Planetary Boundary Layer Parameterization Research Articles

Improving Lake-Breeze Simulation with WRF Nested LES and Lake Model over a Large Shallow Lake

AbstractThe Weather Research and Forecasting (WRF) Model is used in large-eddy simulation (LES) mode to investigate a lake-breeze case occurring on 12 June 2012 over the Lake Taihu region of China. Observational data from 15 locations, wind profiler radar, and the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to evaluate the WRF nested-LES performance in simulating lake breezes. Results indicate that the simulated temporal and spatial variations of the lake breeze by WRF nested LES are consistent with observations. The simulations with high-resolution grid spacing and the LES scheme have a high correlation coefficient and low mean bias when evaluated against 2-m temperature, 10-m wind, and horizontal and vertical lake-breeze circulations. The atmospheric boundary layer (ABL) remains stable over the lake throughout the lake-breeze event, and the stability becomes even stronger as the lake breeze reaches its mature stage. The improved ABL simulation with LES at a grid spacing of 150 m indicates that the non-LES planetary boundary layer parameterization scheme does not adequately represent subgrid-scale turbulent motions. Running WRF fully coupled to a lake model improves lake-surface temperature and consequently the lake-breeze simulations. Allowing for additional model spinup results in a positive impact on lake-surface temperature prediction but is a heavy computational burden. Refinement of a water-property parameter used in the Community Land Model, version 4.5, within WRF and constraining the lake-surface temperature with observational data would further improve lake-breeze representation.

A preliminary sensitivity study of Planetary Boundary Layer parameterisation schemes in the weather research and forecasting model to surface winds in coastal Ghana

There is growing interest in the use of Weather Researching and Forecasting (WRF) model for assessment of wind energy potential. The influence of parameterisation schemes in these models depends on meteorological processes, which tend to differ with geographic regions. In this paper, we test the sensitivity of surface winds in an area in Ghana, to 11 of the Planetary Boundary Layer schemes available in WRF. Thirty-six days were simulated with the schemes. Hourly simulated wind speeds and directions were compared with measurements taken at 40, 50, and 60m above ground level, and the schemes ranked according to a prediction skill score calculated according to how well their predictions compared to observations. The local closure MYNN schemes offered consistently good performance; often predicting the average wind speed with a Root Mean Square Error of less than <2 m/s, indicating good performance. However, the GBM and UW schemes produced relatively better results for days selected from a period in which monthly average winds at this location are highest. Based on our results, we recommend the MYNN3 (and the GBM, depending on the season of the year) for wind simulations in this area, and areas with similar topography and climate in Ghana.

Sensitivity of Hurricane Intensity and Structure to Two Types of Planetary Boundary Layer Parameterization Schemes in Idealized HWRF Simulations

ABSTRACT This paper investigates the sensitivity of simulated hurricane intensity and structure to two planetary boundary layer (PBL) schemes in the Hurricane Weather and Research Forecast model including 1) the GFS scheme (control run) that uses the K-profile method to parameterize turbulent fluxes, and 2) the MYJ scheme that is based on turbulent kinetic energy (TKE) budget for turbulent closure. Idealized simulations with these two PBL schemes show that the storm in the TKE run is stronger than that in the control run after three days into simulation. Multi-scale structures are evaluated and compared between the control and the TKE runs prior to the divergence of the model-simulated intensity to elucidate the mechanism underlying such a difference in the intensity between the two runs. It is found that the storm in the TKE run has i) a shallower boundary layer with a stronger PBL inflow, ii) stronger boundary layer convergence closer to the storm center, iii) higher vorticity and inertial stability inside the RMW; iv) stronger and deeper updrafts in regions further inward from the radius of maximum wind (RMW), and v) more convective bursts located near the RMW as compared to the control run. Angular momentum budget analysis suggests that the convergence of angular momentum in the boundary layer is much stronger in the TKE run than in the control run, which is responsible for faster spin-up of the hurricane vortex in the TKE run.

