scholarly journals The Performance of Different Boundary-Layer Parameterisations in Meteorological Modelling in a Southwestern Coastal Area of the Iberian Peninsula

2012 ◽  
Vol 2012 ◽  
pp. 1-13
Author(s):  
M. A. Hernández-Ceballos ◽  
J. A. Adame ◽  
J. P. Bolivar ◽  
B. A. De la Morena
Keyword(s):  
Boundary Layer ◽  
Coastal Area ◽  
Meteorological Parameters ◽  
Wrf Model ◽  
Near Surface ◽  
Diurnal Cycles ◽  
Medium Range Forecast ◽  
Critical Richardson Number ◽  
Standard Configuration ◽  
Meteorological Modelling

The performance of four atmospheric boundary layer (ABL) schemes in reproducing the diurnal cycles of surface meteorological parameters as well as the ABL structure and depth over a coastal area of southwestern Iberia was assessed using the mesoscale meteorological Weather Research and Forecasting (WRF) model. The standard configuration of the medium-range forecast (MRF) and the Yonsei University (YSU) ABL schemes were employed. Modified versions of each, in which the values of the bulk critical Richardson number () and the coefficient of proportionality () were varied, were also used. The results were compared to meteorological measurements representative of SW-NW and NE synoptic flows. The WRF model in its basic configuration was found to yield satisfactory forecasting results for nearly all near-surface atmospheric variables. Modifications in and did not influence the simulation of surface meteorological parameters. Both parameterisations appeared to be optimal predictors of ABL structure, and all four ABL schemes tended to produce a cold ABL during both periods, although this ABL was drier in the SW-NW flow season and wetter in the NE flow season. Considering all the parameters analysed, the MRF ABL parameterisation with the lowest values of and coefficients tested (0.25 and 0.0, resp.) tends to show a realistic simulation.

scholarly journals Leeside Boundary Layer Confluence and Afternoon Thunderstorms over Mayaguez, Puerto Rico

2013 ◽  
Vol 52 (2) ◽  
pp. 439-454 ◽  
Author(s):  
Mark R. Jury ◽  
Sen Chiao
Keyword(s):  
Boundary Layer ◽  
Puerto Rico ◽  
Wind Shear ◽  
Wrf Model ◽  
Sea Breeze ◽  
Shear Zones ◽  
Near Surface ◽  
Diurnal Cycles ◽  
High Resolution Models ◽  
Island Wake

AbstractThe midsummer boundary layer (BL) circulation and afternoon thunderstorm convection on the lee side of Puerto Rico is studied using observations and high-resolution models. Satellite infrared data help to identify cases on 5 and 14 June 2010 when midday surface temperatures show a 2°C gradient between land and sea and afternoon cloud-top temperatures <−60°C. Acoustic sounder profiles are analyzed for climatology, wind shear, turbulence, and diurnal cycles in the 40–300-m layer. Weather Research and Forecasting (WRF) model simulations indicate that sea-breeze flow is entrained into convective cells near Mayaguez, Puerto Rico. The simulated BL wind shear is too weak (0.5 × 10−2 s−1) in comparison with the acoustic sounder (2 × 10−2 s−1). Model 900-hPa winds are southeasterly and spread simulated convection too far north in comparison with radar. The pattern of near-surface winds in the island wake triggers afternoon thunderstorms near Mayaguez. A feature of the confluent circulation around Puerto Rico is opposing shear zones on the leeward corners of the island and a sea breeze of 5 m s−1 over the west coast during midday.

Relating Satellite-Observed Cloud Properties from MODIS to Meteorological Conditions for Marine Boundary Layer Clouds

2010 ◽  
Vol 23 (6) ◽  
pp. 1374-1391 ◽  
Author(s):  
Guang J. Zhang ◽  
Andrew M. Vogelmann ◽  
Michael P. Jensen ◽  
William D. Collins ◽  
Edward P. Luke
Keyword(s):  
Boundary Layer ◽  
Meteorological Parameters ◽  
Marine Boundary Layer ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Liquid Water Path ◽  
Near Surface ◽  
Cloud Properties ◽  
Lower Tropospheric Stability

Abstract This study examines 6 yr of cloud properties observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the NASA Terra satellite in five prominent marine boundary layer (MBL) cloud regions (California, Peru, Canary, Angola, and Australia) and investigates their relationships with near-surface meteorological parameters obtained from NCEP reanalyses. About 62 000 independent scenes are used to examine the instantaneous relationships between cloud properties and meteorological parameters that may be used for global climate model (GCM) diagnostics and parameterization. Cloud liquid water path (LWP) generally increases with lower-tropospheric stability (LTS) and lifting condensation level (LCL), whereas cloud drizzle frequency is favored by weak LTS and negligible cold air advection. Cloud fraction (CF) depends strongly on variations in LTS, and to a lesser extent on surface air temperature advection and LCL, although the relationships vary from region to region. The authors propose capturing the effects of these three parameters on CF via their linear combination in terms of a single parameter, the effective lower-tropospheric stability (eLTS). Results indicate that eLTS offers a marked improvement over LTS alone in explaining the median CF variations within the different study regions. A parameterization of CF in terms of eLTS is provided, which produces results that are improved over those of Klein and Hartmann’s LTS-only parameterization. However, the new parameterization may not predict the observed variability correctly, and the authors propose a method that might address this shortcoming via a statistical approach.

