issues for global modeling and new experiments siegfried schubert global modeling and assimilation...
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Issues for Global Modeling and New Experiments
Siegfried SchubertGlobal Modeling and Assimilation Office
NASA/Goddard
Fifth Meeting of the NAME Science Working GroupPuerto Vallarta, Mexico
6-7 November 2003
Outline
• Overview of NAME Modeling and Data Assimilation Strategic Plan
• Review of NAMAP1
• What next? NAMAP2, CPTs…
• Are we addressing global modeling issues?– How/why do we expect NAME to improve
predictions?
Overview of NAME Modeling and Data Assimilation Strategic Plan
Multi-scale Model Development
Multi-tier Synthesis and Data Assimilation
Prediction and Global-scale Linkages
provide constraints at the process level
assess the veracity of phenomena and the linkages to regional and larger-scales
provide initial and boundary conditions and verification data for predictions
Role of Observations in Model Development and Assessment
I. Multi-scale Model Development
The underlying premise of the NAME modeling strategy is that deficiencies in our ability to model "local" processes are among
the leading factors limiting forecast skill in the NAME region.
Specifically:
•moist convection in the presence of complex terrain and land/sea contrasts;
• land/atmosphere interactions in the presence of complex terrain and land/sea contrasts;
• ocean/atmosphere interactions in coastal regions with complex terrain.
will require both improvements to the physical parameterizations and improvements to how we model the interactions between the local processes and regional and larger scale variability
“Bottom-up” and “top-down” approaches:
1. Multi-scale modeling1. Multi-scale modeling
Cloud-system-resolving models having computational domain(s) large enough to represent interaction/feedback with large scales
Multiscale models explicitly represent convective cloud systems
2. Global/regional models2. Global/regional models
Examine impact of resolution, diagnose behavior of parameterizations in the presence of complex terrain, and larger-scale organization
Understand behavior and limitations of current parameterizations at higher resolutions, pursue improved parameterizations
II. Multi-tier Synthesis and Data Assimilation
Data assimilation is critical to enhancing the value and extending the impact of the Tier I observations
The specific objectives are:
To better understand and simulate the various components of the NAM and their interactions
To quantify the impact of the NAME observations
To identify model errors and attribute them to the underlying model deficiencies
III. Prediction and Global-Scale Linkages
One of the measures of success of the NAME program will be the extent to which predictions of the NAMS are improved
The key issue to be addressed is to determine the extent to which model improvements (and improved boundary and initial conditions) translate into improved dynamical predictions.
“Regional” improvements => improved regional/global scale interactions => improved predictions
Basic idea is that:
Review of NAMAP1
NAMAPModel Assessment for the North American Monsoon
Experiment
D.S. Gutzler H.-K. Kim University of New Mexico NOAA/NCEP/CPC
NAMAP analysis goalsa) Motivate a set of baseline control simulations for
more focused research by each group
b) Identify and describe inter-model consistencies and differences; tentatively suggest physical explanations for differences
c) Provide measurement targets for NAME 2004 field campaign
d) Examine effects of core monsoon (Tier I) convection differences on larger-scale (Tier II) circulation
NAMAP participating models/groups
Model
Institution / Group ResolutionMoist Convection
RSM NCEP / Juang et al. 20 km / 28LArakawa-Schubert
RSM SIO ECPC / Kanamitsu 20 km / 28LArakawa-Schubert
MM5 UNM / Ritchie 15 km / 23L Kain-Fritsch
Eta NCEP / Mitchell & Yang 32 km / 45LBetts-Miller-Janjic
SFM NCEP / Schemm2.52.5°/ 28L
Arakawa-Schubert
NSIPPNASA / Schubert & Pegion
11°/ 34L Relaxed A-S
Reg
ion
al
Glo
bal
Lateral boundary conditions: Reanalysis SST: NOAA OIv2 11° weekly analysis
Land surface treatments vary
Summer 1990simulations
No obs here! What is the “true” diurnal cycle? All models show convective max between 21Z-04Z How much nocturnal rain should be falling?
Moisture transport & the Gulf of Calif LLJ
Eta: Berbery (2001) RAMS: Fawcett et al (2002)
qv x-sec at 31°N qv map at 925 hPa{Centered on Gulf} {mostly on slopes}
NAMAP low-level jets I (925 hPa, July 12Z avg)
MM5 results “look like” Berbery’s Eta jet in the northern GofC, with a slope jet farther south
NSIPP just generates a slope jet
MM5 NSIPP-1 [regional] [global]
NAMAP: What have we learned so far?
• All models simulate a summer precip maximum; the two global models exhibit delayed monsoon onset (Aug instead of Jul)
• Precipitation diurnal cycle issues: magnitude of late-day convection, amount of nocturnal rainfall?
• Surface quantities (T, LH, SH fluxes) seem very poorly constrained; huge model differences (no validation data)
• Great Plains LLJ weakens after monsoon onset
• Low-level (slope?) jets occur -- but only weakly tied to NAME precipitation? Needs additional analysis, and close observation in 2004 field season
NAMAP2
Greater Focus (compared with NAMAP1)
• Precipitation (emphasizing diurnal cycle) in key NAME regions
• Surface energy budget (land surface interactions) • Comparative analysis of LLJs in Gulf of California
and Gulf of Mexico• Integrate with field campaign• Prediction component
Challenges
Strengthening linkages between modeling, data assimilation and observational activities/programs
•relevancy - timing is everything --> path to operations
•doesn’t happened naturally - requires programmatic nudging/support
Developing “CPT-like” effort -> focus on diurnal cycle
Are we addressing global modeling issues?– How/why do we expect NAME to improve
predictions?
Global modeling issues• Basic “universal” problems relevant to NAMS
– Poor simulation of warm season continental climates– Poor simulation of diurnal cycle (related to above)– Poor predictions of warm season precipitation
• Resolution issues– Need to resolve key phenomena– Application specific (e.g. regional impacts, extreme events)– Computational issues: need for long runs, large ensembles
• Physics issues– Limitations of convection parameterizations, but intimately linked to surface
interactions, atmospheric boundary layer, clouds, etc.– Schemes largely untested at high resolution
• Prediction issues– Role of SSTs (especially other than ENSO)– Role of land surface feedbacks (strength, time scales)– Role of intraseasonal variability (e.g. MJO)– Seasonal differences in predictability (e.g. impact of ENSO)
“Snapshot” of water vapor (white) and precipitation (orange) from a simulation with the NASA Seasonal-to-Interannual Prediction Project (NSIPP) AGCM run at 1/2 degree lat/lon resolution.
Winter (DJF) Summer (JJA)Signal/Total (Z200)
Full
Eddy
Prediction Issues• Winter
– Strong wave response to SST: impacts storm tracks– Models do reasonable job in getting above, and show
some skill in precipitation prediction
• Summer– Stronger zonally-symmetric response to SST: more
subtle interactions with orography, land, etc– Models do poorly in such warm season global/regional
interactions– Getting “local/regional” processes right and their
interactions with global scale is critical to improving predictions