d. Open access institutional repositoriesThe AMS understands there is increasing demand for institutions to provide open access to the published research being produced by employees, such as faculty, of that institution. In recognition of this, the AMS grants permission to each of its authors to deposit the definitive version of that author's published AMS journal article in the repository of the author's institution provided all of the following conditions are met: The article lists the institution hosting the repository as the author's affiliation.  The copy provided to the repository is the final published PDF of the article (not the EOR version made available by AMS prior to formal publication; see section 6).  The repository does not provide access to the article until six months after the date of publication of the definitive version by the AMS.  The repository copy includes the AMS copyright notice. T he Deep Propagating Gravity Wave Experiment (DEEPWAVE) was the first comprehensive measurement program devoted to quantifying the evolution of gravity waves (GWs) arising from sources at lower altitudes as they propagate, interact with mean and other wave motions, and ultimately dissipate from Earth's surface into the mesosphere and lower thermosphere (MLT). Research goals motivating the DEEPWAVE measurement program are summarized in Table 1. To achieve our research goals, DEEPWAVE needed to sample regions having large horizontal extents because of large horizontal GW propagation distances for some GW sources. DEEPWAVE accomplished this goal through airborne and ground-based (GB) measurements that together provided sensitivity to multiple GW sources and their propagation to, and effects at, higher altitudes. DEEPWAVE was performed over and around the GW "hotspot" region of New Zealand (Fig.1, top) during austral winter, when strong vortex edge westerlies provide a stable environment for deep GW propagation into the MLT.DEEPWAVE airborne measurements employed two research aircraft during a core 6-week airborne field program based at Christchurch, New Zealand, from 6 June to 21 July 2014. The National Science 425MARCH 2016 AMERICAN METEOROLOGICAL SOCIETY | Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V (GV) provided in situ, dropsonde, and microwave temperature profiler (MTP) measurements extending from Earth's surface to ~20 km throughout the core field program (see Table 2). The GV also carried three new instruments designed specifically to address DEEPWAVE science goals: 1) a Rayleigh lidar measuring densities and temperatures from ~20 to 60 km, 2) a sodium resonance lidar measuring sodium densities and temperatures from ~75 to 100 km, and 3) an advanced mesosphere temperature mapper (AMTM) measuring temperatures in a horizontal plane at ~87 km with a field of view (FOV) of ~120 km along track and 80 km cross track. AMTM measurements were augmented by two side-viewing infrared (IR) airglow "wing" cameras also viewing an ~87-km altitude that extended the cross-track FOV to ...

The North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe.

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SUMMARYThe Kim-Arakawa orographic gravity-wave drag parametrization scheme, which is a component of the US Navy's NOGAPS ALPHA (Navy Operational Global Atmospheric Prediction System, Advanced-Level Physics and High Altitude), is extended to include the effects of orographic anisotropy and low-level flow blocking. The algorithms to calculate the orographic statistics needed for the parametrization are also revised. The extended scheme is evaluated against mountain waves explicitly simulated with COAMPS † (Coupled Ocean/Atmosphere Mesoscale Prediction System) of NRL (Naval Research Laboratory).Mountain-wave simulations over Boulder, Colorado, USA, are used for representing realistic situations of different wave activity including severe downslope windstorms. The simulations are area-averaged and interpolated to the vertical grid of NOGAPS, and are used as the input to the extended Kim-Arakawa scheme. The scheme is calibrated by comparing the parametrized vertical distribution of the momentum fluxes with the counterpart obtained from the explicit mesoscale simulations. Overall, the calibrated scheme successfully represents the simulated magnitudes and vertical divergences of the momentum fluxes. A flow regime diagram is constructed utilizing a time series of the simulations to further evaluate the parametrization. The robustness of the orographic statistics, together with an approximate method to improve it, are also addressed.

Numerical model simulations of idealized and observed flows are used to investigate the dynamics of low-level jet streams that form in stratified flow downstream of the vertex of large elliptical barriers such as the southern tip of Greenland, hereafter referred to as ''tip jets''. The tip jet dynamics are governed by conservation of Bernouli function as parcels accelerate down the pressure gradient during orographic descent. In some circumstances, the Greenland tip jet is influenced by baroclinic effects such as differential horizontal (cross-stream) thermal advection and/or vertical shear. In contrast, in the barotropic situation upstream flow is diverted around and over the obstacle into laminar (Bernouli conservation) and turbulent (Bernouli deficit) regimes, respectively. In both situations, a downstream geostrophic balance is achieved, characterized by baroclinicity and vertical shear associated with the surface-based tip-jet front. The strength of the tip-jet is most sensitive to changes in the basic state dimensionless mountain height (Nh/U) and Rossby number, underscoring the importance of the orographic deflection of airstreams and Lagrangian accelerations on the slope. Enhanced surface-based forcing of the ocean circulation occurs in the region of the tip jet core through large air-sea energy exchange (upward surface-heat fluxes >800 W m−2), and at the tip jet flank through localized surface stress forcing.