Atmospheric rivers are narrow, filamentary structures of water vapor in the atmosphere responsible for 90% of the meridional poleward water vapor transport. Recent studies demonstrated that these atmospheric rivers were present and played an important role during many recent major flooding events along the California coast. Current routine monitoring of the events include satellite observations of integrated water vapor content and coastal weather stations with wind profilers and Global Positioning System meteorological (GPS-Met) packages providing integrated water vapor flux estimates. A significant gap exists, however, in description of the structure of the events offshore. During dedicated experiments, observations from the NOAA P-3 aircraft using dropsondes have been obtained. Targeted observations such as these during events have demonstrated the potential for significant improvements in precision forecasting of the intensity and location of major precipitation. This talk presents a concept for inclusion of Unmanned Aircraft Systems (UAS) into an integrated observing system (IOS) for atmospheric river events being explored as part of the NOAA UAS project.

Mission concepts include sampling with both high and low altitude aircraft. Deployment of dropsondes from a high altitude long endurance (HALE) UAS would enable continuous monitoring of the evolution of events as the approach landfall over periods of up to 30 hours. Small low altitude aircraft would provide sampling of heat and moisture fluxes into the rivers from the ocean surface below as well as potential transects through the rivers at multiple levels. Integration of these observations would provide an unprecedented description of the structure of the events for application to forecasting efforts. Through partnership with Scripps Institution of Oceanography, a flux measurement system for small UAS is being developed and tested. Current mission plans and timelines will be presented along with the status of the flux measurement capability. Connection with other satellite and surface-based atmospheric river threat indicators being developed as part of the NOAA Hydrometeorological Testbed (HMT) will also be explored.