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18 pages, 7309 KiB

Open AccessArticle

A Statistical-Based Model for Typhoon Rain Hazard Assessment

by Jiyang Gu, Xizhong Cui and Hanping Hong

Atmosphere 2022, 13(8), 1172; https://doi.org/10.3390/atmos13081172 - 24 Jul 2022

Cited by 2 | Viewed by 1391

Abstract

Extreme typhoon rainfall can lead to damaging floods near the coastal region in mainland China. In the present study, we calibrate the parameters for a parametric hurricane rain model by using the precipitation radar (PR) data from the Tropical Rainfall Measuring Mission (TRMM) [...] Read more.

Extreme typhoon rainfall can lead to damaging floods near the coastal region in mainland China. In the present study, we calibrate the parameters for a parametric hurricane rain model by using the precipitation radar (PR) data from the Tropical Rainfall Measuring Mission (TRMM) (i.e., PR-TRMM) and the TRMM microwave imager (TMI) data (i.e., TMI-TRMM). To show the applicability of the model for the tropical cyclone (TC) rain hazard assessment, we combine the developed rainfall intensity model with historical and synthetic TC tracks to estimate the T-year return period value of the accumulated rainfall in 24 h, Q_A_24-T. We map Q_A_24-100 for part of the coastal region in mainland China, showing that the spatial variation of Q_A_24-100 is relatively smooth. It was found that the estimated Q_A_24-100 using the model developed, based on the snapshots from PR-TRMM, is about 60% of that obtained using the model developed based on the snapshots from TMI-TRMM. This reflects the differences in the rainfall intensities reported in TMI-TRMM and PR-TRMM. As part of verification, we compare the estimated return period value to that obtained by using the record from surface meteorological stations at a few locations. The comparison indicates that, on average, Q_A_24-100 based on gauge data is about 1.4 and 2.3 times that obtained using the model developed based on the snapshots from PR-TRMM and TRM-TRMM, respectively. This suggests that, for TC rain hazard estimation, one may consider the empirical scaling factor of 1.4 and 2.4 for the rainfall intensity models developed based on snapshots from PR-TRMM and TMI-TRMM, respectively. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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19 pages, 5797 KiB

Open AccessArticle

Wind Lidar and Radiosonde Measurements of Low-Level Jets in Coastal Areas of the German Bight

by Thomas Rausch, Beatriz Cañadillas, Oliver Hampel, Tayfun Simsek, Yilmaz Batuhan Tayfun, Thomas Neumann, Simon Siedersleben and Astrid Lampert

Atmosphere 2022, 13(5), 839; https://doi.org/10.3390/atmos13050839 - 20 May 2022

Cited by 3 | Viewed by 2464

Abstract

For wind energy, the knowledge of the available wind resource is essential. Therefore, specific wind phenomena at the altitude range of wind turbines are currently the focus of investigations. One such specific feature is the low-level jet (LLJ). The article analyses LLJ properties [...] Read more.

For wind energy, the knowledge of the available wind resource is essential. Therefore, specific wind phenomena at the altitude range of wind turbines are currently the focus of investigations. One such specific feature is the low-level jet (LLJ). The article analyses LLJ properties at two locations in the German Bight: A wind lidar system for measuring wind profiles at heights from 50 m to 500 m a.g.l. (above ground level) was first installed at the offshore island of Heligoland, Germany, and then at the coastal island of Norderney, Germany, for one year. The LLJ is defined here as a maximum horizontal wind speed in the vertical profile of horizontal wind speed followed by a minimum wind speed, independent of the mechanism or origin of the phenomenon. The two sites showed a similar annual and diurnal distribution of LLJ events with a maximum occurrence in spring and summer and during the night, and a most frequent jet core height of around 120 m a.g.l. Based on radiosondes launched from Norderney at midnight and noon, it is shown that LLJ events at noon are most frequent when atmospheric conditions are stable. A case study shows the horizontal extent of an LLJ event over at least 100 km by simultaneous wind lidar measurements at four sites in the German Bight and mesoscale simulations with the weather research and forecast (WRF) model. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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18 pages, 7070 KiB

Open AccessArticle

Influence Mechanism of a Bridge Wind Barrier on the Stability of a Van-Body Truck under Crosswind

by Zhiqun Yuan, Dandan Xia, Xiaobo Lin, Li Lin, Yufeng Liu and Yuehan Li

Atmosphere 2022, 13(2), 360; https://doi.org/10.3390/atmos13020360 - 21 Feb 2022

Viewed by 1881

Abstract

Understanding the crosswind stability of cars under strong wind loads and research on wind resistance methods is important for improving the safety performance of wind-induced driving on bridges. Taking van-body trucks as the research object, numerical calculation methods and wind tunnel test methods [...] Read more.

