- Slides: 34
Initialization, Prediction and Diagnosis of the Rapid Intensification of Tropical Cyclones using the Australian Community Climate and Earth System Simulator, ACCESS Michael Reeder, Noel Davidson, Jeff Kepert, Craig Bishop, Peter Steinle and Kevin Tory with Yi Xiao, Harry Weber, Yimin Ma, Hongyan Zhu, Xingbao Wang, Mai Nguyen, Lawrie Rikus, Richard Dare, Ying Jun Chen And Roger Smith and Michael Montgomery (Honorary Members) Special thanks to WEP and ESM Programs, and UKMO Weather and Environmental Prediction and Environmental System Modelling Groups CAWCR, Centre for Australian Weather and Climate Research A Partnership between CSIRO and the Bureau of Meteorology Acknowledgments: Kamal Puri, Gary Dietachmayer The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
Tropical Cyclone Characteristics in the Australian Region TC behaviour and forecast issues: • Track, • Genesis, • Intensification/RI/Decay, • Structure Change (size, etc), • ET • Landfall!!! Points of Origin Points with Min. CP (Dare and Davidson, 2004, MWR) Points of Final Decay
Scope of Talk • Operational ACCESS-TC • ACCESS-TC System Configuration VS, 4 DVAR Initialization, Verification (track, intensity, structure) • Related, Diagnostic Projects (Shudder, Shudder Points of collaboration) (Testing new params, new data sources, even mechanisms/processes) • Future Plans The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
ACCESS-TC Verification: NMOC Real-time Forecasts 2011 WNP Region, 10 TCs: Number of Forecasts Mean Track Error, Mean ABS Central Pressure Error, (B-corrected), A-TC and Persistence
Not All Good News …
Track Forecasts from available operational systems for Heidi and Iggy (A-TC, EC, UK, JMA, GFS, NGP, GFDN, …… Deficiencies in (a) LSE, and/or (b) Vortex Structure ? ? ?
ACCESS-TC vs ECMWF for TC IGGY from base times 20120126/12 Z and 20120127/00 Z Left Panels: Observed and forecast tracks and central pressures from ACCESS-TC Centre Panels: 72 -hour forecasts of MSLP from ACCESS-TC; Right Panels: 72 -hour forecasts of MSLP from ECMWF
ACCESS-TC for Operations and Research 1. Resolution: 0. 110 X 50 L, re-locatable grid, with TC near centre of domain, option for higher-resolution forecasts. 2. Vortex Specification: (a) Structure based on observed location, central pressure and size (tuned and validated using ~6000 dropsonde observations from the Atlantic) (b) Only synthetic MSLP obs used in the 4 DVAR to (a) relocate the storm to observed location, (b) define the inner-core circulation, and (c) impose steering flow asymmetries consistent with the past motion. 3. Initialization using 4 DVAR Assimilation: 5 cycles of 4 DVAR over 24 hours. Uses all standard obs data, plus synthetic MSLP obs (no upper air synthetic obs). 4 DVAR then: (a) Defines the horizontal structure of the inner-core at the observed location, (CP, VMAX, RMW, R 34) (b) Builds the vertical structure from MSLP obs, (c) Constructs the secondary circulation, (d) Creates a balanced TC circulation at the observed location, with correct (? ) structure and intensity. (e) Creates a structure which is responsive to environmental wind shear without imposing constraints on the vertical-stacking or tilt of the circulation. (important for vortex dynamics and cloud asymmetries) 4. Forecast Model: UKMO Unified Model from ACCESS. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
Verification of large scale forecasts MSLP RMSE: Global forecasts over the Australian Region Þ Improved Prediction of the LSE of storms, The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
OBS Network Without Vortex Specification : Initial Position/Intensity Errors for TC Anthony were ~ 230 km and 5 h. Pa With Vortex Specification: Initial Position/Intensity Errors reduced to 40 km and 0 h. Pa VS: blue MSLP obs in upper left panel: dense enough to define Vmax at RMW, extensive enough to merge with LSE. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
For Anthony at Landfall: Obsvd and fcast track and intensity without and with VS 500 h. Pa Initial Condition without and with VS (synthetic MSLP obs only) Note construction of 3 -D structure 4 DVAR defines depth and tilt, important for evolution of vortex The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
Vortex Specification (Weber, 2011) Figure 2: Tangential wind v(r) in m s-1 as a function of radius in km of Hurricane Fran on September 29, 1996 (top) and Hurricane Floyd on September 19, 1999 (bottom). Thick lines represent the average v(r) of all flight passes and the AVSM output v(r) (smoother curve). The thin lines define an envelope given by the minimum and maximum v(r) of all flight passes at each radial grid point. The input parameters of AVSM are operational estimates of roci and vm – c in (e), (f). Validation of Vortex Structure: Use EXBT data sets for the NA and NP to validate TC structures obtained from the Vortex Specification (RMW, R 34). (CLOK: Charlie Lok)
