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PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS

PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS, MD 300 PM EDT FRI AUGUST 21 2009

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PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS

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  1. PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS, MD 300 PM EDT FRI AUGUST 21 2009 THE OPERATIONAL 00Z AND 06Z GFS MODEL SOLUTIONS BEGIN TO BREAK DOWN THE RIDGE OVER THE PACIFIC NORTHWEST WHILE THE HIGH RESOLUTION 00Z ECMWF MAINTAINS A STRONG RIDGE THERE. TELECONNECTIONS FROM THE UPSTREAM TROUGH OVER THE GULF OF ALASKA AND WESTERN ALEUTIAN RIDGE BOTH SUPPORT RIDGING OVER WESTERN NORTH AMERICA WHICH AGREES MORE WITH THE 00Z ECMWF SOLUTION. THIS, IN COMBINATION WITH VERY HIGH 500-HPA ANOMALY CORRELATIONS EXHIBITED DURING THE PAST 60 DAYS, RESULTED IN THE ECMWF-BASED SOLUTIONS BEING FAVORED IN TODAYS OFFICIAL 500-HPA HEIGHT BLEND CHART. TODAY'S OFFICIAL 500-HPA BLEND CONSISTS OF 10% OF TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 8...20% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 8...20% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8...40% OF TODAY'S 0Z ECMWF ENSEMBLE MEAN CENTERED ON DAY 8...AND 10% OF TODAY'S 0Z CMC ENSEMBLE MEAN CENTERED ON DAY 8.

  2. Generic Levels of EM Uncertainty – Lessons from geophysical modeling and current studies of climate impacts Nicholas Bond1 Kerim Aydin2, Anne Hollowed2, James Overland3 and Muyin Wang1 1 University of Washington/JISAO 2 NOAA/AFSC 3NOAA/PMEL

  3. Techniques for Incorporating Model Ensembles • Simple means • Means w/ individual bias corrections • Means w/ collective bias corrections • Regularization via EOFs • Bayesian techniques

  4. Forecast error (24-h Temp.) Rixen et al. (J. Mar. Sys., 2009)

  5. Time series of uncertainty

  6. Models Contributed to IPCC AR4

  7. Walsh et al. (2007)

  8. Bayesian Model Averaging (BMA) • Considers an ensemble of plausible models • Key Idea - The models vary in their skill, and calibration of this skill produces better forecasts • Forecast PDF estimated through weighting the PDFs of the individual models, with weights determined by posterior model probabilities • BMA possesses a range of properties optimal from a theoretical point of view; works well in short-term weather prediction

  9. p(y) is the forecast PDF; fk is the kth forecast model; wk is the posterior probability of forecast k being the best; gk(y | fk) is the PDF conditional on fk being the best forecast. Weighted ensemble mean of parameter y

  10. Estimating Weights by Maximum Likelihood • Yields parameter values (weights) that make observed data most likely • Likelihood function maximized over time and space through determination of model weights for a particular parameter • Method uses expectation-maximization (EM) algorithm, which resembles a “hotter-colder” game • Final weights related to how often a particular model constitutes the best model • Training data set consists of last 40 days of short-term weather forecasts

  11. Ensemble Model Projections for North Pacific Marine Ecosystems • Initial Selection - Pick models that replicate the observed character of the PDO in their 20th century hindcasts (12 of 22 pass test) • Regional Perspective - Examine specific parameter(s) in region of interest; consider means, variances, seasonality, etc. • Model projections - Use quasi-Bayesian method based on “distance” between hindcasts and observations; form weighted ensemble means • Uncertainty/Confidence - Estimate based on a combination of inter-model and intra-model variances in projections

  12. Present Application • Limited statistics for evaluation (there has been a single outcome for the past climate) • Compare 20th century hindcast simulations by the climate models to observations on a regional basis • Observations based on NCEP Reanalysis; good match of spatial scales • Consider mean, variance, and other measures (trend, seasonality, etc.) if appropriate • Estimate weights for projections following a scheme developed for objective analysis of weather observations, Wk = exp(-Dk/Dm) • Apply intra-model variance from models with 5+ runs to models with fewer runs

