A New Vertical Diffusion Package with an Explicit Treatment of Entrainment Processes
TL;DR: In this article, a revised vertical diffusion algorithm with a nonlocal turbulent mixing coefficient in the planetary boundary layer (PBL) is proposed for weather forecasting and climate prediction models, which improves several features compared with the Hong and Pan implementation.
Abstract: This paper proposes a revised vertical diffusion package with a nonlocal turbulent mixing coefficient in the planetary boundary layer (PBL). Based on the study of Noh et al. and accumulated results of the behavior of the Hong and Pan algorithm, a revised vertical diffusion algorithm that is suitable for weather forecasting and climate prediction models is developed. The major ingredient of the revision is the inclusion of an explicit treatment of entrainment processes at the top of the PBL. The new diffusion package is called the Yonsei University PBL (YSU PBL). In a one-dimensional offline test framework, the revised scheme is found to improve several features compared with the Hong and Pan implementation. The YSU PBL increases boundary layer mixing in the thermally induced free convection regime and decreases it in the mechanically induced forced convection regime, which alleviates the well-known problems in the Medium-Range Forecast (MRF) PBL. Excessive mixing in the mixed layer in the presenc...
Citations
More filters
DOI•
01 Jan 2008
TL;DR: The Technical Note series provides an outlet for a variety of NCAR manuscripts that contribute in specialized ways to the body of scientific knowledge but which are not suitable for journal, monograph, or book publication.
Abstract: The Technical Note series provides an outlet for a variety of NCAR manuscripts that contribute in specialized ways to the body of scientific knowledge but which are not suitable for journal, monograph, or book publication. Reports in this series are issued by the NCAR Scientific Divisions ; copies may be obtained on request from the Publications Office of NCAR. Designation symbols for the series include: Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation.
9,022 citations
01 Jan 1989
TL;DR: In this article, a two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea.
Abstract: Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...
3,813 citations
TL;DR: In this paper, the surface layer formulation of the Weather Research and Forecasting (WRF) model was modified to provide more suitable similarity functions to simulate surface layer evolution under strong stable/unstable conditions.
Abstract: This study summarizes the revision performed on the surface layer formulation of the Weather Research and Forecasting (WRF) model. A first set of modifications are introduced to provide more suitable similarity functions to simulate the surface layer evolution under strong stable/unstable conditions. A second set of changes are incorporated to reduce or suppress the limits that are imposed on certain variables in order to avoid undesired effects (e.g., a lower limit in u * ). The changes introduced lead to a more consistent surface layer formulation that covers the full range of atmospheric stabilities. The turbulent fluxes are more (less) efficient during the day (night) in the revised scheme and produce a sharper afternoon transition that shows the largest impacts in the planetary boundary layer meteorological variables. The most important impacts in the near-surface diagnostic variables are analyzed and compared with observations from a mesoscale network.
1,006 citations
Cites methods from "A New Vertical Diffusion Package wi..."
...The PBL is parameterized with the Yonsei University scheme (Hong et al. 2006) with the first model level that defines the surface layer at 28 m (h 5 0.993)....
[...]
...The PBL is parameterized with the Yonsei University scheme (Hong et al. 2006) with the first model level that defines the surface layer at 28 m (h 5 0....
[...]
ETH Zurich1, Brandenburg University of Technology2, Danish Meteorological Institute3, Centre national de la recherche scientifique4, University of Graz5, University of Bonn6, Max Planck Society7, Royal Netherlands Meteorological Institute8, Swedish Meteorological and Hydrological Institute9, University of Hohenheim10
TL;DR: In this article, an evaluation of the ERA-Interim-driven EURO-CORDEX regional climate model (RCM) ensemble is presented, focusing on near-surface air temperature and precipitation, and using the E-OBS data set as observational reference.
