the path forward: high-resolution next-generation cesm ... · with focus on tcs by reed et al....
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The Path Forward: High-Resolution Next-Generation CESM Simulations and Scale-Aware Physics Christiane Jablonowski, Diana Thatcher, Jared Ferguson
(University of Michigan) Colin Zarzycki, Andrew Gettelman, Julio Bacmeister, Jadwiga Richter, Rich Neale, Cecile Hannay, Peter Lauritzen, Patrick Callaghan & Others (NCAR) Vincent Larson (University of Wisconsin), Kevin Reed (Stony Brook University), Paul Ullrich (UC Davis), Michael Wehner (LBNL), Mark Taylor (Sandia National Laboratories) & Others
CESM Meeting 2015, June/17/2015
High-Resolution Climate Modeling
High- and variable-resolution acts as a magnifying glass
Non-conforming block- structured AMR with Chombo
CAM Spectral Element with conforming static nests
14 km
55 km
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Motivation & State of the Art for CESM
• NRC Report (2012) and the NCAR strategic plan (2014) highlight the pressing need for high-resolution climate simulations
• High-res simulations are paramount for regional climate change assessments with current horizontal spacings ranging between 10-30 km.
• CAM5-Finite Volume (FV) and CAM5-Spectral Element (SE) configurations have utilized uniform grid spacings of about 28 km (0.25o).
• CAM-SE’s variable-resolution mesh is explored down to 14 and 7 km.
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Current High-Res Simulations with CESM
• CAM4 and CAM5 Finite Volume (FV) 0.23° x 0.31°(≈25 km) with 30 vertical levels (L30): 25-year AMIP simulations by Bacmeister et al. (2014)
• CAM5.1 FV 0.23° x 0.31°L30 (≈25 km): 27-year AMIP simulations with focus on TCs by Wehner et al. (2014, 2015)
• CAM5 Spectral Element (SE) 0.25° L30 (≈28 km): 100-year coupled simulations with 0.1° ocean model by Small et al. (2014)
• CAM5.3 FV and SE 0.25°L30: 20-25 year AMIP simulations with focus on TCs by Reed et al. (2015)
• Variable-resolution CAM5.3 SE L30 (14 – 110 km) in AMIP mode: Zarzycki et al. (2014a, 2014b, 2015), Zarzycki and Jablonowski (2014, 2015), Rhoades et al (2015), Huang et al (2015). 7 km simulations by Bacmeister and Callaghan
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TC Representation with 250 & 50 km Grids
1000 km
250
km
• Refined model resolution around 50 km helps capture the key physical processes for tropical cyclones
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Captured Processes in Climate Models
Characteristic Length Scale
104 km 102 km 1 km 10 m 10 cm
1 s
1 min
10 min
1 hr
1 day
10 days
Cha
ract
eris
tic T
ime
Sca
le
Today: 14-28 km High-resolution global climate models capture tropical cyclone processes, improved topographic effects (precip, GW, winds)
110 km: Standard operational climate model resolution in 2012
Future: 3 km cloud-permitting cloud-resolving scale
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Using CAM-SE for multi-scale simulations
• Atmospheric Model Intercomparison Project (AMIP) protocols • Observed SST, O3,
aerosol, solar forcing, etc.
• 1980-2002 (23 years) • North Atlantic
Refinement • CAM-SE variable-
resolution configuration with CAM5 physics
~28 km
~110 km
Multi-resolution global circulation (28 km)
Total precipitable water (TPW), Sept 1-16
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Spontaneous generation of tropical cyclones in high-resolution domain!
Animation by Colin Zarzycki
TC Pressure-Wind Relation & CAM5 Physics
• Both CAM5.3 SE (red) and FV (blue) tend to overestimate the strengths of tropical cyclones (TCs) at grid spacings of 28 km
• Suggests mesh sensitivities in the physics or even inadequate physics (especially cloud processes, ZM convection in CAM5)
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observations
CAM
from Reed et al. (2015)
TC Structure & Physics at High-res • Hurricane Leslie (2012) forecast experiment: CAM5 versus CAM5-
CLUBB physics at 14 km grid spacing in SE
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weak inflow & outflow
Radial wind (m/s) Tangential wind (m/s) Vertical pressure velocity (Pa/s)
weak & broad
Reduced updrafts
Zarzycki and Jablonowski (2015)
Physics Scale Sensitivities: Aqua-Planet
• CAM5-CLUBB, CAM5 and CAM4 resolution sensitivities in SE aqua-planet simulations (by Gettelman, Callaghan, Li, Lauritzen, Taylor)
• Total precipitation rate (mm/day) is very scale sensitive in CAM4 • Sensitivity reduced in CAM5, CLUBB is designed to be scale-insensitive (to
be investigated further, cloud forcings across resolutions suggest this)
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Enhanced scale sensitivity
28 km
110 km
Pushing the Frontiers with CESM: 14 km
• CAM5.3-SE variable-resolution AMIP simulations with focus on California precipitation and snowpack
• Research by Ullrich, Rhoades, Huang (UC Davis) and Zarzycki (NCAR)
• Orographically-driven precipitation patterns improve at high resolution
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110 km 28 km 14 km observations
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• CAM-SE “forecast mode” • Equivalent 1° (110 km)
global grid refined by a factor of 8 to 1/8°(~14 km) over western Atlantic Ocean
Sandy, 10/26/12 12Z
at 850 hPa
Pushing the Frontiers with CESM: 14 km
Zarzycki and Jablonowski
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Pushing the Frontiers with CESM: 6-7 km
Bacmeister et al.