The Interaction Between Boundary Layer and Convection Schemes in a WRF Simulation of Post Cold Frontal Clouds Over the ARM East North Atlantic Site

AbstractThe correct representation of low‐level midlatitude clouds found in the wake of cold fronts strongly relies on the representation of planetary boundary layer (PBL) and convection processes, which are typically parameterized separately in numerical models. Using the Weather Research and Forecasting Model (WRF), this study investigates how distinct pairs of PBL and convection parameterization schemes represent cloud fraction in the post cold frontal region. The simulations focus on the region of the Department of Energy Atmospheric Radiation Measurement (ARM) Eastern North Atlantic observation site in the Azores Islands in the wake of a cold front that passed on 25 December 2015. Different PBL and convection schemes are combined to create 12 distinct configurations. The main differences between the selected physical parameterizations are the strength of vertical mixing and the entrainment. The simulations produce a wide range of cloud fractions, where some configurations significantly underestimate while others clearly overestimate satellite and surface‐based estimates of cloud fraction. A skill score is used to quantitatively assess the performance of each configuration with respect to ground‐based radar data. The key processes that are found to significantly impact the cloud fraction distribution are the strength of the PBL decoupling, the vertical wind shear, entrainment and detrainment rates in shallow convection, and the occurrence of drizzle. This indicates that to successfully simulate post cold frontal clouds, modeled physics must balance strong internal vertical mixing and weak exchange with the free troposphere. For this case study, cloud fraction was more sensitive to the choice of convection scheme than PBL scheme.

Characterizing and Constraining Uncertainty Associated with Surface and Boundary Layer Turbulent Fluxes in Simulations of Lake-Effect Snowfall

Abstract Lake-effect snow (LeS) storms are driven by strong turbulent surface layer (SL) and planetary boundary layer (PBL) fluxes of heat and moisture caused by the flow of cold air over relatively warm water. To investigate the sensitivity of simulated LeS to the parameterization of SL and PBL turbulence, high-resolution simulations of two major storms, downwind of Lakes Superior and Ontario, are conducted using the Weather Research and Forecasting Model. Multischeme and parameter sensitivity experiments are conducted. Measurements of overlake fluxes and downwind snowfall are used to evaluate the simulations. Consistent with previous studies, LeS is found to be strongly sensitive to SL and PBL parameterization choices. Simulated precipitation accumulations differ by up to a factor of 2 depending on the schemes used. Differences between SL schemes are the dominant source of this sensitivity. Parameterized surface fluxes of sensible and latent heat can each vary by over 100 W m−2 between SL schemes. The magnitude of these fluxes is correlated with the amount of downwind precipitation. Differences between PBL schemes play a secondary role, but have notable impacts on storm morphology. Many schemes produce credible simulations of overlake fluxes and downwind snowfall. However, the schemes that produce the largest surface fluxes produce fluxes and precipitation accumulations that are biased high relative to observations. For two SL schemes studied in detail, unrealistically large fluxes can be attributed to parameter choices: the neutral stability turbulent Prandtl number and the threshold friction velocity used for defining regimes in the overwater surface roughness calculation.

Simulating Sundowner Winds in Coastal Santa Barbara: Model Validation and Sensitivity

This study investigates the influence of planetary boundary layer (PBL) schemes and land surface models (LSMs) on the performance of the Weather Research &amp; Forecasting model in simulating the development of downslope windstorms in the lee of the Santa Ynez Mountains in Santa Barbara, California (known as Sundowner winds). Using surface stations, a vertical wind profiler, and a multi-physics ensemble approach, we found that most of the wind speed biases are controlled by the roughness length z 0 , and so by the choice of LSM. While timing characteristics of Sundowners are insensitive to both LSM and PBL schemes, a clear sensitivity in the horizontal extent of strong surface winds is found for both PBL parameterization and z 0 , which are related to patterns of self-induced wave-breaking near the mountaintop, and the erosion of the marine layer. These results suggest that LSMs with relatively high values of z 0 , and TKE-based or hybrid PBL schemes adequately simulate downslope windstorms in the lee of mountain ranges, specifically in areas where downslope windstorms interact with the marine boundary layer with stably stratified characteristics.

