Sensitivity of tropical cyclone simulations to parametric uncertainties in Air-Sea fluxes and implications for parameter estimation

Benjamin W. Green, Fuqing Zhang

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Tropical cyclones (TCs) are strongly influenced by fluxes of momentum and moist enthalpy across the air-sea interface. These fluxes cannot be resolved explicitly by current-generation numerical weather prediction models, and therefore must be accounted for via empirical parameterizations of surface exchange coefficients (CD for momentum and Ck for moist enthalpy). The resultant model uncertainty is examined through hundreds of convection-permitting Weather Research and Forecasting Model (WRF) simulations of Hurricane Katrina (2005) by varying four key parameters found in commonly used parameterizations of the exchange coefficient formulas. Two of these parameters effectively act as multiplicative factors for the exchange coefficients over all wind speeds (one each for CD and Ck); the other two parameters control the behavior of CD at very high wind speeds (i.e., above 33 m s-1). It is found that both the intensity and the structure of TCs are highly dependent upon the two multiplicative parameters. The multiplicative parameter for CD has a considerably larger impact than the one for Ck on the relationship between maximum 10-m wind speed and minimum sea level pressure: CD alters TC structure, with higher values shifting the radius of maximum winds inward and strengthening the low-level inflow; Ck only affects structure by uniformly strengthening/weakening the primary and secondary circulations. The TC exhibits the greatest sensitivities to the two multiplicative parameters after a few hours of model integration, suggesting that these parameters could be estimated by assimilating near-surface observations. The other two parameters are likely more difficult to estimate because the TC is only marginally sensitive to them in small areas of high wind speed.

Original languageEnglish (US)
Pages (from-to)2290-2308
Number of pages19
JournalMonthly Weather Review
Volume142
Issue number6
DOIs
StatePublished - Jan 1 2014

Fingerprint

tropical cyclone
air
simulation
wind velocity
enthalpy
parameterization
momentum
Hurricane Katrina 2005
weather
parameter estimation
parameter
sea
sea level pressure
inflow
convection
prediction

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

@article{fa2c66e1dbfb455a9dd909070c8dad91,
title = "Sensitivity of tropical cyclone simulations to parametric uncertainties in Air-Sea fluxes and implications for parameter estimation",
abstract = "Tropical cyclones (TCs) are strongly influenced by fluxes of momentum and moist enthalpy across the air-sea interface. These fluxes cannot be resolved explicitly by current-generation numerical weather prediction models, and therefore must be accounted for via empirical parameterizations of surface exchange coefficients (CD for momentum and Ck for moist enthalpy). The resultant model uncertainty is examined through hundreds of convection-permitting Weather Research and Forecasting Model (WRF) simulations of Hurricane Katrina (2005) by varying four key parameters found in commonly used parameterizations of the exchange coefficient formulas. Two of these parameters effectively act as multiplicative factors for the exchange coefficients over all wind speeds (one each for CD and Ck); the other two parameters control the behavior of CD at very high wind speeds (i.e., above 33 m s-1). It is found that both the intensity and the structure of TCs are highly dependent upon the two multiplicative parameters. The multiplicative parameter for CD has a considerably larger impact than the one for Ck on the relationship between maximum 10-m wind speed and minimum sea level pressure: CD alters TC structure, with higher values shifting the radius of maximum winds inward and strengthening the low-level inflow; Ck only affects structure by uniformly strengthening/weakening the primary and secondary circulations. The TC exhibits the greatest sensitivities to the two multiplicative parameters after a few hours of model integration, suggesting that these parameters could be estimated by assimilating near-surface observations. The other two parameters are likely more difficult to estimate because the TC is only marginally sensitive to them in small areas of high wind speed.",
author = "Green, {Benjamin W.} and Fuqing Zhang",
year = "2014",
month = "1",
day = "1",
doi = "10.1175/MWR-D-13-00208.1",
language = "English (US)",
volume = "142",
pages = "2290--2308",
journal = "Monthly Weather Review",
issn = "0027-0644",
publisher = "American Meteorological Society",
number = "6",

}

Sensitivity of tropical cyclone simulations to parametric uncertainties in Air-Sea fluxes and implications for parameter estimation. / Green, Benjamin W.; Zhang, Fuqing.