Validation of Vortex Structure. I: Cloud Fields (Rikus, 20 XX) Actual and Synthetic Cloud Imagery Yasi at t = 0 and t = 46 hours from base time, 12 Z, 20110131 • 4 DVAR initializes the ascent and moisture fields. • Model maintains cloud fields during the forecast. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
Validation of Vortex Structure. II: Cloud Bands and Convective Asymmetries 85 GHz Imagery (left panels) and ACCESS-TC 500 h. Pa vertical motion field at t = 6 (initialized with 4 DVAR) and t = 55 hours for Yasi from base time 00 Z, 20110131 • Note regions of observed active inner rainbands and eyewall convection, and corresponding forecast regions of strong and weak ascent. • Based on use of synthetic MSLP obs and 4 DVAR, structures are consistent from even the early hours of the forecast. • Rainfall in TCs (Ying Jun Chen) The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
Preliminary Validation of Vortex Structure. III: Intensity and Windfields (Verification of R 34) (Y. Ma) Critical for Storm Surge and Rainfall For Yasi from base time 00 Z, 20110131: Time series of forecast (a) Central Pressure, (b) Maximum Wind, (c) Radius of Maximum Wind, (d) Radius of 64, 50 and 34 knot winds. Symbols indicate estimated values, where available Encouraging preliminary verification ***** What defines size and the RMW? <<<<<
Illustrative Example: TC YASI Forecast and Observed Tracks and Intensities from ACCESS-TC at 4 km resolution The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
Tropical Cyclone Projects Verification and Post-analysis of Operational ACCESS-TC Enhancements to the Boundary Layer Parameterization for ACCESS-TC. Secondary Eyewall Formation and Eyewall Replacement Cycles in Tropical Cyclone Simulations Genesis Applications: OWZ Diagnostics and ACCESS-TC Downstream Development during the Extratropical Transition of Tropical Cyclones: Observational Evidence and Influence on Storm Structure. Sensitivity of Prediction of Intensity and Vortex Structure to Initial Vortex Structure Rainfall in TCs Inner-core Structure Change during Rapid Intensification Amplifying Planetary Rossby Waves and Extreme Rain Events in Current and Future Climates
ACCESS-TC – Improving air-sea exchange parameterisation, plus inclusion of sea spray processes Yimin Ma and Colleagues Statistics for track and intensity biases (ME, ME ABS: Mean Error, Mean Absolute Error) - Realistic physical representation of air-sea exchange in high wind conditions in TCs. - Validate with CBLAST Data • Small changes in track forecast • Large improvements in intensity forecast • Small changes in outer structure Structure prediction for YASI (2011). Base time 20110131/00 Z The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
BL Parameterisation in TCs: Jeff Kepert • Previous work has shown a substantial sensitivity to choice of parameterisation (Braun and Tao 2000, Smith and Thomsen 2010). • Why are they different? • Which scheme is the most suitable? • Method: • Use diagnostic 3 -d model of TC BL (Kepert and Wang 2001) to make interpretation easier – all simulations are the same above the BL. • Implement four simplified parameterisations in the model, representative of those used in TC modelling. • Compare and work out why. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
Comparing the schemes Scheme Near-surface log layer? Inflow? Supergradient flow? Recommended for use? MM 5 Bulk and No Blackadar Strongest NO! (exceeds obs) Louis Yes Moderate Yes Higher-order Yes (TKE scheme) Moderate Yes (but expensive) K-profile (MRF, YSU) Weaker, depending on BL depth Yes, provided BL depth is ok (check!!). Yes The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
Secondary Eyewall Formation and Eyewall Replacement Cycles in Tropical Cyclone Simulations Xingbao Wang and Colleagues Idealized Initial Vortex in an Acquiescent Environment Nested down to Resolution of 2/3 km. East-west Diameter-time, Hovmoller diagram of Radar Reflectivity and Tangential Wind Radar Reflectivity(d. BZ) Tangential Wind
Radar return from 63 to 86 h Note SEF and start of ERC in bottom 8 panels Hypothesis: As a dynamic response to an Un. Balanced Force in the boundary layer (sum of pressures gradient, centrifugal, Coriolis, friction forces, etc…), a secondary maximum convergence zone (SMCZ) in the radial flow is generated in the boundary layer at a radius of about double the RMW. In the moist, conditionally-unstable atmosphere, the vertical updraft induced by the SMCZ triggers moist convection, which results in the Secondary Eyewall Formation.
