scholarly journals Sensitivity of mesoscale dust simulation to WRF_Chem boundary layer scheme (case study: March 14th 2012)

2019 ◽  
Author(s):  
Elham Mobarak Hassan ◽  
Parvin Ghafarian ◽  
Faranak Bahrami ◽  
Mahnaz Khani ◽  
Morteza Sabori
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Pm10 Concentration ◽  
Observation Data ◽  
Horizontal Visibility ◽  
Khuzestan Province ◽  
Future Prediction ◽  
Boundary Layer Scheme ◽  
Dust Events ◽  
Local Dust

Introduction: Recently, local dust events increased in Khuzestan province. Therefore, knowledge on its properties can have a crucial role in future prediction and planning. Materials and methods: This study investigated the effect of different boundary layer schemes for dust simulation by WRF_Chem model on March 14th 2012 in Khuzestan province. To validate the model, observation data such as horizontal visibility, 10-m wind speed and PM10 were provided. Results: The results indicated that the MYN scheme has the highest correlation between model outputs and observation for 10-m wind speed, PM10 and horizontal visibility. Due to the highest correlation of the 10 m wind speed, horizontal visibility, PM10 respectively with 0.83, -0.76 and 0.76 values and the highest consistency with the day-night variation of PM10, MYN scheme can be selected as the most suitable scheme. At the second level, UW scheme seems to be an appropriate option. In MYN and UW schemes, the maximum wind speed in 925 hPa level was estimated 24 m/s at 03 UTC, March 14th which caused an increase in the 10 m wind speed at 06 and 09UTC. Therefore, the dust emitted from the surface to the air. Although the results of MYJ scheme showed proper correlation and temporal variation with observed, but as it determined PM10 concentration with high difference, it can’t be considered as a suitable scheme for simulation dust concentration. Conclusion: Although the PM10 concentration obtained by WRF_Chem showed difference with the observation for all the selected boundary layer schemes, MYN scheme gives the most appropriate result.

A Study on Characteristics of Atmospheric Boundary Layer during Dust Events in Lanzhou, China and their Relation with PM10 Pollution

2010 ◽  
Vol 113-116 ◽  
pp. 372-377 ◽  
Author(s):  
Xin Yuan Feng ◽  
Shi Gong Wang
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Atmospheric Boundary Layer ◽  
Momentum Flux ◽  
Turbulent Flux ◽  
Layer Structure ◽  
Pm10 Concentration ◽  
Flux Transport ◽  
Strong Inversion ◽  
Dust Events

In order to understand the influence mechanism of dust events on PM10 pollution, the characteristics of atmospheric boundary-layer structure and turbulent flux transport during different kinds of dust events in Lanzhou and their relation with PM10 pollution were analyzed by using the data of PM10 concentration, gradient measurements of meteorological tower and turbulent flux measurements observed at SACOL. As dust events break out, the strong inversion in the boundary layer breaks and a mixing layer develops quickly. With the rise of wind speed, PM10 concentration increases sharply. If there is obvious dust transport from upstream regions, the peak of PM10 concentration can lag behind the peak of wind speed. The vertical transport of momentum flux is very strong. The turbulent momentum downward transport, especially the downward momentum flux of meridional velocity, is the main factor which causes the dust blowing and the heavy PM10 pollution during dust events.

scholarly journals Understanding the Major Impact of Planetary Boundary Layer Schemes on Simulation of Vertical Wind Structure

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 777
Author(s):  
Lei Zhang ◽  
Jinyuan Xin ◽  
Yan Yin ◽  
Wenyuan Chang ◽  
Min Xue ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Wind Energy ◽  
Planetary Boundary Layer ◽  
Wind Field ◽  
Weather Conditions ◽  
Vertical Wind ◽  
Observation Data ◽  
Wind Field Simulation ◽  
Field Simulation

