1 / 13

THE NWP “BREAKTHROUGH” FOR CLIMATE ANALYSIS CENTER MONTHLY PREDICTIONS IN 1981

THE NWP “BREAKTHROUGH” FOR CLIMATE ANALYSIS CENTER MONTHLY PREDICTIONS IN 1981. Bob Livezey Climate Services Division/OCWWS/NWS Symposium on the 50 th Anniversary of Operational NWP College Park, MD, June 17, 2004. OUTLINE. Introduction 1981 Implementation Somerville’s (1980) Experiment

chloe
Télécharger la présentation

THE NWP “BREAKTHROUGH” FOR CLIMATE ANALYSIS CENTER MONTHLY PREDICTIONS IN 1981

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. THE NWP “BREAKTHROUGH” FOR CLIMATE ANALYSIS CENTER MONTHLY PREDICTIONS IN 1981 Bob Livezey Climate Services Division/OCWWS/NWS Symposium on the 50th Anniversary of Operational NWP College Park, MD, June 17, 2004

  2. OUTLINE • Introduction • 1981 Implementation • Somerville’s (1980) Experiment • Verification Evidence • Description of Study for Monthly Mean Temperature Progs • Results • Monthly Mean 700-hPa Forecast Results • Discussion • Monthly Forecast Process • Impact on the Process • Possible Corroborative Study

  3. INTRODUCTION • Aug. 12, 1980 NMC operational NWP suite change • Replacement of 7LPE (Shuman and Hovermale, 1968, JAM) with the Spectral Model (Sela, 1980, MWR). For 00 GMT • 0-48, global, 30 waves, 12 layers • 48-144, hemispheric, 24 waves, 12 layers • Mar. 18, 1981 NMC operational NWP suite change • Extension of the 00 GMT global Spectral Model • 48-84, 24 waves, 12 layers • 84-144, 24 waves, 6 layers • NMC Forecast Div. (now HPC) found that the new system increased “the number of cases with usefull skill” (Cooley’s Feb. 23, 1981 memo)

  4. INTRODUCTION • Somerville’s results (1980, JAS) anticipated the improvements. • 500-hPa errors (30m contours) for 11 January 1973 case.

  5. VERIFICATION EVIDENCEForecast and Control Forecast Definitions and Timing

  6. VERIFICATION EVIDENCE • Verification of monthly mean U.S. surface temperature forecasts • Issued twice-monthly for three categories at “zero” lead (3-5 days) from 1973 through 1994 • Verified with a modified Heidke skill score for 102 mega-divisions • Verification repeated for “operational persistence” • Differences computed to normalize for “predictability” • Smoothed with a 25-forecast running mean

  7. VERIFICATION EVIDENCE

  8. VERIFICATION EVIDENCE • Verification of monthly mean extratropical N.H. 700-hPa heights • Issued twice-monthly at “zero” lead (3-5 days) from 1973 through 1994 • Verified with the spatial anomaly correlation over the Pacific/North American region (Livezey et al., 1995) • Not normalized for “predictability” with “operational persistence” • Smoothed with a 25-forecast running mean

  9. VERIFICATION EVIDENCE NH post-GNWP NH pre-GNWP

  10. MONTHLY FORECAST STRATEGY(Kalnay and Livezey, 1985) • Step 1 of 3-step process, “prognosis of the 700 mb height anomalies” • For step 1, subjective blend of “three available indicators” • “kinematic/synoptic extrapolation of recent anomaly fields”; the five-day mean centered at D-3 • “statistical forecasts derived from lagged correlation fields”; effectively damped operational persistence • “a five-day averaged NMC forecast centered at the 1st day of the month”; D+3

  11. MONTHLY FORECAST STRATEGY D-3 D+3

  12. MONTHLY FORECAST STRATEGY(Kalnay and Livezey, 1985) • “Of these, experience indicates that the dynamical forecast [D+3] is the most skillful. Although the forecast extends only two or three days into the verification period, the five-day averaging process is an effective filter that seems to accurately reveal the low-frequency trend.” • A corroborating test: Comparison of the scores for 6-10 day forecasts (D+8)with persistence of D-3.

  13. MONTHLY FORECAST STRATEGY D-3 D+3 D+8

More Related