DEEPWAVE 2014; Observing Gravity Waves from the Troposphere to the Mesosphere

The recent DEEPWAVE field project in New Zealand ran from May 25 to July 28, 2014. Its objectives were to observe, understand and predict the deep propagation of gravity waves from the Troposphere into the Stratosphere, Mesosphere and Thermosphere. In addition to surface, balloon and satellite-borne sensors, the project used two research aircraft with airborne sensors; the NSF/NCAR Gulfstream V (GV) and the German DLR Falcon. The GV was uniquely instrumented to observe wave launching (dropsondes), waves properties in the low stratosphere (flight level winds, pressure and temperature), waves in the middle stratosphere (MTP and Rayleigh Lidar) and waves near the mesopause (Sodium Lidar and OH IR mapper). In this report, we describe the first results and discoveries from the DEEPWAVE project. An emerging hypothesis from the DEEPWAVE project is that the deep propagation of gravity waves over NZ is controlled by a “valve layer” from 16 to 20km. During about ¾ of the strong wave generation events, the wind speed is too small there and the waves become non-linear, steepen and break. The remaining ¼ time, the waves remain linear and pass through maintaining their vertical energy flux. This hypothesis is tested using flight data and a numerical model. A newly designed spatial filter is used to identify the gravity waves in the complex numerical model output.