The Performance and Data Utility of an Airborne Doppler Wind Lidar in Tropical Cyclone Environments

Although meteorological observations in and near tropical cyclones (TC) have improved in both quality and density, there remain important data-sparse regions that need to be sampled . While Instruments flown on the NOAA’s P3 Orion Hurricane Hunter Aircraft such as the Tail Doppler Radar (TDR) provide comprehensive coverage of the wind field in many areas of the TCs with precipitation, the radar has a difficult time making wind observations where there is no precipitation. This includes significant parts of the TC boundary layer and regions such as moats between the eyewall and outer rainbands or secondary eyewall.

The airborne Doppler Wind Lidar (DWL) is an instrument that can provide this missing information. A coherent DWL measures the motion of aerosols along a laser beam above or below the aircraft to provide line-of-sight (LOS) velocities which in turn are converted to 3-dimensional wind profiles with horizontal spacing of as little as 3 km. In addition, the DWL is able to collect wind measurements down to 100m above the sea surface with vertical resolutions as fine as 25-50 m.

In the 2015 through 2017 hurricane seasons, an airborne Doppler Wind Lidar (DWL) was flown for the first time on the P3 Orion (P3DWL) into TCs of different intensities in the Atlantic and East Pacific. The P3DWL collected over 2000 boundary layer wind profiles in three tropical cyclones: Hurricane Earl (2016), Tropical Storm Javier (2016), and Hurricane Maria (2017).

During this presentation we will discuss the assumptions and challenges involved in making DWL measurements in and around TCs as well as in interpreting the results from the missions noted above and the eventual utility of the data for researchers and modelers. One of the challenges that will be discussed is the discrimination between hydrometeor vertical motion and the attendant air mass velocities.