Bhowmick, S. A., Agarwal, N., Ali, M. M., Kishtawal, C. M., & Sharma, R. (2019). Role of ocean heat content in boosting post-monsoon tropical storms over Bay of Bengal during La-Nina events.
Climate Dynamics, 52(12), 7225–7234.
Abstract: This study aims to analyze the role of ocean heat content in boosting the post-monsoon cyclonic activities over Bay of Bengal during La-Niña events. In strong La-Niña years, accumulated cyclone energy in Bay of Bengal is much more as compared to any other year. It is observed that during late June to October of moderate to strong La-Nina years, western Pacific is warmer. Sea surface temperature anomaly of western Pacific Ocean clearly indicates the presence of relatively warmer water mass in the channel connecting the Indian Ocean and Pacific Ocean, situated above Australia. Ocean currents transport the heat zonally from Pacific to South eastern Indian Ocean. Excess heat of the southern Indian Ocean is eventually transported to eastern equatorial Indian Ocean through strong geostrophic component of ocean current. By September the northward transport of this excess heat from eastern equatorial Indian Ocean to Bay of Bengal takes place during La-Nina years boosting the cyclonic activities thereafter.
DiNapoli, S. (2010).
Determining the Error Characteristics of H*WIND. Master's thesis, Florida State University, Tallahassee, FL.
Abstract: The HRD Real-time Hurricane Wind Analysis System (H*Wind) is a software application used by NOAA's Hurricane Research Division to create a gridded tropical cyclone wind analysis based on a wide range of observations. One application of H*Wind fields is calibration of scatterometers for high wind speed environments. Unfortunately, the accuracy of the H*Wind product has not been studied extensively, and therefore the accuracy of scatterometer calibrations in these environments is also unknown. This investigation seeks to determine the uncertainty in the H*Wind product and estimate the contributions of several potential error sources. These error sources include random observation errors, relative bias between different data types, temporal drift resulting from combining non-simultaneous measurements, and smoothing and interpolation errors in the H*Wind software. The effects of relative bias between different data types and random observation errors are determined by performing statistical calculations on the observed wind speeds. We show that in the absence of large biases, the total contribution of all error sources results in an uncertainty of approximately 7% near the storm center, which increases to nearly 15% near the tropical storm force wind radius. The H*Wind analysis algorithm is found to introduce a positive bias to the wind speeds near the storm center, where the analyzed wind speeds are enhanced to match the highest observations. In addition, spectral analyses are performed to ensure that the filter wavelength of the final analysis product matches user specifications. With increased knowledge of these error sources and their effects, researchers will have a better understanding of the uncertainty in the H*Wind product, and can then judge the suitability of H*Wind for various research applications
Glazer, R. H. (2014).
The Influence of Mesoscale Sea Surface Temperature Gradients on Tropical Cyclones. Master's thesis, Florida State University, Tallahassee, FL.
Guimond, S. R. (2007).
A diagnostic study of the effects of trough interactions on tropical cyclone QPF. Master's thesis, Florida State University, Tallahassee, FL.
Abstract: A composite study is presented analyzing the influence of upper-tropospheric troughs on the evolution of precipitation in twelve Atlantic tropical cyclones (TCs) between the years 2000 � 2005. The TRMM Multi-Satellite Precipitation Analysis (TMPA) is used to examine the enhancement of precipitation within a 24 h window centered on trough interaction (TI) time in a shear-vector relative coordinate system. Eddy angular momentum flux convergence (EFC) computed from European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses is employed to objectively determine the initiation of a TI while adding insight, along with vertical wind shear, into the intensification of TC vortices. The relative roles of the dynamics (EFC and vertical wind shear) and thermodynamics (moist static energy potential) in TIs are outlined in the context of precipitation enhancement that provides quantitative insight into the “good trough”/“bad trough” paradigm. The largest precipitation rates and enhancements are found in the down-shear left quadrant of the storm, consistent with previous studies of convective asymmetries. Maximum mean enhancement values of 1.4 mm/h are found at the 200 km radius in the down-shear left quadrant. Results indicate that the largest precipitation enhancements occur with “medium” TIs; comprised of EFC values between 17 � 22 (m/s)/day and vertical wind shear Sensitivity tests on the upper vertical wind shear boundary reveal the importance of using the tropopause for wind shear computations when a TC enters mid-latitude regions. Changes in radial mean precipitation ranging from 29 � 40 % across all storm quadrants are found when using the tropopause as the upper boundary on the shear vector. Tests on the lower boundary using QuikSCAT ocean surface wind vectors expose large sensitivities on the precipitation ranging from 42 � 60 % indicating that the standard level of 850 hPa, outside of the boundary layer in most storms, is more physically reliable for computing vertical wind shear. These results should help to improve TC quantitative precipitation forecasting (QPF) as operational forecasters routinely rely on crude statistical methods and rules of thumb for forecasting TC precipitation.
