IWTC-VIII: Section 4.4 Oceanic Influences and Air-Sea Interactions In Tropical Cyclones

Transcription

1 IWTC-VIII: Section 4.4 Oceanic Influences and Air-Sea Interactions In Tropical Cyclones Lynn K. Nick Shay Panel Members: M. M. Ali, S. Chen, I. Ginis, G. Halliwell, H-S Kim, Marie-Dominque Leroux, I-I Lin, A. Wada Contributors: E. D Asaro, E. Uhlhorn, W. Teague, M. Donelan, N. Walker, T. Sanford, B. Jaimes, J. Park, P. Sandery, and Y. Yoshikawa shared material. Thank You Prof. I-I Lin!

2 Tracks/Intensity of TCs Global Problem of TC-Ocean Interactions! Sea surface height anomaly (cm)

3 Panel Recommendations: (Not much has Changed since 2010!) Build on experimental and numerical studies, consensus is: Given the range of uncertainty in the surface drag (e.g., wave effects), heat fluxes (e.g., sea spray), and initial conditions (e.g., wind field) beyond 30 m s -1, assess how these combined uncertainties propagate through the coupled ocean-tc model; Develop an archive of data sets and model outputs and make these archives publicly available for research and operational purposes. Investigate the potential use of these data sets in assimilation, evaluation, and verification of ocean models and parameterization schemes; Create an in-situ tropical cyclone ocean-atmosphere observing program for prestorm, storm, and post-storm environments. Develop optimal observing strategies and mixes of sensors for spatial evolution of upper ocean, interface, and atmospheric fields (including secondary circulations); and; Develop improved ocean model initialization schemes through data assimilation of satellite and in situ measurements, and test parameterizations for a spectrum of ocean, wave and atmospheric conditions including the impact of waves on

4 Carton and Integrated thermal structure (OHC). Current and shear central to mixing across depth (h) cooling and, feedback to the storm kj cm -2 D 26 0 OHC cp T z 26 dz, Deeper warm layers and strong background flows, minimal cooling less negative feedback to TC. 3-D Problem!

5 SSTs (color: o C) and SHA s (contours: cm) a) pre (9 Sept) and b) post Ivan (17 Sept) and c) SST and SHA differences where wind speeds from Hurricane Ivan are shown in m s -1 and Chlorophyll a (mg m -3 : right panels) corresponding to similar days for d) pre, e) post and f) 19 Sept for corresponding isotachs derived from the SHA gradients (Combined from Figs 2 and 3 in Walker et al. GRL, 2005).

6 Cartoon of ONR ITOP Operations (D Asaro et al., 2014) Experimental platforms and strategy relative to the locations of the three major ITOP storms at the time of maximum sampling are shown by Typhoon symbols for Fanapi, Megi and Malakas in 2010

7 ITOP Ocean Thermal Measurements (D Asaro et al., BAMS,2013; Mrvaljevic et al., GRL, 2013). Depth [m] Date, /20 9/25 10/1 10/5 10/10 Seaglider 181 Mooring A4 EM-APEX 4907 EM-APEX 4910 Year Day, 2010 Seaglider 167 UCTD Section 1 UCTD Section 2 2-layer 9/21 2-layer 9/18-27 f h ADOS i a b c d e g θ [ C] T(z) between 17 Sept to 12 Oct (1 C) from floats/drifters (a-c), gliders (d) and a mooring (e). Wake cross sections from the shipboard UCTD around 22 Sep (YD 265) (f) and 23 Sept (year day 266) (g) and from a 2-layer reduced gravity model [Shay et al., 2000; Pun et al., 2007) estimate of the X-section using one altimeter track 09/21, and using a 10 day map of SSHA from 09/18 to 09/27 (i). 26 C and 27 C isotherms (contours) show the thickness of the cold wake. Isotherm displacements reflect storm-induced inertial motions (period ~30 hours) and internal tides. Latitude [ N]

8 Observed Responses to Katrina and Rita from Jaimes and Shay, JPO, 2010) in GoM Basin. (a) Mixing parameter ( ) accounting for T(z) differences between OML and thermocline er (smaller values-more mixing); cyclonic and anticyclonic eddies are labeled CCE and WCE, respectively; storm s track is for Katrina. (b) 3-D dispersion of NIOs (Near Inertial Oscillation) during the relaxation stage; Z is the depth at which NIOs are propagating; rays numbered by IP (~one day). (c) Water mass response to Katrina over a cyclonic geostrophic vortex. (d) Rita Response over an anticyclonic geostrophic vortex. Red, green, and blue color in (c, d depict before, during, and after passage; black line is a typical profile over the LC (warm anticyclonic geostrophic feature) during non-wind conditions.