The structure and evolution of the atmospheric planetary boundary layer (PBL) plays an important role in the physical and chemical processes of cloud–radiation interaction, vertical mixing and pollutant transport in the atmosphere. The PBL parameterization scheme describes the vertical transport of atmospheric momentum, heat, water vapor and other physical quantities in the boundary layer. The accuracy of wind field simulation and prediction is one of the most significant parameters in the field of atmospheric science and wind energy. Limited by the observation data, there are few studies on wind energy development. A 3D Doppler wind LiDAR (DWL) providing the high-vertical-resolution wind data over the urban complex underlying surface in February 2018 was employed to systematically evaluate the accuracy of vertical wind field simulation for the first time. 11 PBL schemes of the Weather Research and Forecasting Model (WRF) were employed in simulation. The model results were evaluated in groups separated by weather (sunny days, hazy days and windy days), observation height layers of wind field, and various observation wind speeds. Among these factors, the simulation accuracy is most closely related to the observation height layers of wind field. The simulation is fairly accurate at a height of 1000–2000 m, as most of the relative mean biases for wind speed and wind direction are less than 20% and 6% respectively. Below 1000 m, the wind speed and direction biases are about 30–150% m·s−1 and 6–30%, respectively. Moreover, when the observed wind speed was lower than 5 m·s−1, the biases were usually large, and the wind speed relative mean bias reaches up to 50–300%. In addition, the accuracy of the simulated wind profile is better in the range of 10–15 m·s−1 than other speed ranges, and is better above 1000 m than below 1000 m in the boundary layer. We see that the WRF boundary layer schemes have different applicabilities to different weather conditions. The WRF boundary layer schemes have significant differences in wind field simulations, with larger error under the complex topographies. A PBL scheme is not likely to maintain its advantages in the long term under different conditions including altitude and weather conditions.

scholarly journals The Temporal-Spatial Variations and Potential Causes of Dust Events in Xinjiang Basin During 1960–2015

2021 ◽  
Vol 9 ◽  
Author(s):  
Lamei Mu ◽  
Jing Su ◽  
Xinyue Mo ◽  
Nan Peng ◽  
Ying Xu ◽  
...  
Keyword(s):  
Wind Speed ◽  
Correlation Coefficient ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Spatial Variations ◽  
Observation Data ◽  
Active Period ◽  
Significant Downward Trend ◽  
Dust Events ◽  
Southern Xinjiang

Dust events not only cause local ecosystem degradation and desertification, but also have profound impacts on regional and global climate system, as well as air quality and human health. Dust events in Xinjiang Basin, as the important dust source of Eastern Asia, have undergone a significant change under the global warming background and may be in a new active period after 2000, which is worthy of study. This study provides the temporal and spatial variations of dust events in the Xinjiang Basin based on surface meteorological station observation data during 1960–2015. The results show that Southern Xinjiang is the main dust occurrence region where dust events are significantly more than that in the Northern Xinjiang, and each year more than 73% of dust events occurred in spring and summer. The dust index (DI), which is defined to represent the large-scale variation of dust event, shows a significant downward trend during the past 56 years with a linear decreasing rate −8.2 years−1 in Southern Xinjiang. The DI is positively correlated to surface wind speed with a mean correlation coefficient of 0.79. The declining trend of surface wind speed could explain dust events variation during 1960–2000. But in the new active period after 2000, the increase of DI is not consistent with the rising wind speed with the correlation coefficient decreasing to 0.34. It is found that, compared with 1960–1999, the average annual precipitation and frequency increased by 17.4 and 13% during 2000–2015, respectively, and the NDVI also increased at the same time, which indicates that the surface condition changes induced by the increase of precipitation might suppress the occurrence of dust. Moreover, the analysis of high-altitude wind field shows that the variation of the East Asian general circulation’s intensity, dominating the upper-level wind fields in the Xinjiang basin, will change the surface wind speed and precipitation, and further affect the occurrence of dust events.

Prediction of Atmospheric Turbulence Characteristics for Surface Boundary Layer using Empirical Spectral Methods

2020 ◽  
Author(s):  
Yagya Dutta Dwivedi ◽  
Vasishta Bhargava Nukala ◽  
Satya Prasad Maddula ◽  
Kiran Nair
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Surface Roughness ◽  
Wind Speed ◽  
Atmospheric Turbulence ◽  
Surface Boundary ◽  
Low Frequencies ◽  
Surface Boundary Layer ◽  
Power Spectral ◽  
Mean Wind Speed

