Research Notes : United States : A greenhouse method of screening soybeans for resistance to Fusarium wilt

Fusarium wilt of soybean (causal organism: Fusarium oxysporum Schlecht. emend. Snyd. & Hans.) has become an increasingly severe disease in the breed-ing plots at Gainesville and may be an undiagnosed or misdiagnosed problem in soybean production fields. At Gainesville, severity of Fusarium wilt, or a complex which includes F. oxysporum, has reduced yields in some plots to near-ly zero

A framework for convection and boundary layer parameterization derived from conditional filtering

A new theoretical framework is derived for parameterization of subgrid physical processes in atmospheric models; the application to parameterization of convection and boundary layer fluxes is a particular focus. The derivation is based on conditional filtering, which uses a set of quasi-Lagrangian labels to pick out different regions of the fluid, such as convective updrafts and environment, before applying a spatial filter. This results in a set of coupled prognostic equations for the different fluid components, including subfilter-scale flux terms and entrainment/detrainment terms. The framework can accommodate different types of approaches to parameterization, such as local turbulence approaches and mass-flux approaches. It provides a natural way to distinguish between local and nonlocal transport processes, and makes a clearer conceptual link to schemes based on coherent structures such as convective plumes or thermals than the straightforward application of a filter without the quasi-Lagrangian labels. The framework should facilitate the unification of different approaches to parameterization by highlighting the different approximations made, and by helping to ensure that budgets of energy, entropy, and momentum are handled consistently and without double counting. The framework also points to various ways in which traditional parameterizations might be extended, for example by including additional prognostic variables. One possibility is to allow the large-scale dynamics of all the fluid components to be handled by the dynamical core. This has the potential to improve several aspects of convection-dynamics coupling, such as dynamical memory, the location of compensating subsidence, and the propagation of convection to neighboring grid columns

A nonlocal three‐dimensional turbulence parameterization (NLT3D) for numerical weather prediction models

With increasing resolution of numerical weather prediction (NWP) models, classical subgrid‐scale processes become increasingly resolved on the model grid. In particular, turbulence in the planetary boundary layer (PBL) is vertically already partially resolved in contemporary models. For classical local PBL schemes, resulting up‐gradient heat transports cannot be treated correctly. Thus, nonlocal turbulence schemes have been developed in the past. As the horizontal grid sizes of NWP models become smaller than a few kilometers, the large turbulence eddies in the PBL will also start to become partially resolved in the horizontal direction. A very flexible way to formulate nonlocal turbulent exchange is the transilient matrix method, which is used here to develop a new turbulence parameterization. The resulting NLT3D scheme applies transilient mixing matrices to subgrid‐scale transports in all three dimensions. We compare results of WRF real‐case simulations including our scheme, a classical local turbulence scheme (MYNN), and an existing nonlocal one‐dimensional scheme (ACM2) with observations from field campaigns over homogeneous terrain (CASES‐99) and complex terrain (CAPTEX). Over homogeneous terrain, all three schemes similarly well capture the observed surface fluxes and radiosonde profiles, whereas over complex terrain more differences become obvious. During a tracer release experiment (CAPTEX) over the Appalachian mountain region, the mixing and vertical extent of the PBL turn out to be decisive to reproduce the observed advection speed of the tracer‐marked air mass. Deeper mixing not only accelerates surface winds but also enables tracer to travel faster at higher altitudes and then mix back to the ground. As results from a version of NLT3D with only standard horizontal Smagorinsky diffusion (NLT1D) demonstrate, simulating three‐dimensional turbulence can be beneficial already at horizontal grid sizes of a few kilometers.Decreasing grid sizes in numerical weather prediction models demand the inclusion of nonlocal effects and horizontal turbulence in turbulence parameterizations. This is the motivation for the development of the nonlocal three‐dimensional turbulence (NLT3D) scheme. Vertical nonlocal mixing accelerates the horizontal transport of near‐surface tracers by fast advection at higher altitudes (see figure), and horizontal turbulence enhances tracer dispersion. As validated by observations, both effects are beneficial to the forecast quality already at grid sizes of a few kilometers.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/50110000165

A hybrid convection scheme for use in non-hydrostatic numerical weather prediction models

The correct representation of convection in numerical weather prediction (NWP) models is essential for quantitative precipitation forecasts. Due to its small horizontal scale convection usually has to be parameterized, e.g. by mass flux convection schemes. Classical schemes originally developed for use in coarse grid NWP models assume zero net convective mass flux, because the whole circulation of a convective cell is confined to the local grid column and all convective mass fluxes cancel out. However, in contemporary NWP models with grid sizes of a few kilometers this assumption becomes questionable, because here convection is partially resolved on the grid. To overcome this conceptual problem we propose a hybrid mass flux convection scheme (HYMACS) in which only the convective updrafts and downdrafts are parameterized. The generation of the larger scale environmental subsidence, which may cover several grid columns, is transferred to the grid scale equations. This means that the convection scheme now has to generate a net convective mass flux exerting a direct dynamical forcing to the grid scale model via pressure gradient forces. The hybrid convection scheme implemented into the COSMO model of Deutscher Wetterdienst (DWD) is tested in an idealized simulation of a sea breeze circulation initiating convection in a realistic manner. The results are compared with analogous simulations with the classical Tiedtke and Kain-Fritsch convection schemes

