AVAPS Users Group Meeting - April 2025

​NSF NCAR dropsondes at the center of storms

Hurricanes are among the most dangerous and destructive weather phenomena impacting communities along all eastern and southern coastlines. They require close monitoring and detailed observations to be able to provide early and accurate predictions of their expected strength and their location of landfall. Aircraft launched dropsondes are one of the most important observing systems, which are carried into storms by hurricane hunter aircraft and released to provide information about the vertical structure of the temperature, humidity, and winds and they accurately report the surface pressure in the eye of a storm.

Dropsondes measuring winds were developed at NSF NCAR over 50 years ago and are still one of the important tools to study our atmosphere, not just in extreme conditions such as hurricanes, but in any region, where observations from land are difficult to make. That includes the oceans, which cover two thirds of the planet’s surface and land areas, where observations from the ground are difficult to make. Although wind finding dropsondes were first designed and built over 5 decades ago, their development continues. Today’s measurements achieve an unprecedented level of accuracy, and their reliability makes them the go-to instrument for expensive deployments such as flying manned aircraft into hurricanes and atmospheric rivers. This level of technology has been achieved by a team of outstanding engineers and scientists, that continuously look for the best available technology. Their work is closely integrated with the scientific and observational community to meet their needs.

During the annual AVAPS® users group meetings, the community discusses the current state of science and technology of in situ weather observations. The 27th AVAPS® meeting took place in April 2025 with 84 participants in person and online. Hurricane hunters from NOAA and the Air Force reported their recent experiences, and national and international research groups shared results of their recent studies. The core of the discussions focused on advancing our observational capabilities and broadening our scientific understanding. In addition, several private sector companies participated in this meeting, who serve both as suppliers of instrumentation and as developers of new commercial applications.

Over the past years, almost all users of the NSF NCAR developed dropsonde, which is mass produced and sold by Vaisala, have completed the transition to the smaller NRD41 model. This latest development jump moved the global dropsonde community to the latest and most trustworthy dropsonde model coming out of NSF NCAR. NOAA and the Air Force reported significantly higher numbers of successful soundings during their last operational seasons, which had been one of the main drivers for this switch.

 NSF NCAR continues to innovate and presented the most recent software and hardware developments, which NSF NCAR will make available to the larger scientific community soon. Aside from hardware and software developments, NCAR also presented procedures to evaluate the data quality. Instruments released from aircraft into hazardous atmospheric conditions must generate reliable observations and must be free from artifacts that may occur in these extreme conditions. A critical review of the observations under these conditions and close data management are as important as the observations themselves. 

This year’s meeting had the most scientific presentations ever and covered observations in the Pacific and Atlantic basins and studies of air-sea turbulent fluxes in the boundary layer, which are the main drivers for hurricanes. There are also dropsonde developments by other companies, observations using air-launched Unmanned Aerial Systems (UAS), and long duration profiling balloons, which may also include some dropsondes in the future. These presentations underscore the importance of high quality in situ profiling data to better forecast storms over the oceans and of the role that NSF NCAR plays in fostering stimulating scientific discussions and developments.

With these activities, NSF NCAR remains a national and global center for instrument development, deployment of unique observing systems, discovery of new science, and managing of the observational data for use in current and future research to advance our understanding of our changing and sometimes hazardous environment.