scholarly journals A Case Study of Offshore Advection of Boundary Layer Rolls over a Stably Stratified Sea Surface

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Nina Svensson ◽  
Erik Sahlée ◽  
Hans Bergström ◽  
Erik Nilsson ◽  
Merete Badger ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Land Surface ◽  
Wind Field ◽  
Vertical Component ◽  
Wrf Model ◽  
Horizontal Wind ◽  
Coastal Regions ◽  
Sar Images ◽  
Streaky Structures ◽  
The Baltic

Streaky structures of narrow (8-9 km) high wind belts have been observed from SAR images above the Baltic Sea during stably stratified conditions with offshore winds from the southern parts of Sweden. Case studies using the WRF model and in situ aircraft observations indicate that the streaks originate from boundary layer rolls generated over the convective air above Swedish mainland, also supported by visual satellite images showing the typical signature cloud streets. The simulations indicate that the rolls are advected and maintained at least 30–80 km off the coast, in agreement with the streaks observed by the SAR images. During evening when the convective conditions over land diminish, the streaky structures over the sea are still seen in the horizontal wind field; however, the vertical component is close to zero. Thus advected feature from a land surface can affect the wind field considerably for long times and over large areas in coastal regions. Although boundary layer rolls are a well-studied feature, no previous study has presented results concerning their persistence during situations with advection to a strongly stratified boundary layer. Such conditions are commonly encountered during spring in coastal regions at high latitudes.

scholarly journals An investigation of ozone and planetary boundary layer dynamics over the complex topography of Grenoble combining measurements and modeling

2003 ◽  
Vol 3 (1) ◽  
pp. 797-825 ◽  
Author(s):  
O. Couach ◽  
I Balin ◽  
R. Jiménez ◽  
P. Ristori ◽  
S. Perego ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Land Surface ◽  
Mesoscale Model ◽  
Ozone Production ◽  
Horizontal Wind ◽  
Maximum Height ◽  
Complex Topography ◽  
Atmospheric Measurements ◽  
Model Calculations

Abstract. This paper concerns an evaluation of ozone (O3) and planetary boundary layer (PBL) dynamics over the complex topography of the Grenoble region through a combination of measurements and mesoscale model (METPHOMOD) predictions for three days, during July 1999. The measurements of O3 and PBL structure were obtained with a Differential Absorption Lidar (DIAL) system, situated 20 km south of Grenoble at Vif (310 m a.s.l.). The combined lidar observations and model calculations are in good agreement with atmospheric measurements obtained with an instrumented aircraft (METAIR). Ozone fluxes were calculated using lidar measurements of ozone vertical profiles concentrations and the horizontal wind speeds measured with a Radar Doppler wind profiler (DEGREANE). The ozone flux patterns indicate that the diurnal cycle of ozone production is controlled by local thermal winds. The convective PBL maximum height was some 2700 m above the land surface while the nighttime residual ozone layer was generally found between 1200 and 2200 m. Finally we evaluate the magnitude of the ozone processes at different altitudes in order to estimate the photochemical ozone production due to the primary pollutants emissions of Grenoble city and the regional network of automobile traffic.

scholarly journals The Effects of Complex Terrain on Severe Landfalling Tropical Cyclone Larry (2006) over Northeast Australia

2008 ◽  
Vol 136 (11) ◽  
pp. 4334-4354 ◽  
Author(s):  
Hamish A. Ramsay ◽  
Lance M. Leslie
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Land Surface ◽  
Wind Field ◽  
Complex Terrain ◽  
Mesoscale Model ◽  
Surface Wind ◽  
Small Scale ◽  
Precipitation Pattern ◽  
Intense Storm

