Getting Organized Convection into

Climate Models

PROWESS International Conference

25th Anniversary of NCMRWF

February 17-20 2014

Mitch Moncrieff

NCAR Earth System Laboratory

Climate & Global Dynamics Division

Boulder, Colorado, USA

Weather Climate

MJO

30 - 90 days

Contents

• Dynamical system approach to organized convection parameterization

• Propagating orogenic MCS over the continental U.S.

• Madden - Julian Oscillation (MJO)

• Year of Tropical Convection (YOTC)

• Conclusions

• Underlying chaotic order, analogous to coherent structures in turbulent flow

• Upscale and downscale transport of energy and momentum

• Affects precipitation distribution, intensity, type

• Key part of the global water cycle

Organized convection

Cumulonimbus

O (10 km)

Supercell storm

O (100 km)

Tropical cyclone O (1000 km)

Madden-Julian Oscillation (MJO)

O (10000 km)

Mesoscale convective system (MCS) O (100 km)

Mesoscale Convective System (MCS)

• Provides about half the total tropical rainfall

• Long-lasting, propagates ~10m/s, with regional impact

• Transport properties distinct from turbulent cumulus mixing

• Affects structure of diabatic heating, convective and radiative

• Dynamically interactive, building block of larger-scale organization

Precipitation bias occurs within days … in regions of

large-scale convective organization

CAPT Program, LLNL

Fraction of rainfall from MCS

(TRMM satellite)

Tao & Moncrieff (2009)

MCSs are missing from traditional

climate models ...

• Cumulus parameterizations were not designed with organized

convection in mind ---

• MCS: Dynamical system distinct from cumulus convection

• Resolution of traditional climate models insufficient to simulate MCS

New Era: Mesoscale-permitting climate models:

O (10km) mesh

Physical resolution of numerical models is about an order of

magnitude coarser than its computational mesh, therefore:

i) O (100 m) mesh: cumulus parameterization not needed

ii) O (1 km) mesh: mesoscale organization resolved

iii) O (10 km) mesh: mesoscale organization permitted

Horizontal scale

Mesh

size

Cumulus

Scale-gap

~1 km ~100 km

Cumulus parameterization assumes a scale gap

Horizontal

scale

Cumulus

Mesoscale

Systems

~100 km ~1 km

But no scale gap in the real world

Mesh

size

Cumulus parameterization

MCS

Turbulent mixing

Single vertical column

L ~ 1-10 km

L < H

H ~ 10 km

L ~ 100 km

Slantwise quasi-

laminar flow

L >> H

H ~ 10 km

MCS as a Dynamical System Distinct from Cumulus

Dynamics of slantwise overturning

*c = U (z )

*z = z

( ,z )c, F

0

2 ( )z

z

FG dz

0z

Baroclinic generation of

vorticity

Vorticity

Shear

buoyancy

Steering level

latent heating

evaporative cooling

Convective Froude number:

Bernoulli Number:

0U (z) - c/p

Environmental shear

2

0U /CAPEcF

2102

U

2102

/E p U

Moncrieff (1992)

Propagating slantwise overturning

3 Categories of Energy: Potential, Kinetic, Pressure work

2102

( )UR

CAPE

c

2102

( )c

pE

U

E R

Representing MCS in Global Models:

Slantwise (Tilted) Heating in Shear Flow

Multi-scale Structural Paradigm

Propagating Orogenic MCS over US

Continent

Propagating MCS downstream of mountains

Laing and Fritsch (1997)

Continental US

W. Africa

Propagation and Diurnal Cycle

Afternoon

Next morning

~1000 km

Elevated heating:Start position /time of MCS

Mesoscale

descent

MCS – Family of

cumulonimbus

Vertical shear a) Organizes mesoscale dynamics

b) Controls propagation

C ~ 10 m/s

Simulated Propagating MCS:

Resolution Dependence and Observational Validation

3-km explicit NEXRAD analysis Carbone et al. (2002) 10-km Betts-Miller 10-km explicit

Moncrieff and Liu (2006)

Explicit vs Parameterized Precipitation

Parameterized Explicit Total

Superparameterized Community Atmospheric Model (SP-CAM)

Standard CAM - no MCS

SP- CAM - Propagating MCS

Second-baroclinic heating/cooling

communicated from CRM grid to

climate grid organized by vertical shear

Pritchard, Moncrieff and Somerville (2011)