scholarly journals Validation of urban NO<sub>2</sub> concentrations and their diurnal and seasonal variations observed from space (SCIAMACHY and OMI sensors) using in situ measurements in Israeli cities

2009 ◽  
Vol 9 (1) ◽  
pp. 4301-4333 ◽  
Author(s):  
K. F. Boersma ◽  
D. J. Jacob ◽  
M. Trainic ◽  
Y. Rudich ◽  
I. DeSmedt ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Seasonal Variation ◽  
Transport Model ◽  
Source Region ◽  
Chemical Transport Model ◽  
Data Set ◽  
Near Surface ◽  
Weekly Cycle ◽  
Diurnal Cycles ◽  
Diurnal Difference

Abstract. We compare a full-year (2006) record of surface air NO2 concentrations measured in Israeli cities to coinciding retrievals of tropospheric NO2 columns from satellite sensors (SCIAMACHY aboard ENVISAT and OMI aboard Aura). This provides a large statistical data set for validation of NO2 satellite measurements in urban air, where validation is difficult yet crucial for using these measurements to infer NOx emissions by inverse modeling. Assuming that NO2 is well-mixed throughout the boundary layer (BL), and using observed average seasonal boundary layer heights, near-surface NO2 concentrations are converted into BL NO2 columns. The agreement between OMI and (13:45) BL NO2 columns (slope=0.93, n=542), and the comparable results at 10:00 h for SCIAMACHY, allow a validation of the seasonal, weekly, and diurnal cycles in satellite-derived NO2. OMI and BL NO2 columns show consistent seasonal cycles (winter NO2 1.6–2.7× higher than summer). BL and coinciding OMI columns both show a strong weekly cycle with 45–50% smaller NO2 columns on Saturday relative to the weekday mean, reflecting the reduced weekend activity, and validating the weekly cycle observed from space. The diurnal difference between SCIAMACHY (10:00) and OMI (13:45) NO2 is maximum in summer when SCIAMACHY is up to 40% higher than OMI, and minimum in winter when OMI slightly exceeds SCIAMACHY. A similar seasonal variation in the diurnal difference is found in the source region of Cairo. The surface measurements in Israel cities confirm this seasonal variation in the diurnal cycle. Using simulations from a global 3-D chemical transport model (GEOS-Chem), we show that this seasonal cycle can be explained by a much stronger photochemical loss of NO2 in summer than in winter.

scholarly journals Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework

2019 ◽  
Vol 19 (4) ◽  
pp. 2477-2487 ◽  
Author(s):  
Liguang Wu ◽  
Qingyuan Liu ◽  
Yubin Li
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Large Scale ◽  
Surface Wind ◽  
Wrf Model ◽  
Surface Wind Speed ◽  
Horizontal Scale ◽  
Lower Altitude ◽  
Near Surface ◽  
Research Aircraft

Abstract. A tornado-scale vortex in the tropical cyclone (TC) boundary layer (TCBL) has been observed in intense hurricanes and the associated intense turbulence poses a severe threat to the manned research aircraft when it penetrates hurricane eyewalls at a lower altitude. In this study, a numerical experiment in which a TC evolves in a large-scale background over the western North Pacific is conducted using the Advanced Weather Research and Forecast (WRF) model by incorporating the large-eddy simulation (LES) technique. The simulated tornado-scale vortex shows features similar to those revealed with limited observational data, including the updraft–downdraft couplet, the sudden jump of wind speeds, the location along the inner edge of the eyewall, and the small horizontal scale. It is suggested that the WRF–LES framework can successfully simulate the tornado-scale vortex with grids at a resolution of 37 m that cover the TC eye and eyewall. The simulated tornado-scale vortex is a cyclonic circulation with a small horizontal scale of ∼1 km in the TCBL. It is accompanied by strong updrafts (more than 15 m s−1) and large vertical components of relative vorticity (larger than 0.2 s−1). The tornado-scale vortex favorably occurs at the inner edge of the enhanced eyewall convection or rainband within the saturated, high-θe layer, mostly below an altitude of 2 km. In nearly all the simulated tornado-scale vortices, the narrow intense updraft is coupled with the relatively broad downdraft, constituting one or two updraft–downdraft couplets, as observed by the research aircraft. The presence of the tornado-scale vortex also leads to significant gradients in the near-surface wind speed and wind gusts.

