Vertical resolution in the next generation CAM &

WACCMJadwiga (Yaga) Richter & Brian Medeiros

CGD/NCAR

Your Input is needed•Vertical resolution & model top are critical issues to settle

for CAM7/WACCM7

•Yaga Richter & Brian Medeiros will lead revision of

CAM/WACCM’s grid

• Few things to think about….

CAM7/WACCM7

• ENSO, MJO• Mean state (U/T/Precip) • ITCZ• Aerosols/Clouds• Paelo

Climate Studies:

Middle/upper atmospheric dynamics/chemistry:

• Low U/T biases• QBO, SSWs• Water vapor,

ozone transport• Aerosols

Initialized Prediction:

• ENSO, QBO, MJO • Stratospheric factors• External forcings

(volcanos etc)CAM7

WACCM7

Historical Perspective

(Richter et al. 2014a)

1983: CCM0: 4.4 x 7.5o 9L

1990: CCM1: 4.4 x 7.5o 12L

1994: CCM2: 2.8 x 2.8o 18L

2006: CAM3: 2.8 x 2.8o 26L (66L)

2013: CAM4: 0.95x1.25o 26L (66L)

2015: CAM5: 0.95x1.25o 30L (70L)

2018: CAM6: 0.95x1.25o 32L (70L)

WACCM

Boundary Layer (very bottom):• Very bottom layer should be 20 m (midpoint at 10 m) for adequate exchanges

between ocean and atmosphere • Want to resolve the depth of the stable BL (up to 200 m)

Where we are now:

Δz1= 110m Δz2= 132m

700 hPa

Where we would like to go:Δz1= 20m

+ levels at 40, 65, 90, 120, 160, 210m~7

Boundary Layer (200 m – 3 km):

ATEX, Stevens et al. 2001ASTEX, Chung et al. 2012 BOMEX, Xue & Feingold. 2006BOMEX, Siebesma et al. 2003

500m300m

250m 500m

Large-Eddy Simulations

• Studies suggest Δz ≤ 200m required to capture the effects of turbulence on clouds

Lenderink & Holtslag (2000), van Meijgaard & van Ulden (1998)

• Desired resolution of 100 – 150 m up to 700 hPa

Boundary Layer (200 m – 3 km):Where we are now:

Δz= 150 – 600 m

700 hPa

Ideal: Δz ~ 100 - 150m

+ levels at 20, 40, 65, 90, 120, 160, 210 m7

+ ~ 18 levels between 300–3000 m

CMIP5 Models

Total levels (levels below 700hPa)

Free troposphere/stratosphere:(For Quasi-geostrophic flows;Lindzen & Fox-Rabinovitz 1989, Boville 1991)

Current Δz 20o 45o 65o

Troposphere 1.2 km 0.5 km 1 km 1.3 km

Stratosphere 1.5 km 0.23 km 0.5 km 0.6 km

Free troposphere/stratosphere:Where we are now:

Δz ~ 1200 m - 1800 m in Free troposphere and lower stratosphere

CAM6

WACCM6

High vertical resolution CAMIn 2013: Doubled vertical resolution: 60LCAM

• Cut-down near-tropopause T biases by 2K• Improved Kelvin & Mixed Rossby-Gravity

waves• First internally generated QBO in CAM

(Richter et al. 2014a)

High vertical resolution

Richter et al. 2014a, JGR

30L60L 60L - 30L

MR-GWs

Kelvin WavesKiladis et al. 2009

High vertical resolution CAM

Richter et al. 2014b, JGR

2oS to 2oN U

60L+GW

30L

OBS

• QBO has stronger effect on

MJO than ENSO in boreal

winter (Son et al. 2017)

• MJO amplitude stronger

during easterly QBO

(Yoo and Son 2016)

Why care about QBO?

110L: WACCM

110L WACCM: Built by J. Richter and R. Garcia for QBOi

110L WACCM QBOERAI

70L WACCM(CESM2)

110L WACCM

Impacts on MJO

110L WACCM QBO & RG WavesEP Flux Div (shading)

Descending QBO W

Coherance2 Amp at k=8

Phase linesNo coherence with lower levels -> in situ generation of RG waves

Short vertical wavelengths (needing high vertical resolution)Garcia and Richter (2018, in prep)

Other Models:

Butchart et al. 2018, GMD

∆z: 10-15 km

∆z: 15-20 km

∆z: 20-25 km

CAM6/WACCM6

Desired for CAM7/WACCM7

7 levels between 0 and 200 m

~ 70 - 72 levels

+ ~ 40 levels mideal ∆z ~ 500 - 700 m

+ ~ 50 - 60 levels mideal ∆z ~ 500 - 700 m

~ 5 – 7 levelsnear model top

~ 5 – 7 levelsnear model top

+ 40 – 50 levels

120 - 140 levels total

18 levels between 300–3000 m

+ ~ 50 - 60 levels mideal ∆z ~ 500 - 700 m

+ 25– 35 levels

~ 5 – 7 levelsnear model top

105 – 125 levels total

QBOi Models

CAM7/WACCM7

CAM7+

WACCM7Option II

CAM7

HVR(~140L)HVR(~70 - 120L)LVR (32L)

CAM7

WACCM7Option I

HVR(~140L)LVR (32L)

WACCM7Option III

HVR(~140L)

CAM7/WACCM7

CAM7+WACCM7

Option II

HVR(~140L)HVR(~70 - 120L)LVR (32L)

WACCM7Option I

HVR(~140L)

Summary• Vertical resolution & model top are critical issues to settle

for CAM7/WACCM7

• YOUR INPUT IS NEEDED

• Yaga Richter (jrichter@ucar.edu) & Brian Medeiros

(brianpm@ucar.edu) will lead revision of CAM/WACCM’s grid

• 2 Telecons between March 1 – May 30 to arrive at a prototype grid(s)

to be presented in the June CESM meeting

• Email your opinion and/or willingness to participate in further

discussions