An Overview of the Tropical Cyclone Data Assimilation Activities at NOAA’s Hurricane Research Division

Altug Aksoy*

At NOAA’s Hurricane Research Division (HRD), a variety of ensemble-based data assimilation activities are being pursued, primarily focusing on the high-resolution observations that are collected within tropical cyclones (TCs) during research and operational flight missions. For this purpose, the Hurricane Ensemble Data Assimilation System (HEDAS) was developed to combine a square-root ensemble Kalman filter with NOAA’s Hurricane Weather Research and Forecasting (HWRF) modeling system, and later augmented with a storm-relative observation processing capability. Observations that are routinely assimilated in HEDAS are obta ined from NOAA P-3 and G-IV as well as Air Force Reserve C-130 research and reconnaissance flights (dropwindsonde, flight level, Stepped-Frequency Microwave Radiometer [SFMR], and tail Doppler radar [TDR]), NASA and NOAA unmanned aircraft system (UAS) platforms such as the Global Hawk and the experimental Coyote, satellite Atmospheric Motion Vectors (AMVs), and retrieved thermodynamic profiles from the Atmospheric InfraRed Sounder (AIRS) and Global Positioning System (GPS) Radio Occultation.

This talk will first introduce the general philosophy and approach adopted by HRD to tackle the problem of vortex-scale TC data assimilation and explain some of the details of HEDAS and its observation processing system, followed by results from specific research projects actively undertaken by HRD in recent years, such as:

  • Data impact studies for the NOAA P-3 and G-IV TDR observations, Global Hawk dropsonde and remote sensing observations, experimental Coyote observations, AMVs, and AIRS retrievals;
  • Assimilation of all-sky radiance observations in tropical cyclones;
  • Optimization of HEDAS for improved surface wind analyses;
  • Observing system simulation experiments (OSSEs) to optimize sampling strategies for various TC aircraft platforms; and
  • Parallelization and algorithm development activities in HEDAS.

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    *Preference: Oral