Regional Decadal Climate Predictions Using an Ensemble of WRF Parameterizations Driven by the MIROC5 GCM

AbstractRegional climate models (RCMs) are expected to provide better representations of the climate dynamics because of their higher spatial resolutions. Here, we generated an ensemble of decadal (2006–36) RCM predictions for the area of Israel, which spans a considerable climatic gradient and comprises complex terrain. We used the WRF Model forced by the MIROC5 global climate model (GCM). The ensemble was generated by choosing different combinations of radiation, microphysics, surface layer, and planetary boundary layer parameterizations. The simulation results were compared with meteorological station data for the first simulated decade. For the minimum surface temperature, all the RCM configurations performed better than the driving GCM, while for the maximum surface temperature, only three out of eight configurations improved the predictions. The RCM configurations had higher errors in predicting the precipitation, but four configurations had comparable errors to the GCM. For the next two decades, the ensemble average predicts an increase of 0.51° and 0.40°C decade−1 for the average daily minimum and maximum surface temperatures, respectively. No significant change is predicted in the precipitation. We found that all the parameterizations affect the predictions of the surface temperatures and precipitation [e.g., the CAM radiation scheme simulates colder temperatures than the RRTM for GCMs (RRTMG)] but the PBL and surface layer scheme has the largest effect on the errors. Spectral nudging was found to have a considerable effect on the deviations of the precipitation predicted by the WRF configurations from the predictions of the GCM and a much smaller effect on the surface temperature predictions.

Validation and sensitivity analysis of the WRF mesoscale model PBL schemes over Tunisia using dynamical downscaling approach

Regional-scale atmospheric circulations play a critical role in air pollutants transport. The planetary boundary layer height, in conjunction with other components, is a key factor in atmospheric dispersion. In this study, planetary boundary layer parameters over two coastal locations (Skhira and Marsa-Dhouiba) in Tunisia were simulated using the Weather Research and Forecasting (WRF) v.4.0 dynamical core. Regarding the validation process, the model evaluation demonstrated reasonable agreement with measurements in the study sites and periods. In general, the model slightly overestimates the observed values of near-surface temperature as well as the wind speed in Skhira and slightly underestimates the observed values in Marsa-Dhouiba. For wind direction, however, WRF simulations give opposite results. This preliminary study showed that the model is able to predict the considered meteorological fields in an accurate way with both final analysis (FNL) and Era-Interim boundary datasets. Therefore, the required meteorological fields to initialize an atmospheric dispersion model can be captured reasonably well at regional scale after dynamical downscaling. Integrating our results into project studies aiming at tracing air transports could serve the purpose of reducing environmental pollution over Tunisia.

High Resolution Waves and Weather Forecasts Using Adapted Wavewatch III and WRF Models

High-resolution waves forecast for inland water body was proposed with the use of WAVEWATCH III wave model forced with wind data from WRF atmospheric model. Different surface layer parameterizations and planetary boundary layer parameterizations were tested within WRF. The results were compared with the results of the in-situ measurements.

Numerical Study of Boundary Layer Structure and Rainfall after Landfall of Typhoon Fitow (2013): Sensitivity to Planetary Boundary Layer Parameterization

