P34 The
MYNN Turbulence Parameterization:
Recent Development and Current Capabilities
Kenyon, Jaymes, Joe Olson, Cooperative
Institute for Research in Environmental Sciences (CIRES) and National Oceanic
and Atmospheric Administration (NOAA)/Earth System Research Laboratory (ESRL),
John Brown, NOAA/ESRL, Wayne Angevine, CIRES and
NOAA/ESRL, Dave Turner, Jian-Wen Bao, NOAA/ESRL, Branko Kosivic, and Pedro
Jimenez, National Center for Atmospheric
Research
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The Mellor–Yamada–Nakanishi–Niino (MYNN) turbulence parameterization in WRF–ARW
has been under intensive development since 2014, driven by imperatives to
advance forecast quality in NOAA's operational RAP and HRRR models, and by
the objectives of the second Wind Forecast Improvement Project (WFIP2). From this development effort, the MYNN
scheme has emerged with an array of new capabilities and features, all of
which incorporate so-called "scale-aware" considerations, allowing
the scheme to self-adapt according to the horizontal grid spacing. Among these new capabilities, the MYNN
can now operate as an eddy-diffusivity/mass-flux (EDMF) scheme, providing a
better representation of the convective boundary layer. Additionally, a reformulated
mixing-length calculation is offered, intended to improve the representation
of both PBL and free-atmosphere turbulence, especially in stably stratified
conditions. Subgrid-scale
cloud representation has also been improved in the MYNN, affording better
forecasts of solar irradiance at the surface. These features are available to the
WRF–ARW community as of the version 3.9 release. |