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Upper Ocean response before and after the cyclone from Argo floats

Upper Ocean response before and after the cyclone from Argo floats. M. Ravichandran, G. Anita and Uday Bhaskar. Indian National Centre for Ocean Information Services, Hyderabad, INDIA. Objective. How Argo can contribute to cyclone prediction system? Cyclone genesis

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Upper Ocean response before and after the cyclone from Argo floats

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  1. Upper Ocean response before and after the cyclone from Argo floats M. Ravichandran, G. Anita and Uday Bhaskar Indian National Centre for Ocean Information Services, Hyderabad, INDIA

  2. Objective • How Argo can contribute to cyclone prediction system? Cyclone genesis Intensity of the storm Track of the cyclone

  3. Introduction • Storm intensity is particularly sensitive to the thermodynamic structure of the upper ocean, accurate prediction of hurricane intensity requires knowledge of upper ocean thermal structure ahead of the storm (Emanuel, K. A, 1999, Nature) • Upper ocean Heat content is important since it provides an estimate of the ocean heat available to the atmosphere (shay et al 2000, MWR ) • the rightward bias of the maximum SST decreases and increase in MLD are primarily due to entrainment mixing (shay, 1999, RSMAS Tech Report) • The large entrainment flux on the right side of the Hurricane was presumably due to the much larger inertial currents and shear. (D’Asaro, 2003, JPO). • The intensification of most hurricanes are linked to the Variability of the integrated vertical temperature under the storm track (Goni etal, 1986, JGR)

  4. Gerry – storm track 121 Depression -10 Tropical storm 9 cyclone-1 -12 cyclone-3 -14 8th 11 -16 53 -18 12 52 51 Latitude -20 13 First intense TC of the season Peak wind 130 kts Min pressure 938 mb -22 50 14 -24 -26 15th Before storm -28 After storm -30 50 52 54 56 58 60 62 64 66 68 Longitude

  5. Genesis location (121) persistence of warm water Formation of low density Heat content ( x 108 J/m2) Decrease in salinity

  6. 2900094 May 2003 (01 B) May 2002 (01 A) 2900159

  7. Radar altimetry better indicator of warm water Interpolated SHA data corresponding to a 10-day period ending on the date 09 Feb 2003 31 Jan – Feb 9 Source: http://www.aoml.noaa.gov/phod/dataphod/work/trinanes/INTERFACE/index.html Intensity of cyclone increase if the track followed the warm water regions.

  8. Temperature Left side of the trajectory Right side of the trajectory 52 50 near 51 53 MLD deepening much faster, warm water pushed down Strong entrainment (strong inertial currents, D’Asaro, 2003) Not much change

  9. Right side of the trajectory Left side of the trajectory Salinity 50 52 53 51

  10. Depth of 20 & 26 deg isotherm

  11. Mixed layer depth Vertical mixing is one of the important physical processes in the ML deepening and downward transport of heat energy 50 52 53 51

  12. Hurricane Heat Potential Cold core 61.4 x 108 J/m2 Along the trajectory the hhp is not decreases after the storm passage

  13. Right side of the track (freshening) Freshen due to precipitation Cooled due to heat and moisture transfer into the atmosphere 50 downwelling

  14. Left side of the track (upwelling) Upwelling Intense vertical mixing

  15. Temperature Strong cooling due to mixing with underlying cold water and mixing with surrounding cold water with a small contribution from heat loss to the atmosphere

  16. Salinity Freshening in the top layer

  17. Observations Left Right • The rate of deepening MLD is higher (BS) • Rate of increase in HHP is higher (BS) • Upwelling (AS) • Density increases (AS) • Strong vertical mixing (AS) • MLD is not deepening as that of LS • less • Freshening • Density decreases • Less mixing BS – Before storm AS- After storm

  18. Density fieldsGerry (9th feb – 31st Jan 2003) 0 m 25 m 50 m 75 m

  19. Arabian sea (9th May - 29th April) 25 m 0 m 50 m 75 m Cyclone (01 A) in the Arabian sea during May 2002

  20. Arabian sea (9th May - 4th May) 0 m 25 m 25 m 0 m 50 m 75 m 50 m 75 m

  21. conclusion • Cyclo-genesis (density) Low density field in the near upper layer • Cyclone intensity (temp) Intensity of cyclone increases if the cyclone passes over warm waters (SSHA, higher MLD, higher HHP, etc) • Cyclone track (density) The change in density field, MLD, HHP etc may provide clue for the track

  22. Thank you

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