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Organized Convection in a New Era for Global Models
Pisharoty Distinguished Lecture - 2016Indian Meteorological Society, Pune ChapterInternational Institute for Tropical Meteorology
February 23, 2016
Mitchell W. MoncrieffClimate & Global Dynamics Laboratory
National Center for Atmospheric Research Boulder, CO 30305, USA
Weather Climate
Subseasonal-to-Seasonal
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Underlying Chaotic Order, Multiscale Coherent Structures in a Turbulent Environment
Affects: Distribution, Intensity and Type of precipitation; Diabatic Heating;
Transport of Momentum; Cascade of Kinetic Energy
Formidable Parameterization Challenge
Organized Convection
Large-scale Organizatione.g., MJO, Monsoons
O (10,000 km)
Mesoscale Organizatione.g., MCSO (100 km)
Towards
Mesoscale - PermittingClimate Models
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Two Interacting Worlds of Convective Organization
ExtratropicsQuasi-horizontal large-scale slope convection
controlled by potential vorticity dynamics, with embedded mesoscale organization
Downscale Control
Tropics: Multiscale convective organization as anintegral part of the tropical circulation
Upscale Cascade
Total Column Water Courtesy: Chris Velden, U. Wisconsin/Madison
Courtesy: Dundee Satellite Receiving Station, Scotland
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Mesoscale Convective Systems (MCS)
MCS provide over 1/2 total tropical rainfall Long-lasting & propagating, MCS affects entire regions
Organized momentum transport is the antithesis of turbulent mixing Top-heavy convective - stratiform heating is an important characteristic
BUT MCS ARE MISSING FROM TRADITIONAL O(100 km)-grid CLIMATE MODELS
- Cumulus parameterizations fail to represent them
- Model resolution is too coarse to simulate them
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New Era: Mesoscale-Permitting Global Models
Physical resolution of a numerical model is 5-10 times coarser than the computational grid:
O (100 km) grid: traditional convective parameterization
O (10 km) grid: mesoscale organization permitted, cumulus parameterized
O (1 km) grid: mesoscale organization resolved, cumulus permitted
O (100 m) grid: cumulus parameterization redundant
10-km grid is the mesoscale-permitting threshold for global models requiring a paradigm shift in thinking for organized convection parameterization
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Fraction of Rain from MCS (TRMM satellite)
Tao & Moncrieff (2009)
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Organized Convection Parameterization:
Coherent Multiscale Structure in a Turbulent Environment
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Coherent Structure Paradigm
Scale-Selection Principles
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Topics
1. Orogenic Mesoscale Convective Systems (MCS)
2. Madden-Julian Oscillation (MJO)
3. Dynamically Based Coherent Structure Parameterization
1. Virtual Global Field Campaigns
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Topic 1: Orogenic MCS
Laing & Fritsch (1997)
Continental US
Tropical Africa
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Propagating MCSs Modulate the Diurnal Cycle
+Afternoon
Next morning
~1000 km
Elevated heating sets
start position of MCS
Mesoscaledescent
MCS Family of cumulonimbus
Vertical shear
Organizes mesoscale circulationsand system propagation
C ~ 10 m/s
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MCS: Resolution Dependence & Observational Validation
3-km explicitNEXRAD analysisCarbone et al. (2002) 10-km Betts-Miller10-km explicit
Moncrieff and Liu (2006)
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Parameterized vs. Expicit Precipitation
Parameterized ExplicitTotal
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Resolution Dependence of Convective Heating
30 km
10 km
3 km
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Dynamical Structure
=10 km =30 km =3 km
3-km & 10-km grids realistic & similar
30-km grid unrealistic
a) Flow organization & cloud structure
b) Flow vectors & zonal component of velocity
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Super-parameterized Community Atmospheric Model (SP-CAM3.5)
Standard CAM: No MCS
SPCAM: MCS heating simulated bymultiple CRM grids is communicated to the climate grid and organized by the large-scale vertical shear
Pritchard, Moncrieff, Somerville (2011)
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Super-Parameterized Community Atmospheric Model (SP-CAM3)
Pritchard, Moncrieff & Somerville (2011)
Standard CAM: No MCS, no propagation
SP-CAM3: MCS-like organization, propagation
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Regional-Refined Community Model (RRCM)
Courtesy, Julio Bacmeister, NCAR
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Convective Organization in RRCM (6-km grid)
Courtesy, Julio Bacmeister, NCAR
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Is the CMIP5 Warm Surface Temperature Bias over U.S. Continent a Propagating Convection Issue?
