Assessment of the NCEP CFS Hindcast Runs on Predicting the North American Monsoon

Assessment of the NCEP CFS Assessment of the NCEP CFS Hindcast Runs on Predicting Hindcast Runs on Predicting the North American Monsoon the North American Monsoon

Lindsey Long and Jae SchemmLindsey Long and Jae Schemm

NOAA/NWS/NCEP/CPCNOAA/NWS/NCEP/CPC

[email protected]@noaa.gov

Runs courtesy of Suranjana SahaRuns courtesy of Suranjana Saha

NOAA/NWS/NCEP/EMCNOAA/NWS/NCEP/EMC

IntroductionIntroduction

Focus on Precipitation and Atmospheric Focus on Precipitation and Atmospheric CirculationCirculation

Look at both seasonal and interannual Look at both seasonal and interannual variabilityvariability

Five varying runs allow us to look at the Five varying runs allow us to look at the affect of:affect of: Lead TimeLead Time Updates to the CFS modelUpdates to the CFS model Horizontal ResolutionHorizontal Resolution

Description of RunsDescription of Runs 5 different hindcast runs from 1981-20065 different hindcast runs from 1981-2006 Two 15-member ensemble mean Two 15-member ensemble mean

hindcasts from current operational CFShindcasts from current operational CFS 1-month lead (May)1-month lead (May) 3-month lead (March)3-month lead (March)

Three single runs with differing horizontal Three single runs with differing horizontal resolutions using an updated CFSresolutions using an updated CFS T62T62 T126T126 T382T382

RunRun CFS VersionCFS Version ResolutioResolutionn

Initial Initial ConditionCondition

# of Runs# of Runs

11 GFS 2007 / GFS 2007 / MOM3MOM3

T382T382 May 15thMay 15th SingleSingle

22 GFS 2007 / GFS 2007 / MOM3MOM3


33 GFS 2007 / GFS 2007 / MOM3MOM3


44 OperationalOperational T62T62 MayMay 15-15-Member Member

Ensemble Ensemble MeanMean

55 OperationalOperational T62T62 MarchMarch 15-15-MemberMember

Ensemble Ensemble MeanMean

Summary of RunsSummary of Runs

Complex TerrainComplex TerrainDemonstrates the need for finer horizontal resolution

Gulf of California

Sierra MadreOccidental

Gulf of Mexico

BajaCalifornia

NAME Sub RegionsNAME Sub Regions

Arizona/New Arizona/New Mexico Mexico Region Region (AZNM) ; (AZNM) ; (Higgins et al. (Higgins et al. 1998)1998)

CORE Region CORE Region (Gutzler (Gutzler 2004)2004)

Tier 1.5 Tier 1.5 Region Region (NAMAP2)(NAMAP2)

TIER 1.5

CORE

AZNM

T62 Oper T62 May Ensm Oper T62 March Ensm

CFS JJAS Precipitation [cm], 1981-2006 URD (1x1) T382 T126


CFS JJAS Precipitation Model Minus Obs [cm], 1981-2006 URD (1x1) T382

T126

Seasonal Seasonal Cycle of Cycle of

PrecipitationPrecipitation CORE Region CORE Region

shows good shows good example of example of increased accuracy increased accuracy with resolution and with resolution and model upgrademodel upgrade

TIER 1.5 shows less TIER 1.5 shows less improvement with improvement with new model runsnew model runs

c) TIER 1.5

b) CORE

a) AZNM

URD T382 T126 T62 T62 May

T62 March

Seasonal Seasonal Cycle of Cycle of

PrecipitationPrecipitation CORE Region shows CORE Region shows

good example of good example of increased accuracy increased accuracy with resolution and with resolution and model upgrademodel upgrade

TIER 1.5 shows less TIER 1.5 shows less improvement with improvement with new model runsnew model runs

In all regions, T382 In all regions, T382 run does well run does well capturing monsoon capturing monsoon onset (June-July)onset (June-July)

c) TIER 1.5

b) CORE

a) AZNM


T62 March

AZNM CORE

South East Great Plains Mountain

l

CFS Diurnal Cycle of Precipitation JJAS (mm/day)

T62

T126

T382

NARR

InterannuaInterannual Variability l Variability

Anomalous Anomalous Precipitation Precipitation for JJASfor JJAS

c) TIER 1.5

b) CORE

a) AZNM


T62 March

InterannuaInterannual Variability l Variability

Anomalous Anomalous Precipitation Precipitation for JJASfor JJAS

Decadal Decadal Trend Trend present in present in observations observations and CFSand CFS

c) TIER 1.5

b) CORE

a) AZNM


T62 March

c) TIER 1.5 Monthly

b) CORE Monthly

a) AZNM Monthly

f) TIER 1.5 Seasonal

e) CORE Seasonal

Precipitation Correlations to URDd) AZNM Seasonal

T382 T126 T62 T62 May

T62 March

Atmospheric CirculationAtmospheric Circulation

Prominent upper-air features in the Prominent upper-air features in the NAME region:NAME region: Anticyclonic flow over the regionAnticyclonic flow over the region Low-level jet over the Gulf of MexicoLow-level jet over the Gulf of Mexico Low-level jet over the Gulf of CaliforniaLow-level jet over the Gulf of California

300 mb Streamlines, 850 mb Wind VectorsNARR T382 T126

Atmospheric Circulation (JJA)Atmospheric Circulation (JJA)


300 mb Streamlines, 850 mb Wind VectorsNARR T382 T126


Atmospheric Circulation (JAS)Atmospheric Circulation (JAS)

Gulf of California LLJ, 850 mb WindsGulf of California LLJ, 850 mb WindsStrong Southerly Flow Weak Westerly

FlowNARR T382

ConclusionsConclusions As expected with the complex terrain of the NAMS, As expected with the complex terrain of the NAMS,

increased resolution does improve the precipitation increased resolution does improve the precipitation forecast.forecast. Correlations show Interannual Variability is improving with Correlations show Interannual Variability is improving with

resolutionresolution Improvement also seen at the Seasonal and Diurnal time Improvement also seen at the Seasonal and Diurnal time

scales.scales.

Comparisons of the T62 runs highlight the Comparisons of the T62 runs highlight the improvement provided by the updated atmospheric improvement provided by the updated atmospheric GCM model.GCM model.

Change in lead time for Ensemble Mean hindcasts Change in lead time for Ensemble Mean hindcasts show only a slight improvement in May versus March show only a slight improvement in May versus March

The general circulation is still a problem area. The general circulation is still a problem area. Missing anticyclonic flow over the monsoon areaMissing anticyclonic flow over the monsoon area Lacking the southerly flow associated with the LLJ; therefore, Lacking the southerly flow associated with the LLJ; therefore,

the warm moisture brought into the region by this jet is the warm moisture brought into the region by this jet is missing.missing.

Thank you!Thank you!

Questions?Questions?

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Assessment of the NCEP CFS Hindcast Runs on Predicting the North American Monsoon