9 Differentiated cooling in the LC system (Jaimes and Shay, JPO, 2010) T ~ -1 o C Loop Current Cold Ring T ~ -4.5 o C T ~ -0.5 o C Warm ring Cluster-averaged temperature profiles.

10 Surface Current Response to a Typhoon Mari (04) High Frequency Radars (Yoshikawa et al., JGR, 2009). Before After Mari

11 Profiling Floats in Western Pacific Ocean From June 2011-April 2013 (left panel) and T/S from floats During Several Typhoons (Wada et al., 2014) Responses were highly spatial dependent consistent with previous studies.

12 Based on 13 years ( ) of observations, it is found that the warm ocean eddies in the South Eddy Zone of the Western North Pacific are important boosters to restrain the self-induced cooling for typhoons to intensify to cat-5 (Lin et al., MWR, 2008)

13 Composite SST (left) and Current/Shear Response (right) from Floats During Francis in 2004 From ONR CBLAST (D Asaro et al., GRL, 2007; Sanford et al., GRL, 2007). APEX Float Measurements 2 Rmax

14 Northern Cyclone Southern Cyclone Observed and simulated TC Ivan (2004) current shear response at NRL SEED Moorings along the Northern GOM shelf. Observed (TMI) and Model SST Analyses relative to Ivan s track. From Halliwell et al. (MWR, 2010)

15 LES Simulations of Response to Hurricane Gustav (Rabe et al., JPO, 2014). Cross sections of vertical velocity normalized by u in the LES simulations of Hurricane Gustav at two specific time points, day (top) and (bottom) for the Langmuir turbulence (left) and shear turbulence (right). Cross sections are taken at the depth above z/h = 0.5. Note large differences in patterns!

16 Approach From Altimetry (Shay and Brewster, MWR, 2010; Meyers et al., JAOT, 2014). 2.5-layer model. Daily climatology from GDEM/WOA. Blend and objectively map SHA from altimeters. Infer H 20 using mapped SHA and daily climatology. Estimate H 26 relative to H 20. Estimate OHC relative to 26 o C using H26, h, and SST. Evaluate isotherm depths and OHC Caution applied to SHA data over shallow ocean areas.

17 Systematically Merged Pacific Ocean Regional Temperature and Salinity (SPORTS) Evaluation (McCaskill and Shay, AMS, 2014) Follows SMARTS approach (Meyers et al., JAOT, 2014) with 60,000 profiles. ~267,540 qc-ed data points over 12-yr period ( ) from multiple platforms. Slope=0.99 Slope=0.96 Slope=1.02

18 ST Haiyan Track/Intensity Relative to OHC (color) and Mixed Layer Depth (contour).

19 Monthly Regression-Based Analysis in Western Pacific Ocean Basin (from Pun et al., IEEE, 2014). Schematic of (a) REGWNP-derived profile and (b) TLM-derived profile. (c) Zoom-in area of (a) compares the profiles from the REGWNP (green) and Argo (black). (d) Zoom-in area of (b) compares the profiles from the TLM (red) and Argo (black). Shaded areas in (c) and (d) indicate the UOHC, their values are also shownwestern Pacific MDR domain-averaged D26 (in red, left axis) and TCHP (in blue, right axis) has increase by 12% in the past 2 decades. The error bars are standard deviations. The D26 (TCHP) curve passes 99% (80%) statistical significance test. (After Pun et al. 2014)

20 Western Pacific MDR domain-averaged D26 and TCHP (from Pun et al., GRL, 2013). TCHP (in blue, right axis) has increased by 12% in the past 2 decades. Error bars are standard deviations. The D26 (TCHP) curve passes 99% (80%) statistical significance test.

21 OHC/TCHP Variations Relative to Locations of Severe TCs in the Western Pacific Ocean Basin. From Wada et al. (2012).

22 Ocean response to tropical cyclone Fay at 24 March 2004 off the north-west shelf of Australia : (a) Comparison of analysis and forecasts (SLP); (b) Forecasted and analysed track; Post storm (c) Ocean Data Assimilation system (BODAS) analysed SST; (d) SST observations from AMSR-E; (e) simulated SST from CLAM. Figures f-h as per c-e and illustrate corresponding sea-level anomalies and depthaveraged currents (200 m) (Sandery et al. 2010).