Ma et al. (2014)
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Topic 2: Madden-Julian Oscillation (MJO)
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Multiscale Coherent Structures in the MJO
Nakazawa (1988)
EastwardPropagating
CloudEnvelopes
MJOs(A, B,C,D)
WestwardPropagating
Meso-synopticFeatures
(C)
AB
CD
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Courtesy: Marat Khairoutdinov
Superparameterized MJO
Courtesy: Marat Khairoutdinov
2-D CRMs in climate models simulate MCS, periodic boundary conditions trap them in CRM domains
MCSs can be generated on, and propagate across, the climate grid but are under-resolved and biased, e.g., mesoscale downdrafts distorted or missing
Super-parameterization in a 10 km-grid (mesoscale permitting) GCM would alleviate this bias, but be excessively expensive to run.
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ECMWF Integrated Forecast System (IFS)
Moncrieff et al. (2012)
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Global cloud-system resolving models
The NICAM Team
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MJO and MCS Interaction in 7km-grid Global CRM (NICAM)
Miyakawa et al. (2012)
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Mesoscale Momentum Transport: Average of 13,000 samples
Miyakawa et al. (2012)
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Organized Convective Momentum Transport and Upscale Kinetic Energy Cascade
( )........... m mconvection
u uu wt z t
+ = =
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Topic 3: Dynamically Based Coherent Structure Parameterization
a) Multi-cloud Model (Khouider & Majda, 2006)
b) Slantwise Layer Overturning Model (Moncrieff 2010)
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Coherent Structure Paradigm forOrganized Convection Parameterization
O (10 km) Computational Grid Global Weather Models
Experimental Climate ModelsOrganized Convection
Parameterization
O (1 km) GridCloud-System
Resolving Models(CSRM)
MultiscaleTropical
Convection
Monsoons
IntraseasonalVariability
InterTropicalConvergence
Zone
Atmospheric Water Cycle
Dynamical Analogs
CoherentStructureParadigm
O (100 km) Computational Grid
Traditional Climate Models
Cumulus Parameterization
Organized Convection
ParameterizationPhysical & Dynamical
Processes
Multi-cloud Model & Slantwise Layer Overturning
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P: Deep convection (1st baroclinic)
Hs: Upper-tropospheric stratiform region & evaporatively driven mesoscale downdrafts (2nd baroclinic)
Hc: Lower-tropospheric cumulus congestus & upper-tropospheric radiative cooling (2nd baroclinic)
Khouider & Majda (2006)
a) Multi-cloud Model: 1st and 2nd Baroclinic Heating
Dynamically Passive Planetary Boundary-layer
Dynamically Active Troposphere
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Multicloud Parameterization: MJO in an idealized GCM
Ajayamohan et al (2013)
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b) Slantwise Layer Overturning Model
= +
0
2 ( )z
z
FG dz
( )0z
BaroclinicGeneration
Vorticity Shear
Steering level
Latent heating
Evaporative cooling
0U (z) - c
Environmental shear
2102 U
C
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Slantwise Layer Overturning Parameterization Experiments (SLOPE)
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Topic 4: Virtual Global Field Campaigns
Year of Tropical Convection (YOTC)
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YOTC-ECMWF
Virtual Global FieldCampaign
May 2008 April 2010
yotc.ucar.edu
Moncrieff & Waliser (2012)
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YOTC MJOs
La Ninaconditions
El Nino conditions
2008
2009
2010
Moncrieff et al. (2012)
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YOTC MJO Task Force Three intercomparison projects:
20-year Climate Simulations (24 GCMs)20-day Hindcasts2-day Hindcasts
Jiang et al. (2015)
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Conclusions
10-km grid is a threshold resolution for explicit rrepresentation of organized convection in GCMs target for next-generation GCMs
New approaches to organized convection parameterization for GCMs based on multiscale coherent structures in a turbulent environment:
i) Multi-cloud model (Khouider & Majda 2006) ii) Slantwise layer overturning model (Moncrieff 2010; Moncrieff &
Waliser 2015)
Future work:
- WCRP-WWRP Subseasonal-to-Seasonal Prediction (S2S) program- Years of Maritime Continent (YMC) from mid-2017 to mid-2019- 2nd Virtual Global Field Campaign, 10 km grid ECMWF IFS- Regional-Refined Global Models, e.g., U.S. Continent, Maritime Continent
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References Ajayamohan, R.S., and Coauthors, 2013: Realistic initiation and dynamics of the Madden-Julian
oscillation in a coarse resolution aquaplanet GCM. Geophys. Res. Let., 40, doi:10.1002/2013GL058187.
