scholarly journals Influence on the Temperature Estimation by the Planetary Boundary Layer Scheme with Different Minimum Eddy Diffusivity in WRF v3.9.1.1

2021 ◽  
Author(s):  
Hongyi Ding ◽  
Le Cao ◽  
Haimei Jiang ◽  
Wenxing Jia ◽  
Yong Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Urban Areas ◽  
Eddy Diffusivity ◽  
Mountain Areas ◽  
Temperature Estimation ◽  
Temperature Deviation ◽  
Stable Conditions ◽  
Pbl Scheme ◽  
Boundary Layer Scheme

Abstract. The minimum eddy diffusivity (Kzmin) in the planetary boundary layer (PBL) scheme is able to influence the performance of the model in simulating meteorological parameters such as the temperature. However, detailed studies on the sensitivities of the simulated temperature to the settings of Kzmin are still lacking. Thus, in this study, we evaluated the performance of the ACM2 (Asymmetrical Convective Model, version 2) scheme in the WRF (Weather Research and Forecasting) model with different settings of Kzmin, in simulating the spatiotemporal distribution of the temperature in the region of Beijing, China. Five constant values as well as a function were implemented in the model to calculate Kzmin, and the simulation results with different settings of Kzmin were compared and analyzed. The results show that the increase of Kzmin leads to an elevation of the 2-m temperature, especially in the nighttime. We figured out that the deviation of the 2-m temperature at night is mainly caused by the different estimation of the turbulent mixing under stable conditions in simulation scenarios with different Kzmin settings. Moreover, the spatial distribution of the temperature deviation indicates that under various underlying surface categories, the change of Kzmin exerts a different influence on the prediction of the 2-m temperature, and the influence was found stronger during the nighttime than during the daytime, in plain areas than in mountain areas, in urban areas than in non-urban areas. In the nighttime of the urban areas, the influence on the simulated 2-m temperature brought about by the change of Kzmin was found the strongest. In addition, we found that the implementation of a functional type Kzmin in the ACM2 scheme helps to improve the performance of the model in capturing the diurnal change and the vertical distribution of the temperature in this region, compared with that using a constant Kzmin.

scholarly journals Influence on the temperature estimation of the planetary boundary layer scheme with different minimum eddy diffusivity in WRF v3.9.1.1

2021 ◽  
Vol 14 (10) ◽  
pp. 6135-6153
Author(s):  
Hongyi Ding ◽  
Le Cao ◽  
Haimei Jiang ◽  
Wenxing Jia ◽  
Yong Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Urban Areas ◽  
Model Performance ◽  
Eddy Diffusivity ◽  
Spatiotemporal Distribution ◽  
Mountain Areas ◽  
Temperature Deviation ◽  
Stable Conditions ◽  
Pbl Scheme

Abstract. The minimum eddy diffusivity (Kzmin⁡) in the planetary boundary layer (PBL) scheme can influence the model performance when simulating meteorological parameters such as temperature. However, detailed studies on the sensitivities of the simulated temperatures to the settings of Kzmin⁡ are still lacking. Thus, in this study we evaluated the performance of the ACM2 (Asymmetrical Convective Model version 2) scheme in the WRF (Weather Research and Forecasting) model with different Kzmin⁡ settings when simulating the spatiotemporal distribution of the temperature in the region of Beijing, China. Five constant values and a function were implemented in the model to calculate Kzmin⁡, and the simulation results with different Kzmin⁡ settings were compared and analyzed. The results show that the increase in Kzmin⁡ leads to an elevation of the 2 m temperature, especially at nighttime. We figured out that the deviation in the 2 m temperature at night is mainly caused by the different estimations of the turbulent mixing under stable conditions in simulation scenarios with different Kzmin⁡ settings. Moreover, the spatial distribution of the temperature deviation indicates that under various underlying surface categories, the change in Kzmin⁡ exerts a distinct influence on the prediction of the 2 m temperature. This influence was found to be stronger during the nighttime than during the daytime, in plain areas than in mountain areas, and in urban areas than in non-urban areas. During the night in the urban areas, the influence on the simulated 2 m temperature brought about by the change in Kzmin⁡ is the strongest. In addition, the model performance using a functional-type Kzmin⁡ in the ACM2 scheme for capturing the spatiotemporal distribution of the temperature in this region was also compared with that using a constant Kzmin⁡.

