Spatial and Temporal Variation of the Near-Surface Wind Environment in the Sahara Desert, North Africa

The Sahara Desert is the largest source of dust on Earth, and has a significant impact on global atmospheric changes. Wind is the main dynamic factor controlling the transport and intensity of dust in the Sahara Desert. This study comprehensively analyzed the spatial and temporal variation in the wind regime of the Sahara Desert from 1980 to 2019 using data from 17 meteorological stations to improve awareness of global atmospheric changes and the intensity of regional aeolian activities. All wind speed parameters decreased from northwest to southeast. While there were significant differences in the trends of temporal variation in wind speed among the different regions, there was an overall decreasing trend across the Sahara Desert, with an average wind speed of 0.09 m s−1 10 a−1. This decrease was closely related to wind frequency. The easterly, westerly, and northerly winds dominated, with more complex wind direction in the northern region. Seasonal differences in wind direction were observed in all regions. The wind direction frequency of wind speeds >6 m s−1 exceeded those with wind speeds <6 m s−1 in the western and northern regions, whereas other regions showed an opposite pattern. The highest drift potential (DP) and resultant drift potential (RDP) were found in the western and northern regions, and during spring and winter. There was a trend of decreasing annual variation in DP and RDP in all regions. The directional variability (RDP/DP) indicated mostly intermediate and high variability in wind direction. Resultant drift direction (RDD) indicated that a mainly southwest wind direction. No apparent trends in temporal variation in RDD and RDP/DP were observed. Total DP was strongly influenced by DP and the magnitude and frequency of strong winds in the prevailing wind direction. No strong correlation between wind regimes and dune types was observed in this desert, indicating the complexity of factors affecting dune morphology.

Aerosol particle characteristics measured in the United Arab Emirates and their response to mixing in the boundary layer

Aerosol particles play an important role in the microphysics of clouds and hence in their likelihood to precipitate. In the changing climate already-dry areas such as the United Arab Emirates (UAE) are predicted to become even drier. Comprehensive observations of the daily and seasonal variation in aerosol particle properties in such locations are required, reducing the uncertainty in such predictions. We analyse observations from a 1-year measurement campaign at a background location in the United Arab Emirates to investigate the properties of aerosol particles in this region, study the impact of boundary layer mixing on background aerosol particle properties measured at the surface, and study the temporal evolution of the aerosol particle cloud formation potential in the region. We used in situ aerosol particle measurements to characterise the aerosol particle composition, size, number, and cloud condensation nuclei (CCN) properties; in situ SO2 measurements as an anthropogenic signature; and a long-range scanning Doppler lidar to provide vertical profiles of the horizontal wind and turbulent properties to monitor the evolution of the boundary layer. Anthropogenic sulfate dominated the aerosol particle mass composition in this location. There was a clear diurnal cycle in the surface wind direction, which had a strong impact on aerosol particle total number concentration, SO2 concentration, and black carbon mass concentration. Local sources were the predominant source of black carbon as concentrations clearly depended on the presence of turbulent mixing, with much higher values during calm nights. The measured concentrations of SO2, instead, were highly dependent on the surface wind direction as well as on the depth of the boundary layer when entrainment from the advected elevated layers occurred. The wind direction at the surface or of the elevated layer suggests that the oil refineries and the cities of Dubai and Abu Dhabi and other coastal conurbations were the remote sources of SO2. We observed new-aerosol-particle formation events almost every day (on 4 d out of 5 on average). Calm nights had the highest CCN number concentrations and lowest κ values and activation fractions. We did not observe any clear dependence of CCN number concentration and κ parameter on the height of the daytime boundary layer, whereas the activation fraction did show a slight increase with increasing boundary layer height due to the change in the shape of the aerosol particle size distribution where the relative portion of larger aerosol particles increased with increasing boundary layer height. We believe that this indicates that size is more important than chemistry for aerosol particle CCN activation at this site. The combination of instrumentation used in this campaign enabled us to identify periods when anthropogenic pollution from remote sources that had been transported in elevated layers was present and had been mixed down to the surface in the growing boundary layer.

Full-Scale Measurements of Translational and Torsional Dynamics Characteristics of a High-Rise Building during Typhoon Sarika

The field measurement of wind-induced response is of great significance to the wind resistance design of high-rise buildings, in particular torsional responses measured from high-rise buildings under typhoons. The measured high-rise building, with a height of 108 m, has 32 stories and is supported by giant trusses with four massive columns. Acceleration responses along translational and torsional directions were monitored synchronously and continuously during the passage of Typhoon Sarika on 18 October 2016. The wind speed and wind direction at the height of 115 m, the translational accelerations on a total of six floors and the angular accelerations on a total of four floors were recorded. The time and frequency domain characteristics of translational acceleration and torsional angular accelerations were analyzed. The amplitude-dependent translational and torsional modal frequencies of the measured building were identified by NExT-ERA, SSI, and RDT methods. The full-scale study is expected to provide useful information on the wind-resistant design of high-rise buildings in typhoon-prone regions.

Influence of Longitudinal Fin Tubes Arrangement in LNG Ambient Air Vaporizers on the Wind Load

The article presents the results of computational fluid dynamics (CFD) analysis of the wind action on liquefied natural gas (LNG) ambient air vaporizers (AAVs). A study concerning AAV with a 6 × 6 tubes array is presented to demonstrate how the distribution of longitudinal finned tubes and wind direction affect the average load and wind pressure acting on the vaporizer structure. The main goal of the study is to estimate the wind load on the structure and wind pressure on individual tubes depending on the pitch of the tubes arrangement. The above parameters are crucial for the strength analysis of the vaporizer structure. The derived analysis results provide important data on the variation of pressure on individual tubes, wind velocity inside AVV structure and indicate a significant increase in the average wind load acting on the structure for a wind direction of 45 degrees compared to a perpendicular direction.

