Ana Nunes and John Roads* ECPC Scripps Institution of Oceanography,

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NARCCAP Workshop: September 10-11, 2009

Ana Nunes and John Roads*Ana Nunes and John Roads*

ECPCECPC

Scripps Institution of Oceanography, Scripps Institution of Oceanography,

University of California, San Diego, University of California, San Diego,

La Jolla, CA, USALa Jolla, CA, USA

The Experimental Climate Prediction Center The Experimental Climate Prediction Center (ECPC)’s (ECPC)’s

Regional Spectral ModelRegional Spectral Model

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Dynamical downscaling became more popular in the last decade due to the improvements in the nesting approaches used in regional models to downscale the global analyses.

In contrast to the statistical downscaling, the regional downscaling through dynamically consistent numerical models can represent the evolution of non-linear systems from large-scale analyses.

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global model

Well resolved

Insufficiently resolved

Spatial scales

Courtesy of Hans von Storch

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Well resolved

Insufficiently resolved

Spatial scales

vari

ance regional model

Added valueCourtesy of Hans von Storch

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The ECPC-Regional Spectral Model (RSM) is a The ECPC-Regional Spectral Model (RSM) is a hydrostatic, primitive equation system, with “normalized hydrostatic, primitive equation system, with “normalized pressure” or “sigma” as vertical coordinate. pressure” or “sigma” as vertical coordinate. In the ECPC’s system, regional and global models In the ECPC’s system, regional and global models share most of their codes. share most of their codes. The new ECPC-RSM is coupled to an updated The new ECPC-RSM is coupled to an updated version of the 4-layer Noah Land-Surface Model (Noah version of the 4-layer Noah Land-Surface Model (Noah LSM; Mitchell LSM; Mitchell et alet al. 2004), and also includes the Scale-. 2004), and also includes the Scale-Selective Bias Correction (SSBC; Kanamaru and Selective Bias Correction (SSBC; Kanamaru and Kanamitsu 2007) that is similar to the spectral nudging Kanamitsu 2007) that is similar to the spectral nudging technique described in von Storch technique described in von Storch et al.et al. (2000). (2000).

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One of the strategies used to improve high-resolution downscaled long-term simulations is the spectral nudging, which is an attempt to preserve the large-scale features from the global solution into the regional domain during long integrations.

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Scale-Selective Bias Correction (SSBC; Kanamaru and Kanamitsu 2007)

• Tendency of perturbation (dP/dt) is damped for U and V.• Area average is corrected for T and q.

• Surface pressure (lnps) correction is also applied.€

dP

dt

new

=1

1+ α

dP

dt

old

P: PerturbationP=F-Fanl

α = 0.9

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Advantages of Spectral Nudging: No dependency on domain size

LB Nudging

Spectral Nudging

Kanamaru and Kanamitsu, MWR 2007

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SSBC: Kanamaru and Kanamitsu, MWR 2007

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Description of IR and solar radiation schemes: SW radiation scheme based on Chou (1992) includes the absorption and scattering due to ozone, water vapor, oxygen, carbon dioxide, clouds, and aerosols. LW radiation scheme from Chou and Suarez, 1994.

Principal references: Chou, M. D, 1992: A solar-radiation model for use in climate studies. J. Atmos. Sci., 49, 762-772. Chou, M. D., and M. J. Suarez, 1994: An efficient thermal infrared radiation parameterization for use in general circulation models. Technical Report Series on Global Modeling and Data Assimilation/NASA Technical Memorandum 1994-104606, 3, 85 pp.

The cloud scheme is based on relative humidity threshold values (Slingo, 1987).Principal reference: Slingo, J. M., 1987: The development and verification of a cloud prediction model for the ECMWF model. Quart. J. Roy. Meteor. Soc.,113, 899-927.

Physics I

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Description of deep convection scheme: Simplified Arakawa-Schubert (SAS) formerly by Grell (1993), version from Pan and Wu (1995), adapted by Hong and Pan (1998).