Abstract The interaction between complex terrain and a landfalling tropical cyclone (TC) over northeastern Australia is investigated using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5). Severe TC Larry (in March 2006) made landfall over an area of steep coastal orography and caused extensive damage. The damage pattern suggested that the mountainous terrain had a large influence on the TC wind field, with highly variable damage across relatively small distances. The major aims in this study were to reproduce the observed features of TC Larry, including track, intensity, speed of movement, size, decay rate, and the three-dimensional wind field using realistic high-resolution terrain data and a nested grid with a horizontal spacing of 1 km for the finest domain (referred to as CTRL), and to assess how the above parameters change when the terrain height is set to zero (NOTOPOG). The TC track for CTRL, including the timing and location of landfall, was in close agreement with observation, with the model eye overlapping the location of the observed eye at landfall. Setting the terrain height to zero resulted in a more southerly track and a more intense storm at landfall. The orography in CTRL had a large impact on the TC’s 3D wind field, particularly in the boundary layer where locally very high wind speeds, up to 68 m s−1, coincided with topographic slopes and ridges. The orography also affected precipitation, with localized maxima in elevated regions matching observed rainfall rates. In contrast, the precipitation pattern for the NOTOPOG TC was more symmetric and rainfall totals decreased rapidly with distance from the storm’s center. Parameterized maximum surface wind gusts were located beneath strong boundary layer jets. Finally, small-scale banding features were evident in the surface wind field over land for the NOTOPOG TC, owing to the interaction between the TC boundary layer flow and land surface characteristics.

High-resolution temperature and wind field observations in the atmospheric boundary layer

2020 ◽  
Author(s):  
Matthias Zeeman ◽  
Marwan Katurji ◽  
Tirtha Banerjee
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Land Surface ◽  
Wind Field ◽  
Single Point ◽  
Sonic Anemometer ◽  
Atmospheric Stability ◽  
Surface Boundary ◽  
Three Dimensional Model ◽  
Local Flow

<p>Do we get a better picture of the world around us if we simultaneously observe many aspects instead of a few? Dense sensing networks are an elaborate way to validate our representation of land surface boundary layer processes commonly derived from single point monitoring stations or a three-dimensional model world. More samples promise unique insights into interactions that occur at different scales, separated in space and time.</p><p>We present a combination of techniques that purvey a) observations of the temperature and wind field in high detail and b) the extraction of information about dynamic interactions near the surface. A field experiment was conducted in complex terrain, in which landscape features dramatically modulate local flow patterns and the atmospheric stability during summer days rapidly transitions on a diurnal scale and between locations. Wind and temperature were simultaneously observed using a network of Doppler lidar, sonic anemometer, fiber-optic temperature sensing (DTS) and thermal imaging velocimetry (TIV) instrumentation, centered around the TERENO/ICOS preAlpine grassland observatory station Fendt, Germany, during the ScaleX Campaigns (https://scalex.imk-ifu.kit.edu). Data analyses relied on signal decomposition and statistical clustering, aimed at the characterization of (non-)turbulent motions and their feedback on turbulent mixing near the surface. The combination of methods offered multiple levels of detail about the development and impact of organized structures in the atmospheric boundary layer.</p><p>The study shows that the exploration of novel micrometeorological and data sciences techniques helps advance our knowledge of fundamental aspects of atmospheric turbulence, and provides new avenues for theoretical and numerical studies of the atmospheric boundary layer.</p>

scholarly journals Genesis of Tibetan Plateau Vortex: Roles of Surface Diabatic and Atmospheric Condensational Latent Heating

2019 ◽  
Vol 58 (12) ◽  
pp. 2633-2651 ◽  
Author(s):  
Feimin Zhang ◽  
Chenghai Wang ◽  
Zhaoxia Pu
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Diabatic Heating ◽  
Vertical Component ◽  
Wrf Model ◽  
Cloud Microphysics ◽  
Lower Atmosphere ◽  
Positive Contribution ◽  
Simulation Performance ◽  
Tibetan Plateau Vortex