In: Monthly Weather Review, Vol. 142, No. 6, 01.01.2014, p. 2290-2308.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Sensitivity of tropical cyclone simulations to parametric uncertainties in Air-Sea fluxes and implications for parameter estimation

AU - Green, Benjamin W.

AU - Zhang, Fuqing

PY - 2014/1/1

Y1 - 2014/1/1

N2 - Tropical cyclones (TCs) are strongly influenced by fluxes of momentum and moist enthalpy across the air-sea interface. These fluxes cannot be resolved explicitly by current-generation numerical weather prediction models, and therefore must be accounted for via empirical parameterizations of surface exchange coefficients (CD for momentum and Ck for moist enthalpy). The resultant model uncertainty is examined through hundreds of convection-permitting Weather Research and Forecasting Model (WRF) simulations of Hurricane Katrina (2005) by varying four key parameters found in commonly used parameterizations of the exchange coefficient formulas. Two of these parameters effectively act as multiplicative factors for the exchange coefficients over all wind speeds (one each for CD and Ck); the other two parameters control the behavior of CD at very high wind speeds (i.e., above 33 m s-1). It is found that both the intensity and the structure of TCs are highly dependent upon the two multiplicative parameters. The multiplicative parameter for CD has a considerably larger impact than the one for Ck on the relationship between maximum 10-m wind speed and minimum sea level pressure: CD alters TC structure, with higher values shifting the radius of maximum winds inward and strengthening the low-level inflow; Ck only affects structure by uniformly strengthening/weakening the primary and secondary circulations. The TC exhibits the greatest sensitivities to the two multiplicative parameters after a few hours of model integration, suggesting that these parameters could be estimated by assimilating near-surface observations. The other two parameters are likely more difficult to estimate because the TC is only marginally sensitive to them in small areas of high wind speed.

AB - Tropical cyclones (TCs) are strongly influenced by fluxes of momentum and moist enthalpy across the air-sea interface. These fluxes cannot be resolved explicitly by current-generation numerical weather prediction models, and therefore must be accounted for via empirical parameterizations of surface exchange coefficients (CD for momentum and Ck for moist enthalpy). The resultant model uncertainty is examined through hundreds of convection-permitting Weather Research and Forecasting Model (WRF) simulations of Hurricane Katrina (2005) by varying four key parameters found in commonly used parameterizations of the exchange coefficient formulas. Two of these parameters effectively act as multiplicative factors for the exchange coefficients over all wind speeds (one each for CD and Ck); the other two parameters control the behavior of CD at very high wind speeds (i.e., above 33 m s-1). It is found that both the intensity and the structure of TCs are highly dependent upon the two multiplicative parameters. The multiplicative parameter for CD has a considerably larger impact than the one for Ck on the relationship between maximum 10-m wind speed and minimum sea level pressure: CD alters TC structure, with higher values shifting the radius of maximum winds inward and strengthening the low-level inflow; Ck only affects structure by uniformly strengthening/weakening the primary and secondary circulations. The TC exhibits the greatest sensitivities to the two multiplicative parameters after a few hours of model integration, suggesting that these parameters could be estimated by assimilating near-surface observations. The other two parameters are likely more difficult to estimate because the TC is only marginally sensitive to them in small areas of high wind speed.

UR - http://www.scopus.com/inward/record.url?scp=84901627088&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84901627088&partnerID=8YFLogxK

U2 - 10.1175/MWR-D-13-00208.1

DO - 10.1175/MWR-D-13-00208.1

M3 - Article

VL - 142

SP - 2290

EP - 2308

JO - Monthly Weather Review

JF - Monthly Weather Review

SN - 0027-0644

IS - 6

ER -