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Influence of rain-rate initialization, cloud microphysics, and cloud torques on hurricane intensity

Pattnaik, S and Inglish, C and Krishnamurti, TN (2011) Influence of rain-rate initialization, cloud microphysics, and cloud torques on hurricane intensity. Monthly Weather Review, 139 (2). pp. 627-649.

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Abstract

This study examines the impact of rain-rate initialization (RINIT), microphysical modifications, and cloud torques (in the context of angular momentum) on hurricane intensity forecasts using a mesoscale model the Advanced Research Weather Research and Forecasting model (ARW-WRF) at a cloud-resolving resolution of 2.7 km. The numerical simulations are performed in a triple-nested manner (25, 8.3, and 2.7 km) for Hurricane Dennis of 2005. Unless mentioned otherwise, all the results discussed are from the innermost grid with finest resolution (2.7 km). It is found that the model results obtained from the RINIT technique demonstrated robust improvement in hurricane structure, track, and intensity forecasts compared to the control experiment (CTRL; i.e., without RINIT). Thereafter, using RINIT initial conditions datasets three sensitive experiments are designed by modifying specific ice microphysical parameters (i.e., temperature-independent snow intercept parameter, doubling number of concentrations of ice, and ice crystal diameter) within the explicit parameterization scheme i.e., the WRF Single-Moment 6-class (WSM6). It is shown that the experiment with enhanced ice mass concentration and temperature-independent snow intercept parameter produces the strongest and weakest storms, respectively. The results suggest that the distributions of hydrometeors are also impacted by the limited changes introduced in the microphysical scheme (e.g., the quantitative amount of snow drastically reduced to 0.1-0.2 g kg -1 when the intercept parameter of snow is made independent of temperature). It is noted that the model holds ice at a warmer temperature for a longer time with a temperature-independent intercept parameter. These variations in hydrometeor distribution in the eyewall region of the storm affect diabatic heating and vertical velocity structure and modulated the storm intensity. However, irrespective of the microphysical changes the quantitative amount of graupel hydrometeors remained nearly unaffected. Finally, the indirect effect of microphysical modifications on storm intensity through angular momentum and cloud torques is examined. A formulation to predict the short-term changes in the storm intensity using a parcel segment angular momentum budget method is developed. These results serve to elucidate the indirect impact of microphysical modifications on tropical cyclone intensity changes through modulation in cloud torque magnitude.

Item Type: Article
Additional Information: Copyright of this article belongs to American Meteorological Society.
Uncontrolled Keywords: Advanced researches; Angular momentum budget; Cloud microphysics; Cloud-resolving; Control experiments; Data sets; Diabatic heating; Eyewall; Hurricane intensity; Hurricane-intensity forecast; Ice crystals; Ice mass; Indirect effects; Initial conditions; Intensity forecasts; Intercept parameters; Mesoscale model; Microphysical parameters; Model results; Numerical simulation; Numerical weather prediction/forecasting; Parameterization schemes; Rain rates; Rainfall; Storm intensity; Tropical cyclone intensity change; Vertical velocity; Weather Research and Forecasting models, Angular momentum; Clouds; Experiments; Hurricanes; Ice; Physics; Rain; Snow; Storms; Torque, Weather forecasting, atmospheric structure; climate prediction; cloud microphysics; computer simulation; data set; hurricane; hydrometeorology; numerical method; parameterization; precipitation intensity; storm track; weather forecasting
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 11 Aug 2014 11:01
Last Modified: 11 Aug 2014 11:01
URI: http://moeseprints.incois.gov.in/id/eprint/690

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