scholarly journals Impacts of Modifications to a Local Planetary Boundary Layer Scheme on Forecasts of the Great Plains Low-Level Jet Environment

2018 ◽  
Vol 33 (5) ◽  
pp. 1109-1120 ◽  
Author(s):  
David E. Jahn ◽  
William A. Gallus
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Planetary Boundary Layer ◽  
Great Plains ◽  
Potential Temperature ◽  
Specific Humidity ◽  
Low Level ◽  
Stable Conditions ◽  
Pbl Scheme ◽  
Low Level Jet

Abstract The Great Plains low-level jet (LLJ) is influential in the initiation and evolution of nocturnal convection through the northward advection of heat and moisture, as well as convergence in the region of the LLJ nose. However, accurate numerical model forecasts of LLJs remain a challenge, related to the performance of the planetary boundary layer (PBL) scheme in the stable boundary layer. Evaluated here using a series of LLJ cases from the Plains Elevated Convection at Night (PECAN) program are modifications to a commonly used local PBL scheme, Mellor–Yamada–Nakanishi–Niino (MYNN), available in the Weather Research and Forecasting (WRF) Model. WRF forecast mean absolute error (MAE) and bias are calculated relative to PECAN rawinsonde observations. The first MYNN modification invokes a new set of constants for the scheme closure equations that, in the vicinity of the LLJ, decreases forecast MAEs of wind speed, potential temperature, and specific humidity more than 19%. For comparison, the Yonsei University (YSU) scheme results in wind speed MAEs 22% lower but specific humidity MAEs 17% greater than in the original MYNN scheme. The second MYNN modification, which incorporates the effects of potential kinetic energy and uses a nonzero mixing length in stable conditions as dependent on bulk shear, reduces wind speed MAEs 66% for levels below the LLJ, but increases MAEs at higher levels. Finally, Rapid Refresh analyses, which are often used for forecast verification, are evaluated here and found to exhibit a relatively large average wind speed bias of 3 m s−1 in the region below the LLJ, but with relatively small potential temperature and specific humidity biases.

scholarly journals Implementation in the NCEP GFS of a Hybrid Eddy-Diffusivity Mass-Flux (EDMF) Boundary Layer Parameterization with Dissipative Heating and Modified Stable Boundary Layer Mixing

2016 ◽  
Vol 31 (1) ◽  
pp. 341-352 ◽  
Author(s):  
Jongil Han ◽  
Marcin L. Witek ◽  
Joao Teixeira ◽  
Ruiyu Sun ◽  
Hua-Lu Pan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mass Flux ◽  
Stable Boundary Layer ◽  
Eddy Diffusivity ◽  
Dissipative Heating ◽  
Tropical Ocean ◽  
Medium Range Weather Forecast ◽  
Stable Boundary ◽  
Stable Conditions ◽  
Pbl Scheme

Abstract The current operational eddy-diffusivity countergradient (EDCG) planetary boundary layer (PBL) scheme in the NCEP Global Forecast System (GFS) tends to underestimate the PBL growth in the convective boundary layer (CBL). To improve CBL growth, an eddy-diffusivity mass-flux (EDMF) PBL scheme is developed, where the nonlocal transport by large turbulent eddies is represented by a mass-flux (MF) scheme and the local transport by small eddies is represented by an eddy-diffusivity (ED) scheme. For the vertical momentum mixing, the MF scheme is modified to include the effect of the updraft-induced pressure gradient force. While the EDMF scheme displays better CBL growth than the EDCG scheme, it tends to overproduce the amount of low clouds and degrades wind vector forecasts over the tropical ocean where strongly unstable PBLs are rarely found. In order not to degrade the forecast skill in the tropics, a hybrid scheme is developed, where the EDMF scheme is applied only for the strongly unstable PBL, while the EDCG scheme is used for the weakly unstable PBL. Along with the hybrid EDMF scheme, the heating by turbulent kinetic energy (TKE) dissipation is parameterized to reduce an energy imbalance in the GFS. To enhance a too weak vertical turbulent mixing for weakly and moderately stable conditions, the current local scheme in the stable boundary layer (SBL) is modified to use an eddy-diffusivity profile method. The hybrid EDMF PBL scheme with TKE dissipative heating and modified SBL mixing led to significant improvements in some key medium-range weather forecast metrics and was operationally implemented into the NCEP GFS in January 2015.