AbstractNumerical simulations of a nighttime-generated Tibetan Plateau vortex (TPV) are conducted using the advanced Weather Research and Forecasting (WRF) Model. It is found that the nighttime TPV forms as a result of the merging of convections. Although the WRF Model can reproduce the genesis of the nighttime TPV well, colder and drier biases in the lower atmosphere and drier biases in the upper atmosphere are still presented, thus degrading the simulation performance. Intercomparisons among the experiments indicate that the simulations are more sensitive to land surface schemes than to cloud microphysics schemes. The development of convection is more favorable when daytime surface diabatic heating is vigorous. Surface diabatic heating during daytime plays a dominant role in the development of daytime convection and the genesis of nighttime TPV. Further diagnosis of the PV budget reveals that the obvious increase in PV in the lower atmosphere is associated with the evidently strengthened cyclonic vorticity during TPV genesis. This could be attributed to the increased vertical component of net cross-boundary PV fluxes during the merging of convections as well as the significant positive contribution of diabatic heating effects in the lower atmosphere. Therefore, strong daytime surface diabatic heating, which is essential to convection development, could provide a favorable condition for nighttime TPV genesis. Overall results illuminate the complicated process of TPV genesis.

scholarly journals Modeling of land-surface interactions in the PALM model system 6.0: Land surface model description, first evaluation, and sensitivity to model parameters

2020 ◽  
Author(s):  
Katrin Frieda Gehrke ◽  
Matthias Sühring ◽  
Björn Maronga
Keyword(s):  
Boundary Layer ◽  
Energy Balance ◽  
Surface Potential ◽  
Land Surface ◽  
Potential Temperature ◽  
Land Surface Model ◽  
Model System ◽  
Horizontal Wind ◽  
Surface Model ◽  
Near Surface

Abstract. In this paper the land-surface model embedded in the PALM model system is described and evaluated against in-situ measurement data in Cabauw. For this, two consecutive clear-sky days are simulated and the components of surface energy balance, as well as near-surface potential temperature, humidity and horizontal wind speed are compared against observation data. For the simulated period, components of the energy balance agree well during day- and nighttime, and also the daytime Bowen ratio agrees fairly well compared to the observations. Although the model simulates a significantly more stably-stratified nocturnal boundary layer compared to the observation, near-surface potential temperature and humidity agree fairly well during day. Moreover, we performed a sensitivity study in order to investigate how much the model results depend on land-surface and soil specifications, as well as atmospheric initial conditions. By this, we find that a false estimation of the leaf area index, the albedo, or the initial humidity causes a serious misrepresentation of the daytime turbulent sensible and latent heat fluxes. During night, the boundary-layer characteristics are mostly affected by grid size, surface roughness, and the applied radiation schemes.

scholarly journals Development and Testing of Polar Weather Research and Forecasting (WRF) Model. Part I: Greenland Ice Sheet Meteorology*

2008 ◽  
Vol 136 (6) ◽  
pp. 1971-1989 ◽  
Author(s):  
Keith M. Hines ◽  
David H. Bromwich
Keyword(s):  
Boundary Layer ◽  
Land Surface ◽  
Mesoscale Model ◽  
Ice Sheet ◽  
Wrf Model ◽  
Greenland Ice Sheet ◽  
Forecast Skill ◽  
Weather Research And Forecasting ◽  
Surface Model ◽  
Weather Research

Abstract A polar-optimized version of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) was developed to fill climate and synoptic needs of the polar science community and to achieve an improved regional performance. To continue the goal of enhanced polar mesoscale modeling, polar optimization should now be applied toward the state-of-the-art Weather Research and Forecasting (WRF) Model. Evaluations and optimizations are especially needed for the boundary layer parameterization, cloud physics, snow surface physics, and sea ice treatment. Testing and development work for Polar WRF begins with simulations for ice sheet surface conditions using a Greenland-area domain with 24-km resolution. The winter month December 2002 and the summer month June 2001 are simulated with WRF, version 2.1.1, in a series of 48-h integrations initialized daily at 0000 UTC. The results motivated several improvements to Polar WRF, especially to the Noah land surface model (LSM) and the snowpack treatment. Different physics packages for WRF are evaluated with December 2002 simulations that show variable forecast skill when verified with the automatic weather station observations. The WRF simulation with the combination of the modified Noah LSM, the Mellor–Yamada–Janjić boundary layer parameterization, and the WRF single-moment microphysics produced results that reach or exceed the success standards of a Polar MM5 simulation for December 2002. For summer simulations of June 2001, WRF simulates an improved surface energy balance, and shows forecast skill nearly equal to that of Polar MM5.