Implementing the HYbrid MAss flux Convection Scheme (HYMACS) in ICON – First idealized tests and adaptions to the dynamical core for local mass sources

In this study, the Hybrid MAss flux Convection Scheme (HYMACS) is implementedin the ICOsahedral Non-hydrostatic (ICON) weather prediction model.In contrast to conventional convection parametrization schemes, the convectiveup- and downdraughts are solely treated as subgrid-scale processes inHYMACS,whereas the environmental subsidence is passed to the grid-scale dynamicsof the hosting model. It is shown that the operational anisotropic divergencedamping in ICON distorts the grid-scale dynamical response on the net masstransport parametrized by HYMACS. Thus, a revised numerical filter configurationis developed which focuses on both the compatibility to local mass sources(sinks) and the effective suppression of numerical modes inherent from themodel's triangular grid. Evaluation of Jablonowski–Williamson dynamical coreexperiments reveal that the combination of an isotropic second-order divergencedamping with a modified version of the fourth-order divergence damping outperformsagainst numerical filters based on diffusion. The obtained results aresimilar to the operational set-up indicating just a minor effect on the propertiesof the dynamical core.Moreover, a series of dry mass lifting experiments with therevised numerical filter confirms its compatability with HYMACS. The distortionof the grid-scale circulation is removed while gravity waves are still retaineddespite the potentially degenerative effect of the fourth-order divergence damping.Analyses of kinetic energy spectra confirm the effective suppression ofcheckerboard noise for a wide range of different situations. The present studymay be understood as a base for future applications ofHYMACS with a full cloudmodel in real-case studies

Potential for narrow leaves in vogetable-type soybeans.

O objetivo deste estudo foi determinar as vantagens e desvantagens do carácter folha estreita em tipos vegetais de soja e estudar seus efeitos em fatores associados com o rendimento. Seis pares de genótipos com folhas largas e estreitas foram testadas em 1982, e outros seis pares de linhas quase isogênicas, diferindo na forma da folha, foram estudadas em 1983. Quanto ao rendimento, os genótipos com folha larga e estreita não apresentaram diferenças significativas, em 1982 e 1983. Os genótipos com folha estreita, no entanto, apresentaram 8% mais sementes por vagem e sementes 6% menores, em 1983. Estas diferenças cancelaram uma a outra resultando num mesmo peso de sementes por vagem. Portanto não há nenhuma vantagem para qualquer um dos dois tipos de folhas, quanto ao rendimento e eficiência de debulha manual. Nos dois anos, os genótipos com folhas estreitas apresentaram menor índice de área foliar (IAF) no estádio vegetativo, o que não ocorreu no estádio reprodutivo. Em 1983, no estádio vegetativo (V7-V9), o IAF dos genótipos com folhas estreitas foi 14% menor, mas no estádio reprodutivo (R4-R5), o IAF foi somente 7% menor e estatisticamente igual aos genótipos de folha larga. Esta redução na diferença de IAF, em R4-R5 pode ser devido retenção de 11% mais folhas no caule dos genótipos com folha estreita, como resultado de uma melhor distribuição de luz penetrando através da planta e principalmente sobre as folhas inferiores.The purpose of this study was to determine advantages and disadvantages of the narrow leaf trait in vegetable-type soybeans and to study the effects of narrow leaves on factors associated with seed yield. Six pairs of narrow and broad leaf genotypes were studied in 1982, and a different set of six pairs of near isogenic lines differing in leaf shape were studied in 1983. No significant differences in seed yield were observed between leaf shape types in 1982 or in 1983. In 1983, narrow leaf types had 8% more seeds per pod but 6% smaller seed. These differences cancelled each other resulting in the same weight of seeds per pod. Therefore, there was no advantage for either leaf shape types for seed yield or hand-shelling efficiency. In both years, narrow leaf genotypes had a significantly lower leaf area index (LAI) at the vegetative stage, but not at the reproductive stage. At growth stage V7-V9, LAI of narrow leaf types was significantly (14%) less, but at growth stage R4-R5 LAI was only 7% less and the difference was not statistically significant. The smaller percentage difference at R4-R5 apparently resulted from narrow leaf types retaining 11% more leaflets on the stem, as a result of better light distribution throughout the canopy

Research Notes : United States : A greenhouse method of screening soybeans for resistance to Fusarium wilt

Fusarium wilt of soybean (causal organism: Fusarium oxysporum Schlecht. emend. Snyd. & Hans.) has become an increasingly severe disease in the breed-ing plots at Gainesville and may be an undiagnosed or misdiagnosed problem in soybean production fields. At Gainesville, severity of Fusarium wilt, or a complex which includes F. oxysporum, has reduced yields in some plots to near-ly zero.</p