RUC development on ceiling/visibility forecasts

Transcription

1 RUC development on ceiling/visibility forecasts Stan Benjamin John M. Brown NOAA / FSL Stan.Benjamin@noaa.gov john.m.brown@noaa.gov Bill Moninger Ed Szoke Barry Schwartz Tracy Lorraine Smith UQAM 14 juin 2005

2 Presentation updated version of NCV discussion at NRL-Monterey, CA 23 March 2004 Topics all in 13km RUC implementation - scheduled for 28 June 2005 Assimilation of METAR cloud/vis obs Modification to RUC/NCAR microphysics Modifications to visibility translation algorithm Monitoring / verification web sites developed at FSL Areas of limitation / inquiry / development Initial conditions Forecast model Post-processing 2

3 3-d RUC weather data updated hourly Turbulence Convection h forecast Terminal / surface Ceiling/visibility Icing Better weather products require improved high-frequency high-resolution models with high-refresh data to feed them 3

4 2005- Implementation of 13km RUC in operations at NCEP Assimilation of new observations - GPS-precipitable water improved moisture forecasts - METAR cloud/vis/current weather improved ceiling and vis fcsts - Mesonet MHz boundary-layer profilers, RASS temperatures - Soil moisture/temp nudging Model changes New versions of - mixed-phase cloud microphysics (NCAR-FSL) - Grell-Devenyi convective parameterization - Revised radiation cloud effects - Corrected treatment of frost formation improved icing and convection forecasts, cloud/sfc temp, vis forecasts Improved post-processing visibility, precip type, 20km/40km look-alike Hourly forecasts to be extended to 9h from 3h duration (at 01z, 02z, 04z, 05z, ) 4

5 AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE GOODLAND KS 1155 AM MDT SUN MAY UPDATE... A SHORTWAVE TROF WAS EVIDENT THIS MORNING AT BOTH 700 AND 500 MB OVER SOUTHEAST WYOMING...SPREADING TOWARD THE TRI STATE AREA IN NORTHWESTERLY FLOW ALOFT. THE ETA/NAM WAS HANDLING THIS FEATURE WELL. THE RUC IS A BIT TOO DRY. What is different qualitatively in precip/surface behavior with the RUC13? - Definitely a wetter model than the previous RUCs - Surface dewpoint, moisture aloft -CAPE - Precipitation - But drier over warm oceans 5

6 20km RUC 13km RUC Soil moisture 22z - 21 Feb 2005 Dark blue = water More detailed coastline with 13km resolution6

7 13-km 3DVAR running at FSL since summer 2004, NCEP testing in progress 4 aspects of RUC13 3DVAR analysis: 1. New observations assimilated 2. Cloud analysis (GOES, METAR ceiling/vis/curr-wx) 3. Revised control variable for moisture (pseudo-rh) 4. Soil moisture/temp nudging

8 Observations used in RUC Data Type ~Number Freq Rawinsonde 80 /12h NOAA profilers 30 / 1h VAD winds / 1h Aircraft (V,temp) / 1h Surface/METAR / 1h Buoy/ship / 1h GOES precip water / 1h GOES cloud winds / 1h GOES cloud-top pres 10 km res / 1h SSM/I precip water / 6h GPS precip water ~300 / 1h Mesonet (no cloud) ~5000 / 1h PBL prof/rass ~25 / 1h METAR-cloud-vis-wx ~1500 / 1h Cloud analysis variables NCEP RUC20 operational RUC13 (at NCEP June 2005)

9 RUC Cloud Analysis Use multiple data types to modify cloud, hydrometeor, and moisture fields: -- GOES cloud-top pressure/temp (implemented in 2002 w/ RUC20) -- Surface METAR (clouds, weather, visibility) (2005 w/ RUC13) Construct 3-d logical arrays (YES/NO/UNKNOWN) for clouds and precipitation from all info Clear/build moisture, cloud, precipitation fields Safeguards for known problems (marine stratus, convective clouds, snow, nocturnal inversion)

10 Assimilation of METAR cloud/wx/vis Better analysis, prediction of ceiling and visibility -Nearest station up to 100 km distance - Assigned in ASL, includes terrain intersection for low clouds - Maps info to 3-d cloud, precip. Y/N/Unknown arrays - Change cloud water, cloud ice, water vapor fields as follows: Build for BKN / OVC / Vertical Visibility - 40 mb thick layer (2+ model levels) mb thick for precip. + GOES clouds - Can build multiple broken layers Clear - Up to cloud base (if needed) - to 12,000 feet for CLR report

11 Added assimilation of visibility obs - Feb 2004 Use inverse of Kunkel / Stoelinga-Warner visibility translation algorithm Use FG or BR reports from METARS Only when Precip is not also reported T-Td < 1K Build at lowest 2 levels in RUC (5 m, 20 m) 11