OWZ Diagnostics for Genesis Vertically-aligned, moist regions with curvature vorticity in low shear Kevin Tory and Colleagues
Application of ACCESS-TC to Genesis Forecasting: 72, 60, 48, 36 hour forecasts verifying at 00 UTC, 20111226: ~ Genesis time for Grant.
Downstream Development during the Extratropical Transition of Tropical Cyclones: Lili Liu, Noel Davidson and Hongyan Zhu Time-longitude series of Stream Function Anomaly (deviation from zonal mean) at 45 N on 250 h. Pa level for (a) Hurricane Michael, (b) Hurricane Wilma, (c) Hurricane Maria, and (d) Hurricane Rita (non-ET). The arrow is the propagation direction of trough/ridge wave train and the black dot is the position of the hurricane around ET time. ET is often associated with Downstream Development Events
Capture and ET of Hurricane Maria Fig. 10: Dry, No-Initial-Vortex Simulation of MSLP for Maria. (a) Base time 00 UTC 3 Sep 2005. (b) , (c), (d) are 24 -, 48 - and 72 - hour MSLP simulations. The black dot is the position of Hurricane Maria at the valid simulation time. DD Dynamics can establish the large scale environment and capturing trough for ET
LARGE VARIABILITY IN Tropical Cyclone STRUCTURE (Ma and Davidson, 2012) Structure and Structure Change critical for Rainfall and Storm Surge => Need for Mesoscale DA and Correct Initial Vortex Structure. LARGE NATURAL VARIABILITY IN Tropical Cyclone STRUCTURE: (VMAX, CP, RMW, R 34, ROCI) What determines the variability? What determines the RMW? Is storm structure important for the evolution of the storm? Correct prediction of CP and Vmax (intensity) does not imply correct prediction of structure. *** Visualize the differences in rainfall and storm surge associated with different structures. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology
Initialized and 48 -hour forecasts of the radial profiles of tangential wind from the 7 synthetic structures at t = 0 (top panels) and t = 48 hours (bottom panels) for Bonnie, Ivan and Katrina from base times 12 UTC 23 August 1998, 00 UTC, 12 September 2005 and 00 UTC, 27 August 2005. Plotted symbols indicate estimated values of Vmax, R 64, R 50 and R 34. Units are m/s for wind and kms for radius.
Rainfall in TCs : Ying Jun Chen, Kevin Walsh, Beth Ebert, Noel Davidson example Analyse (TRMM, Atoll rain, rain gauge obs), Verify, Predict TC Rainfall
Mai NGUYEN: Rapid Intensification: Inner-Core Processes: Internal Structure Change during RI (Vacillation Cycles, QJRMS, 2011)
Amplifying Planetary Rossby Waves and Extreme Rain Events in Current and Future Climates Left panel: Analysis of 24 -hour rainfall accumulations for 29 January 1990. Centre and right panels: 500 h. Pa wind valid 24 and 29 January 1990, respectively. X marks the approximate location of Tropical Cyclone Tina at the analysis times, as it moves to the southeast and is captured and transitions into a midlatitude system. Figure 1: (a) Number of extreme rain events by month, and (b) percentage of events occurring within each latitude zone, by month.
ACCESS-TC: Future Plans • Upgrades to APS 1(more satellite data, higher resolution, improved physics, …. ) • NWP and basic research applications from special experimental data sets: TPARC/TCS 08, PREDICT: Genesis and Rapid Intensification (NOPP/ONR) • Specification, Prediction and Validation of TC Structure (CP, Vmax, RMW, R 34, ROCI): Critical for prediction of track, intensity, structure, storm surge and rainfall • Experiments with High Resolution Initialization and Prediction; Experiments with Ensemble Prediction; Experiments with Revised and New Physics; Diagnostics for TC boundary layer and moist processes • Enhancements with 4 DVAR (inner and outer loops) (NOPP/ONR) Impact of extra observation types • Rainfall in TCs (Ying Jun Chen, Walsh, Ebert, Davidson) • Influence of Amplifying Rossby Waves on TC structure and intensity (NOPP/ONR) • Inner-core Dynamics (eg, What defines RMW and R 34? Mai Nguyen) (NOPP/ONR) • Challenge: Initialize CAT 3 - 5 storms without the use of reconnaissance data or vortex specification? • Happy to collaborate on and/or provide data for (i) testing assimilation of new obs data, (ii) testing new parameterisations, (iii) assessing mechanisms.