Preliminary Evaluation of the First Rocket-Deployed Dropsonde Observations in a Tropical Cyclone: A Project EXOTICCA Case Study in STY Mujigae (2015)

On October 3, a meteorological rocket was launched for the first time into a tropical cyclone in the east of Hainan Island. Four dropsondes were subsequently deployed simultaneously from the rocket and sent the collected data during descent into Typhoon Mujigae. Detailed profiles were obtained in the typhoon outflow layer, mid-tropospheric wave-like oscillations and boundary layer low-level jet in the left quadrant of Mujigae at a radius of 100 km. Peak winds in the outflow and boundary layer jets were nearly identical at 26 m/s. Surface winds were 18 m/s, just in excess of gale force. Concurrent Haikou radar observations indicated that the dropsondes fell along a trajectory in between and parallel to two small ranbands in the typhoon core periphery. Designed as a proof-of-concept mission, the four profiles obtained at a 1 Hz data rate were virtually indistinguishable, except for the boundary layer where small-scale turbulent eddies, possibly previously-described roll vortex circulations. Outflow winds from the dropsondes were 50% greater than high-level CIMSS AMV winds in the 200-300 mb layer, while estimated 10-m surface winds were 30% greater than ASCAT scatterometer surface wind observations. For all four sondes, only 32 lines of bad data had to be rejected out of 4500 total seconds, while approximately 400 data drop-outs occurred, representing less than 1% data loss during the 19 minute descent times of the 4 good sondes. Thus, the dropsonde data based on rocket platform in this experiment have showed high quality and high precision and qualified for offshore tropical cyclone experiment. Future plans call for a more powerful rocket to be use to deploy more dropsondes from above 20 km altitude to detect the inner structure of tropical cyclone.