Principal reference: Hong, S. –Y., and H. –L. Pan, 1998: Convective trigger function for a mass-flux cumulus parameterization scheme. Mon. Wea. Rev., 126, 2599-2620.

Description of boundary layer scheme: Boundary layer diffusion scheme based on Troen and Mahrt (1986) nonlocal diffusion. The turbulent diffusivity coefficients are function of the boundary layer heights and scale parameters derived from similarity (Hong and Pan, 1996).

Principal reference: Hong, S. -Y., and H. -L. Pan, 1996: Nonlocal boundary layer vertical diffusion in a Medium-Range Forecast Model. Mon. Wea. Rev., 124, 2322-2339.

Physics II

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Description of land surface scheme: Updated four-layer (0-10 cm, 10-40 cm, 40-100 cm, 100-200cm) soil model Noah (Mitchell et al., 2004).

Principal reference: Mitchell, K. E., and Coauthors, 2004: The multi-institution North American Land Data Assimilation System (NLDAS): Utilizing multiple GCIP products and partners in a continental distributed hydrological modeling system. J. Geophys. Res., 109, D07S90, doi:10.1029/2003JD003823.

Physics III

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Simplified Arakawa-Schubert cumulus

convection scheme

(SAS; Hong and Pan 1998)

Boundary Forcing: Scale-

Selective Bias Correction(SS

BC; Kanamaru

and Kanamitsu

2007)

Noah

Land-Surface Model

(Mitchell et al. 2004);

4-soil layers

50-km resolution, 28

vertical layers

Hydrostatic, Primitive

Equations

(RSM; Juang et al.

1997)

ECPC-Regional Spectral Model:

NARCCAP General Configuration

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The 50-km/28-layer Model Domain

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Direct Transverse Circulation

Indirect Transverse Circulation

Jet Streak

From Nunes and Roads JGR 2009

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The 50-km/28-layer Model Domain

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The NARCCAP The NARCCAP ECPC-RSM ECPC-RSM shows more shows more precipitation over precipitation over the western and the western and dryness over the dryness over the central US in central US in comparison to comparison to PIRCS, R-2 and PIRCS, R-2 and NARR.NARR.

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Both ECPC-RSMs Both ECPC-RSMs show a weaker jet show a weaker jet streak, with a streak, with a precipitation core precipitation core shifted northeast shifted northeast of the observed of the observed location pictured in location pictured in NARR and R-2.NARR and R-2.

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ECPC-RSM AOGCM Forced RunsECPC-RSM AOGCM Forced Runs• Phase IIa: control [1968-2000] and future climate [2038-2070] Phase IIa: control [1968-2000] and future climate [2038-2070] runsruns

• ECPC-RSM will be using initial and boundary conditions from ECPC-RSM will be using initial and boundary conditions from the GFDL CM2.1 and the HADCM3, over a new domain, for the the GFDL CM2.1 and the HADCM3, over a new domain, for the regional climate simulation of the present or control climate and regional climate simulation of the present or control climate and SRES A2 future climate projections. SRES A2 future climate projections.

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181x156

New Domain: Sponge Zone FreeReanalysis Forcing AOGCM Forcing

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This research used NCEP/DOA AMIP-II reanalysis obtained from the This research used NCEP/DOA AMIP-II reanalysis obtained from the NCEP (NOMADS2) data serverNCEP (NOMADS2) data server, and , and the NCEP North American Regional the NCEP North American Regional Reanalysis (NARR) data from Reanalysis (NARR) data from http://www.emc.ncep.noaa.gov/mmb/rreanlhttp://www.emc.ncep.noaa.gov/mmb/rreanl. . The NOAA/Climate Prediction Center provided daily precipitation values. The NOAA/Climate Prediction Center provided daily precipitation values.

AcknowledgmentsAcknowledgments

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Ana Nunes and John Roads* ECPC Scripps Institution of Oceanography,