The Path Forward: High-Resolution Next-Generation CESM ... · with focus on TCs by Reed et al. (2015) • Variable-resolution CAM5.3 SE L30 (14 – 110 km) in AMIP mode: Zarzycki

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