scholarly journals An investigation of ozone and planetary boundary layer dynamics over the complex topography of Grenoble combining measurements and modeling

2003 ◽  
Vol 3 (3) ◽  
pp. 549-562 ◽  
Author(s):  
O. Couach ◽  
I. Balin ◽  
R. Jiménez ◽  
P. Ristori ◽  
S. Perego ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Land Surface ◽  
Mesoscale Model ◽  
Ozone Production ◽  
Horizontal Wind ◽  
Maximum Height ◽  
Complex Topography ◽  
Atmospheric Measurements ◽  
Model Calculations

Abstract. This paper concerns an evaluation of ozone (O3) and planetary boundary layer (PBL) dynamics over the complex topography of the Grenoble region through a combination of measurements and mesoscale model (METPHOMOD) predictions for three days, during July 1999. The measurements of O3 and PBL structure were obtained with a Differential Absorption Lidar (DIAL) system, situated 20 km south of Grenoble at Vif (310 m ASL). The combined lidar observations and model calculations are in good agreement with atmospheric measurements obtained with an instrumented aircraft (METAIR). Ozone fluxes were calculated using lidar measurements of ozone vertical profiles concentrations and the horizontal wind speeds measured with a Radar Doppler wind profiler (DEGREANE. The ozone flux patterns indicate that the diurnal cycle of ozone production is controlled by local thermal winds. The convective PBL maximum height was some 2700 m above the land surface while the nighttime residual ozone layer was generally found between 1200 and 2200 m. Finally we evaluate the magnitude of the ozone processes at different altitudes in order to estimate the photochemical ozone production due to the primary pollutants emissions of Grenoble city and the regional network of automobile traffic.

scholarly journals Study of the Thermal Internal Boundary Layer in Sea Breeze Conditions Using Different Parameterizations: Application of the WRF Model in the Greater Vitória Region

2016 ◽  
Vol 31 (4 suppl 1) ◽  
pp. 593-609 ◽  
Author(s):  
Nadir Salvador ◽  
◽  
Ayres G. Loriato ◽  
Alexandre Santiago ◽  
Taciana T.A. Albuquerque ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Land Surface ◽  
Wrf Model ◽  
Coastal Region ◽  
Sea Breeze ◽  
Internal Boundary Layer ◽  
Internal Boundary ◽  
Surface Model ◽  
Thermal Internal Boundary Layer ◽  
Local Closure

Abstract In the present study, the physical parameterizations of the Weather Research and Forecasting (WRF) model are verified for making accurate inferences about the dynamics of the Thermal Internal Boundary Layer (TIBL) generated by sea breeze in an urban center with an island in a bay along a coastal region with rugged topography. The simulations were performed using parameterizations from Yonsei University (YSU), Mellor-Yamada-Janjic (MYJ) and Asymmetric Convective Model version 2 (ACM2) for the atmospheric boundary layer (ABL) and Noah and Rapid Update Cycle (RUC) for the Land Surface Model (LSM). The data inferred by the WRF model were compared with those obtained by a Surface Meteorological Station (SMS) and by measurements generated using Light Detection and Ranging (LIDAR), Sonic Detection and Ranging (SODAR) and radiosonde. The simulations showed that although the object of this research was a region with high geographical complexity, the YSU parameterization set (non-local closure) for the ABL and the Noah parameterization for the LSM presented satisfactory results in determining ABL height generated by the sea breeze on the day in question.