Hart, R. E., Maue, R. N., & Watson, M. C. (2007). Estimating Local Memory of Tropical Cyclones through MPI Anomaly Evolution.
Mon. Wea. Rev., 135(12), 3990–4005.
Holbach, H. M., & Bourassa, M. A. (2014). The Effects of Gap-Wind-Induced Vorticity, the Monsoon Trough, and the ITCZ on East Pacific Tropical Cyclogenesis.
Mon. Wea. Rev., 142(3), 1312–1325.
Holbach, H. M., Uhlhorn, E. W., & Bourassa, M. A. (2018). Off-Nadir SFMR Brightness Temperature Measurements in High-Wind Conditions.
J. Atmos. Oceanic Technol., 35(9), 1865–1879.
Abstract: Wind and wave-breaking directions are investigated as potential sources of an asymmetry identified in off-nadir remotely sensed measurements of ocean surface brightness temperatures obtained by the Stepped Frequency Microwave Radiometer (SFMR) in high-wind conditions, including in tropical cyclones. Surface wind speed, which dynamically couples the atmosphere and ocean, can be inferred from SFMR ocean surface brightness temperature measurements using a radiative transfer model and an inversion algorithm. The accuracy of the ocean surface brightness temperature to wind speed calibration relies on accurate knowledge of the surface variables that are influencing the ocean surface brightness temperature. Previous studies have identified wind direction signals in horizontally polarized radiometer measurements in low to moderate (0�20 m s−1) wind conditions over a wide range of incidence angles. This study finds that the azimuthal asymmetry in the off-nadir SFMR brightness temperature measurements is also likely a function of wind direction and extends the results of these previous studies to high-wind conditions. The off-nadir measurements from the SFMR provide critical data for improving the understanding of the relationships between brightness temperature, surface wave�breaking direction, and surface wind vectors at various incidence angles, which is extremely useful for the development of geophysical model functions for instruments like the Hurricane Imaging Radiometer (HIRAD).
LaRow, T. (2013). An analysis of tropical cyclones impacting the Southeast United States from a regional reanalysis.
Reg Environ Change, 13(S1), 35–43.
Maue, R. N. (2004).
Evolution of Frontal Structure Associated with Extratropical Transitioning Hurricanes. Master's thesis, Florida State University, Tallahassee, FL.
Abstract: Many tropical cyclones move poleward, encounter vertical shear associated with the midlatitude circulation, and undergo a process called extratropical transition (ET). One of the many factors affecting the post-transition extratropical storm in terms of reintensification, frontal structure, and overall evolution is the upper-level flow pattern. Schultz et al. (1998) categorized extratropical cyclones according to two of the many possible cyclone paradigms in terms of the upper-level trough configuration: The Norwegian cyclone model (Bjerknes and Solberg 1922) associated with high-amplitude diffluent trough flow and the Shapiro-Keyser cyclone lifecycle (1990) with low-amplitude confluent troughs. Broadly speaking, the former category is associated with a strong, meridionally oriented cold front with a weak warm front while the latter lifecycle usually entails a prominent, zonally oriented warm front. However, as will be shown, simple antipode lifecycle definitions fail to capture hybrid or cross-lifecycle evolution of transitioned tropical cyclones. To exemplify the importance upper-level features such as jet streaks and troughs, a potential vorticity framework is coupled with vector frontogenesis functions to diagnose the interaction between the poleward transitioning cyclone and the midlatitude circulation. Particular focus is concentrated upon the evolution and strength of frontal fracture from both a PV and frontogenesis viewpoint. The final outcome of extratropical transition is highly variable depending on characteristics of the tropical cyclone, SSTs, and environmental factors such as strength of vertical shear. Here, three storms (Irene 1999, Fabian 2003, and Kate 2003) typify the inherent variability of one such ET outcome, warm seclusion. Very strong winds are often observed in excess of 50 ms-1 along the southwestern flank of the storm down the bent-back warm front. The low-level wind field kinematics are examined using vector frontogenesis functions and QuikSCAT winds. A complex empirical orthogonal function (CEOF) technique is adapted to temporally interpolate ECMWF model fields (T, MSLP) to overpass times of the scatterometer, an improvement over simple linear interpolation. Overall, the above diagnosis is used to support a hypothesis concerning the prevalence of hurricane-force winds surrounding secluded systems.
Keywords: Extratropical Transition, Frontogenesis, Fronts, Quikscat, Cyclone Lifecycles, Warm Seclusion, Frontal Fracture, Potential Vorticity, Hurricane Kate, Hurricane Irene, Hurricane Fabian, Tropical Cyclones
Misra, V., Selman, C., Waite, A. J., Bastola, S., & Mishra, A. (2017). Terrestrial and Ocean Climate of the 20th Century. In E. P. Chassignet, J. W. Jones, V. Misra, & J. Obeysekera (Eds.),
Florida's climate: Changes, variations, & impacts (pp. 485–509). Gainesville, FL: Florida Climate Institute.