Wind Speed Profile Statistics from Acoustic Soundings at a Black Sea Coastal Site

More than seven years of remote sensing data with high spatial and temporal resolution were investigated in this study. The 20-min moving averaged wind profiles form the acoustic sounding with Scintec MFAS sodar were derived every 10 min. The profiles covered from 30 to 600 m height with vertical resolution of 10 m. The wind speed probability and the Weibull distribution parameters were calculated by the maximum likelihood method at each level and then the profiles of the Weibull scale and shape parameters were analyzed. Diurnal wind speed at heights above 200 m has shown a well-expressed increase in the averaged values during the night hours, while during the day lower wind speeds were observed. The reversal height was explored from spatially and temporally homogenized diurnal wind speed data with applied quadratic functions for better interpretation of the results. In addition, analyses by type of air masses (land or sea air mass) were performed. One of the outcomes of the study was assessment of the internal boundary layer height, which was estimated to 50–80 m at the location of the sodar. The obtained information forms the basis for climatological insights on the vertical structure of the coastal boundary layer and is unique long-term data set important not only for Bulgaria but for coastal meteorology in general.

Spatio-temporal Kriging of Lower Caribbean Wind Data

Planning of a wind farm location requires significant data. However, wind speed data sets in the lower Caribbean are usually incomplete. This paper considers imputation by spatio-temporal kriging using data from neighbouring locations. Temporal basis functions with spatial covariates are used to model diurnal wind speed cyclicity. The residual set of our spatio-temporal model is modelled as a Gaussian spatial random field. Fitted models may be used for spatial prediction as well as imputation. Examples of predictions are illustrated using two months of hourly data from eight Caribbean locations with prediction accuracy being assessed by cross validation and residuals.

Automated Probabilistic Analysis and Parametric Modelling of the Seasonal-Diurnal Wind Vector

A refined and extended version of the Offset Elliptical Normal mixture model has been developed to parameterise the seasonal diurnal wind vector automatically. Automated using R scripts, the method eliminates any potential risk of confirmation bias posed by the manual supervision in the original method. Refinements to the method include the latest algorithms for clustering of Gaussian mixtures, with Bayesian regularisation to set the number of components and to limit the predisposition to overfit. A new extension uses fuzzy logic to evaluate the probability distributions, autocovariances and spectra of the random perturbations around the mean seasonal-diurnal variations for each component of the mixture. These additional parameters allow the predictions of the OEN model to be validated and its automated application demonstrated using the hourly METAR reports of mean wind speeds at Adelaide, South Australia, showing significant improvements over the previously published analysis. The OEN mixture model is directly applicable to a wide range of wind engineering applications where seasonal and diurnal variation is of importance.

Examination of the Daily Cycle Wind Vector Modes of Variability from the Constellation of Microwave Scatterometers and Radiometers

Offshore of many coastal regions, the ocean surface wind varies in speed and direction throughout the day, owing to forcing from land/sea temperature differences and orographic effects. Far offshore, both diurnal and semidiurnal wind vector variability has been noted in the Tropical Atmosphere Ocean-TRIangle Trans-Ocean buoy Network (TAO-TRITON) mooring data in the tropical Pacific Ocean. In this manuscript, the tropical diurnal wind variability is examined with microwave radiometer-derived winds from the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM), merged with RapidScat and other scatterometer data. Since the relationship between wind speed and its zonal and meridional components is nonlinear, this manuscript describes an observationally based methodology to merge the radiometer and scatterometer-based wind estimates as a function of observation time, to generate a multi-year dataset of diurnal wind variability. Compared to TAO-TRITON mooring array data, the merged satellite-derived wind components fairly well replicate the semidiurnal zonal wind variability over the tropical Pacific but generally show more variability in the meridional wind components. The meridional component agrees with the associated mooring location data in some locations better than others, or it shows no clear dominant diurnal or semidiurnal mode. Similar discrepancies are noted between two forecast model reanalysis products. It is hypothesized that the discrepancies amongst the meridional winds are due to interactions between surface convergence and convective precipitation over tropical ocean basins.

Precipitation Diurnal Cycle over the Maritime Continent Modulated by the Climatological Annual Cycle

The modulation of diurnal cycle (DC) of precipitation over the Maritime Continent (MC) by the background annual cycle mean state was studied for the period of 1998-2014 through observational analyses and high-resolution simulations using the Weather Research and Forecasting (WRF) model. The observational analyses reveal that there are statistically significant differences in the DC amplitude between boreal winter and summer. The amplitude of precipitation DC reduces by about 35% during boreal summer compared to boreal winter, especially over the MC major islands and adjacent oceans. A precipitation budget analysis indicates that the DC amplitude difference is primarily attributed to vertically integrated convergence of the mean moisture by diurnal winds. The relative roles of the background dynamic and thermodynamic states in causing the enhanced diurnal wind activity in boreal winter are further investigated through idealized WRF simulations. The results show that the seasonal mean background moisture condition is most critical in inducing the winter-summer difference of the precipitation DC over the MC, followed by atmospheric static stability (i.e., vertical temperature gradient) and circulation conditions.

The Role of Weather during the Greek–Persian “Naval Battle of Salamis” in 480 B.C.

The Battle of Salamis in 480 B.C. is one of the most important naval battles of all times. This work examines in detail the climatically prevailing weather conditions during the Persian invasion in Greece. We perform a climatological analysis of the wind regime in the narrow straits of Salamis, where this historic battle took place, based on available station measurements, reanalysis and modeling simulations (ERA5, WRF) spanning through the period of 1960–2019. Our results are compared to ancient sources before and during the course of the conflict and can be summarized as follows: (i) Our climatological station measurements and model runs describing the prevailing winds in the area of interest are consistent with the eyewitness descriptions reported by ancient historians and (ii) The ancient Greeks and particularly Themistocles must have been aware of the local wind climatology since their strategic plan was carefully designed and implemented to take advantage of the diurnal wind variation. The combination of northwest wind during the night and early morning, converging with a south sea breeze after 10:00 A.M., formed a “pincer” that aided the Greeks at the beginning of the clash in the morning, while it brought turmoil to the Persian fleet and prevented them to escape to the open sea in the early afternoon hours.