12 Sample modification of cloud water from METAR cloud/weather/ visibility observations Background (previous 1h fcst) Cloud water mixing ratio 1700 UTC 27 Jan Pres (mb) analysis with METAR cloud/ visibility obs Cloud water mixing ratio Relative Humidity

13 Sample ceiling analysis impact Analysis WITH cld/wx/ vis obs Ceiling from RUC hydrometeors 1800 UTC 17 Nov 2003 Observations Aviation Flight Rules LIFR IFR MVFR VFR CLR cloud ceiling height (meters) Analysis NO cld/wx/ 13 vis obs

14 RUC13 analysis includes nudging of soil moisture and temperature Oper RUC20 Dependent on: 2m T/Td 1h forecast errors Only in daytime (zen angle > 0.3) with no clouds or precipitation (defined after METAR/GOES cloud assimilation) Para RUC13 Developed as part of NOAA New England High-Resolution Temperature (NEHRT) Program - FSL, ETL, NSSL, NCEP/EMC 14

15 MODEL PHYSICS CHANGES FOR RUC13 -Land-surface model: When ground temp < 0 C, vapor deposition on ground now based on ice saturation, not water * Diminishes unrealistic widespread nighttime fog formation, especially over snow cover Evident in real-time comparisons between RUC13 and oper RUC20 for visibility forecasts, especially at night. 15

16 Test of Ice Saturation for Surface Latent-heat Flux 13 Apr h fcst valid 06z Cloud-water mixing ratio at lowest model level Oper RUC20 Revised RUC20 Reduction in fog, especially over snow. Much improved visibility forecasts, avoids high bias 16

17 RUC13 Model Physics Changes (cont) -Convection (Grell-Devenyi scheme) * Empirically estimated ensemble weights to improve quantitative precipitation forecasts RUC20 - dcape/dt - Kain-Fritsch CAPE relaxation - low-level vertical velocity RUC13 - moisture convergence - adds Arak-Schu scheme for cloud work fn - no KF over ocean, reweighted all closures Addition of convection-inhibition ensemble members CAPE dp 25, 75, 125 mb fn ( TKE) Does not produce significant outflows (slightly more in RUC13) Still no shallow convection in RUC13 Grell-Dev scheme Still much less sounding modification than NAM/BMJ Eliminated extreme surface drying showing up in certain situations 17

18 RUC13 Model Physics Changes (cont) - Microphysics [NCAR and FSL] Overall goal: To incorporate best understanding of warm-rain and mixed-phase processes important for cold-season aviation operations (inflight icing, pre-takeoff deicing requirements, low ceiling, visibility) into operational NWP models. Major changes for RUC13 Dropsize distribution now transitions between drizzle and rain Replace Kessler with Barry-Reinhardt autoconversion (collision-coalescence cloud droplets to rain) Correct ice-particle accretion (ice snow more readily) Ice particle fall speed no longer set to 1 m/s 18

19 RUC13 Model Physics Changes (cont) * - Snow - Diagnosis of snow-particle size distribution - Operational RUC20: - Depends on snow mixing ratio -RUC13: -Depends on temperature -Graupel - Growth/depletion via deposition/sublimation: Change size distribution from gamma to inverse exponential - Results in less graupel 19

20 EAST COAST BOMB JAN 2005 RUC13 9h Forecast for 0900 UTC 23 Jan Sfc wind, temp, 3-h pcpn X-sec Snow Precipitation type Rain 20

21 HYDROMETEOR CROSS SECTIONS RUC 9h Forecasts for 0900 UTC 23 Jan RUC13 CLOUD-WATER MIXING RATIO (qc) RUC20 - OPER Atlantic MA ME 21

22 Hydrometeor Mixing Ratios (Cont) RUC 9h Forecasts for 0900 UTC 23 Jan RAIN WATER (qr) RUC13 Oper - RUC20 Atlantic MA ME More rain in RUC13 different rain processes 22

23 Hydrometeor Mixing Ratios (Cont) RUC 9h Forecasts for 0900 UTC 23 Jan CLOUD ICE (qi) RUC13 Oper RUC20 Atlantic MA ME Less ice in RUC13 modified ice-particle accretion 23

24 Hydrometeor Mixing Ratios (Cont) RUC 9h Forecasts for 0900 UTC 23 Jan SNOW (qs) RUC13 Oper RUC20 Atlantic MA ME More snow in RUC13 modified ice-particle accretion 24

25 Hydrometeor Mixing Ratios (Cont) RUC 9h Forecasts for 0900 UTC 23 Jan GRAUPEL (qg) RUC13 Oper RUC20 Atlantic MA ME Less graupel in RUC13 More supercooled liquid water (important for icing/aviation) 25

