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In-situ measurements in deep convective systems, tropical cyclones, etc., are difficult to perform. Few if any people would like to fly a small aircraft close to its core, and radiosondes or larger balloons would be ripped to pieces. Even flying high above the top of such a system may not be a pleasant idea. However, with unmanned aerial vehicles (UAVs or drones), perhaps higher risks can be taken than with manned aircraft. And whereas radiosondes cannot be launched, dropsondes should not be a problem.

Are there any projects, either operationally or for research purposes, that involve dropping sondes from UAVs flying above deep convective systems, in order to measure profiles of pressure, temperature, as well as cloud and precipitation properties?

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    $\begingroup$ The Gale UAS is being developed for this purpose, but I don't know if any such dropsonde missions have been performed yet. $\endgroup$ – called2voyage Apr 15 '14 at 18:35
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    $\begingroup$ University of Colorado has a UAS they were going to use in VORTEX2, but due to the limited area they were approved to fly it in, I don't believe it ever flew a mission with V2. vortex2.org/instruments/display.php?name=UAS $\endgroup$ – casey Apr 25 '14 at 2:44
  • $\begingroup$ Is this question about UAVs specifically? Dropsondes are almost routinely deployed in hurricanes during reconnaissance flights, see: aoml.noaa.gov/hrd/data_sub/hurr.html $\endgroup$ – milancurcic Dec 5 '14 at 14:03
  • $\begingroup$ @IRO-bot I was under the impression that living pilots are reluctant to fly over hurricanes. Perhaps I'm wrong. $\endgroup$ – gerrit Dec 5 '14 at 15:54
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    $\begingroup$ They actually launch radiosondes into deep convection too. In fact, NSSL had (or has?) a refitted ambulance just for this purpose. Search MGAUS NSSL. Not much information on it, but it's out there. $\endgroup$ – JeopardyTempest Nov 6 '17 at 9:26
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NOAA flies routine dropsonde missions into tropical convection if there is anticipated threat to land. You can find information about these missions in the routine NHC updates for each storm. This data is used in estimation of hurricane intensity and some of the models assimilate this data to improve storm track and intensity forecasts.

You can learn more about NOAA's hurricane hunters here.


Dropsonde missions over the continental US are problematic. The mesoscale predictability experiment (MPEX) use dropsondes to determine if better upper air observations could improve predictability in the mesoscale. One big issue they had is restrictions in where they could drop from the FAA. They had to provide notice well in advance of the flights and could only conduct missions during certain time windows. This provided big restrictions in dropsonde missions and would probably make it unsuitable for drops into deep convection (though one might argue with air traffic routing around such convection, that would make drops feasible from an FAA standpoint).

There were some recent talks about MPEX at the 27th Conference on Severe Local Storms in a session about MPEX. In particular, a talk by Morris Weisman (video) talks a bit about the dropsonde missions.


From another perspective was the DC3 project, which I provided nowcasting in support of aircraft operations. This project didn't use dropsondes, but instead used aircraft in vertical flight profiles to collect observations from near-surface to tropopause levels. These profiles were in the vicinity of deep convection, but not within. This project was primarily interested in how the chemical composition of near-surface air was modified by convection and then transported in upper air outflow.

These aircraft were not dropping dropsondes but I'm not confident a UAV would have been able to fly too much closer to convection to drop into the storms.


In summary, maritime dropsondes are common for getting in-situ measurements of tropical convection, but for continental applications FAA restrictions on dropping things from airplanes makes routine dropsonde missions unfeasible (and I'm assuming these would be done by UAVs as getting NSF aircraft assets to do this would be restricted to short term experiments and not routine operational missions).

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