scholarly journals A Review and Evaluation of Planetary Boundary Layer Parameterizations in Hurricane Weather Research and Forecasting Model Using Idealized Simulations and Observations

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1091
Author(s):  
Jun A. Zhang ◽  
Evan A. Kalina ◽  
Mrinal K. Biswas ◽  
Robert F. Rogers ◽  
Ping Zhu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Planetary Boundary Layer ◽  
Doppler Radar ◽  
Deep Convection ◽  
Eddy Diffusivity ◽  
Intensity Change ◽  
Weather Research And Forecasting ◽  
Pbl Scheme ◽  
Weather Research

This paper reviews the evolution of planetary boundary layer (PBL) parameterization schemes that have been used in the operational version of the Hurricane Weather Research and Forecasting (HWRF) model since 2011. Idealized simulations are then used to evaluate the effects of different PBL schemes on hurricane structure and intensity. The original Global Forecast System (GFS) PBL scheme in the 2011 version of HWRF produces the weakest storm, while a modified GFS scheme using a wind-speed dependent parameterization of vertical eddy diffusivity (Km) produces the strongest storm. The subsequent version of the hybrid eddy diffusivity and mass flux scheme (EDMF) used in HWRF also produces a strong storm, similar to the version using the wind-speed dependent Km. Both the intensity change rate and maximum intensity of the simulated storms vary with different PBL schemes, mainly due to differences in the parameterization of Km. The smaller the Km in the PBL scheme, the faster a storm tends to intensify. Differences in hurricane PBL height, convergence, inflow angle, warm-core structure, distribution of deep convection, and agradient force in these simulations are also examined. Compared to dropsonde and Doppler radar composites, improvements in the kinematic structure are found in simulations using the wind-speed dependent Km and modified EDMF schemes relative to those with earlier versions of the PBL schemes in HWRF. However, the upper boundary layer in all simulations is much cooler and drier than that in dropsonde observations. This model deficiency needs to be considered and corrected in future model physics upgrades.

“Gray Zone” Simulations using a Three-Dimensional Planetary Boundary Layer Parameterization in the Weather Research and Forecasting Model

2021 ◽  
Author(s):  
Timothy W. Juliano ◽  
Branko Kosović ◽  
Pedro A. Jiménez ◽  
Masih Eghdami ◽  
Sue Ellen Haupt ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Three Dimensional ◽  
Grid Cell ◽  
Weather Research And Forecasting ◽  
Forecasting Model ◽  
Gray Zone ◽  
Pbl Scheme ◽  
3D Effects ◽  
Mesoscale Simulations

AbstractGenerating accurate weather forecasts of planetary boundary layer (PBL) properties is challenging in many geographical regions, oftentimes due to complex topography or horizontal variability in, for example, land characteristics. While recent advances in high-performance computing platforms have led to an increase in the spatial resolution of numerical weather prediction (NWP) models, the horizontal grid cell spacing (Δ x) of many regional-scale NWP models currently fall within or are beginning to approach the gray zone (i.e., Δ x ≈ 100 – 1000 m). At these grid cell spacings, three-dimensional (3D) effects are important, as the most energetic turbulent eddies are neither fully parameterized (as in traditional mesoscale simulations) nor fully resolved [as in traditional large eddy simulations (LES)]. In light of this modeling challenge, we have implemented a 3D PBL parameterization for high-resolution mesoscale simulations using the Weather Research and Forecasting model. The PBL scheme, which is based on the algebraic model developed by Mellor and Yamada, accounts for the 3D effects of turbulence by calculating explicitly the momentum, heat, and moisture flux divergences in addition to the turbulent kinetic energy. In this study, we present results from idealized simulations in the gray zone that illustrate the benefit of using a fully consistent turbulence closure framework under convective conditions. While the 3D PBL scheme reproduces the evolution of convective features more appropriately than the traditional 1D PBL scheme, we highlight the need to improve the turbulent length scale formulation.

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