Global aviation turbulence forecasting using the Graphical Turbulence Guidance (GTG) for the WAFS Block Upgrades

Transcription

1 Global aviation turbulence forecasting using the Graphical Turbulence Guidance (GTG) for the WAFS Block Upgrades R. Sharman 1, J.-H. Kim 2, and C. Bartholomew 3 National Center for Atmospheric Research, Boulder, CO, USA 1 NOAA/Aviation Weather Center, Kansas City, MO, USA 2 The Met Office, Exeter, UK 3

2 Aviation Turbulence: Background Many sources From Lester 1994 Aircraft scale turbulence from all sources is too small to directly predict (~100m-1 km) Must infer its presence from larger scales

3 Turbulence forecasting for the World Area Forecast System (WAFS) Provides global forecasts of significant weather for strategic flight planning Based on forecasts from 2 WAFCs (World Area Forecast Centers) in London UK and Washington DC USA Established and administered by ICAO and WMO ICAO requested upgrades provided at regular intervals to accommodate new technologies in aviation weather forecasting Implemented in Aviation System Block Upgrade (ABSU) Current: 6-36 hr forecasts updated every 6-hr on 1.25 x1.25 grid ABSU 0 (~2019): Same forecasts but on 0.5 x 0.5 grid ABSU 1 (~2024): Probabilistic forecasts on 0.25 x 0.25 grid ABSU 2 (~2030): Integrated flight planning

4 Introduction to WAFS Significant Weather (SIGWX) charts (Prog charts) - World Area Forecast Center (WAFC) Washington (US; AWC) and London (UK; MO) Man-made Progchart Jet, CAT, and Cb Issues 4 times a day at 00, 06, 12, 18 UTC 24-hr forecast snapshot Layer and Freq. info.

5 Introduction to WAFS WAFS grids for Jet, CAT, and Cb top - WAFS Blended Max between two WAFCs. Automated grid forecasts hr fcsts with 3-hr interval Issues at 00, 06, 12, 18 UTC Potentials for Clear-Air Turbulence using Ellrod index

6 WAFS Upgrade for turbulence forecasting WAFS upgrade plan until 2019 (ICAO ASBU 0): Use the Graphical Turbulence Guidance (GTG) Forecasts energy dissipation rate (ε)^1/3 (EDR)» ICAO reporting standard for turbulence measurements» metric for atmospheric turbulence intensity (aircraft independent)» Directly related to aircraft loads» convenient 0-1 scale (m 2/3 s -1 )» For mid-sized aircraft: light ~0.15, moderate ~0.22, severe ~0.35 Provides explicit forecasts of clear-air turbulence (CAT) and mountain wave turbulence (MWT) both EDR Based on NWP models from London and Washington WAFCs» Unified model (UM) ~10 km» Global forecast system (GFS) ~ 13 km Final product is a blend of the two

7 Graphical Turbulence Guidance (GTG)* Use NWP model (global or regional) to compute a suite of turbulence diagnostics typically related to large scale spatial variations Multiple causes require multiple forecasting strategies GTG = W 1 D 1 * + W 2 D 2 * + W 3 D 3 * +. Ds depend on source ( CAT, MWT, CIT) and altitude region (high, middle, low) D*s are calibrated Ds to EDR assuming a log-normal distribution of EDR in upper troposphere and lower stratosphere (UTLS) Ws from turbulence measurements GTG (or G-GTG) is weighted ensemble mean Verified against 1000s of PIREPs and in situ EDR data *Ref: Sharman et al. Wea Fcsting 2006,Sharman and Pearson JAMC 2017

8 Some Traditional Turbulence Diagnostics Richardson Number Frontogenesis function (good at upper levels) 1 θ θ u θ v θ w θ θ u θ v θ w θ θ u θ v θ w F3D= θ x x x y x z x y x y y y z y z x z y z z z Divergence tendency t 2 Φ+ + 2 ( units = ) 2 Juv (, ) fζ βu s Deformation x shear ( Ellrod index ) v 2 2 ( ) 1/2 2 I = DEF + r, DEF = D + D (units = s ) SH ST z t D Ri = N v z SH 2 2 < Ri c (nondimensional) v u u v = + D = " Ellrod3": r 0 ST x y x y (Ellrod and Knox Wea. Forecasting 2010)

9 G-GTG schematic MO UM NOAA GFS Compute CAT, MWT diagnostics (typically 10-15) Compute CAT, MWT diagnostics (typically 10-15) Remap diagnostics to EDR Remap diagnostics to EDR Combine diagnostics (ensemble mean or probabilistic) Combine diagnostics (ensemble mean or probabilistic) } Blended GTG

10 Example remapping case: GFS

11 GTG CAT, MWT, MAX

12 GTG from NOAA GFS, UK UM CAT MWT MAX GFS UM diff

13 GFS/UM Blend

14 Verification: Case study of MWT over Greenland

15 Statistical verification against automated EDR reports from DAL aircraft

16 Use GTG diagnostics as ensemble to produce probabilities of exceeding a certain EDR

17 Ensemble mean vs probability of EDR>0.22 Ensemble mean Probability

18 Can use G-GTG Ds computed with different NWP ensembles to produce probabilities: GEFS Ensemble Prob. > 0.2 EDR 12-h fcst 18-h fcst 5 CAT/5 MWT diagnostics x 21 GEFS ensemble members = Ensemble Probability > 0.2 EDR

19 Need for more observations In the GTG approach performance depends on large dataset of observations to form reliable statistical performance metrics Observations of EDR are preferred since they correspond to what is being predicted and EDR is the ICAO standard for reporting In particular need more observations in the S. Hemisphere In situ EDR measurements are being expanded Boeing offers EDR package on new aircraft with AIMS-2 avionics EDR software package is free to interested air lines from NCAR DAL 767s and 777s currently implemented International carriers may soon implement this (Xiamen, Air France, Lufthansa, Qantas ) Private vendors (accessibility, standard?) Courtesy Tim Rahmes, Boeing Courtesy Tim Rahmes, Boeing 19

20 Summary and future work G-GTG has been developed for use with several regional and global NWP models: (NOAA GFS, UK UM, ECMWF, NOAA RAP, NOAA HRRR) G-GTG will become turbulence forecast product provided by the World Area Forecast System (WAFS) Washington: Uses NOAA GFS at EMC London: Uses UKMO UM at Exeter Grids merged at EMC Performing case studies Gathering more global observations Developing CIT diagnostics Testing with ensembles using GEFS and MOGREPS-G to predict probabilities of exceeding certain EDR level Ref: Kim et al., Aviation Turbulence Forecast Technique for the World Area Forecast System (WAFS) Submitted to Bull. Amer. Meteror. Soc. This research is in response to requirements and funding by the Federal Aviation Administration (FAA). The views expressed are those of the authors and do not necessarily represent the official policy or position of the FAA. 20

21 Thank you