110 km
7 km
• CAM-SE at hydrostatic limit
• No physics changes
• Currently under evaluation
• Planned: simulations with CLUBB
Aggressive zoom into the region of interest
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Computational Benefits
• Atmosphere: ~15-20x speedup with variable-resolution vs. 1/8° uniform grid • Scales with number of elements and fixed compute load
• For same cost of global uniform/quasi-uniform… • Higher regional resolution • Additional ensemble simulations • Longer model runs
18,584 elements
345,600 elements
~18
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An Often Dismissed Issue: Vertical Levels
• Horizontal refinements must be accompanied by vertical refinements to keep dynamic consistency
• CAM’s vertical resolution has been stagnant for 10+ years • Urgent need to double/triple vertical resolutions and explore
their benefits (vertical wave propagation, QBO, etc) • Benefits easily visible in idealized moist dynamical core
experiments with mountains (e.g. in pressure velocity) SE 110 km L30 SE 110 km L60 SE 55 km L30
Improved gravity waves
Resolution mismatch creates noise
gravity waves weak
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Community Input: Increase Vertical Levels • Yaga Richter leads a future configuration of WACCM6-V with
model top at 120 km and enhanced vertical resolution (about 140 levels)
• Input wanted from community where levels should be placed • Provide feedback within next two weeks ([email protected])
Current level configuration and spacing in CAM and WACCM
Enhanced resolution wanted everywhere
High-Res CESM Modeling: Going Forward
• Larson, Gettelman, Jablonowski and co-workers were recently awarded 22 Million GAUs to pursue high-res CESM research with CAM-SE CLUBB: AMIP, coupled and short-term forecast (CAPT) mode
• Planned experiments over the next year will include uniform 28-km simulations as well as variable-resolution CAM-SE configurations
• Simulations will also explore enhanced vertical resolutions • Research questions to be addressed:
• Adequacy of the CAM5.5 physics in multi-scale simulations • Tuning parameters for balanced radiation budgets • Physics scale sensitivities and remedies • Process-level investigations (mesoscale systems, diurnal precip
cycle, extreme events) and climate statistics using CAM5.5-SE-CLUBB across multiple resolutions
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• Bacmeister, J. T., M. F. Wehner, R. B. Neale, A. Gettelman, C. Hannay, P. H. Lauritzen, J. M. Caron and J. E. Truesdale (2014), Exploratory high-resolution climate simulations using the Community Atmosphere Model (CAM), J. Climate, 27, 3073-3099
• Huang, X., A. M. Rhoades, P. A. Ullrich, C. M. Zarzycki (2015), High-resolution regional climate model evaluation using variable-resolution CESM over California. J. Climate, in review
• Reed, K. A., J. T. Bacmeister, N. A. Rosenbloom, M. F. Wehner, S. C. Bates, P. H. Lauritzen, J. E. Truesdale, C. Hannay (2015), Impact of the dynamical core on the direct simulation of tropical cyclones in a high-resolution global model. Geophys. Res. Lett., Vol. 42 (9), 3603-3608
• Rhoades, A. M., X. Huang, P. A. Ullrich, C. M. Zarzycki (2015), Characterizing Sierra Nevada Snowpack Using Variable-Resolution CESM. J. Climate, in review
• Wehner, M. F., K. A. Reed, F. Li, Prabhat, J. Bacmeister, C.-T. Chen, C. Paciorek, P. J. Gleckler, K. R. Sperber, W. D. Collins, A. Gettelman and C. Jablonowski (2014), The effect of horizontal resolution on simulation quality in the Community Atmospheric Model, CAM5.1, J. Adv. Model. Earth Syst., Vol. 6, 980-997
• Wehner, M. F., Prabhat, K. A. Reed, D. Stone, W. D. Collins, and J. T. Bacmeister (2015), Resolution dependence of future tropical cyclone projections of CAM5.1 in the U.S. CLIVAR Hurricane Working Group idealized configurations, J. Climate, Vol. 28, 3905-3925
• Zarzycki, C. M., C. Jablonowski and M. A. Taylor (2014a), Using Variable Resolution Meshes to Model Tropical Cyclones in the Community Atmosphere Model, Mon. Wea. Rev., Vol. 142, 1221-1239
• Zarzycki, C. M., M.. N. Levy, C. Jablonowski, M. A. Taylor, J. Overfelt, and P. A. Ullrich (2014b), Aqua Planet Experiments Using CAM's Variable Resolution Dynamical Core. J. Climate, Vol. 27, 5481-5503
• Zarzycki, C. M., C. Jablonowski (2014): A multidecadal simulation of Atlantic tropical cyclones using a variable-resolution global atmospheric general circulation model. J. Adv. Model. Earth Syst., Vol. 6, 805-828
• Zarzycki, C. M., C. Jablonowski, D.. R. Thatcher, M. A. Taylor (2015): Effects of localized grid refinement on the general circulation and climatology in the Community Atmosphere Model. J.Climate, Vol. 28, 2777-2803
• Zarzycki, C. M. and C. Jablonowski (2015): Experimental tropical cyclone forecasts using a variable-resolution global model. Mon. Wea. Rev., in review
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References