BOUNDARY LAYER STRUCTURE IN TYPHOON SAOMAI (2006): UNDERSTANDING THE EFFECTS OF EXCHANGE COEFFICIENT

MING Jie; SONG Jin-jie; CHEN Bao-jun; WANG Ke-fa

doi:10.3969/j.issn.1006-8775.2012.02.009

Abstract:

Recent studies have shown that surface fluxes and exchange coefficients are particularly important to models attempting to simulate the evolution and maintenance of hurricanes or typhoons. By using an advanced research version of the Weather Research and Forecasting (ARW) modeling system, this work aims to study the impact of modified exchange coefficient on the intensity and structures of typhoon Saomai (2006) over the western North Pacific. Numerical experiments with the modified and unmodified exchange coefficients are used to investigate the intensity and structure of the storm, especially the structures of the boundary layer within the storm. Results show that, compared to the unmodified experiment, the simulated typhoon in the modified experiment has a bigger deepening rate after 30-h and is the same as the observation in the last 12-h. The roughness is leveled off when wind speed is greater than 30 m/s. The momentum exchange coefficient (CD) and enthalpy exchange coefficient (CK) are leveled off too, and CD is decreased more than CK when wind speed is greater than 30 m/s. More sensible heat flux and less latent heat flux are produced. In the lower level, the modified experiment has slightly stronger outflow, stronger vertical gradient of equivalent potential temperature and substantially higher maximum tangential winds than the unmodified experiment has. The modified experiment generates larger wind speed and water vapor tendencies and transports more air of high equivalent potential temperature to the eyewall in the boundary layer. It induces more and strong convection in the eyewall, thereby leading to a stronger storm.

Get Citation+

MING Jie, SONG Jin-jie, CHEN Bao-jun, et al. BOUNDARY LAYER STRUCTURE IN TYPHOON SAOMAI (2006): UNDERSTANDING THE EFFECTS OF EXCHANGE COEFFICIENT [J]. Journal of Tropical Meteorology, 2012, 18(2): 195-206, https://doi.org/10.3969/j.issn.1006-8775.2012.02.009

Export:

Article Metrics

BOUNDARY LAYER STRUCTURE IN TYPHOON SAOMAI (2006): UNDERSTANDING THE EFFECTS OF EXCHANGE COEFFICIENT

Key Laboratory of Mesoscale Severe Weather and School of Atmospheric Sciences, Nanjing University, Nanjing 210093 China

Climate Center, Meteorological Bureau of Jiangsu Province, Nanjing 210008 China

Received Date: 2011-09-30

Rev Recd Date: 2012-02-16

Abstract: Recent studies have shown that surface fluxes and exchange coefficients are particularly important to models attempting to simulate the evolution and maintenance of hurricanes or typhoons. By using an advanced research version of the Weather Research and Forecasting (ARW) modeling system, this work aims to study the impact of modified exchange coefficient on the intensity and structures of typhoon Saomai (2006) over the western North Pacific. Numerical experiments with the modified and unmodified exchange coefficients are used to investigate the intensity and structure of the storm, especially the structures of the boundary layer within the storm. Results show that, compared to the unmodified experiment, the simulated typhoon in the modified experiment has a bigger deepening rate after 30-h and is the same as the observation in the last 12-h. The roughness is leveled off when wind speed is greater than 30 m/s. The momentum exchange coefficient (CD) and enthalpy exchange coefficient (CK) are leveled off too, and CD is decreased more than CK when wind speed is greater than 30 m/s. More sensible heat flux and less latent heat flux are produced. In the lower level, the modified experiment has slightly stronger outflow, stronger vertical gradient of equivalent potential temperature and substantially higher maximum tangential winds than the unmodified experiment has. The modified experiment generates larger wind speed and water vapor tendencies and transports more air of high equivalent potential temperature to the eyewall in the boundary layer. It induces more and strong convection in the eyewall, thereby leading to a stronger storm.