The boundary layer structure and related heavy rainfall of Typhoon Fitow (2013), which made landfall in Zhejiang Province, China, are studied using the Advanced Research version of the Weather Research and Forecasting model, with a focus on the sensitivity of the simulation to the planetary boundary layer parameterization. Two groups of experiments—one with the same surface layer scheme and including the Yonsei University (YSU), Mellor–Yamada–Nakanishi–Niino Level 2.5, and Bougeault and Lacarrere schemes; and the other with different surface layer schemes and including the Mellor–Yamada–Janjic and Quasi-Normal Scale Elimination schemes—are investigated. For the convenience of comparative analysis, the simulation with the YSU scheme is chosen as the control run because this scheme successfully reproduces the track, intensity and rainfall as a whole. The maximum deviations in the peak tangential and peak radial winds may account for 11% and 33% of those produced in the control run, respectively. Further diagnosis indicates that the vertical diffusivity is much larger in the first group, resulting in weaker vertical shear of the tangential and radial winds in the boundary layer and a deeper inflow layer therein. The precipitation discrepancies are related to the simulated track deflection and the differences in the simulated low-level convergent flow among all tests. Furthermore, the first group more efficiently transfers moisture and energy and produces a stronger ascending motion than the second, contributing to a deeper moist layer, stronger convection and greater precipitation.

Evaluation of WRF planetary boundary layer parameterization schemes for simulation of monsoon depressions over India

This study evaluates the fidelity of five planetary boundary layer (PBL) parameterization schemes in the advanced weather research and forecasting model for simulating monsoon depressions (MDs) over India. Five PBL schemes include; nonlocal first-order medium-range forecasting (MRF) and Yonsei University (YSU); hybrid first-order Asymmetric Convective Model version 2 (ACM2), and local one-and-a-half-order Bougeault–Lacarrere (BouLac) and Mellor–Yamada–Nakanishi–Niino (MYNN2). PBL schemes show significant impact on rainfall along with dynamical and thermodynamical parameters associated with MDs at the surface as well as at the upper levels. MRF simulates a relatively shallower, warmer and drier boundary layer compared to others. Results reveal that strong upper-level divergence and high moisture content within the lower levels are favorable for the occurrence of heavy rain associated with MDs. However, stronger wind shear within the mid-troposphere weakens the system and reduces the rain intensity. Based on the results and keeping the rainfall product in view, it is found that nonlocal PBL schemes (MRF and ACM2) have better forecast skills score than local PBL schemes (BouLac and MYNN2) over the Indian region.

Simulation of extreme heat events over the Valencia coastal region: Sensitivity to initial conditions and boundary layer parameterizations

The Valencia coastal region (Western Mediterranean) is especially sensitive to extreme heat events, where they are really common. However, due to its geophysical characteristics and climatic conditions, the incidence of high and extreme temperatures may still be modulated over this area by means of sea breeze circulations, defining a Sea Breeze Convergence Zone (SBCZ) due to the meet and interaction of these mesoscale conditions and Western synoptic-scale wind regimes. A proper definition of this convergence zone is of significant importance over the study area for the simulation and forecast of intense-heat meteorological events. This study analyses a week period in August 2010 over this area, which alternates the presence of meteorological conditions prone to high and extreme temperatures with sea breeze conditions that temper these extreme temperatures. The simulations have been performed using the mesoscale model Regional Atmospheric Modeling System (RAMS). The analysis focuses on the ability of different initial conditions and technical features and two widely used planetary boundary layer parameterizations to forecast and reproduce the observed high and extreme temperatures, as well as to properly capture the main associated atmospheric patterns. It has been found that an increased horizontal resolution in the initial atmospheric fields produces a better representation of the regional and local wind flows simulated by the mesoscale model, leading to an accurate characterization of the temperature fields when these wind circulations dominate over the area of study. However, no significant differences are obtained within the intense-heat situations, associated with atmospheric synoptic-scale forcings. Regarding PBL parameterizations, the local PBL scheme tends to underestimate the daytime temperatures, while the non-local scheme produces higher temperatures than the local scheme, skilfully reproducing the observations. Additionally, the non-local scheme overestimates temperatures at night-time, but it suitably captures the observed high minimum temperatures produced by the Western synoptic conditions.

