Towards the Sea Wind Measurement with the Airborne Scatterometer Having the Rotating-Beam Antenna Mounted over Fuselage

Extension of the existing airborne radars’ applicability is a perspective approach to the remote sensing of the environment. Here we investigate the capability of the rotating-beam radar installed over the fuselage for the sea surface wind measurement based on the comparison of the backscatter with the respective geophysical model function (GMF). We also consider the robustness of the proposed approach to the partial shading of the underlying water surface by the aircraft nose, tail, and wings. The wind retrieval algorithms have been developed and evaluated using Monte-Carlo simulations. We find our results promising both for the development of new remote sensing systems as well as the functional enhancement of existing airborne radars.

Decomposition-Based Multistep Sea Wind Speed Forecasting Using Stacked Gated Recurrent Unit Improved by Residual Connections

Sea wind speed forecast is important for meteorological navigation system to keep ships in safe areas. The high volatility and uncertainty of wind make it difficult to accurately forecast multistep wind speed. This paper proposes a new decomposition-based model to forecast hourly sea wind speeds. Because mode mixing affects the accuracy of the empirical mode decomposition- (EMD-) based models, this model uses the variational mode decomposition (VMD) to alleviate this problem. To improve the accuracy of predicting subseries with high nonlinearity, this model uses stacked gate recurrent units (GRU) networks. To alleviate the degradation effect of stacked GRU, this model modifies them by adding residual connections to the deep layers. This model decomposes the nonlinear wind speed data into four subseries with different frequencies adaptively. Each stacked GRU predictor has four layers and the residual connections are added to the last two layers. The predictors have 24 inputs and 3 outputs, and the forecast is an ensemble of five predictors’ outputs. The proposed model can predict wind speed in the next 3 hours according to the past 24 hours’ wind speed data. The experiment results on three different sea areas show that the performance of this model surpasses those of a state-of-the-art model, several benchmarks, and decomposition-based models.

She Listened: Vardian Self-Portraiture and Auto-Refrains of Sea, Wind, and Sand

This article considers Vardian acts of listening and (self-)portraiture. With works that celebrate the material world in its myriad forms and scales, from a beloved button to a bottomless sea, Agnès Varda developed a method of empathetic engagement. Her encounters grasped relations extending from a person, family, or group, to a greater world-memory and duration comprising “us” all. As it heeds these foldings of the world, this article considers subjectification processes that take into a self all elements of nature. With sustained awareness of the “hundreds of thousands of people” she doesn't know, through her acts of listening and portraiture, in her later years Varda simultaneously attained a recognizable persona and an imperceptibility that gestured to an inward-outward movement her works so often foretell: that of a self's full dissolution into memory and world. In line with Varda's lifelong commitment to new forms of making visible the invisible, and her embrace of a sea as a groundless source of intersubjective relations, limits transform via her works into reflective, dissolving surfaces. A doubling of the personal and cosmic—that movement that so singularizes Varda—emanates through this weave of her art and life. As a chiasmatic double herself whose encounters brought extremes into contact, Varda demonstrated a concern for the future of the world that persisted alongside an awareness of her own mortality. Beyond the duration of her own life, Varda's works expose us to ourselves while always foregrounding the woman, and women, behind, before, and beyond the lens.

Sea spray icing: The physical process, and review of prediction models and winterization techniques

Ice accretion on marine vessels and offshore structures is a severe hazard in the Polar Regions. There is increasing activities related to oil and gas exploration, tourism, cargo transport, and fishing in the Arctic. Ice accretion can cause vessel instability, excess load on marine structures and represents a safety risk for outdoor working environment and operations. Freezing sea spray is the main contributor to marine icing. For safe operations in cold climate, it is essential to have verified models for prediction of icing. Sea spray icing forecast models have improved. Empirical and theoretical models providing icing rates based may be useful as guidelines. For predicting the distribution of icing on a surface at the design stage, Computational Fluid Dynamics has to be applied along with a freezing module. State-of-the-art models for numerical simulation of sea spray icing are still not fully capable of modelling complex ship-sea-wind interactions with spray generation and impact of shipped water. Existing models include good understanding of spray flow effects and freezing. Further development should focus on developing models for dynamic ship-sea-wind interactions, in particular including spray generation, effects of shipped water and distribution of icing on the vessel surface. More experimental and full-scale data is needed for development and verification of new and improved models. Models that estimate ice distribution may improve the winterization design process and reduce effort required for de-icing. Improved methods for de-icing and anti-icing will reduce the impact of sea spray icing and increase safety for marine operations in cold waters.