Horizontal Meandering as a Distinctive Feature of the Stable Boundary Layer

2019 ◽  
Vol 76 (10) ◽  
pp. 3029-3046 ◽  
Author(s):  
L. Mortarini ◽  
D. Cava ◽  
U. Giostra ◽  
F. Denardin Costa ◽  
G. Degrazia ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Velocity ◽  
Stable Boundary Layer ◽  
Vertical Component ◽  
Low Frequency ◽  
Horizontal Wind ◽  
Southeastern Brazil ◽  
Stable Boundary ◽  
Low Wind Speed ◽  
Temperature Spectra

Abstract Oscillations in the horizontal components of the wind velocity associated with oscillations in air temperature during low–wind speed episodes are ubiquitous in the stable boundary layer and are labeled as wind meandering. The meandering structure is recognizable by a clear negative lobe in the Eulerian autocorrelation functions of the horizontal wind velocity components and of the sonic temperature and by a corresponding peak at low frequency in the velocity components and temperature spectra. These distinctive features are used to isolate meandering occurrences and to study its properties in relation to the classical description of the planetary stable boundary layer. It is shown that the ratio of the variance of the wind velocity vertical component over the variance of the composite of the wind velocity horizontal components splits the frequency distribution of meandering and nonmeandering events and divides the nocturnal boundary layer in two different regimes characterized by different turbulent properties. The data comparison with a turbulence model based on Rotta return to isotropy showed that meandering and nonmeandering cases may have similar dynamics. This suggests that meandering may not be connected to a laminarization of the flow and shows that the Rotta scheme may still describe the energetic transfer between wind velocity components in the very stable boundary layer if the Rotta similarity constant c depends on the flux Richardson number. The data confirm a c value of 2.2 for Rif = 0 compatible with its conventional value. The analysis presented refers to one year of continuous measurements on 10 levels carried out at a coastal site in southeastern Brazil.

scholarly journals The Making of the New European Wind Atlas, Part 1: Model Sensitivity

2020 ◽  
Author(s):  
Andrea N. Hahmann ◽  
Tija Sile ◽  
Björn Witha ◽  
Neil N. Davis ◽  
Martin Dörenkämper ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Wind Speed ◽  
Planetary Boundary Layer ◽  
Land Surface ◽  
Roughness Length ◽  
Wrf Model ◽  
Model Sensitivity ◽  
Surface Roughness Length ◽  
Wind Climate

Abstract. This is the first of two papers that documents the creation of the New European Wind Atlas (NEWA). It describes the sensitivity analysis and evaluation procedures that formed the basis for choosing the final setup of the mesoscale model simulations of the wind atlas. An optimal combination of model setup and parameterisations was found for simulating the climatology of the wind field at turbine-relevant heights with the Weather Research and Forecasting (WRF) model. Initial WRF model sensitivity experiments compared the wind climate generated by using two commonly used planetary boundary layer schemes and were carried out over several regions in Europe. They confirmed that the largest differences in annual mean wind speed at 100 m above ground level mostly coincide with areas of high surface roughness length and not with the location of the domains or maximum wind speed. Then an ensemble of more than 50 simulations with different setups for a single year was carried out for one domain covering Northern Europe, for which tall mast observations were available. Many different parameters were varied across the simulations, for example, model version, forcing data, various physical parameterisations and the size of the model domain. These simulations showed that although virtually every parameter change affects the results in some way, significant changes on the wind climate in the boundary layer are mostly due to using different physical parameterisations, especially the planetary boundary layer scheme, the representation of the land surface, and the prescribed surface roughness length. Also, the setup of the simulations, such as the integration length and the domain size can considerably influence the results. The degree of similarity between winds simulated by the WRF ensemble members and the observations was assessed using a suite of metrics, including the Earth Mover's Distance (EMD), a statistic that measures the distance between two probability distributions. The EMD was used to diagnose the performance of each ensemble member using the full wind speed distribution, which is important for wind resource assessment. The most realistic ensemble members were identified to determine the most suitable configuration to be used in the final production run, which is fully described and evaluated in the second part of this study.

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