The Impact of Low-Cost Lagrangian Drifters on Analyses and Short-Range Forecasts of Hurricane Floyd (1999)

ENSCO, Inc. is designing and developing a new observing system known as Global Environmental Micro Sensors (GEMS). The main component of the GEMS system is an ensemble of airborne probes that will take measurements of pressure, temperature, moisture, and wind velocity as they are carried passively by the wind at various levels in the atmosphere. In order to maximize the time probes remain airborne, their design is based on a self-contained, super pressure balloon filled with helium to make them neutrally buoyant.

Each probe will have on-board power, communications, limited processing, and sensing capabilities using one-way RF communication with low-earth orbiting satellites to provide data exfiltration. The probes will contain micro global positioning systems for wind velocity measurements and micro electro mechanical system sensors for pressure, temperature, and moisture measurements. ENSCO has developed initial prototypes that are currently being field-tested over east central Florida in a collaborative effort funded in part by the National Aeronautics and Space Administration.

The novel aspect of the GEMS system is the integration of micro and eventually nanotechnology to develop probes with significantly lower mass, size, and cost. Given these attributes, large ensembles of probes could be deployed for research and operational missions thereby greatly expanding the amount of in situ observations, especially over data sparse oceanic regions. The GEMS system would be ideal for adaptive or targeted observing campaigns such as tropical cyclone reconnaissance where it is only cost effective and practical to obtain in situ, high-resolution, spatial and temporal measurements over limited domains.

This paper focuses on a series of high resolution, mesoscale observing system simulation experiments during the initial genesis and rapid strengthening of Hurricane Floyd over the central Atlantic Ocean from 6-12 September 1999. The results show that GEMS data can be used to map the four dimensional storm structure and near real-time intensity changes over very small time scales. Additionally, data assimilation results indicate that high-resolution GEMS data can also be used to initialize and spin up a strong tropical cyclone from a weak low-pressure system over a 6-hour data assimilation window, without using a tropical cyclone bogussing scheme. Such a study could help to identify the appropriate mix of data from current and future observing systems (including dropsondes and manned/unmanned aircraft as well as current/next generation remote sensor) that will maximize the impact on tropical cyclone analysis and forecasting.. If a GEMS system can be implemented practically with such capability in a cost-effective manner, it could provide more than just incremental improvements in the ability to observe and predict tropical cyclones for research and operational meteorology.