Resolution Dependence of Convective Heating

30 km

10 km

3 km

Madden-Julian Oscillation (MJO)

Multi-scale Convective Organization

in Global Model Frameworks

A) Traditional climate models

B) High-resolution global NWP

C) Global cloud-system resolving models

D) Superparameterized global models

E) Multicloud parameterization

A) Tropical precipitation: Aqua-planet climate models

(5S - 5N average)

D. Williamson (NCAR), M. Blackburn (U. Reading)

“Truth”

Global Cloud-System

Resolving Model

(NICAM)

B) MJO Hindcasts for ECMWF IFS

Vitard et al (2011)

2004 2010 Analysis

C) Global cloud-system resolving models

The NICAM Team

MJO-like systems and MCS-like Organization

in NICAM (7km)

Miyakawa et al. (2012)

Mesoscale momentum transport

........... m m

convection

u uu w

t z t

Mesoscale Momentum Transport : 13000-section Average

Miyakawa et al. (2012)

Courtesy: Marat Khairoutdinov

D) Superparameterized MCS-like systems and MJO-like Organization

Courtesy Marat Khairoutdinov

E) Multi-cloud parameterization for the MJO:

Representing Slantwise Dynamics

Khouider and Majda (2006)

Dynamically active free atmosphere:

2 vertical modes

Passive boundary layer

• Deep convection

(P)

• Upper-tropospheric stratiform anvils & evaporatively driven

mesoscale downdrafts

(Hs)

• Lower tropospheric cumulus congestus & upper-tropospheric

radiative cooling

(Hc)

Khouider & Majda (2006)

Categories of Diabatic Heating

MJO-like Systems in AquaPlanet Climate Model

with Multi-cloud Parameterization

Ajayamohan, Khouider, Majda (2013)

WCRP/WWRP Year of Tropical

Convection (YOTC))

May ‘08 – Apr ’10

Focus Areas

MJO & CCEWs

Easterly Waves & TCs

Trop-ExtraTrop Interaction

Diurnal Cycle

Monsoons

yotc.ucar.edu

TARGETED APPROACH TO SEAMLESS PREDICTION

MJOs during

YOTC

(May ‘08 – Apr ‘10)

La Nina

conditions

El Nino

conditions

2

0

0

8

2

0

0

9

2

0

1

0

Moncrieff et al. (2012)

MJO Diabatic Heating Estimates: Reanalysis and TRMM

1. Climatology– multi-year simulations coupled or

atmosphere only

2. Short-range hindcasts – daily 48hr lead during

~20 days of the MJO

3. Medium-range hindcasts – daily 20-day lead

time

Vertical Structure and Diabatic Processes of

the MJO: Global Model Evaluation Project MJO Task Force/YOTC/GASS

Time step / 2 –Day Physics Errors

Daily / Weekly Forecast Errors

Long-Term Climate Simulation Errors

yotc.ucar.edu/mjo/vertical-structure-and-diabatic-heating-mjo

Conclusions: Organized Convection

• Organized convection is ubiquitous around the world, but missing

from climate models & incomplete in global weather models

• Single-column model used in cumulus parameterization fails to

represent organized dynamics

• Dynamical system approach: Vertical profile of diabatic/convective

heating is key to slantwise structure of diabatic heating and

organized convective momentum transport

• 10 km mesh for a global cliamte model is about the maximum for

the simulation of MCS having reasonable vertical structure and

propagation characteristics

• Multi-cloud parameterization approximating the dynamical system

approach in the form of slantwise heating successfully simulates

MJO-like features by representing MCS- and supercluster-like

features

•

Conclusions: YOTC

• YOTC, a targeted approach to seamless prediction, is focused

on organized tropical convection and its scale interactions

• Virtual global field-campaign framework complements actual

field campaigns and global-scale systems such as the MJO

• GEWEX Atmospheric System Study (GASS) utilizes the YOTC-

ECMWF database in the MJO Vertical Structure and Diabatic

Heating Evaluation project

• YOTC will formally finish at end of 2014, but research will

continue in other guizes, e.g.,

- WWRP Subseasonal- to-Seasonal (S2S) prediction project

- YOTC MJO Task Force has been moved to WGNE

http://yotc.ucar.edu

Thanks for your attention