Development of longitudinal dunes under Pangaean atmospheric circulation

As a result of the large difference in heat capacity between land and ocean, global climate and atmospheric circulation patterns in the supercontinent Pangaea were significantly different from today. Modelling experiments have suggested the seasonal overturning of cross-equatorial Hadley circulation; however, there are large discrepancies between model-generated surface wind patterns and the reported palaeo-wind directions from aeolian dune records. Here, we present the results of measurements of spatial distribution of dune slip-face azimuths recorded in Lower Jurassic aeolian sandstones over a wide area of the western United States (palaeolatitude: ~19°–27° N). The azimuth data of dune slip-faces reveal a bi-directional and oblique angular pattern that resembles the internal structures of modern longitudinal dunes. Based on the spatial pattern of slip-face directions and outcrop evidences, we suggest most of Lower Jurassic aeolian sandstones to be NNE–SSW- to NNW–SSE- oriented longitudinal dunes, which likely formed as the result of a combination of westerly, northwesterly, and northeasterly palaeo-winds. The reconstructed palaeo-wind pattern at ~19°–27° N appears to be consistent with the model-generated surface wind pattern and its seasonal turnover. The reconstructed palaeo-wind patterns also suggest an influence of orbitally induced changes in atmospheric pressure configuration in Pangaea.

A synoptic and thermodynamic analysis for forecasting of squalls at Agartala

Thunderstorms accompanied with squalls cause a serious damage in Agartala and its neighbouring areas in the pre-monsoon season. In this paper, the synoptic conditions, stability indices and lower level wind pattern associated with squalls at Agartala (23.90° N, 93.25° E) during 2011 - 2020 are analysed to obtain their percentage contributions and critical values in occurrence of the events. Five major synoptic conditions are found to have contribution to the events, with varying percentages. The critical values of Showalter Index, Lifted Index, K-Index, SWEAT Index, Total Totals Index are obtained based on their contribution for at least 80% of the events. Wind direction at 925 hPa and 850 hPa with southerly component is found to be another important precursor for occurrence of the squalls.

Analysis of climate indicator association with hotspots in Indonesia using heterogeneous correlation map

In several regions, land and forest fires of Indonesia occurred almost annually during the drought season. The severity of Indonesia's drought season is mainly influenced by the Australian Monsoon, local cloud formation controlled by Sea Surface Temperature (SST) around Indonesia. Moreover, it affects the severity of land and forest fires itself indirectly. This research aims to examine the association of the Australian Monsoon and local SST with land and forest fires in Indonesia. This research uses the Australian Monsoon Index (AUSMI) as an indicator for the Australian Monsoon and SST in the Karimata Strait and the Java Sea as indicators of local SST. An indicator of land and forest fires that will be used is the number of hotspots. A heterogeneous Correlation Map (HCM) is used to describe hotspots associated with AUSMI and local SST. The analysis shows that the east wind pattern of AUSMI associated with hotspots in Indonesia, especially in years when zonal winds enter an upward phase more slowly. Karimata Strait’s SST is associate with hotspots in the coastal part of Riau. Meanwhile, Java Sea’s SST is associate with hotspots in Lampung, South Sumatra, Jambi, and Kalimantan.

Visualisation of Naturally Ventilated House in Tropical Hilly Area of Indonesia, Case Study: Vatutela Village, Tondo Hills, Palu

The settlement of Vatutela village’s in Tondo hills Palu has only one road access with a linear residential pattern following the topography. This situation affects the pattern of wind flowing through the settlement areas, which is undoubtedly affecting the house’s temperature and humidity profile and influencing thermal comfort of the occupants. The research was conducted to visualise the pattern of the wind flow entering the house through openings in the perspective of building’s thermal performance. The method used to visualise the air movement was the smoke decay method. The method was performed in two scaled dwelling Models representing brick-constructed houses and wood-constructed raised floor houses in Vatutela village. The smoke decay result is elaborated with the results of microclimate measurements using Hobo data loggers to analyse the thermal condition in the houses. The results showed that a design strategy is needed to achieve a thermal comfort zone in both types of houses. The design strategy can be in the form of the arrangement of openings and additional building elements, such as adding ceilings, fins, sunscreens. Additionally, the opening placement, width, and type should be reconsidered for the houses in the area according to houses’ plan and section. This study is expected to give a visual evidence of wind pattern in a naturally ventilated house with a three-layers plan.

Regression-based Gap-filling Methods Show Air Temperature Reductions and Wind Pattern Changes During the 2019 Total Eclipse in Chile

Singular disruptive events like solar eclipses affect the measured values of meteorological variables at the earth’s surface. To quantify such an impact, it is necessary to estimate what value the parameter would have taken had the event not occurred. We design and compare several methods to perform such an estimate based on longer observational timeseries from individual meteorological surface stations. Our methods are based on regularized regressions (including a Bayesian variant) and provide both a point an associated error estimate of the disruptive event’s impact. With their help, we study the effect of the total solar eclipse of July 2 nd , 2019, in the Coquimbo Region of Chile, on near-surface air temperatures and winds. The observational data used have been collected by the meteorological surface station network of the Centro de Estudios Avanzados en Zonas Áridas (CEAZA). Most stations inside the eclipse’s umbra registered a temperature drop of 1-2 • C, while the most extreme estimated temperature drop surpassed 6 • C. The presence of an ‘eclipse cyclone’ can neither be proven nor refuted. Application of the regression methods to other, comparable problems, like volcanic eruptions, forest fires or simply gap filling of observational data, are conceivable.