Jiang, X., and Co authors, 2015: Vertical structure and physical processes of the Madden-Julian oscillation: Exploring key model physics in climate simulations. J. Geophys. Res, Atmos., 120, 4718-4748.
Khouider, B., and M.W. Moncrieff, 2015: Organized convection parameterization for the ITCZ. J. Atmos. Sci.,72,3073-3096, doi: http://dx.doi.org/10.1175/JAS-D-15-0006.1.
Ma, H-Y, and Coauthors , 2014: On the Correspondence between Mean Forecast Errors and Climate Errors in CMIP5 Models. J. Climate 27:4, 1781-1798. doi: http://dx.doi.org/10.1175/JCLI-D-12-00134.1
Miyakawa, T. ,and Coauthors, 2012: Convective momentum transport by rainbands within a Madden-Julian oscillation in a global nonhydrostatic model. J. Atmos. Sci., 69, 1317-1338, doi: 10.1175/JAS-D-11-024.1.
Moncrieff, M.W., 1992: Organized convective systems: Archetypal models, mass and momentum flux theory, and parameterization. Quart. J. Roy. Meteor. Soc., 118, 819-850.
Moncrieff, M. W., 2010: The multiscale organization of moist convection and the intersection of weather and climate. In Climate Dynamics: Why Does Climate Vary? Geophys. Monogr. Ser., Vol. 189, Eds. D-Z. Sun and F. Bryan, pp. 326, doi: 10.1029/2008GM000838.
Moncrieff, M.W., and Coauthors, 2012: Multiscale convective organization and the YOTC Virtual Global Field Campaign Bull. Amer. Meteorol. Soc., 93, 1171-1187, doi:10.1175/BAMS-D-11-00233.1
Moncrieff, M.W., and D.E. Waliser, 2015: Organized Convection and the YOTC Project., Seamless Prediction of the Earth-System: From Minutes to Months, (G. Brunet, S. Jones, P.M. Ruti Eds., WMO-No. 1156), ISBN 978-92-63-11156-2, Geneva.
Waliser, D.E., and Coauthors, 2012: The Year of Tropical Convection (May 2008 to April 2010): Climate variability and weather highlights. Bull. Amer. Meteorol. Soc., 93,1189-1218, doi:10.1175/2011BAMS3095.1
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Thanks for your attention
Organized Convection in a New Era for Global Models Slide Number 2Slide Number 3Mesoscale Convective Systems (MCS)New Era: Mesoscale-Permitting Global ModelsFraction of Rain from MCS (TRMM satellite)Organized Convection Parameterization:Coherent Multiscale Structure in a Turbulent Environment Coherent Structure Paradigm Topics Topic 1: Orogenic MCS Propagating MCSs Modulate the Diurnal CycleMCS: Resolution Dependence & Observational ValidationParameterized vs. Expicit PrecipitationResolution Dependence of Convective HeatingDynamical StructureSuper-parameterized Community Atmospheric Model (SP-CAM3.5)Super-Parameterized Community Atmospheric Model (SP-CAM3)Regional-Refined Community Model (RRCM)Convective Organization in RRCM (6-km grid) Is the CMIP5 Warm Surface Temperature Bias over U.S. Continent a Propagating Convection Issue?Topic 2: Madden-Julian Oscillation (MJO) Multiscale Coherent Structures in the MJOSlide Number 24Slide Number 25Global cloud-system resolving models MJO and MCS Interaction in 7km-grid Global CRM (NICAM)Mesoscale Momentum Transport: Average of 13,000 samplesOrganized Convective Momentum Transport and Upscale Kinetic Energy Cascade Topic 3: Dynamically Based Coherent Structure Parameterization a) Multi-cloud Model (Khouider & Majda, 2006) b) Slantwise Layer Overturning Model (Moncrieff 2010)Coherent Structure Paradigm forOrganized Convection Parameterization Slide Number 32Multicloud Parameterization: MJO in an idealized GCM b) Slantwise Layer Overturning ModelSlantwise Layer Overturning Parameterization Experiments (SLOPE)Topic 4: Virtual Global Field CampaignsYear of Tropical Convection (YOTC) Slide Number 37Slide Number 38YOTC MJO Task Force ConclusionsReferences Thanks for your attention
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