Energy partitioning and evapotranspiration over a black locust plantation in the Yellow River Delta

Woody plantations play a curtail role in ecological security along coastal zones. Understanding of energy partitioning and evapotranspiration (ET) over black locust plantations can reveal land-atmosphere interaction process and help us to optimize this plantation for land management in the Yellow River Delta. In this study, we investigated energy fluxes, ET in particular, and their related biophysical factors using eddy covariance techniques over a black locust plantation in 2016, 2018, and 2019. Downward longwave radiation offsets 84%–85% of upward longwave radiation, upward shortwave radiation accounted for 12%–13% of downward shortwave radiation, and the ratio of net radiation (Rn) to downward radiation was 18%–19%in the three years. During growing seasons, latent heat flux was the largest components among radiation balance terms; during non-growing seasons, sensible heat flux was a dominant component. ET was mainly controlled by Rn, air temperature, vapor pressure deficit and leaf area index (LAI). Annual ET was smaller than the sum of precipitation and irrigation, and cumulative ET was larger than cumulative precipitation during non-growing seasons. The phenology of black locust influenced the seasonal variation in daily ET, mainly via LAI. ET was larger under sea wind than under land wind, mainly because soil water content at 10-cm depth was greater under sea wind in daytime. Seasonal patterns of daily evaporative fraction, Bowen ratio, crop coefficient, Priestley–Taylor coefficient, surface conductance (gs), and decoupling coefficient were mainly controlled by LAI, and the threshold value of daily gs was approximately 8 mm s−1 over the studied plantation.

Airflow modelling predicts seabird breeding habitat across islands

Wind is a fundamental driver of the distribution and energy expenditure of birds at sea. Wind can also influence mortality at the nest. Yet airflows have never been fully integrated into models of breeding habitat selection. We use computational fluid dynamics to provide the first assessment of whether and how airflows predict the distribution of seabird colonies, taking common guillemots (Uria aalge) breeding on Skomer island as our study system. We reveal that air pressure predicts occupancy, demonstrating the importance of exposure (rather than wind speed) in habitat selection. Our simple model with pressure and slope correctly identified 80% of the largest colonies and 93% of avoided sites. While previous approaches have not predicted space use in novel sites, our model predicted 73% of the largest colonies on a neighbouring island. This suggests generality in the mechanisms linking airflows and breeding distributions, and highlights a novel route by which seabirds may be affected by global change.

Dutch Offshore Wind Atlas Validation against Cabauw Meteomast Wind Measurements

The Dutch Offshore Wind Atlas (DOWA) is validated against wind speed and direction measurements from the Cabauw meteorological mast for a 10-year period and at heights between 10 m and 200 m. The validation results are compared to the Royal Netherlands Meteorological Institute (KNMI) North Sea Wind (KNW) atlas. It is found that the average difference (bias) between DOWA wind speeds and those measured at Cabauw varies for the different heights between −0.1 m/s to 0.3 m/s. Significant differences between DOWA and KNW are only found at altitudes of 10 m and 20 m, where KNW performs better. For heights above 20 m, there is no significant difference between DOWA and KNW with respect to the 10-year averaged wind speed bias. The diurnal cycle is better captured by DOWA compared to KNW, and the hourly correlation is slightly improved. In addition, a comparison with the global European Center for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and ERA5 reanalyses (used for KNW and DOWA, respectively) is made, highlighting the added skill provided by downscaling those global datasets with the weather model HARMONIE.