Understanding the crosswind stability of cars under strong wind loads and research on wind resistance methods is important for improving the safety performance of wind-induced driving on bridges. Taking van-body trucks as the research object, numerical calculation methods and wind tunnel test methods are used to conduct the wind-induced driving safety analyses of van trucks on a cross-sea bridge. The influence of the structural parameters of the barrier-type wind barrier on the aerodynamic characteristics and straight-line driving stability of the trucks on the bridge is studied and analyzed quantitatively. The results show that the decrease in the porosity of the wind barrier can effectively reduce the average wind speed of the bridge deck, and increasing the height of the wind barrier can effectively reduce the wind speed and increase the occlusion height of the bridge deck. The lateral acceleration, yaw rate, and lateral displacement of trucks decrease with the decrease in the porosity of the wind barrier and decrease with the increase in the height of the wind barrier. The research conclusions can not only provide data support for wind-induced driving safety analysis and the wind-resistant design of bridges but also provide a new method to balance the requirements of bridge wind-induced driving safety and bridge wind-induced structure safety. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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14 pages, 4481 KiB

Open AccessArticle

Improvement of Airflow Distribution and Contamination Control for a Biotech Cleanroom

by Fujen Wang, Indra Permana, Kwowhei Lee, Dibakar Rakshit and Parisya Premiera Rosulindo

Atmosphere 2022, 13(2), 335; https://doi.org/10.3390/atmos13020335 - 17 Feb 2022

Cited by 5 | Viewed by 3379

Abstract

The biotech cleanroom industry presents a biological basis for living organisms or their components (bacteria or enzymes) to produce helpful medicine. However, biotech industries such as vaccine production need a clean critical environment and contamination control that is always a vital concern for [...] Read more.

The biotech cleanroom industry presents a biological basis for living organisms or their components (bacteria or enzymes) to produce helpful medicine. However, biotech industries such as vaccine production need a clean critical environment and contamination control that is always a vital concern for the manufacturing process. This study investigates a biotech cleanroom through a comprehensive field measurement and numerical simulation. The field measurement test results conformed to the design specification to satisfactorily meet with the cleanroom standard of PIC/S and EU GMP. Furthermore, the field measurement data were used as a basic validation and boundary condition for numerical simulation. The numerical simulation results revealed that the concentration distribution in case 1 as a baseline case showed satisfactory results, with a removal efficiency of 75.2% and ventilation efficiency of 80%. However, there was still a high concentration accumulated in certain areas. The improvement strategy was analyzed through non-unidirectional flow ventilation with different face velocities and by adding one return air grille for case 2 and two return air grilles for case 3. The results revealed that case 2 presented the best results in this study, with a removal efficiency of 86.7% and ventilation efficiency of 82% when supplying air velocity at 0.2 m/s. In addition, increasing the supply air velocity to 0.3 m/s could enhance removal ventilation by around 19% and ventilation efficiency by around 5%. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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11 pages, 3589 KiB

Open AccessArticle

Effects of Wind Barriers on Wind Fields and Vehicle Stability on Bridges

by Xiaobo Lin, Bin Lin, Dandan Xia, Li Lin and Zhiqun Yuan

Atmosphere 2022, 13(2), 318; https://doi.org/10.3390/atmos13020318 - 14 Feb 2022

Cited by 1 | Viewed by 2512

Abstract

To explore the influence of bridge wind barriers, with their specific opening shapes and arrangements, on bridge deck wind fields and vehicle driving stability under different crosswinds, five bridge wind barrier schemes were designed. For two incoming wind speeds, the wind speed at [...] Read more.