scholarly journals Tornado-Scale Vortices in the Tropical Cyclone Boundary Layer: Numerical Simulation with WRF-LES Framework

2018 ◽  
Author(s):  
Liguang Wu ◽  
Qingyuan Liu ◽  
Yubing Li
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Large Scale ◽  
Surface Wind ◽  
Wrf Model ◽  
Surface Wind Speed ◽  
Horizontal Scale ◽  
Lower Altitude ◽  
Near Surface ◽  
Research Aircraft

Abstract. The tornado-scale vortex in the tropical cyclone (TC) boundary layer (TCBL) has been observed in intense hurricanes and the associated intense turbulence poses a severe threat to the manned research aircraft when it penetrates hurricane eyewalls at a lower altitude. In this study, a numerical experiment in which a TC evolves in a large-scale background over the western North Pacific is conducted using the Advanced Weather Research and Forecast (WRF) model by incorporating the large eddy simulation (LES) technique. The simulated tornado-scale vortex shows the similar features as revealed with the limited observational data, including the updraft/downdraft couplet, the sudden jump of wind speeds, the favorable location, and the horizontal scale. It is suggested that the WRF-LES framework can successfully simulate the tornado-scale vortex with the grids at the resolution of 37 m that cover the TC eye and eyewall. The simulated tornado-scale vortex is a cyclonic circulation with a small horizontal scale of ~ 1 km in the TCBL. It is accompanied by strong updrafts (more than 15 m s−1) and large vertical components of relative vorticity (larger than 0.2 s−1). The tornado-scale vortex favorably occurs at the inner edge of the enhanced eyewall convection or rainband within the saturated, high-θe layer, mostly below the altitude of 2 km. Nearly in all the simulated tornado-scale vortices, the narrow intense updraft is coupled with the relatively broad downdraft, constituting one or two updraft/downdraft couplets or horizontal rolling vortices, as observed by the research aircraft. The presence of the tornado-scale vortex also leads to significant gradients in the near surface wind speed and wind gusts.

Simulation on Wind Characteristics in Extremely High Atmospheric Boundary Layer over Northwest China

2013 ◽  
Vol 807-809 ◽  
pp. 106-112
Author(s):  
Min Jin Ma
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Model Simulation ◽  
Wrf Model ◽  
Northwest China ◽  
Wind Effect ◽  
Average Height ◽  
Near Surface ◽  
Boundary Parameter ◽  
Wind Characteristics

Extremely high atmospheric boundary layer is observed during 29 May to 3 June 2000 over Dunhuang in Northwest China. Average height of the atmospheric boundary layer is more than 3500m during the observation. Environmental conditions such as wind related to the extremely high atmospheric boundary layer are analysed combined with numerical simulation. Of the first three days in the observation there are low-level jets and large wind shear near surface observed on 29 and 31 May. Wind speed variation in these three days agrees well with variation of the atmospheric boundary layer heights. WRF model is applied to simulate atmospheric boundary layer height and investigate wind characteristics. The model simulation ability is checked and the simulation results find a significant west jet exists over northern Dunhuang. The momentum from the jet transfers downward to Dunhuang to supply kinetic energy developing atmospheric boundary layer. At last two sensitive experiments are performed to study wind effect on the height. The sensitive experiments demonstrate that wind as a lateral boundary parameter heavily influences the atmospheric boundary layer development.

Convective cold pools in long-term boundary layer mast observations

2021 ◽  
Author(s):  
Bastian Kirsch ◽  
Felix Ament ◽  
Cathy Hohenegger
Keyword(s):  
Boundary Layer ◽  
Specific Humidity ◽  
Cold Pool ◽  
Temperature Perturbation ◽  
Statistical Characterization ◽  
Near Surface ◽  
Air Masses ◽  
Diurnal Cycles ◽  
Cold Pools ◽  
Rapid Temperature

AbstractCold pools are mesoscale features, that are key for understanding the organization of convection, but are insufficiently captured in conventional observations. This study conducts a statistical characterization of cold-pool passages observed at a 280 m high boundary layer mast in Hamburg (Germany) and discusses factors controlling their signal strength. During 14 summer seasons 489 cold-pool events are identified from rapid temperature drops below -2 K associated with rainfall. The cold-pool activity exhibits distinct annual and diurnal cycles peaking in July and mid afternoon, respectively. The median temperature perturbation is -3.3 K at 2-m height and weakens above. Also the increase in hydrostatic air pressure and specific humidity is largest near the surface. Extrapolation of the vertically weakening pressure signal suggests a characteristic cold-pool depth of about 750 m. Disturbances in the horizontal and vertical wind speed components document a lifting-induced circulation of air masses prior to the approaching cold-pool front. According to a correlation analysis, the near-surface temperature perturbation is more strongly controlled by the pre-event saturation deficit (r=-0.71) than by the event-accumulated rainfall amount (r=-0.35). Simulating the observed temperature drops as idealized wet-bulb processes suggests that evaporative cooling alone explains 64 % of the variability in cold-pool strength. This number increases to 92 % for cases that are not affected by advection of mid-tropospheric low-Θe air masses under convective downdrafts.

