Relative Humidity in Tropical Weather Systems

Gray, William M.; Ruprecht, Eberhard; Phelps, Ronald P.

doi:10.1175/1520-0493(1975)103<0685:rhitws>2.0.co;2

Cited by 58 publications

(35 citation statements)

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“…4). Note that the mean temperature at 100 hPa averaged over 4o-8o area of typhoons is -78oC (Gray et al, 1975). The climatological tropopause temperature, which might be thought to give a lower bound estimate of the outflow temperature (DK), increases toward the north away from the egrlator (higher tropopause height toward the equator) .…”

Section: Data and Analysis Methodsmentioning

confidence: 91%

A Climatology of Sea Surface Temperature and the Maximum Intensity of Western North Pacific Tropical Cyclones

Baik

Paek

1998

Journal of the Meteorological Society of Japan

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Using a 31-year (1960-1990) sample of western North Pacific tropical cyclones and monthly mean sea surface temperature (SST) for each year, an empirical relationship between SST and the maximum intensity of western North Pacific storms is determined and used to calculate the relative intensity, a measure of how close a storm reaches its maximum potential intensity. The analysis method in this study follows that by DeMaria and Kaplan (1994b) and results are compared with observations over the North Atlantic and theoretical studies.Similar to previous studies, an upper bound of storm intensity for a given SST was determined. It is shown that a larger fraction of Pacific storms are observed over warm waters than Atlantic storms and the maximum potential intensity of Pacific storms tends to be stronger than that of Atlantic storms or theoretically calculated storms. The analyses of the relative intensity at the time of each storm's life-time maximum intensity indicate that the maximum intensity of Pacific storms is well below the maximum potential intensity. The average relative intensity of the total sample is 37% (47%) when the regression curve for the maximum (99th) intensity percentile is used to compute the relative intensity, implying that environmental influences appear to be more important than SST in determining the maximum intensity of Pacific storms. The average relative intensity of late-season storms tends to be, as in the Atlantic, larger than that of early-season storms, and the yearly-averaged relative intensity shows to some extent interannual variability but with little correlation either with quasi-biennial oscillation or with El Nino.

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Section: Data and Analysis Methodsmentioning

confidence: 91%

A Climatology of Sea Surface Temperature and the Maximum Intensity of Western North Pacific Tropical Cyclones

Baik

Paek

1998

Journal of the Meteorological Society of Japan

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“…The mass field is derived from the wind field corresponding to an axisymmetric cyclonic vortex of maximum surface tangential wind set to 15 m s 21 at 90 km from the vortex center that is embedded in a quiescent flow. The temperature and humidity profiles of the far field are based on Jordan's Caribbean sounding (Jordan 1958;Gray et al 1975). In all of the experiments, the sea surface temperature is set to 302 K (approximately 298C).…”

Section: Experimental Designmentioning

confidence: 99%

Impact of Physics Representations in the HWRFX on Simulated Hurricane Structure and Pressure–Wind Relationships

Bao¹,

Gopalakrishnan

Michelson

et al. 2012

Monthly Weather Review

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A series of idealized experiments with the NOAA Experimental Hurricane Weather Research and Forecasting Model (HWRFX) are performed to examine the sensitivity of idealized tropical cyclone (TC) intensification to various parameterization schemes of the boundary layer (BL), subgrid convection, cloud microphysics, and radiation. Results from all the experiments are compared in terms of the maximum surface 10-m wind (VMAX) and minimum sea level pressure (PMIN)-operational metrics of TC intensity-as well as the azimuthally averaged temporal and spatial structure of the tangential wind and its material acceleration.The conventional metrics of TC intensity (VMAX and PMIN) are found to be insufficient to reveal the sensitivity of the simulated TC to variations in model physics. Comparisons of the sensitivity runs indicate that (i) different boundary layer physics parameterization schemes for vertical subgrid turbulence mixing lead to differences not only in the intensity evolution in terms of VMAX and PMIN, but also in the structural characteristics of the simulated tropical cyclone; (ii) the surface drag coefficient is a key parameter that controls the VMAX-PMIN relationship near the surface; and (iii) different microphysics and subgrid convection parameterization schemes, because of their different realizations of diabatic heating distribution, lead to significant variations in the vortex structure.The quantitative aspects of these results indicate that the current uncertainties in the BL mixing, surface drag, and microphysics parameterization schemes have comparable impacts on the intensity and structure of simulated TCs. The results also indicate that there is a need to include structural parameters in the HWRFX evaluation.

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“…Consequently, it is not surprising that the observed large-scale fluctuations of the freetropospheric humidity are closely tied to convection. This was first documented by Gray (1973) and Gray et al (1975) by combining low-resolution satellite imagery with tropical radiosonde data. The composite analysis demonstrated that large-scale regions featuring deep convection are, on average, significantly more humid than regions classified as void of deep convection.…”

Section: Introductionmentioning

confidence: 99%

Moisture–convection feedback in the tropics

Grabowski

Moncrieff

2004

Quart J Royal Meteoro Soc

145

111

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SUMMARYThis paper discusses the large-scale moisture-convection feedback in the tropics, where spatial fluctuations of deep convection cause perturbations of free-tropospheric moisture which, in turn, affect the spatial distribution of deep convection. A simple heuristic argument using the timescale of free-tropospheric humidity change explains why moisture-convection feedback is particularly relevant for tropical intraseasonal oscillations.The large-scale dynamical context for moisture-convection feedback is investigated in idealized rotating constant-sea-surface-temperature ('tropics everywhere') aquaplanet using cloud-resolving convection parametrization (CRCP; super-parametrization) and a traditional convective parametrization (the Emanuel scheme). The large-scale organization of convection within the equatorial waveguide takes the form of MJO-like (Madden-Julian Oscillation) coherent structures. First, CRCP simulations are performed in which development of large-scale free-tropospheric moisture perturbations is artificially suppressed using relaxation with a timescale of one day. As in previous simulations where much shorter relaxation timescale was used, MJO-like coherences do not develop and, if already present, they disintegrate rapidly. Second, CRCP simulations that start from planetaryscale moisture perturbation in the free troposphere are conducted. The ensuing large-scale velocity perturbations have e-folding times of five and seven days, respectively, for interactive and prescribed radiation simulations. This supports the conjecture that interactive radiation enhances moisture-convection feedback; an enhanced largescale circulation results from differences in radiative cooling between areas having enhanced and suppressed convectively-generated moisture and cloudiness. Additional support for the role of moisture-convection feedback in intraseasonal oscillations is seen in simulations that apply the Emanuel scheme. The standard configuration of the Emanuel scheme is insensitive to free-tropospheric humidity and results in weak MJO-like coherences. A simple modification of the Emanuel scheme that enhances its sensitivity to free-tropospheric humidity dramatically improves the simulated MJO-like coherences.

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Relative Humidity in Tropical Weather Systems

Cited by 58 publications

References 0 publications

A Climatology of Sea Surface Temperature and the Maximum Intensity of Western North Pacific Tropical Cyclones

A Climatology of Sea Surface Temperature and the Maximum Intensity of Western North Pacific Tropical Cyclones

Impact of Physics Representations in the HWRFX on Simulated Hurricane Structure and Pressure–Wind Relationships

Moisture–convection feedback in the tropics

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