Abstract: . EURO-CORDEX is an international climate downscaling initiative that aims to provide high-resolution climate scenarios for Europe. Here an evaluation of the ERA-Interim-driven EURO-CORDEX regional climate model (RCM) ensemble is presented. The study documents the performance of the individual models in representing the basic spatiotemporal patterns of the European climate for the period 1989–2008. Model evaluation focuses on near-surface air temperature and precipitation, and uses the E-OBS data set as observational reference. The ensemble consists of 17 simulations carried out by seven different models at grid resolutions of 12 km (nine experiments) and 50 km (eight experiments). Several performance metrics computed from monthly and seasonal mean values are used to assess model performance over eight subdomains of the European continent. Results are compared to those for the ERA40-driven ENSEMBLES simulations. The analysis confirms the ability of RCMs to capture the basic features of the European climate, including its variability in space and time. But it also identifies nonnegligible deficiencies of the simulations for selected metrics, regions and seasons. Seasonally and regionally averaged temperature biases are mostly smaller than 1.5 °C, while precipitation biases are typically located in the ±40% range. Some bias characteristics, such as a predominant cold and wet bias in most seasons and over most parts of Europe and a warm and dry summer bias over southern and southeastern Europe reflect common model biases. For seasonal mean quantities averaged over large European subdomains, no clear benefit of an increased spatial resolution (12 vs. 50 km) can be identified. The bias ranges of the EURO-CORDEX ensemble mostly correspond to those of the ENSEMBLES simulations, but some improvements in model performance can be identified (e.g., a less pronounced southern European warm summer bias). The temperature bias spread across different configurations of one individual model can be of a similar magnitude as the spread across different models, demonstrating a strong influence of the specific choices in physical parameterizations and experimental setup on model performance. Based on a number of simply reproducible metrics, the present study quantifies the currently achievable accuracy of RCMs used for regional climate simulations over Europe and provides a quality standard for future model developments.
778 citations
TL;DR: In this article, an improved Mellor-Yamada turbulence closure model (myNN model) was proposed and its performance was demonstrated against a large-eddy simulation (LES) of a convective boundary layer.
Abstract: An improved Mellor–Yamada (MY) turbulence closure model (MYNN model: Mellor–Yamada– Nakanishi–Niino model) that we have developed is summarized and its performance is demonstrated against a large-eddy simulation (LES) of a convective boundary layer. Unlike the original MY model, the MYNN model considers effects of buoyancy on pressure covariances and effects of stability on the turbulent length scale, with model constants determined from a LES database. One-dimensional simulations of Day 33 of the Wangara field experiment, which was conducted in a flat area of southeastern Australia in 1967, are made by the MY and MYNN models and the results are compared with horizontal-average statistics obtained from a three-dimensional LES. The MYNN model improves several weak points of the MY model such as an insufficient growth of the convective boundary layer, and underestimates of the turbulent kinetic energy and the turbulent length scale; it reproduces fairly well the results of the LES including the vertical distributions of the mean and turbulent quantities. The improved performance of the MYNN model relies mainly on the new formulation of the turbulent length scale that realistically increases with decreasing stability, and partly on the parameterization of the pressure covariances and the expression for stability functions for third-order turbulent fluxes.
714 citations
Cites methods from "A New Vertical Diffusion Package wi..."
...First-order turbulence closure models, such as the K-profile model (e.g., Troen and Mahrt 1986; Hong et al. 2006), the KE (so-called one-anda-half order closure) model (e.g., Therry and Lacarrère 1983; Bougeault and Lacarrère 1989), and the standard k e model (e.g., Hanjalic and Launder 1972),…...
[...]
...First-order turbulence closure models, such as the K-profile model (e.g., Troen and Mahrt 1986; Hong et al. 2006), the KE (so-called one-anda-half order closure) model (e....
[...]
References
More filters
TL;DR: A rapid and accurate radiative transfer model (RRTM) for climate applications has been developed and the results extensively evaluated as discussed by the authors, which is performed using the correlated-k method: the k distributions are attained directly from the LBLRTM line-byline model, which connects the absorption coefficients used by RRTM to high-resolution radiance validations done with observations.