Abstract Atmospheric turbulence is an unsteady phenomenon found in nature and plays significance role in predicting natural events and life prediction of structures. In this work, turbulence in surface boundary layer has been studied through empirical methods. Computer simulation of Von Karman, Kaimal methods were evaluated for different surface roughness and for low (1%), medium (10%) and high (50%) turbulence intensities. Instantaneous values of one minute time series for longitudinal turbulent wind at mean wind speed of 12 m/s using both spectra showed strong correlation in validation trends. Influence of integral length scales on turbulence kinetic energy production at different heights is illustrated. Time series for mean wind speed of 12 m/s with surface roughness value of 0.05 m have shown that variance for longitudinal, lateral and vertical velocity components were different and found to be anisotropic. Wind speed power spectral density from Davenport and Simiu profiles have also been calculated at surface roughness of 0.05 m and compared with k−1 and k−3 slopes for Kolmogorov k−5/3 law in inertial sub-range and k−7 in viscous dissipation range. At high frequencies, logarithmic slope of Kolmogorov −5/3rd law agreed well with Davenport, Harris, Simiu and Solari spectra than at low frequencies.

scholarly journals Saharan dust and giant quartz particle transport towards Iceland

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
György Varga ◽  
Pavla Dagsson-Walhauserová ◽  
Fruzsina Gresina ◽  
Agusta Helgadottir
Keyword(s):  
Numerical Models ◽  
Saharan Dust ◽  
Atmospheric Environment ◽  
The Arctic ◽  
Dust Particles ◽  
Atmospheric Flow ◽  
Dust Transport ◽  
Strong Winds ◽  
Dust Events ◽  
Local Dust

AbstractMineral dust emissions from Saharan sources have an impact on the atmospheric environment and sedimentary units in distant regions. Here, we present the first systematic observations of long-range Saharan dust transport towards Iceland. Fifteen Saharan dust episodes were identified to have occurred between 2008 and 2020 based on aerosol optical depth data, backward trajectories and numerical models. Icelandic samples from the local dust sources were compared with deposited dust from two severe Saharan dust events in terms of their granulometric and mineralogical characteristics. The episodes were associated with enhanced meridional atmospheric flow patterns driven by unusual meandering jets. Strong winds were able to carry large Saharan quartz particles (> 100 µm) towards Iceland. Our results confirm the atmospheric pathways of Saharan dust towards the Arctic, and identify new northward meridional long-ranged transport of giant dust particles from the Sahara, including the first evidence of their deposition in Iceland as previously predicted by models.

Modeling the Atmospheric Boundary Layer Wind Response to Mesoscale Sea Surface Temperature Perturbations

2014 ◽  
Vol 142 (11) ◽  
pp. 4284-4307 ◽  
Author(s):  
Natalie Perlin ◽  
Simon P. de Szoeke ◽  
Dudley B. Chelton ◽  
Roger M. Samelson ◽  
Eric D. Skyllingstad ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Coupling Coefficient ◽  
Eddy Viscosity ◽  
Sea Surface ◽  
Coupling Coefficients ◽  
Wind Response ◽  
Speed Response

Abstract The wind speed response to mesoscale SST variability is investigated over the Agulhas Return Current region of the Southern Ocean using the Weather Research and Forecasting (WRF) Model and the U.S. Navy Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) atmospheric model. The SST-induced wind response is assessed from eight simulations with different subgrid-scale vertical mixing parameterizations, validated using Quick Scatterometer (QuikSCAT) winds and satellite-based sea surface temperature (SST) observations on 0.25° grids. The satellite data produce a coupling coefficient of sU = 0.42 m s−1 °C−1 for wind to mesoscale SST perturbations. The eight model configurations produce coupling coefficients varying from 0.31 to 0.56 m s−1 °C−1. Most closely matching QuikSCAT are a WRF simulation with the Grenier–Bretherton–McCaa (GBM) boundary layer mixing scheme (sU = 0.40 m s−1 °C−1), and a COAMPS simulation with a form of Mellor–Yamada parameterization (sU = 0.38 m s−1 °C−1). Model rankings based on coupling coefficients for wind stress, or for curl and divergence of vector winds and wind stress, are similar to that based on sU. In all simulations, the atmospheric potential temperature response to local SST variations decreases gradually with height throughout the boundary layer (0–1.5 km). In contrast, the wind speed response to local SST perturbations decreases rapidly with height to near zero at 150–300 m. The simulated wind speed coupling coefficient is found to correlate well with the height-averaged turbulent eddy viscosity coefficient. The details of the vertical structure of the eddy viscosity depend on both the absolute magnitude of local SST perturbations, and the orientation of the surface wind to the SST gradient.

Sign in / Sign up

Export Citation Format

Share Document