An important source of error in numerical model forecasts is believed to be linked to the various parameterized diabatic processes. Past research efforts have largely focused on warm conveyer belt dynamics in both mid-latitude baroclinic maritime cyclones and tropical cyclones undergoing extra-tropical transition. The majority of theoretical development and research in this area focused on dry atmospheric dynamics – however, this effort will advance our understanding beyond dry adiabatic potential vorticity arguments into moist thermodynamic processes. Potential vorticity advection and hydrostatic development largely address propagation phase speed while consideration of non-hydrostatic moist diabatic and multi-scale processes is essential to understanding storm intensity and effects such as gale and storm force winds, precipitation rate and flooding, and other hazardous weather phenomena. Recently, there is increased interest in characterization and predictability of atmospheric rivers – long, narrow streams of meridional and poleward moisture transport. Although the source regions for enhanced atmospheric moisture have been observed in microwave imagery, from a predictive perspective very little research has gone into the air-sea flux and transport processes leading to the formation of the “headwaters” of these features. Enhanced moisture plume–waveguide interactions are tied to a variety of disturbances, including Fall/Winter explosive cyclogenesis over western boundary currents, Winter sequences of intense atmospheric rivers, Summer/Fall transitioning tropical cyclones (TCs), Predecessor Rain Events (PRE) ahead of TCs, maritime deepening of extratropical cyclones, and diabatic Rossby vortices. Each of these interactions may strongly modify the PV waveguide and the role of ocean boundary currents and mesoscale features and variability on intensification in otherwise similar events has had minimal attention.
This Departmental Research Initiative (DRI) intends to increase our understanding of the physical processes associated with air-sea interaction and diabatic amplification (in which energy is transported through latent heating due to water vapor transport) that perturb the waveguide along sloping mid-latitude fronts interacting with warm water vapor reservoirs in the tropics, which in turn leads to strong baroclinic development in maritime midlatitude storms and additionally can launch deep propagating Rossby and gravity waves into the stratosphere. In particular, ONR will contribute to a large, multi-agency and international effort to better understand the role of ocean surface variability and vertical or slant-wise transport of moisture into the warm conveyer belt region of mid-latitude maritime cyclogenesis and decay by focusing on upstream development in atmospheric river source regions. It is anticipated that collaborative efforts will include a sea-based observational perspective, multi-modal air and space-based profiles, and unique moist dynamics sensitivity analysis and atmospheric and oceanic predictability modeling studies.
Objective
The basic premise of the SAFARI DRI and collaborating projects is that, although significant improvement has been made in the average forecast skill of operational numerical ocean and weather prediction models, systematic errors continue, and that instances of extreme forecast failures or forecast “busts” do occur. Recent publications show that these skill drops are often associated with Rossby-wave breaking or waveguide perturbations in the midlatitudes waveguide that are initiated far upstream and that result in upscale energy transfer and formation of atmospheric rivers. The atmospheric river related processes we seek to understand are further affected by enhanced baroclinicity and enthalpy flux associated with air-sea processes and upper ocean temperature structure and variability. The SAFARI DRI will participate in and coordinate with the dynamic process studies and specifically focus on processes associated with maritime enthalpy flux and advective transport at the thermodynamic source regions.
In SAFARI, it is hypothesized that improving our fundamental understanding of atmospheric rivers will lead to better simulations of the global hydrological cycle and more skillful high impact weather forecasts from local to extended ranges. In particular, SAFARI expects that improved constraints in air-sea coupled processes that modulate formation and predictability of atmospheric rivers can be directly transitioned to improve model prediction systems. Specific proposals that seek to join this effort should describe how research will improve understanding in these factors:
How atmospheric rivers are initiated and sustained
The structure and amplitude of the source disturbances and their thermodynamic profiles
The coupled exchange processes, dynamics, and non-local or large-scale phenomena that control the formation and evolution of ARs at timescales from days to weeks
How multiple factors, together with initial condition uncertainty, model error, and multi-scale coupled processes impact predictability and prediction skill
The air-sea interaction and air-mass diabatic modulation that occur from diurnal through sub-seasonal timescales
Proposed methodologies should consider one or more of the following approaches in addressing the above studies:
Contributing to, and/or leveraging, a successful observing strategy for measurements of air-sea coupled processes, water vapor budget, and moisture flux convergence from the boundary layer into the free troposphere. Combining multi-modal in-situ and remote sensing (sea, aircraft, satellites) to understand the importance of cloud diabatic heating on moisture maintenance and transport.
Beyond the measurements of key dynamic and physical processes, a concentrated effort will be to evaluate predictability in terms of impacts to data assimilation, initial condition sensitivities, utility of ensemble prediction systems, and improved model strategies and parameterizations.
Predictability tools, including moist adjoint, ensemble-based, and machine learning methods, should be used to diagnose the behavior of rapidly growing perturbations as well as the best sampling strategy for the two-way interaction between clouds and mesoscale dynamics in and around atmospheric rivers, warm conveyer belts, and lower tropospheric/Marine Boundary Layer. Efforts are encouraged to also address representation of the cloud microphysics to facilitate analysis of perturbation growth at much smaller scales than have been previously considered.
State of the art numerical models are nonhydrostatic, allow accurate mesoscale representation, and offer variable resolution in global or regional areas. These dynamic model cores provide a tool that can, for the first time, directly simulate the multi-scale processes on a grid that is numerically non-dispersive, high order, but also computationally affordable to run highly realistic cases using the field data directly. Numerical simulations leveraging this technology should describe how variable resolution modeling can support improved research of this topic.
Request for Planning Letters
The first step in the DRI process is for prospective investigators to prepare planning letters. The purpose of the planning letters is to allow investigators to submit a short (three pages maximum) summary of their ideas on this topic for ONR to evaluate, provide technical feedback and indicate whether a full proposal would have a reasonable chance of success.
Refer to the current Marine Meteorology Planning Letter guidelines and indicate your desire to work with the SAFARI project and team. Please note "SAFARI Planning Letter ‘Your Last Name’" in your email subject line. If you do not receive acknowledged receipt within 10 days, please follow-up with a resend.
Important Dates
The foundational science team has been formed for the SAFARI DRI and science activities commenced in FY24. However, planning letters and full proposals for up to three-year efforts will be accepted on a rolling basis, as funding allows through the course of the SAFARI program.
All planning letters should be submitted by email to the ONR Marine Meteorology team: Josh Cossuth (joshua.h.cossuth.civ@us.navy.mil), Dan Eleuterio (daniel.p.eleuterio.civ@us.navy.mil), and Anna Wilson (anna.m.wilson84.civ@us.navy.mil). You may also write directly to the whole team at ONR.NCR.322MM@us.navy.mil.