On the short-term simulation of heat waves in the Southeast Mediterranean: Sensitivity of the WRF model to various physics schemes

The current study investigated the impact of the Weather Research and Forecasting (WRF) (a) surface layer (SL), (b) land surface and (c) planetary boundary layer (PBL) physics on the short-term simulation of the meteorological and human thermal comfort conditions during 15 heat waves identified between 2004 and 2013 in the southeast Mediterranean and Balkan Peninsula. Four widely used PBL-SL schemes (YSU-MM5, MYJ-Eta, ACM2-Revised MM5, YSU-Revised MM5) and land surface models (LSMs; Noah, Noah-MP, CLM4, RUC) were tested. Comparisons with ground-based observations in 60 measuring sites showed that the WRF model is characterized by a cold bias leading to the underestimation of the extreme heat stress conditions over the entire study region. The MYJ-Eta experiment simulated greater sensible heat fluxes compared to the other PBL-SL scenarios due to the high surface heat exchange coefficient provided by the Eta SL scheme. This contributed to the high MYJ-Eta-modeled daytime 2-m air temperature (T2) and physiologically equivalent temperature (PET) values that were close to the observations. The ACM2 PBL algorithm produced significantly higher PBL heights compared to rest of the tested PBL parameterizations reflecting the strong vertical mixing generated in this scheme. This contributed to the most accurate ACM2-Revised MM5-modeled T2 and PET results in overall. The use of the RUC LSM strengthened significantly the modeled sensible heat fluxes contributing directly to the satisfactory replication of the observed T2 and PET values. However, the RUC-induced enhanced sensible heating relative to the latent heating is may related to a possible underestimation of the soil moisture, as indicated by the notable dry biases during the RUC experiment. Thus, the most accurate T2 and PET results provided by the RUC model may arise from the wrong reason.

Sensitivity of Turbine-Height Wind Speeds to Parameters in the Planetary Boundary-Layer Parametrization Used in the Weather Research and Forecasting Model: Extension to Wintertime Conditions

We extend the model sensitivity analysis of Yang et al. (Boundary-Layer Meteorol 162: 117–142, 2017) to include results for February 2011, in addition to May of the same year. We investigate the sensitivity of simulated hub-height wind speeds to the selection of 12 parameters applied in the Mellor–Yamada–Nakanishi–Niino planetary boundary-layer parametrization in the Weather Research and Forecasting model, including parameters used to represent the dissipation of turbulence kinetic energy (TKE), Prandtl number (Pr), and turbulence length scales. Differences in the sensitivity of the ensemble of simulated wind speed to the various parameters can largely be explained by changes in the static stability. The largest monthly differences are found during the day, while the sensitivity to many of the parameters during the night is similar regardless of the month. This finding is consistent with an increased frequency of daytime stable conditions in February compared to May. The spatial variability of the sensitivity to TKE dissipation and Pr can also be attributed to variability in the static stability across the domain at any point in time.

An Evaluation of Paired Regional/Convection-Allowing Forecast Vertical Thermodynamic Profiles in Warm-Season, Thunderstorm-Supporting Environments

Abstract This study evaluates forecast vertical thermodynamic profiles and derived thermodynamic parameters from two regional/convection-allowing model pairs, the North American Mesoscale Forecast System and the North American Mesoscale Nest model pair and the Rapid Refresh and High Resolution Rapid Refresh model pair, in warm-season, thunderstorm-supporting environments. Differences in bias and mean absolute error between the regional and convection-allowing models in each of the two pairs, while often statistically significant, are practically small for the variables, parameters, and vertical levels considered, such that the smaller-scale variability resolved by convection-allowing models does not degrade their forecast skill. Model biases shared by the regional and convection-allowing models in each pair are documented, particularly the substantial cool and moist biases in the planetary boundary layer arising from the Mellor–Yamada–Janjić planetary boundary layer parameterization used by the North American Mesoscale model and the Nest version as well as the middle-tropospheric moist bias shared by the Rapid Refresh and High Resolution Rapid Refresh models. Bias and mean absolute errors typically have larger magnitudes in the evening, when buoyancy is a significant contributor to turbulent vertical mixing, than in the morning. Vertical thermodynamic profile biases extend over a deep vertical layer in the western United States given strong sensible heating of the underlying surface. The results suggest that convection-allowing models can fulfill the use cases typically and historically met by regional models in operations at forecast entities such as the Storm Prediction Center, a fruitful finding given the proposed elimination of regional models with the Next-Generation Global Prediction System initiative.

