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- Author or Editor: Ian Turner x
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Abstract
Proper behavior of physics parameterizations in numerical models at grid sizes of order 1 km is a topic of current research. Modifications to parameterization schemes to accommodate varying grid sizes are termed “scale aware.” The general problem of grids on which a physical process is partially resolved is called the “gray zone” or “terra incognita.” Here we examine features of the Mellor–Yamada–Nakanishi–Niino (MYNN) boundary layer scheme with eddy diffusivity and mass flux (EDMF) that were intended to provide scale awareness, as implemented in WRF, version 4.1. Scale awareness is provided by reducing the intensity of nonlocal components of the vertical mixing in the scheme as the grid size decreases. However, we find that the scale-aware features cause poorer performance in our tests on a 600-m grid. The resolved circulations on the 600-m grid have different temporal and spatial scales than are found in large-eddy simulations of the same cases, for reasons that are well understood theoretically and are described in the literature. The circulations [model convectively induced secondary circulations (M-CISCs)] depend on the grid size and on details of the model numerics. We conclude that scale awareness should be based on effective resolution, and not on grid size, and that the gray-zone problem for boundary layer turbulence and shallow cumulus cannot be solved simply by reducing the intensity of the parameterization. Parameterizations with different characteristics may lead to different conclusions.
Abstract
Proper behavior of physics parameterizations in numerical models at grid sizes of order 1 km is a topic of current research. Modifications to parameterization schemes to accommodate varying grid sizes are termed “scale aware.” The general problem of grids on which a physical process is partially resolved is called the “gray zone” or “terra incognita.” Here we examine features of the Mellor–Yamada–Nakanishi–Niino (MYNN) boundary layer scheme with eddy diffusivity and mass flux (EDMF) that were intended to provide scale awareness, as implemented in WRF, version 4.1. Scale awareness is provided by reducing the intensity of nonlocal components of the vertical mixing in the scheme as the grid size decreases. However, we find that the scale-aware features cause poorer performance in our tests on a 600-m grid. The resolved circulations on the 600-m grid have different temporal and spatial scales than are found in large-eddy simulations of the same cases, for reasons that are well understood theoretically and are described in the literature. The circulations [model convectively induced secondary circulations (M-CISCs)] depend on the grid size and on details of the model numerics. We conclude that scale awareness should be based on effective resolution, and not on grid size, and that the gray-zone problem for boundary layer turbulence and shallow cumulus cannot be solved simply by reducing the intensity of the parameterization. Parameterizations with different characteristics may lead to different conclusions.
Abstract
Thorough understanding of aerosols, clouds, boundary layer structure, and radiation is required to improve the representation of the Arctic atmosphere in weather forecasting and climate models. To develop such understanding, new perspectives are needed to provide details on the vertical structure and spatial variability of key atmospheric properties, along with information over difficult-to-reach surfaces such as newly forming sea ice. Over the last three years, the U.S. Department of Energy (DOE) has supported various flight campaigns using unmanned aircraft systems [UASs, also known as unmanned aerial vehicles (UAVs) and drones] and tethered balloon systems (TBSs) at Oliktok Point, Alaska. These activities have featured in situ measurements of the thermodynamic state, turbulence, radiation, aerosol properties, cloud microphysics, and turbulent fluxes to provide a detailed characterization of the lower atmosphere. Alongside a suite of active and passive ground-based sensors and radiosondes deployed by the DOE Atmospheric Radiation Measurement (ARM) program through the third ARM Mobile Facility (AMF-3), these flight activities demonstrate the ability of such platforms to provide critically needed information. In addition to providing new and unique datasets, lessons learned during initial campaigns have assisted in the development of an exciting new community resource.
Abstract
Thorough understanding of aerosols, clouds, boundary layer structure, and radiation is required to improve the representation of the Arctic atmosphere in weather forecasting and climate models. To develop such understanding, new perspectives are needed to provide details on the vertical structure and spatial variability of key atmospheric properties, along with information over difficult-to-reach surfaces such as newly forming sea ice. Over the last three years, the U.S. Department of Energy (DOE) has supported various flight campaigns using unmanned aircraft systems [UASs, also known as unmanned aerial vehicles (UAVs) and drones] and tethered balloon systems (TBSs) at Oliktok Point, Alaska. These activities have featured in situ measurements of the thermodynamic state, turbulence, radiation, aerosol properties, cloud microphysics, and turbulent fluxes to provide a detailed characterization of the lower atmosphere. Alongside a suite of active and passive ground-based sensors and radiosondes deployed by the DOE Atmospheric Radiation Measurement (ARM) program through the third ARM Mobile Facility (AMF-3), these flight activities demonstrate the ability of such platforms to provide critically needed information. In addition to providing new and unique datasets, lessons learned during initial campaigns have assisted in the development of an exciting new community resource.
Abstract
The Australian marine research, industry, and stakeholder community has recently undertaken an extensive collaborative process to identify the highest national priorities for wind-waves research. This was undertaken under the auspices of the Forum for Operational Oceanography Surface Waves Working Group. The main steps in the process were first, soliciting possible research questions from the community via an online survey; second, reviewing the questions at a face-to-face workshop; and third, online ranking of the research questions by individuals. This process resulted in 15 identified priorities, covering research activities and the development of infrastructure. The top five priorities are 1) enhanced and updated nearshore and coastal bathymetry; 2) improved understanding of extreme sea states; 3) maintain and enhance the in situ buoy network; 4) improved data access and sharing; and 5) ensemble and probabilistic wave modeling and forecasting. In this paper, each of the 15 priorities is discussed in detail, providing insight into why each priority is important, and the current state of the art, both nationally and internationally, where relevant. While this process has been driven by Australian needs, it is likely that the results will be relevant to other marine-focused nations.
Abstract
The Australian marine research, industry, and stakeholder community has recently undertaken an extensive collaborative process to identify the highest national priorities for wind-waves research. This was undertaken under the auspices of the Forum for Operational Oceanography Surface Waves Working Group. The main steps in the process were first, soliciting possible research questions from the community via an online survey; second, reviewing the questions at a face-to-face workshop; and third, online ranking of the research questions by individuals. This process resulted in 15 identified priorities, covering research activities and the development of infrastructure. The top five priorities are 1) enhanced and updated nearshore and coastal bathymetry; 2) improved understanding of extreme sea states; 3) maintain and enhance the in situ buoy network; 4) improved data access and sharing; and 5) ensemble and probabilistic wave modeling and forecasting. In this paper, each of the 15 priorities is discussed in detail, providing insight into why each priority is important, and the current state of the art, both nationally and internationally, where relevant. While this process has been driven by Australian needs, it is likely that the results will be relevant to other marine-focused nations.