To explore the influence of bridge wind barriers, with their specific opening shapes and arrangements, on bridge deck wind fields and vehicle driving stability under different crosswinds, five bridge wind barrier schemes were designed. For two incoming wind speeds, the wind speed at different heights over three traffic lanes and the aerodynamic six-component force of the vehicle model were measured, and the influence of the wind barrier parameters on the vehicle driving stability was analyzed. The equivalent wind speed reduction coefficient of the wind barrier was compared with the dimensionless coefficients of the aerodynamic side force, roll moment, and aerodynamic lift to verify the accuracy of the shielding effect evaluation indices. The final conclusions provide a useful reference for designing bridge wind barriers. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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23 pages, 12666 KiB

Open AccessArticle

Investigations on Wind Characteristics for Typhoon and Monsoon Wind Speeds Based on Both Stationary and Non-Stationary Models

by Zhiqing Qin, Dandan Xia, Liming Dai, Qingsong Zheng and Li Lin

Atmosphere 2022, 13(2), 178; https://doi.org/10.3390/atmos13020178 - 21 Jan 2022

Cited by 8 | Viewed by 2126

Abstract

Stationary models are usually applied for wind characteristics analysis. However, nonstationarity has been found in the field measurements of typhoons in recent studies; therefore, using traditional models with stationary assumptions to conduct wind characteristics is inadequate. In this research, data acquisition of typhoon [...] Read more.

Stationary models are usually applied for wind characteristics analysis. However, nonstationarity has been found in the field measurements of typhoons in recent studies; therefore, using traditional models with stationary assumptions to conduct wind characteristics is inadequate. In this research, data acquisition of typhoon wind speeds and monsoon are conducted based on the wind field measurements. Wind speeds of typhoon “Maria” passing through Pintan, Fujian Province, China and the monsoon from 2017.10–2018.10 were obtained to investigate wind characteristics. The run test method is utilized to show that non-stationarity exists in both typhoon and monsoon wind speed, and the percent of non-stationary increases with the increase in time interval. Additionally, results show that stronger non-stationarity exists in typhoon wind speed compared with monsoons. Based on a self-adaptive procedure to extract time varying mean wind speed, a non-stationary model is established to compare with the non-stationary model, which has been applied in the traditional wind characteristic analysis. The fluctuating wind characteristics such as turbulence intensity, gust factor, turbulence integral scale, and wind speed spectrum are analyzed to compare the two models. Results show that the difference of such characteristics between the two models increases with the time interval, indicating the necessity of consideration of non-stationary models, especially for design specifications with larger time intervals. Influences of time intervals are investigated, and relevant recommendations are provided for wind resistance specifications. Our conclusions may provide reference for wind resistance design in engineering applications. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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16 pages, 6331 KiB

Open AccessArticle

Iteration-Based Recycling and Reshaping Method for Inflow Turbulence Generation and Its Evaluation

by Yuxin Zhang, Shuyang Cao and Jinxin Cao

Atmosphere 2022, 13(1), 72; https://doi.org/10.3390/atmos13010072 - 31 Dec 2021

Cited by 1 | Viewed by 1274

Abstract

For the analysis of the aerodynamic characteristics of the buildings immersed in the atmospheric boundary layer (ABL), it is necessary to generate a turbulence velocity field with similar temporal and special characteristics to the ABL to obtain a reliable result. In this paper, [...] Read more.

For the analysis of the aerodynamic characteristics of the buildings immersed in the atmospheric boundary layer (ABL), it is necessary to generate a turbulence velocity field with similar temporal and special characteristics to the ABL to obtain a reliable result. In this paper, an improved precursor simulation method called the recycling and reshaping method (RRM) is proposed to generate a turbulent boundary layer in an LES model. The laminar inflow is firstly disturbed by the virtual roughness blocks realized by adding drag force term in the momentum equation, then the inflow velocity profile is reshaped every several steps to adjust the streamwise velocity profile in the downstream target area to meet the requirements. The final turbulence field generated by RRM with virtual roughness blocks is in good agreement with the target velocity conditions. Then, the simulation of the wind-induced pressure on an isolated low-rise building surface is carried out, using the generated turbulence boundary layer as inflow. The comparison between numerical results and TPU aerodynamic database shows that the time-averaged wind-induced surface pressure obtained by LES can be considered in good accordance with the measurements over the whole building surface. However, the non-ignorable deviations for the fluctuating pressure result in the flow separation corners still exist. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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15 pages, 9059 KiB