Evaluation of Forecasts of a Convectively Generated Bore Using an Intensively Observed Case Study from PECAN

Abstract This paper presents a case study from an intensive observing period (IOP) during the Plains Elevated Convection at Night (PECAN) field experiment that was focused on a bore generated by nocturnal convection. Observations from PECAN IOP 25 on 11 July 2015 are used to evaluate the performance of high-resolution Weather Research and Forecasting Model forecasts, initialized using the Gridpoint Statistical Interpolation (GSI)-based ensemble Kalman filter. The focus is on understanding model errors and sensitivities in order to guide forecast improvements for bores associated with nocturnal convection. Model simulations of the bore amplitude are compared against eight retrieved vertical cross sections through the bore during the IOP. Sensitivities of forecasts to microphysics and planetary boundary layer (PBL) parameterizations are also investigated. Forecasts initialized before the bore pulls away from the convection show a more realistic bore than forecasts initialized later from analyses of the bore itself, in part due to the smoothing of the existing bore in the ensemble mean. Experiments show that the different microphysics schemes impact the quality of the simulations with unrealistically weak cold pools and bores with the Thompson and Morrison microphysics schemes, cold pools too strong with the WDM6 and more accurate with the WSM6 schemes. Most PBL schemes produced a realistic bore response to the cold pool, with the exception of the Mellor–Yamada–Nakanishi–Niino (MYNN) scheme, which creates too much turbulent mixing atop the bore. A new method of objectively estimating the depth of the near-surface stable layer corresponding to a simple two-layer model is also introduced, and the impacts of turbulent mixing on this estimate are discussed.

Investigating the performance of coupled WRF-ROMS simulations of Hurricane Irene (2011) in a regional climate modeling framework

Hurricane Irene (2011) was a category 3 tropical storm that resulted in severe flooding, causing at least 40 deaths and more than $15 billion in damaged property along the US northeastern seaboard (Avila and Cangialosi, 2011). This work analyzes the sensitivity of numerical simulations of this devastating storm to the physical parameterizations in the Weather Research and Forecasting (WRF) model and a coupled modeling framework (WRF and the Regional Ocean Modeling System). Simulations were conducted in two 16-member physics ensembles, each included two radiation schemes, two cumulus schemes, two microphysics schemes, and two planetary boundary layer schemes. The simulations were evaluated primarily on the accuracy of the simulated track and the intensity of the storm compared to observations over a period of 5 days centered on the storm's maximum intensity. Cumulus and planetary boundary layer parameterizations were the most influential physics schemes with radiation and microphysics having much smaller effects. The simulated track, intensity, translational speed, and rainfall rate were particularly sensitive to cumulus schemes given the differences in representation of shallow convection. Tracks and rainfall rates also showed sensitivity to the inclusion or exclusion of local effects in the parameterization of planetary boundary layer processes. Using a grid spacing of 12 km, coupling an ocean model to WRF affected the storm track (with increased sensitivity to the cumulus scheme selected) and translational speed, but had very little effect on the rainfall rate or intensity of the storm. In terms of track accuracy, the optimal combination of physics parameterizations for WRF is not necessarily optimal for the coupled WRF-ROMS system.