HTML

Reference (22)

[1]	MALKUS J S, RIEHL H. On the dynamics and energy transformations in steady-state hurricanes [J]. Tellus, 1960, 12(1): 1-20.
[2]	OOYAMA K V. Numerical experiment of the life cycle of tropical cyclones [J]. J. Atmos. Sci., 1969, 26(1): 3-40.
[3]	EMANUEL K A. An air-sea interaction theory for tropical cyclones. Part I: Steady-state maintenance. [J]. J. Atmos. Sci., 1986, 43(6): 585-605.
[4]	ROTUNNO R, EMANUEL K A. An air-sea interaction theory for tropical cyclones, Part II: Evolutionary study using axisymmetric nonhydrostatic numerical model. [J]. J. Atmos. Sci., 1987, 44(3): 542-561.
[5]	ROSENTHAL S L. The response of a tropical cyclone model to variations in boundary layer parameters, initial conditions, lateral boundary conditions and domain size. [J]. Mon. Wea. Rev., 1971, 99(10): 767-777.
[6]	EMANUEL K A. Sensitivity of tropical cyclones to surface exchange coefficients and a revised steady-state model incorporating eye dynamics. [J]. J. Atmos. Sci., 1995, 52(22): 3969-3976.
[7]	BRAUN S A, TAO W K. Sensitivity of high-resolution experiments of hurricane Bob (1991) to planetary boundary layer parameterizations. [J]. Mon. Wea. Rev., 2000, 128(12): 3941-3961.
[8]	DONELAN M A, HAUS B K, REUL N, et al. On the limiting aerodynamic roughness of the ocean in very strong wind. [J]. Geophys. Res. Lett., 2004, 31, L18306, doi: 10.1029/2004GL019460.
[9]	POWELL M D, VICKERY P J, REINHOLD T A. Reduced drag coefficient for high wind speeds in tropical cyclones. [J] Nature, 2003, 422: 279-283.
[10]	SKAMAROCK W C, KLEMP J B, DUDHIA J, et al. A description of the advanced research WRF: Version 2 [R]. NCAR Tech. Note 468 1 STR, 2005, 88 pp.
[11]	JMA. Outline of the operational numerical weather prediction at the Japan Meteorological Agency [J]. Appendix to WMO numerical weather prediction progress report, 2002.
[12]	HOSOMI T. Implementation of targeted moisture diffusion for the JMA Regional Spectral Model (RSM). CAS/JSC WGNE [J]. Res. Act. Atmos. Ocean. Modeling, 2005, 35(5): 7-8.
[13]	MLAWER E J, TAUBMAN S J, BROWN P D, et al. Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave. [J]. J. Geophys. Res., 1997, 102 (D14), 16663-16682.
[14]	DUDHIA J. Numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model. [J]. J. Atmos. Sci., 1989, 46(20): 3077-3107.
[15]	NOH Y, CHEON W G, HONG S Y, et al. Improvement of the K-profile model for the planetary boundary layer based on large eddy experiment data. [J]. Bound.-Layer Meteor., 2003, 107(2): 421�C427.
[16]	HONG S Y, NOH Y, DUDHIA J. A new vertical diffusion package with an explicit treatment of entrainment processes [J]. Mon. Wea. Rev., 2006, 134(9): 2318-2341.
[17]	LIN Y L, FARLEY R D, ORVILLE H D. Bulk parameterization of the snow field in a cloud model [J]. J. Climate Appl. Meteor., 1983, 22(6): 1065-1092.
[18]	CHEN S H, SUN W Y. A one-dimensional time dependent cloud model. [J]. J. Meteor. Soc. Japan, 2002, 80(1): 99-118.
[19]	CHARNOK H. Wind stress on a water surface [J]. Quart. J. Roy. Meteor. Soc., 1955, 81(350): 639-640.
[20]	BLACK P G, D'ASARO E, DRENNAN W M, et al. Air-sea exchange in hurricanes: Synthesis of observations from the Coupled Boundary Layer Air-Sea Transfer experiment [J]. Bull. Amer. Meteor. Soc., 2007, 88(350): 357-374.
[21]	ZHAO K, LEE W C, JOU J D. Single Doppler radar observation of the concentric eyewall in Typhoon Saomai [J]. 2006, near landfall, [J]. Geophys. Res. Lett., 2008, 35, L07807, doi:10.1029/2007GL032773.
[22]	YAU M K, LIU Y, ZHANG D L, et al. A multiscale study of Hurricane Andrew (1992). Part VI: Small-scale inner-core structures and wind streaks [J]. Mon. Wea. Rev., 2004, 132(6): 1410-1433.

BOUNDARY LAYER STRUCTURE IN TYPHOON SAOMAI (2006): UNDERSTANDING THE EFFECTS OF EXCHANGE COEFFICIENT

Abstract:

References

Get Citation+

Share Article

Article Metrics

Proportional views

Manuscript History

Online:

通讯作者: 陈斌, bchen63@163.com