Abstract: A rapid and accurate radiative transfer model (RRTM) for climate applications has been developed and the results extensively evaluated. The current version of RRTM calculates fluxes and cooling rates for the longwave spectral region (10–3000 cm−1) for an arbitrary clear atmosphere. The molecular species treated in the model are water vapor, carbon dioxide, ozone, methane, nitrous oxide, and the common halocarbons. The radiative transfer in RRTM is performed using the correlated-k method: the k distributions are attained directly from the LBLRTM line-by-line model, which connects the absorption coefficients used by RRTM to high-resolution radiance validations done with observations. Refined methods have been developed for treating bands containing gases with overlapping absorption, for the determination of values of the Planck function appropriate for use in the correlated-k approach, and for the inclusion of minor absorbing species in a band. The flux and cooling rate results of RRTM are linked to measurement through the use of LBLRTM, which has been substantially validated with observations. Validations of RRTM using LBLRTM have been performed for the midlatitude summer, tropical, midlatitude winter, subarctic winter, and four atmospheres from the Spectral Radiance Experiment campaign. On the basis of these validations the longwave accuracy of RRTM for any atmosphere is as follows: 0.6 W m−2 (relative to LBLRTM) for net flux in each band at all altitudes, with a total (10–3000 cm−1) error of less than 1.0 W m−2 at any altitude; 0.07 K d−1 for total cooling rate error in the troposphere and lower stratosphere, and 0.75 K d−1 in the upper stratosphere and above. Other comparisons have been performed on RRTM using LBLRTM to gauge its sensitivity to changes in the abundance of specific species, including the halocarbons and carbon dioxide. The radiative forcing due to doubling the concentration of carbon dioxide is attained with an accuracy of 0.24 W m−2, an error of less than 5%. The speed of execution of RRTM compares favorably with that of other rapid radiation models, indicating that the model is suitable for use in general circulation models.
6,861 citations
"A New Vertical Diffusion Package wi..." refers methods in this paper
...…2.0 of the WRF was used with the Noah land surface model (Chen and Dudhia 2001), and WRF single-moment six-class microphysics (Hong et al. 2004; Hong and Lim 2006), Dudhia (1989) simple cloudinteractive shortwave, and rapid radiative transfer model longwave radiation (Mlawer et al. 1997) schemes....
[...]
TL;DR: In this paper, the authors address and document a number of issues related to the implementation of an advanced land surface-hydrology model in the Penn State-NCAR fifth-generation Mesoscale Model (MM5).
Abstract: This paper addresses and documents a number of issues related to the implementation of an advanced land surface–hydrology model in the Penn State–NCAR fifth-generation Mesoscale Model (MM5). The concept adopted here is that the land surface model should be able to provide not only reasonable diurnal variations of surface heat fluxes as surface boundary conditions for coupled models, but also correct seasonal evolutions of soil moisture in the context of a long-term data assimilation system. In a similar way to that in which the modified Oregon State University land surface model (LSM) has been used in the NCEP global and regional forecast models, it is implemented in MM5 to facilitate the initialization of soil moisture. Also, 1-km resolution vegetation and soil texture maps are introduced in the coupled MM5–LSM system to help identify vegetation/water/soil characteristics at fine scales and capture the feedback of these land surface forcings. A monthly varying climatological 0.15° × 0.15° green ...
4,405 citations
"A New Vertical Diffusion Package wi..." refers methods in this paper
...Version 2.0 of the WRF was used with the Noah land surface model (Chen and Dudhia 2001), and WRF single-moment six-class microphysics (Hong et al. 2004; Hong and Lim 2006), Dudhia (1989) simple cloudinteractive shortwave, and rapid radiative transfer model longwave radiation (Mlawer et al. 1997)…...
[...]
TL;DR: In this article, a two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea.
Abstract: A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...
4,243 citations
"A New Vertical Diffusion Package wi..." refers methods in this paper
...…2.0 of the WRF was used with the Noah land surface model (Chen and Dudhia 2001), and WRF single-moment six-class microphysics (Hong et al. 2004; Hong and Lim 2006), Dudhia (1989) simple cloudinteractive shortwave, and rapid radiative transfer model longwave radiation (Mlawer et al. 1997) schemes....
[...]
...Version 2.0 of the WRF was used with the Noah land surface model (Chen and Dudhia 2001), and WRF single-moment six-class microphysics (Hong et al. 2004; Hong and Lim 2006), Dudhia (1989) simple cloudinteractive shortwave, and rapid radiative transfer model longwave radiation (Mlawer et al. 1997) schemes....
[...]
01 Jan 1995
3,954 citations
01 Jan 1989
TL;DR: In this article, a two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea.
Abstract: Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...
3,813 citations