Spatio-temporal modeling of the wind field over an urban lake subject to wind sheltering

The wind field over an urban lake may exhibit considerable variability due to wind shielding effects from surrounding structures. Field measurements at an urban reservoir in Singapore were augmented by computational fluid dynamics (CFD) model results to develop a wind model over the reservoir surface via a data assimilation approach. The field measurements identified, depending on structure alignment with the prevailing wind direction, wind shielding that impacted wind direction and velocity over the reservoir surface. The wind model integrated the temporal response of the measurements and spatial distribution produced by the CFD modelling. The wind model was used to predict the spatio-temporal pattern of the wind field over the reservoir surface for a full year. The modeling results showed good agreement with measured wind data at three measurement locations on the reservoir surface. The wind model has been incorporated with a hydrodynamics and water quality model to provide the spatio-temporal wind forcing over the reservoir surface.

Offshore wind resource assessment using reanalysis data

The growth rate of offshore wind is increasing due to technological advancement and reduction in cost. An approach using mast measured data at coastline and reanalysis data is proposed for offshore wind resource assessment, especially for developing countries. The evaluation of fifth generation European Reanalysis (ERA5) data was performed against measured data using statistical analysis. ERA5 data slightly underestimates wind speed and wind direction with percentage bias of less than 1%. Wind resource assessment of region in Exclusive Economic Zone (EEZ) of Pakistan was performed in terms of wind speed and Wind Power Density (WPD). The range of monthly mean wind speed and WPD in the region was 4.03–8.67 m/second and 73–515 W/m2 respectively. Most-probable wind speed and dominating wind direction on corners and center of the region were found using probability distributions and wind rose diagrams respectively. Most-probable wind speed ranges 4.41–7.64 m/second and dominating wind direction is southwest.

Uji Model Aeromod Terhadap Sebaran Particulate Matter 10 µm (PM10) di Sekitar Kawasan PT Semen Padang

Penelitian ini bertujuan untuk menguji model AERMOD dalam memprediksi sebaran PM10 di udara ambien kawasan PT Semen Padang. Lokasi penelitian sebanyak 32 titik berdasarkan 8 arah mata angin dengan jarak 0,5 km, 1 km, 1,5 km dan 2 km dari PT Semen Padang. Pengukuran PM10 menggunakan EPAM 5000 Real Time Particulate Air Monitor dilanjutkan pemetaan dengan software Surfer 11. Waktu pengukuran dibagi menjadi 4 shift, yaitu shift 1 (00.00 – 05.59 WIB), shift 2 (06.00 – 11.59 WIB), shift 3 (12.00 – 17.59 WIB) dan shift 4 (18.00 – 23.59 WIB). Pengambilan data meteorologi (temperatur udara, tekanan udara, kelembapan, kecepatan angin dan arah angin) menggunakan alat Meteorological Station PCE-FWS-20 untuk input data pada AERMET, dilanjutkan prediksi sebaran PM10 menggunakan software AERMOD View 8.9.0. Hasil penelitian menunjukkan konsentrasi PM10 dengan EPAM 5000 berkisar antara 21,0 – 79,0 µg/m3 dengan rata-rata 24 jam sebesar 41,7 µg/m3. Konsentrasi PM10 dengan AERMOD berkisar antara 3,5 sampai 68,0 µg/m3 dengan rata-rata 24 jam sebesar 10,6 µg/m3. Jika dibandingkan dengan baku mutu untuk Peraturan Pemerintah No. 22 Tahun 2021 tentang Penyelenggaraan Perlindungan dan Pengelolaan Lingkungan Hidup, lokasi 11 dengan koordinat S 0°56'52.46" dan E 100°27'41.88" pada jarak 1 km kawasan Barat PT Semen Padang tidak memenuhi baku mutu. Model mendekati ideal atau dikatakan sempurna yaitu lokasi arah Timur dan Timur Laut karena elevasi yang lebih tinggi dari sumber emisi dan merupakan arah angin dominan pada siang hari.ABSTRACTThis study aims to test the AERMOD model in predicting the distribution of PM10 in the ambient air of the PT Semen Padang area. The research locations were 32 points based on eight cardinal directions with a radius of 0.5 km, 1 km, 1.5 km, and 2 km from PT Semen Padang. PM10 measurement using EPAM 5000 Real-Time Particulate Air Monitor followed by mapping with Surfer 11 software. The measurement time is divided into four shifts, namely shift 1 (00.00 – 05.59 WIB), shift 2 (06.00 – 11.59 WIB), shift 3 (12.00 – 17.59 WIB), and shift 4 (18.00 – 23.59 WIB). Meteorological data retrieval (air temperature, air pressure, humidity, wind speed and wind direction) using the Meteorological Station PCE-FWS-20 for data input to AERMET, followed by prediction of PM10 distribution using AERMOD View 8.9.0 software. The results showed that the concentration of PM10 with EPAM 5000 ranged from 21.0 – 79.0 g/m3 with a 24-hour average of 41.7 g/m3. The concentration of PM10 with AERMOD ranged from 3.5 - 68.0 g/m3 with a 24-hour average of 10.6 g/m3. When compared with the quality standard for Government Regulation no. 22 of 2021 concerning the Implementation of Environmental Protection and Management, location 11 with coordinates S 0°56'52.46" and E 100°27'41.88" at a distance of 1 km west of PT Semen Padang does not meet the quality standards. The model is close to ideal or is said to be perfect, namely the location of the East and Northeast directions because of the higher elevation of the emission source and the dominant wind direction during the day.