26 Obs radar z -31 Mar 05 RUC13 9h fcst - valid 03z- 31Mar05 RUC20 9h fcst - valid 03z - 31 Mar 05 26

27 Obs radar z - 12 May 05 RUC20 12h fcst - valid 03z- 12May05 RUC13 12h fcst - valid 03z- 12May05 27

28 Further revisions to visibility translation algorithm [RUC algorithm = Combination of hydrometeor basis (Stoelinga-Warner) and RH basis (FSL algorithm)] - Added Rasmussen day/night distinction (higher vis at night with same snow mixing ratio) - Revised hydrometeor basis Previous New Max Qc (levs 1-4) Mean Qc (levs 1-2) (decreased bias from 4-5x down to 2x at night) - Added wind shear term in lowest 25 mb for RH term 28 (Kuchera M.S. thesis)

29 RH term in visibility TA Need - Without RH term and no Qc, vis = 90 km - Current setting - increased extinction coefficient from 75-98% RH - min vis from high RH = 5.4 km at 98% RH - As currently set, not a factor for aviation-significant lower visibility (greater than MVFR threshold) Therefore, all aviation-significant lower visibility must be forecast via non-zero hydrometeor mixing ratios. - Added reduction to strength of RH-based extinction as function of low-level wind shear (Kuchera - AFWA). If V (k=1,5 - ~25 mb) > 4 m/s, reduce RH-based extinction. 29

30 Continuing concern - lowest Qc near ground generally 0.1 g/kg - very rarely as low as 0.01 g/kg BUT - extinction coefficient from cloud water (Kunkel Stoelinga-Warner) gives Cloud water mixing ratio Visibility 0.38 g/kg 70 m m m km How to get mile visibility commonly observed, 30 especially in cold-season, inland situations?

31 Ceiling analysis: comparison of Operational RUC (top) with the NCEP RUC13 (bottom) Scale (AGL): x 1000 ft Analyses at 1800 UTC on 9 May 31

32 Observations: cigs <= 5000 ft only Observations: cigs <= 3000 ft only Observations: cigs <= 500 ft only Point observations at 1800 UTC 9 May, for different ceiling heights, to compare to previous figure. 4 areas of lower cigs are apparent. -New England: Better coverage of lower cigs by RUC13 looks good. -Northern Plains/Midwest: more coverage of lower cigs in RUC13, tho similar coverage for very lowest categories. Again, obs for aob 5000 ft cigs support RUC13. -West Coast: both have lower cigs in LA area. More coverage on RUC13 in intermountain west, not sure if this is overdone or not. -Northeast TX: RUC13 looks better here. 32

33 Ceiling 1h forecasts: comparison of Operational RUC (top) with the NCEP RUC13 (bottom) Scale (AGL): x 1000 ft Forecasts at 1900 UTC on 9 May 33

34 Ceiling 3h forecasts: comparison of Operational RUC (top) with the NCEP RUC13 (bottom) Scale (AGL): x 1000 ft Forecasts at 2100 UTC on 9 May 34

35 Focus on the Midwest and Northern Plains. Quite a few obs have cigs < 3000 ft, but only a few lower vis reports. It does appear that low clouds lurk JUST east of the eastern WI shoreline, like what was found in the RUC Operational run. 35

36 Focus on eastern Texas. Cigs < 3000 ft are relatively widespread. 36

37 Summary Good success in mapping ceiling observations into RUC hydrometeor fields Some success in mapping visibility observations into RUC hydrometeor fields. 37

38 Current issues Analyses Proper depth of cloud Forecasts Sometimes excessive Qc at level near ground at night Dew/frost deposition fix made substantial improvement Proper treatment of mixing in RUC version of Burk- Thompson PBL? (1-d comparison in progress with Mellor- Yamada-Janjic PBL) Retention for ceiling information improved but not great for 3-6h Cleared areas sometimes quickly go back to cloudy Layers too thin? Ceilings too low in IFR conditions No forcing of divergent wind / vertical velocity. Difficult to do in stratiform cloud situations or often irrelevant. 38

39 2005- Implementation of 13km RUC in operations at NCEP Assimilation of new observations - GPS-precipitable water improved moisture forecasts - METAR cloud/vis/current weather improved ceiling and vis fcsts - Mesonet, RASS temperatures Soil moisture/temp nudging Improved moisture analysis pseudo-rh instead of log q Model changes New versions of - mixed-phase cloud microphysics (NCAR-FSL) - Grell-Devenyi convective parameterization - Revised radiation cloud effects - Corrected treatment of frost formation improved icing and convection forecasts, cloud/sfc temp, vis forecasts Improved post-processing visibility, precip type, 20km/40km look-alike Hourly forecasts to be extended to 9h from 3h duration (at 01z, 02z, 04z, 05z, ) 39 (12h forecasts to be continued at 00z, 03, 06 init times)

40 Planned Rapid Refresh domain Current RUC CONUS domain Rapid Refresh -replace RUC km resolution - use WRF model Goals: Hourly NWP update in -Alaska - Wider E. Pacific -- Canada - Caribbean Sea 40