Sensitivity of Tropical Cyclone Intensity and Structure to Planetary Boundary Layer Parameterization

The advanced weather research and forecasting model is used to investigate the influence of planetary boundary layer (PBL) processes on intensity and structure of the storm Phailin (2013). Five simulations are conducted with five PBL schemes; Yonsei University (YSU), Mellor−Yamada−Nakanishi−Niino order2.5 (MYNN2), Assymetric Convective Model2 (ACM2), Medium Range Forecast (MRF), and Bougeault and Lacarrere (BouLac). The simulation duration includes the pre − intensification and rapid intensification phase of Phailin before landfall. Results indicate that during the pre − intensification phase, storm’s track and intensity are not much sensitivity to PBL but structural changes are noted. A significant sensitivity of track and intensity to PBL parameterizations are found during rapid intensification phase. BouLac and MRF produced two extremes with 39 hPa intense and 16 km compact storm for BouLac than MRF. Further analysis reveals an outward movement of air parcel just above the boundary layer which causes spin-down for YSU and MYNN2. BouLac is associated with stronger eddy diffusivity and moisture fluxes within the boundary layer and stronger cyclonic vorticity just above the boundary layer than other experiments. Stronger cyclonic vorticity above the boundary layer in BouLac favors intense updraft, facilitating more moisture transport from the boundary layer to upper layers aiding stronger secondary circulation and robustly intensifying the storm. A relatively deeper and drier inflow layer associated with weaker cyclonic vorticity just above the boundary layer reduces the moisture transport and weaken the secondary circulation for MRF than others.

Performance Analysis of Planetary Boundary Layer Parameterization Schemes in WRF Modeling Set Up over Southern Italy

Predictions of boundary layer meteorological parameters with accuracy are essential for achieving good weather and air quality regional forecast. In the present work, we have analyzed seven planetary boundary layer (PBL) parameterization schemes in a Weather Research and Forecasting (WRF) model over the Naples-Caserta region of Southern Italy. WRF model simulations were performed with 1-km horizontal resolution, and the results were compared against data collected by the small aircraft Sky Arrow Environmental Research Aircraft (ERA) during 7–9 October 2014. The selected PBL schemes include three first-order closure PBL schemes (ACM2, MRF, YSU) and four turbulent kinetic energy (TKE) closure schemes (MYJ, UW, MYNN2, and BouLac). A performance analysis of these PBL schemes has been investigated by validating them with aircraft measurements of meteorological parameters profiles (air temperature, specific humidity, wind speed, wind direction) and PBL height to assess their efficiency in terms of the reproduction of observed weather conditions. Results suggested that the TKE closure schemes perform better than first-order closure schemes, and the MYNN2 closure scheme is close to observed values most of the time. It is observed that the inland locations are better simulated than sea locations, and the morning periods are better simulated than those in the afternoon. The results are emphasizing that meteorology-induced variability is larger than the variability in PBL schemes.

Evaluation of Planetary Boundary Layer Simulation in GFDL Atmospheric General Circulation Models

This study describes the performance of two Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric general circulation models (AGCMs) in simulating the climatologies of planetary boundary layer (PBL) parameters, with a particular focus on the diurnal cycles. The two models differ solely in the PBL parameterization: one uses a prescribed K-profile parameterization (KPP) scheme with an entrainment parameterization, and the other employs a turbulence kinetic energy (TKE) scheme. The models are evaluated through comparison with the reanalysis ensemble, which is generated from European Centre for Medium-Range Weather Forecasts (ECMWF) twentieth-century reanalysis (ERA-20C), ERA-Interim, NCEP CFSR, and NASA MERRA, and the following systematic biases are identified. The models exhibit widespread cold biases in the high latitudes, and the biases are smaller when the KPP scheme is used. The diurnal cycle amplitudes are underestimated in most dry regions, and the model with the TKE scheme simulates larger amplitudes. For the near-surface winds, the models underestimate both the daily means and the diurnal amplitudes; the differences between the models are relatively small compared to the biases. The role of the PBL schemes in simulating the PBL parameters is investigated through the analysis of vertical profiles. The Sahara, which is suitable for focusing on the role of vertical mixing in dry PBLs, is selected for a detailed analysis. It reveals that compared to the KPP scheme, the heat transport is weaker with the TKE scheme in both convective and stable PBLs as a result of weaker vertical mixing, resulting in larger diurnal amplitudes. Lack of nonlocal momentum transport from the nocturnal low-level jets to the surfaces appears to explain the underestimation of the near-surface winds in the models.