radiation in acme - climate model€¦ · philip cameron-smith, acme meeting, summer 2017 (bolger...
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Radiation in ACME To explore issues ACME is facing associated
with radiation, and possible improvements
Philip Cameron-Smith,
ACME meeting, Summer 2017 (Bolger Center)
LLNL-PRES-708641 Prepared by LLNL under Contract DE-AC52-07NA27344.
Radiation affects Atm, Land, Ocn, Ice
Radiation is still uncertain
Key points:
High-resolution surface radiation, temperature, precipitation, humidity, winds are likely to be important drivers of surface processes, especially in the Arctic.
Topography and microtopography controls on surface radiation budgets have large potential impacts in permafrost landscapes (next slide).
(Fig 6.20, IPCC AR5, WG I, 2013)
CO2 feedbacks
Climate feedbacks
Permafrost and
wetlands feedbacks
3
What does “high-resolution ESM gridcell” mean for the Arctic?
Image credits: Jiafu Mao, Salil Mahajan, Michele Thornton
Observations illustrate
interactions among terrain,
vegetation distribution, and snow.
Surface radiation plays an
important role in these
interactions.
Terrain and Microtopography
VegetationSnow
Surface Hydrology
Subsurface Thermal-Hydrology
Soil Biogeochemistry
Detailed studies in several Arctic tundra watersheds on Alaska’s Seward Peninsula (NGEE-Arctic)
Teller watershed: 2.3 km2 HUC-12 containing the Teller watershed: 140 km2
1/9
Impact of surface heterogeneities on land surfacefluxes and states in simulations using an
uncoupled, hyper-resolution land surface model
Gautam Bisht and William Riley
Earth & Environmental Sciences Division,Lawrence Berkeley National Laboratory
June 2, 2017
2/9
Research objectives
Local surface topographic features (e.g. slope, aspect), as well as,non-local topographic features (e.g. terrain shading, sky viewfactor), impacts total amount of solar radiation reaching theEarth’s surface. Yet, the ACME land model assumes a flat Earthwith an unobstructed view of sky.
1. How does surfaceheterogeneities due tosoils, vegetation cover, andtopography impactcoarse-scale surface fluxesand states?
2. What is the relative impactof various sources ofsurface heterogeneities oncoase-scale surface fluxesand states?
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Methodology
I Sources of heterogeneities
1. Soils (POLARIS30)
2. PFT (MODIS)
3. Surface elevation (GTOP30)
I ALM is modified to account for effects of topography (slope andaspect) on downwelling solar radiation
I Surface dataset created at 1km horizontal resolution
I Each watershed was driven by 1× 1 CRUC forcing dataset
I Simulation length was 20-years
I Surface dataset contained 100% naturally vegetated land
I Watersheds
1. Rio Grand headwaters watershed, CO
2. Snake headwater watershed, Wyoming
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Methodology (continued)
I Following set of ALM simulations were performed:
Code Soil PFT Surface elevation
UUF Uniform Uniform FlatVUF Variable Uniform FlatUVF Uniform Variable FlatVVF Variable Uariable FlatUUT Uniform Uniform TopographyVUT Vniform Uniform TopographyUVT Uariable Variable TopographyVVT Variable Variable Topography
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Rio Grande Headwaters
6/9
Rio Grande Headwaters: Monthly R↓shortwave
J F M A M J J A S O N D0
100
200
300
400[W
m−2
]
Rsdown: Mean
UUFVVT
J F M A M J J A S O N D0
5
10
15
20
25
30
[Wm
−2]
Rsdown: Standard dev
UUFVVT
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Rio Grande Headwaters: Monthly sensible heat flux
J F M A M J J A S O N D
0
50
100
150
200[W
m−2
]
SH: Mean
UUFVVT
J F M A M J J A S O N D0
10
20
30
40
50
[Wm
−2]
SH: Standard dev
UUFVVT
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Rio Grande Headwaters: Monthly latent heat flux
J F M A M J J A S O N D0
20
40
60
80
100[W
m−2
]
LH: Mean
UUFVVT
J F M A M J J A S O N D0
5
10
15
20
[Wm
−2]
LH: Standard dev
UUFVVT
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Conclusion
I Surface heterogeneities have negligible impact on domainaverage fluxes and states.
I Surface heterogeneities lead to spatial variability in simulatedfluxes and states.
Conclusion
• Sub-gridscale Land heterogeneity will affect
climate response.
• Correlated land-use with snow affects the
mean response.