This is a collection of completed and ongoing projects. Please refer to the specific details below.
Overview
Since 2008, my primary research focus has been on tropical cyclone (TC) data assimilation. My work spans the development of the HEDAS system, conducting observing system experiments (OSEs) with cutting-edge platforms, and creating specialized algorithms for vortex initialization.
Below is a summary of my key contributions organized by research area.
Development of Ensemble Kalman Filter (EnKF) Techniques
I led the development of the Hurricane Ensemble Data Assimilation System (HEDAS), an advanced system designed to assimilate inner-core observations at vortex scales. This work established the baseline for high-resolution vortex initialization in HWRF.
- Aberson, Aksoy et al. (2015). Assimilation of high-resolution tropical cyclone observations… Evaluation of 2008–11 HWRF forecasts. Mon. Wea. Rev. doi:10.1175/MWR-D-14-00138.1
- Aksoy et al. (2013). Assimilation of high-resolution tropical cyclone observations with an ensemble Kalman filter using HEDAS: Evaluation of the 2008-2011 vortex-scale analyses. Mon. Wea. Rev. doi:10.1175/MWR-D-12-00194.1
- Vukicevic, Aksoy et al. (2013). Joint impact of forecast tendency and state error biases in ensemble Kalman filter data assimilation of inner-core tropical cyclone observations. Mon. Wea. Rev. doi:10.1175/MWR-D-12-00211.1
- Aksoy et al. (2012). The HWRF Hurricane Ensemble Data Assimilation System (HEDAS) for high-resolution data: The impact of airborne Doppler radar observations in an OSSE. Mon. Wea. Rev. doi:10.1175/MWR-D-11-00212.1
Observing System Experiments (OSE) for TC Data Assimilation
I have conducted extensive evaluations of novel observing platforms, including unmanned aircraft systems (UAS) like the Global Hawk and Coyote, to quantify their impact on TC track, intensity, and structure forecasts.
- Sellwood, Sippel, & Aksoy (2023). Assimilation of Coyote small uncrewed aircraft system observations in Hurricane Maria (2017) using operational HWRF. Wea. Forecasting. doi:10.1175/WAF-D-22-0214.1
- Aksoy et al. (2022). Tropical cyclone data assimilation with Coyote uncrewed aircraft system observations, very frequent cycling, and a new online quality control technique. Mon. Wea. Rev. doi:10.1175/MWR-D-21-0124.1
- Christophersen, Aksoy et al. (2018). Composite impact of Global Hawk unmanned aircraft dropwindsondes on tropical cyclone analyses and forecasts. Mon. Wea. Rev. doi:10.1175/MWR-D-17-0315.1
- Christophersen, Aksoy et al. (2017). The impact of NASA Global Hawk unmanned aircraft dropwindsonde observations on tropical cyclone track, intensity, and structure: Case studies. Mon. Wea. Rev. doi:10.1175/MWR-D-16-0332.1
Specialized Techniques for TC Data Assimilation
To address the unique challenges of the hurricane inner core, I have developed specialized numerical and processing techniques, ranging from storm-relative observation processing to axisymmetric initialization methods.
- Aksoy et al. (2017). Axisymmetric initialization of the atmosphere and ocean for idealized coupled hurricane simulations. J. Adv. Model. Earth Syst. doi:10.1002/2017MS000977
- Aksoy et al. (2017). Parallel direct solution of the ensemble square-root Kalman filter equations with observation principal components. J. Atmos. Oceanic Technol. doi:10.1175/JTECH-D-16-0140.1
- Aksoy (2013). Storm-relative observations in tropical cyclone data assimilation with an ensemble Kalman filter. Mon. Wea. Rev. doi:10.1175/MWR-D-12-00094.1
- Lorsolo & Aksoy (2012). Wavenumber analysis of azimuthally distributed data: Assessing maximum allowable gap size. Mon. Wea. Rev. doi:10.1175/MWR-D-11-00219.1
General Contributions
Invited reviews and broad assessments of the state of the art in tropical cyclone data assimilation and field programs.
- Zawislak, J. et al. (2022). Accomplishments of NOAA’s Airborne Hurricane Field Program. Bull. Amer. Meteor. Soc. doi:10.1175/BAMS-D-20-0151.1
- Christophersen, H., Sippel, J., Aksoy, A., & Baker, N. (2022). Recent advancements for tropical cyclone data assimilation. Ann. N.Y. Acad. Sci. doi:10.1111/nyas.14873
- Wick, G. A. et al. (2020). NOAA’s Sensing Hazards with Operational Unmanned Technology (SHOUT) Experiment. Bull. Amer. Meteor. Soc. doi:10.1175/BAMS-D-18-0257.1
- Cione, J. J. et al. (2020). Eye of the Storm: Observing Hurricanes with a Small Unmanned Aircraft System. Bull. Amer. Meteor. Soc. doi:10.1175/BAMS-D-19-0169.1
- Rogers, R. F. et al. (2013). NOAA’s Hurricane Intensity Forecasting Experiment: A Progress Report. Bull. Amer. Meteor. Soc. doi:10.1175/BAMS-D-12-00089.1