Open AccessArticle

Evaluation Schoolyard Wind Comfort Changes Due to Rapid Developments: Case Study of Nanjing, China

by Qiuxia Xu, Zhen Xu and Chayn Sun

Atmosphere 2022, 13(1), 43; https://doi.org/10.3390/atmos13010043 - 28 Dec 2021

Cited by 2 | Viewed by 1639

Abstract

(1) Background: Evaluation of wind environments regarding pedestrian comfort may unveil potential hotspot areas, particularly in the context of the rapid urban development in China since the 1990s. (2) Method: With primary schools in Nanjing as case studies, the authors simulated the wind [...] Read more.

(1) Background: Evaluation of wind environments regarding pedestrian comfort may unveil potential hotspot areas, particularly in the context of the rapid urban development in China since the 1990s. (2) Method: With primary schools in Nanjing as case studies, the authors simulated the wind environment of schoolyards with the computational fluid dynamics (CFD) approach and evaluated relevant wind comfort criteria. (3) Results: The study showed that the comfortable wind environment of schoolyards generally expanded in three primary schools in summer and winter, and wind speed and the comfortable wind level decreased in some outdoor schoolyard spaces. The results also indicate that the mean wind speed of the schoolyards did not linearly correlate to the building density either within or outside the schools. An increase in the building height of the primary schools could improve the wind comfort of the schoolyard, but the increased building height in the vicinity may worsen the wind comfort in the schools. Meanwhile, a lift-up or step-shaped building design for schools can improve wind comfort in schoolyards. (4) Conclusions: This study provided simulated results and an approach for urban designers to evaluate and improve the wind environment for school children’s outdoor activities. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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18 pages, 5284 KiB

Open AccessArticle

Application of Bias Correction to Improve WRF Ensemble Wind Speed Forecast

by Chin-Cheng Tsai, Jing-Shan Hong, Pao-Liang Chang, Yi-Ru Chen, Yi-Jui Su and Chih-Hsin Li

Atmosphere 2021, 12(12), 1688; https://doi.org/10.3390/atmos12121688 - 16 Dec 2021

Cited by 3 | Viewed by 2965

Abstract

Surface wind speed forecast from an operational WRF Ensemble Prediction System (WEPS) was verified, and the system-bias representations of the WEPS were investigated. Results indicated that error characteristics of the ensemble 10-m wind speed forecast were diurnally variated and clustered with the usage [...] Read more.

Surface wind speed forecast from an operational WRF Ensemble Prediction System (WEPS) was verified, and the system-bias representations of the WEPS were investigated. Results indicated that error characteristics of the ensemble 10-m wind speed forecast were diurnally variated and clustered with the usage of the planetary boundary layer (PBL) scheme. To correct the error characteristics of the ensemble wind speed forecast, three system-bias representations with decaying average algorithms were studied. One of the three system-bias representations is represented by the forecast error of the ensemble mean (BC01), and others are assembled from each PBC group (BC03) as well as an independent member (BC20). System bias was calculated daily and updated within a 5-month duration, and the verification was conducted in the last month, including 316 gauges around Taiwan. Results show that the mean of the calibrated ensemble (BC03) was significantly improved as the calibrated ensemble (BC20), but both demonstrated insufficient ensemble spread. However, the calibrated ensemble, BC01, with the best dispersion relation could be extracted as a more valuable deterministic forecast via the probability matched mean method (PMM). Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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11 pages, 4158 KiB

Open AccessArticle

Planetary Boundary Layer Heights from Cruises in Spring to Autumn Chukchi-Beaufort Sea Compared with ERA5

by Mingyi Gu, G. W. K. Moore, Kevin Wood and Zhaomin Wang

Atmosphere 2021, 12(11), 1398; https://doi.org/10.3390/atmos12111398 - 25 Oct 2021

Viewed by 1754

Abstract

The planetary boundary layer height (PBLH) is a diagnostic field related to the effective heat capacity of the lower atmosphere, both stable and convective, and it constrains motion in this layer as well as impacts surface warming. Here, we used radiosonde data from [...] Read more.