scholarly journals Avaliação da esteira de turbulência gerada por um parque eólico teórico na região do Pampa Gaúcho utilizando o modelo WRF

2020 ◽  
Vol 42 ◽  
pp. e27
Author(s):  
Eduardo Stüker ◽  
Franciano Scremin Puhales ◽  
Luiz Eduardo Medeiros ◽  
Felipe Denardin Costa
Keyword(s):  
Boundary Layer ◽  
Wind Farm ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Atmospheric Flow ◽  
Near Surface ◽  
Control Simulation ◽  
Wind Generators ◽  
Farm Model ◽  
Runoff Decrease

The main objective of this study is to analyze the influence of a wind farm on the variables that control the flow in the atmospheric boundary layer. The simulated period was the whole year of 2008, using a control simulation performed with the Weather Research and Forecasting model (WRF), and the wind farm model (the WRF model with the module Fitch, which parameters the influence of wind turbines on atmospheric flow). Both simulations using the Yonsei-University (YSU) boundary layer parameterization. From the control simulation is made the validation of the model, using observational data collected in two automatic stations of the National Institute of Meteorology (INMET) in the cities of Alegrete-RS and Quaraí-RS. The wind farm idealized in this work has 100 wind generators of 3 MW of power with 120 m in height and with rotor measuring 125 m in diameter. Although the wind speed responds adequately, the temperature and turbulence of near-surface runoff decrease. Analysis of the dependence of near-surface turbulence with vertical stability indicates that the turbulence being generated by the turbines is not reaching the surface. This problem may be related to the chosen boundary layer parameterization.

scholarly journals Sensitivity of MM5-Simulated Boundary Layer Characteristics to Turbulence Parameterizations

2005 ◽  
Vol 44 (9) ◽  
pp. 1467-1483 ◽  
Author(s):  
Larry K. Berg ◽  
Shiyuan Zhong
Keyword(s):  
Boundary Layer ◽  
Latent Heat ◽  
Great Plains ◽  
Mesoscale Model ◽  
Salt Lake ◽  
Heat Fluxes ◽  
Near Surface ◽  
Salt Lake Valley ◽  
Boundary Layer Turbulence ◽  
Medium Range Forecast

Abstract The sensitivity of high-resolution mesoscale simulations to boundary layer turbulence parameterizations is investigated using the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) and observations from two field campaigns. Three widely used turbulence parameterizations were selected for evaluation, two of which [Blackadar (BK) and Medium Range Forecast (MRF) schemes] are simple first-order nonlocal schemes and one [Gayno–Seaman (GS) scheme] of which is a more complex 1.5-order local scheme that solves a prognostic equation for turbulence kinetic energy (TKE). The two datasets are the summer 1996 Boundary Layer Experiment (BLX96) in the southern Great Plains and the autumn 2000 Vertical Transport and Mixing (VTMX) field campaign in the Salt Lake Valley in Utah. Comparisons are made between observed and simulated mean variables and turbulence statistics. Despite the differences in their complexity, all three schemes show similar skill predicting near-surface and boundary layer mean temperature, humidity, and winds at both locations. The BK and MRF schemes produced daytime boundary layers that are more mixed than those produced by the GS scheme. The mixed-layer depths are generally overestimated by the MRF scheme, underestimated by the GS scheme, and well estimated by the BK scheme. All of the schemes predicted surface latent heat fluxes that agreed reasonably well with the observed values, but they substantially overestimated surface sensible heat fluxes because of a significant overprediction of net radiation. In addition, each parameterization overestimated the sensible and latent heat flux aloft. The results suggest that there is little gain in the overall accuracy of forecasts with increasing complexity of turbulence parameterizations.

scholarly journals A Revised Scheme for the WRF Surface Layer Formulation

2012 ◽  
Vol 140 (3) ◽  
pp. 898-918 ◽  
Author(s):  
Pedro A. Jiménez ◽  
Jimy Dudhia ◽  
J. Fidel González-Rouco ◽  
Jorge Navarro ◽  
Juan P. Montávez ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Lower Limit ◽  
Planetary Boundary Layer ◽  
Full Range ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Similarity Functions ◽  
Near Surface ◽  
Diagnostic Variables

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.

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