Diurnal Wind Pattern and Climate Condition on the Coastal Region of Qatar

Climate pattern in the Persian Gulf is of great interest due to the strategic geographical location of the gulf as a waterway of major oil transportation and its increasing regional economic importance. However, long term and continues climate observations in this region are rare, especially for high resolution data. High resolution wind pattern and climate conditions were measured at 3 heights on a 9 m tower on the shoreline north of Qatar (26.08 N, 51.36 E) from August 2015 to September 2016. In this work, the annual wind and climate patterns (wind velocity, temperature, relative humidity, and air pressure) are first presented. Drag coefficient, turbulent kinetic energy and sensible heat flux are calculated using the high speed measured data to explain the observed climate pattern. The results show the wind in the southern part of the gulf is dominant by a northwest stream with a diurnal average speed of 4.7 m/s. During the test year, the diurnal average temperature and relative humidity were 27°C and 70%, respectively. The drag coefficient is much higher for the wind from 270o-330o, corresponding to the wind coming mainly from northwest. The Turbulent Kinetic Energy (TKE) is strong during the daytime, especially around noon when the diurnal value is at its peak, and weak during the night. The result of this analysis may be used for better understanding of the local climate, allowing for further assessment of wind energy and pollution diffusion in the region.

Adaptive Pitch Controller of a Large-Scale Wind Turbine Using Multi-Objective Optimization

This paper deals with the control problems of a wind turbine working in its nominal zone. In this region, the wind turbine speed is controlled by means of the pitch angle, which keeps the nominal power constant against wind fluctuations. The non-uniform profile of the wind causes tower displacements that must be reduced to improve the wind turbine lifetime. In this work, an adaptive control structure operating on the pitch angle variable is proposed for a nonlinear model of a wind turbine provided by FAST software. The proposed control structure is composed of a gain scheduling proportional–integral (PI) controller, an adaptive feedforward compensation for the wind speed, and an adaptive gain compensation for the tower damping. The tuning of the controller parameters is formulated as a Pareto optimization problem that minimizes the tower fore-aft displacements and the deviation of the generator speed using multi-objective genetic algorithms. Three multi-criteria decision making (MCDM) methods are compared, and a satisfactory solution is selected. The optimal solutions for power generation and for tower fore-aft displacement reduction are also obtained. The performance of these three proposed solutions is evaluated for a set of wind pattern conditions and compared with that achieved by a classical baseline PI controller.

Time scale dependence of wind speed patterns - implications for wind power site assessment

<p>Characterizing properties of wind speed variability and their dependence on the temporal scale is important: from sub-second intervals (for the design and monitoring of wind turbines) to longer time scales – months, years (for the evaluation of the wind power potential). Wind speed data are usually reported as averages over time intervals of various length (minutes, days, months, etc). The research project presented in this paper addressed the following questions: What aspects of the wind pattern are changed, in what ways and to what extent, in the process of producing time-averaged values? What precautions should be considered when time-averaged values are used in the assessment of wind variability? What are the conditions to be fulfilled for a meaningful comparison of wind pattern characteristics obtained in distinct studies? Our research started from wind speed records sampled at 0.14 second intervals, which were averaged over increasingly longer time intervals. Variability evaluation was based on statistical moments, L-moments, and detrended fluctuation analysis. We present the change suffered by characteristics of temporal variability as a function of sampling rate and the averaging time interval. In particular, the height dependence of wind speed variability, which is of theoretical and practical importance, is shown to be progressively erased when averaging intervals are increased. The paper makes recommendations regarding the interpretation of wind pattern characteristics obtained at different sites as a function of sampling rate and time-averaging intervals.</p>

Identifikasi Angin Silang (Cross Wind) di Sekitar New Yogyakarta International Airport Memakai Plot Wind Rose

<p class="AbstractEnglish"><strong>Abstract:</strong> Wind has important role in aviation safety. The aim of the research is to analyze monthly wind profile and crosswind potential in the area of New Yogyakarta International Airport. The method used by installing 4 (four) AWS (Automatic Weather Station) at the end and the middle of the runway during March to September 2017. The results show that the wind patterns in the March-May period have varying directions with an average speed of 5-8 knots. In June - September, the wind pattern blows from the East - Southeast direction with an average speed of 6-9 knots. The maximum wind speed occurred between 14-20 knots and no crosswind potential was found for the runway length of 3,600 meters.</p><p class="AbstrakIndonesia"><strong>Abstrak:</strong> Angin merupakan unsur cuaca yang sangat penting dalam keselamatan penerbangan. Penelitian ini bertujuan melakukan analisa profil angin bulanan dan potensi terjadinya Crosswind pada area New Yogyakarta International Airport. Metode yang dipakai dengan memasang 4 (empat)buah AWS (Automatic Weather Station) di ujung dan tengah landasan selama bulan Maret hingga September 2017. Hasil pengamatan dan analisa menunjukan bahwa pola angin pada periode Maret – Mei memiliki arah yang bervariasi dengan kecepatan rata-rata 5 – 8 knot. Pada Juni – September, pola angin berhembus dari arah Timur – Tenggara dengan kecepatan rata-rata 6 – 9 knot. Selama periode pengamatan, kecepatan angin maksimum yang terjadi antara 14 – 20 knot dan tidak ditemukan potensi terjadinya cross wind untuk panjang landasan 3.600 meter.</p>