23 TC in Bay of Bengal From Ali et al. (GRL, 2007) Composite topography from several altimetry-derived sea- SHA field (SSHA: cm) from a) 1-10 May and b) b) May 2003 relative to the TC track, c) the along-track time series variation of the SSHA and TC index (CI) for the Bay of Bengal cyclone (from Ali et al. 2007).

24 Evaluation of OHC East Pacific Ocean From XBT Transects (Shay and Brewster, MWR, 2010)

25 Hurricane Juliette (Sept 2001) and Equivalent OHC (Shay and Brewster, MWR, 2010). a) OHC b) Equivalent OHC versus track and intensity (stratification effect) c) Buoyancy Frequency from a Ron Brown CTD profile. OHC_E provides a global context for comparing OHC in differing basins. Costa Rica Dome. Strong stratification inhibits vertical mixing (SST cooling).

26 SFMR Emissivity Versus Surface Wind From GPS sondes (Uhlhorn et al., JAOT, 2007) SMFR measures emissions expressed in terms of brightness temperatures. Foam coverage increases with winds-emits microwave energy more easily. A new model of emissivity and surface winds is compared to GPS sonde data. Model function behaves differently at about 32 m s -1.

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28 Comparison of cd using a) Surface Stress and b) Surface Roughness Methods (Soloviev et al., GRL, 2014). Note COARE 3.0 parameterization (lower bound on drag coefficient), and available data are shown for comparison. Included only the available field observations that report confidence intervals. SS and SR methods are different approaches for unifying two-phase, wave-form, and viscous stresses. COARE parameterization has been used for verification of the unified parameterizations in low to moderate winds.

29 Charnock and Surface Drag Coefficients Versus Wave Age (Moon et al., 2004) Slope change in Charnock Coefficient between 25 to 35 m/s similar to other results. Trend is for higher drag for younger waves. Relationship to enthalpy coefficient still not well understood under very high winds.

30 Cd.vs. Wind Speed (Courtesy of Jeff Kepert) Bell et al. JAS 2012 Holthuijsen et al. JGR 2012

31 Drag Coefficients Versus Wind Speeds (Reichl et al., 2014) Saturation Level Saturation Level Drag coefficient vs wind speed for a 5 m s -1 translating tropical cyclone. The left column is calculated using the Reichl et al. (2014) method, while the right column is calculated using the Donelan et al. (2004) method. The saturation level is set to (top), and (bottom) compared to Donelan s value of from wind wave tank experiments.

32 Simulations without (left panels) and with (right panels) Sea Spray Parameterizations Courtesy of Bao and Fairall

33 Hurricane Earl (2010) Fluxes: Independence on Wind Speed (from Jaimes et al., MWR, 2014) Enthalpy Flux Momentum Flux C1 RI C2 H4 H3 C3 C4 Enthalpy fluxes grow, peak, and decay faster than momentum fluxes. Region of maximum enthalpy fluxes larger than region of maximum momentum fluxes during high wind speed regimes. H4 C5 C6 C7

34 Sensitivity to the C K /C D ratio (Jaimes et al., MWR, 2014) C K /C D = 0.54 C K /C D = 0.7 Red line Green line Weakly stratified Ocean Regimes Highly stratified Warm Transition Cold C K /C D = 1 Blue line DOHC Dt = -( OHC in -OHC pre ) Dt OHC variations in X-track direction (light gray shading) Track dependence Translation speed dependent

35 a) Temperature profiles b) SST and Air Temperatures and c) Enthalpy Fluxes for each ITOP storm (Lin et al., GRL, 2013). Dropsonde and AXBT pairs from the WC-130J and curves are the results from an driven by the observed storms (solid) and same extrapolated to higher wind speeds (dashed). Note that some of the AXBT profiles may be ~5 m shallower due to processing errors.

36 Closing Remarks: As per a recommendation to WMO in 2006, moving towards an evaluated OHC index in the global oceans for forecasting. Within 24 to 48 hours of landfall, positive feedback (less negative) regimes-26 o C isotherm depth is deep (LC/WCR complex NW Caribbean Sea, Kuroshio; Gulf Stream), east Australian Current strong background flows dampen forced currents and shears (more heat and moisture for the TC). Ocean models must get the background state correct before coupling to atmospheric model-important for Landfall Processes since we have strong oceanic fronts close to the coast in many basins. Uncertainty remains in the bulk coefficients (and ratio of Ck/Cd) at high wind speeds in estimating stresses and fluxes- even more complex at landfall. Ocean measurements (T(z), U,V(z)), initialization of basic state using altimetry, floats, gliders, AX, improve mixing schemes and air-sea parameterizations under high winds.