  13. Parameters Evaluated • Bering Sea - Flow through Unimak Pass (Nutrient supply); Spring Winds (Larval flatfish transports); Summer SST & Wind Mixing (Sustained productivity) • Gulf of Alaska - Along-coast winds (Larval fish distribution and abundance); Precipitation (Upper ocean baroclinity and eddy generation) • NE Pacific - Coastal upwelling (Productivity); Zonal winds (LTL communities); Pycnocline depth; Upper-ocean transports; Temperature cross-sections

  14. MIROC_hi MRI GFDL21 GFDL20 MPI CCCMA_t63 MIROC_med UKHadCM3 ECHO-G CCCMA_t47 UKHadGEM1

  15. Downwelling Weighted Ensemble Mean Upwelling

  16. Zooplankton on the Bering Sea Shelf - Coyle et al. (2008) Compared water properties and zooplankton abundance and community structure between a cold and warm year 1999 2004 ------------------------------------------------------------------ Upper Temp 7.0 12.6 (deg. C) Lower Temp 2.0 3.2 Oithona 348 1633 (#/m3) Pseudocalanus 404 1211 Calanus 44 ~0 Thysanoessa 0.33 0.05

  17. CCCMA_t63 MIROC_med MRI UKHadGEM1 UKHadCM3 MIROC_hi CCSM3 ECHO_G CCCMA_t47 GFDL20 GFDL21

  18. SLP Anomalies Strong Wind Mixing Years SLP Anomalies Weak Wind Mixing Years

  19. Overland and Wang (2007) Sea Ice Area Anomaly for Bering Sea

  20. Flatfish in the SE Bering Larval Transport & Recruitment

  21. MRI MIROC_med GFDL21 UKHadCM3 MIROC_hi GFDL20 CCCMA_t47 CCCMA_t63 ECHO-G

  22. Hollowed et al. (2009)

  23. Weighted Mean

  24. BSIERPIntegrated modeling 2 Economic/ecological model FEAST Higher trophic level model Observational Data NPZ-B-D Lower trophic level ROMS Physical Oceanography Nested models BEST Climate scenarios

  25. NITRATE AMMONIUM ICE ICE ALGAE NITRATE Excretion + Respiration AMMONIUM BSIERP NPZ model SMALL PHYTOPLANKTON LARGE PHYTOPLANKTON IRON SMALL MICROZOOPLANKTON LARGE MICROZOOPLANKTON Mortality Predation Egestion Molting PSEUDOCALANUS NEOCALANUS CALANUS EUPHAUSIIDS DETRITUS OCEAN JELLYFISH BENTHOS BENTHIC INFAUNA BENTHIC DETRITUS

  26. *Z *Z *Transport *Z * *Both Transport* Temperature X-Section

  27. Seward Line * PAPA Alaska Peninsula Vancouver Is. Newport

  28. *

  29. Feb SODA ECHAM5 PCM1 Aug Average Temperatures 1990-2000 MirocM MirocH MRI

  30. Feb SODA CCCMAT47_1 CCCMAT47_2 Aug Average Temperatures 1990-2000 CCCMAT47_3 CCCMAT47_4 CCCMAT47_5

  31. Absolute Model Errors

  32. Final Remarks • Global climate model simulations are being used for a host of regional applications • There does not seem to be any single “best” method, but the protocol should include evaluation of model hindcast simulations of key parameters in the region of interest. • Multi-model ensembles represent a key tool for seasonal climate forecasts, and are being used increasingly for short-term weather prediction. • On long time horizons, model structural uncertainty dominates initial condition sensitivity.

  33. From present to mid-21st century, climate change liable to be dominated by thermodynamic effects as opposed to dynamic effects (e.g., winds). The latter will be prone to interannual to decadal natural variability. • The output from global climate models (perhaps subject to statistical downscaling) can complement that from vertically-integrated numerical models with full dynamics.

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