The planetary boundary layer height (PBLH) is a diagnostic field related to the effective heat capacity of the lower atmosphere, both stable and convective, and it constrains motion in this layer as well as impacts surface warming. Here, we used radiosonde data from five icebreaker cruises to the Chukchi and Beaufort Seas during both spring and fall to derive PBLH using the bulk Ri method, which were then compared with results from ERA5 reanalysis. The ERA5 PBLH was similar to but slightly lower than the ship observations. Clear and consistent seasonal changes were found in both the observations and the reanalysis: PBLH decreased from mid-May to mid-June and subsequently increased after August. The comparison with ERA5 shows that, besides surface temperature, biases in PBLH are also a function of wind direction, suggesting that the availability of upwind observations is also important in representing processes active in the boundary layer over the Arctic Ocean. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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14 pages, 1103 KiB

Open AccessArticle

Comparing the Air Turbulence above Smooth and Rough Surfaces in the Amazon Region

by Raoni A. S. Santana, Cléo Q. Dias-Júnior, Roseilson S. do Vale, Júlio Tóta, Rodrigo da Silva, Raphael Tapajós, Antônio O. Manzi and Troy P. Beldini

Atmosphere 2021, 12(8), 1043; https://doi.org/10.3390/atmos12081043 - 14 Aug 2021

Cited by 2 | Viewed by 1566

Abstract

The goal of this work is to compare the main air turbulence characteristics of two common areas in the Amazonian landscape: a dense forest (rough surface) and a water surface (smooth surface). Using wind components data collected at high frequency by sonic anemometers [...] Read more.

The goal of this work is to compare the main air turbulence characteristics of two common areas in the Amazonian landscape: a dense forest (rough surface) and a water surface (smooth surface). Using wind components data collected at high frequency by sonic anemometers located just above these surfaces, turbulence intensity and power spectra, temporal and length scales of the eddies, as well as the main terms of the

TKE

budget (

TKE

= turbulent kinetic energy) were evaluated for each surface type. The results showed that in general, the air turbulence intensity above the forest was higher than above the lake during the daytime, due to the high efficiency of the forest in absorbing the momentum of the turbulent flow. During the nighttime, the situation was reversed, with greater air turbulence intensity above the lake, except in some periods in which intermittent turbulence bursts occured above the forest. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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Review

Jump to: Research

14 pages, 573 KiB

Open AccessReview

Research Progress for Dynamic Effects of Cities on Precipitation: A Review

by Caijun Yue, Zhihui Han, Wen Gu, Yuqi Tang and Xiangyu Ao

Atmosphere 2021, 12(10), 1355; https://doi.org/10.3390/atmos12101355 - 16 Oct 2021

Cited by 7 | Viewed by 2054

Abstract

Citization significantly changes original surface properties. City areas can cause surface winds to decrease; furthermore, ground friction can be transferred layer by layer through the momentum exchange of air movement, which affects the air layers above. Precipitation modification by city environments has been [...] Read more.

Citization significantly changes original surface properties. City areas can cause surface winds to decrease; furthermore, ground friction can be transferred layer by layer through the momentum exchange of air movement, which affects the air layers above. Precipitation modification by city environments has been an active research area. Under the conditions of high wind speed, the dynamic effects of cities on precipitation are relatively obvious. Generally, the dynamic effects fall into two main categories: (1) for weather systems under weak forcing synoptic backgrounds, such as local convective systems, shorter-lived extreme precipitation events and fronts and city barrier effects can delay the movement of weather systems, directly change the horizontal distribution characteristics and occurrence time for precipitation, change the flow field and structure, cause the bifurcation of weather systems, and change the horizontal distribution characteristics of precipitation; (2) for weather systems under strong forcing synoptic backgrounds, such as extratropical systems (with large-scale moisture transport), monsoon systems, landfalling tropical cyclones, and supercell storms, the impact of the dynamic effects of cities cannot lead to the bifurcation of the weather system, nor can it change the horizontal distribution characteristics of the whole precipitation field, but it can have an impact on the local precipitation intensity and distribution. However, currently, people do not agree on the impact of cities on precipitation, especially regarding tropical cyclones. Hence, we provide a review and provide insights into the dynamic effects of cities on precipitation. Full article

(This article belongs to the Special Issue Atmospheric Boundary Layer: Observation and Simulation)

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