Mesospheric Response to Strong and Weak Orographic Forcing During the DEEPWAVE Project

Abstract:

Gravity waves (GWs) are one of the main drivers of the Earth’s atmosphere as they vertically couple energy and momentum throughout its successive layers. Orographic forcing is a well-known source for these waves which can impact the stratosphere (Eckermann and Preusse, 1999), and even the mesosphere (Smith et al., 2009).

During the months of June and July 2014, a large-scale project named DEEPWAVE took place in New Zealand. This international program focused on investigating the generation and deep propagation of atmospheric gravity waves, especially over the mountain range of the Southern Alps. A series of instruments was operated at several ground-based locations and on-board the NSF Gulfstream V aircraft. 25 nighttime research flights were performed to explore possible wave sources and their effects on the middle and upper atmosphere.

On 2 consecutive nights (29^th and 30^th June), research flights 12 and 13 were conducted over New Zealand South Island to compare the effects of 2 different wind forcing: strong during the first flight, then reduced on the following day. As the GV aircraft was repetitively flying over the Southern Alps, the mesospheric gravity wave field was measured using a series of newly developed instruments (Advanced Mesospheric Temperature Mapper, IR side cameras and lidars). This presentation will investigate the differences between the gravity waves observed during these 2 flights and the impact of distinct orographic forcing on the upper atmosphere.