodynalllic resistances
and
r~h); c.) atmospheric eatm, reference height
and stomatal e*(T v) water vapor pressures; d.) soil surface resistance rsrf' 198
a.) Canopy latent heat flux e.) Soil latent heat flux wind [m/5] 400
300 ~ 200 ~ 100
10 15 Hour 20 10 wind 1m/51 400 300
~ 200
~ 100
, , ... :::~"'''~'' 20 10 b.) Canopy sensible heat flux f.)
Soil sensible heat flux wind 1m/5] 300 200
"'e ~ 100 -100 10 15 20 Hour
10 wind 1m/5] - -100
He ~ -200 -300 10 ~. ,,' " .... :, ......
15 20 Hour 10 c.) Canopy net longwave flux g.) Soil net longwave flux ....
' . ..... . 200
100 ~ ~ 10 -100
-200 10 10 wind 1m/5] wind 1m/5J o 20
15 20 Hour 15 " ..... 10 h.) Soil surface temperature 50 40
30 ~ 20 10 10 wind [m/5] 15 20 Hour do) Canopy temperature so 40
~ 20 10 20 Hour
400 300
~ 200
~ 100
Figure 3-16: An illustration of sensitivity of the energy partition and simulated tem- peratures to wind speed for an area vegetated with broadleaf deciduous trees:
a.) canopy latent heat flux >"E;:eg; bo) canopy sensible heat flux H;:eg; c.) canopy net longwave flux
do) canopy temperature Tv; e.) under-canopy soil latent heat
flux >"Egveg; b.) under-canopy soil sensible heat flux
c.) under-canopy soil net longwave flux L;e g ; do) ground surface temperature Tg. 206
a.) Canopy latent heat flux e.) Soil latent heat flux 300 '"E
200 ~ 100 o 10 300 '"E 200
~ 100
.~ .. . . ........... : ..
. . . . . . . . . . . - .. 20 10 wind 1m/5] b.) Canopy sensible heat flux f.) Soil sensible heat flux 100 '"€
0 ;;;, -100 -200 10
'"E 0 ~ -100 -200
...... ; ..... . ~ . 10 10 15 20 Hour
wind [m/51 10 15 20 Hour
wind [m/5] c.) Canopy nat longwave flux g.) Soil net longwava flux 10 ...... ; .....
15 20 Hour 10 wind [m/5] 200 -100
10 - . 15 20 Hour 10 wind 1m/5] do) Canopy temperature .1 - •••• : ••••••••..••• ho) Soil temperature 10 wind [m/5] ............ 20 -'\- . ....... - . Hour 15 . " "':'"
10 ....
:~ .~:
.. :- ~:~. ......... 40 40 30 30 e e 20 20 10 10 10 10 15 20 wind 1m/51 Hour
Figure 3-17: An illustration of sensitivity of the energy partition and simulated tem- peratures to wind speed for an area vegetated with C
4 grass: a.) canopy latent heat flux
b.) canopy sensible heat flux Hvveg; co) canopy net longwave flux i~eg; d.) canopy temperature Tv; e.) under-canopy soil latent heat flux
b.) under- canopy soil sensible heat flux
c.) under-canopy soil net longwave flux
d.)
ground surface temperature Tg. 207
a.) Rainfall 300
250 200
150 b.) Cloudiness e.) Wi nd speed c.) Shortwave radiation d.) Air and dew point temperatures 100
60 :J i? 40 E E 20 0 10 ~ ...!..
I 5 _..
0 1000
N E 500 ~ 0 30 20 () 10 0 0 -10 10 .!!!.
5 E 0 50 Hour Figure
3-18: Hydrol11eteorological observations for Albuquerque (NM), with June 10th, 1991 as the starting date. Note that the rainfall rates are artificially amplified by a factor of rv 5: a.) rainfall rate; b.) cloudiness; c.) global shortwave radiation; d.) air and dew point temperatures; e.) wind speed. 210
a.) Net precipitation i 5: 1 j j~j ~....:..... 1b:... ROin,,,e:92mm .. eT r
0 9.mm.i
j 10 20 30 40 50 60 70 e s - Hour35 - Hour36
- Hour37
- - Hour 38 .- Hour72
0.3 0.4
c.) Soil moisture profiles: hour 35-72 o
profiles: hour 0-30 o 200 e: 200
I .- ~ J - - .- 400 __ 0:-':'."':"""" .• .................. 400 - I 600 / .......... 600 .- E .- E .s 800 ;...- ............ .s 800 ~ ~ g. 1000 g. 1000 I
t • .. . . . . .. . .. c c
/' 1200
. .. . . . . . . . . 1200
.. :/:: . 1400 ~ ....
Initial 1400
- Hour11
- Hour12
1600 - Hour 13 1600 .......
, .. - - Hour 14
Hour 30 1800
1800 0.1
0.2 0.3
0.4 0.1
0.2 70 - Surface - Root zone 60 50 40 Hour 30 20 8 8
integrated with depth 10 10 20 30 40 50 60 70 e.) Drainage from the root zone to lower layers and runoff o o E E 1 en CD ~0.5 -... ~ ~ 0.5 E E Figure 3-19: Soil lnoisture dynalnics and drainage
froln the root zone for
loamy sand soil (surface is vegetated with broadleaf deciduous trees): a.) net precipitation (rainfallless interception losses); b.) instantaneous soil moisture profiles for hour 0 - 30; c.) instantaneous soillnoisture profiles for hour 35 - 72; d.) relative soil moisture content at the surface and root zone; e.) drainage froln the root zone to lower soil layers and runoff. 211
a.) Net precipitation i:t
j~i iJb!
.... Rain",.= t 92mm . .~r,.'3.6mm! j 10 20 30 40 50 60 70
0.35 - Hour35 - Hour36 - Hour37 - - Hour 38 . - Hour 72 '.-:." . . --.". c.) Soil moisture profiles: hour 35-72 o 200 400 600 ... 1. 1400 1600 E 800 oS .r:;
g. 1000 C B. 5 .. ...... .. . . . ......... 1200 -Initial - Hour11 - Hour 12 - Hour 13 - - Hour 14 . - Hour30 1800 0.3 0.35 0.4 0.2 0.25 0.3 e e d.) Relative soil moisture integrated with depth - - ~ ./ . -' " . 0.25 . ~: b.) Soil moisture profiles: hour 0-30 o o CD ~0.5 CD 200
400 600
E 800
oS .r:; g. 1000 C 1200 1400 1600 1800 0.2 8 E E 6 10 20 30 40 50 60 e.) Drainage from the root zone to lower layers and runoff .................. ' . 70 10 20 30 40 Hour 50 60 70 Figure 3-20: Soil 1110isture dyna111ics and drainage from the root zone for clayey soil (surface is vegetated with broadleaf deciduous trees): a.) net precipitation (rainfall less interception losses); b.) instantaneous soil lTIoisture profiles for hour 0 - 30; c.) instantaneous soillTIoisture profiles for hour 35 - 72; d.) relative soillTIoisture content at the surface and root zone; e.) drainage fron1 the root zone to lower soil layers and runoff. 212 |
