Land Surface Fluxes in the Multi-Instance SP-CAM

2014 CESM Workshop, Breckenridge, CO

Morgan Phillips Scott Denning Dave Randall

Ian Baker Mark Branson

Overview

• Super-Parameterization in the CESM

• Comparison of Global Multi-Instance Land simulations in CESM

• Non-linear coupling of land-atmosphere components

Multi-scale Modeling and Super-Parameterization (SP)

Climate Model Grid Cell

Cloud Scale Motion

Super Parameterization in CESM

Strengths • Explicitly resolved turbulence and cloud

scale motion • Cloud-Radiation interactions Weaknesses • 2 Dimensionality • Periodic boundary conditions • Computationally expensive

• 2D ‘curtain’ of Cloud Resolving Model (CRM) in each Global Climate Model (GCM) cell

Courtesy: M. Khairoutdinov

MASL Multi-Atmosphere Single Land

MAML Multi-Atmosphere Multi-Land

LAND LAND

CRM

LAND LAND LAND LAND

SASL Single Atmosphere Single Land

3 Flavors of CESM

Three ways to couple atmosphere to land • Computational cost increases ~200x from SASL -> MASL • Marginal increase in computational cost from MASL -> MAML • Still less expensive than high resolution models!

CRM

Global Model Runs – MAML v. MASL

• Fully coupled land/atmosphere

• Prescribed ocean SSTs

• 5 Year integrations

– Difference plots show MAML - MASL

More Intense Rainfall

drizzle

downpour

mm hr-1

Drizzle Effect

CLM

CLM

CLM

CLM

CR

M

CR

M

CR

M

CR

M

CLM

CR

M

CR

M

CR

M

CR

M

MASL MAML

Hydrology

• Fewer, more intense rain events in MAML • Change in canopy energy balance

- Physical implications - Bio-physiological response

Canopy Interception mm

d

æ

èçö

ø÷Canopy Evaporation

mm

d

æ

èçö

ø÷

Hydrology

Total Water Storage mm( )Transpiration mm

d

æ

èçö

ø÷

f x( ) f x( )C

LM

CLM

CLM

CLM

CR

M

CR

M

CR

M

CR

M

Land cell receives average solar radiation from full CRM curtain

CLM

CR

M

CR

M

CR

M

CR

M

Each land cell receives undiluted clear-sky or shadow from each

CRM cell

Shadow Effect

Shadow Effect

Photosynthesis

– High radiation cells don’t contribute much more to photosynthesis, but shadowed cells contribute less

– Net effect is to reduce photosynthesis in MAML

gC

m2d

æ

èçö

ø÷

Summary

• Multi-Instance land in the SP-CESM

– Relatively inexpensive

• Less interception, more transpiration

– Canopy energy balance has changed in the MAML!

– Less water retained

• Bio-physiological impacts

– Non-linear response to light, soil moisture