Comparing satellite- to ground-based automated and manual cloud coverage observations – a case study

In this case study we compare cloud fractional cover measured by radiometers on polar satellites (AVHRR) and on one geostationary satellite (SEVIRI) to ground-based manual (SYNOP) and automated observations by a cloud camera (Hemispherical Sky Imager, HSI). These observations took place in Hannover, Germany, and in Lauder, New Zealand, over time frames of 3 and 2 months, respectively. Daily mean comparisons between satellite derivations and the ground-based HSI found the deviation to be 6 14% for AVHRR and 8 16% for SEVIRI, which can be considered satisfactory. AVHRR’s instantaneous differences are smaller (2 22 %) than instantaneous SEVIRI cloud fraction estimates (8 29 %) when compared to HSI due to resolution and scenery effect issues. All spaceborne observations show a very good skill in detecting completely overcast skies (cloud cover 6 oktas) with probabilities between 92 and 94% and false alarm rates between 21 and 29% for AVHRR and SEVIRI in Hannover, Germany. In the case of a clear sky (cloud cover lower than 3 oktas) we find good skill with detection probabilities between 72 and 76 %. We find poor skill, however, whenever broken clouds occur (probability of detection is 32% for AVHRR and 12% for SEVIRI in Hannover, Germany). In order to better understand these discrepancies we analyze the influence of algorithm features on the satellite-based data. We find that the differences between SEVIRI and HSI cloud fractional cover (CFC) decrease (from a bias of 8 to almost 0 %) with decreasing number of spatially averaged pixels and decreasing index which determines the cloud coverage in each “cloud-contaminated” pixel of the binary map. We conclude that window size and index need to be adjusted in order to improve instantaneous SEVIRI and AVHRR estimates. Due to its automated operation and its spatial, temporal and spectral resolution, we recommend as well that more automated ground-based instruments in the form of cloud cameras should be installed as they cover larger areas of the sky than other automated ground-based instruments. These cameras could be an essential supplement to SYNOP observation as they cover the same spectral wavelengths as the human eye.DF

Small satellite operations planning for agile disaster response using graph theoretical techniques

Agile, manoeuvrable, satellite constellations have the potential to fundamentally change space mission design by moving away from traditional missions, designed to address predicted demand, and instead providing responsive systems that can react to real-time events, such as natural disasters. The unique advantages of responsive constellations are enhanced by the use of small satellites, whose short development times and low cost can offset the increased risk and shorter mission life inherent in the use of manoeuvrable spacecraft. In addition, newly developed, highly efficient propulsion systems can provide small satellites with agile manoeuvrability. This could enable agile satellite systems where efficient, low-thrust, responsive manoeuvres can be used to ensure rapid flyover of targets on Earth. The authors have previously developed a fully analytical method of designing such manoeuvres, which allows consideration of multiple targeting options, each with different flyover times, view angles, and propellant requirements. However, a long-term, holistic understanding of the concept of operations is required to effectively implement an agile satellite system. To facilitate this, the existing analytical methodology has been combined with graph theoretical techniques to allow the complex trade-space to be perceived as a graph. The connections in the graph represent possible manoeuvres and are rapidly traversed to identify favourable routes to achieve the desired goal. The effect of changes in mission priorities can be assessed by reweighting the graph, avoiding the need to recalculate the manoeuvre options. This work demonstrates that the proposed method can be successfully used to plan sequential flyovers of a moving target; in this case, a tropical storm. For the small spacecraft and low-thrust propulsion system considered, the possible changes in flyover time for each target are small, however, these small adjustments can be used to significantly improve the quality of the obtained data compared to a non-manoeuvring spacecraft

Monitoring ship emissions using Sentinel-5P and AIS data

Ship pollution has become a growing concern due to its environmental impact. Various policies have been introduced to tackle this issue, such as the International Convention for the Prevention of Pollution from Ships (MARPOL) implemented by the International Maritime Organization (IMO) in 1973. The MARPOL limits the number of pollutants that ships can release into the environment and requires ships to reduce their sulfur emissions. For instance, the IMO introduced a sulfur cap of 0.5% in marine fuel that came into effect on January 1, 2020. The European Commission estimates an eventual reduction in sulfur air pollutants by 80% in the Mediterranean. The effectiveness of these policies is analyzed using data from Sentinel-5P and Automatic Identification System (AIS) messages. Data analysis shows a correlation between ship routes and pollution levels over the oceans using data from the past six years. Five-year averages and time lapses of yearly averages from Sentinel-5P are analyzed to further understand temporal correlations between pollution levels and ship tracks. Furthermore, the impact of coastal areas and cities on pollution levels is investigated by studying larger areas. It is found that the assessment of ship pollution using Sentinel-5P has some limitations: while nitrogen dioxide can be monitored effectively offshore, sulfur emissions from ships cannot be detected offshore or distinguished from coastal emissions using Sentinel-5P. This presents a significant challenge in monitoring and enforcing regulations aimed at reducing sulfur emissions from ships, especially in areas such as the Mediterranean Sea, which are highly influenced by coastal regions

Satellite coverage assessment considering cloud cover

Due to cloud cover, the performance provided by optical or lidar satellite systems may differ from the predicted performance. This work presents a means of rapidly assessing the coverage that can be expected from a satellite constellation considering cloud probability. A latitude-specific pseudo-circumference is defined and calculated using a cloud factor to provide insights into the relative coverage available to different regions. Comparison of the results from the presented method with simulated and historical data collected by the Sentinel-2 constellation shows the potential of the proposed method to calculate expected time between cloud free images when averaged over the long-term. Appropriate choice of cloud model is found to be an important consideration to ensure the validity of the method

Commonwealth Futures Climate Research Cohort Nature-based Solutions (NbS) for Coastal Adaptation : a Comparison between Nigeria and Scotland

Scotland's marine and coastal landscapes are facing numerous pressures from climate change, which negatively impacts both ecosystem functioning and communities who live and work along the coasts. Meanwhile in Nigeria, rising sea levels, coastal erosion, increased precipitation, storms, and warmer ocean temperatures pose similar threats to coastal communities and ecosystems. In order to protect coastal communities in both countries from increasing climate change impacts, strategies for adaptation are urgently needed. Nature-based solutions (NbS) - or actions to protect, manage, or restore ecosystems - are promising alternatives to traditional engineering methods for climate adaptation. However, knowledge gaps and uncertainties about NbS currently hamper its widespread uptake. The impacts of NbS are not always recognised at community levels, and high-level science is often misunderstood by the public. Such knowledge gaps are barriers to developing the full potential of NbS for climate, nature, and people across Scotland and Nigeria. Therefore, a clear statement of the implications of NbS for human wellbeing – as well as effective communication with local communities – is vital on the road towards implementing NbS approaches with the buy-in of decision-makers and community stakeholders

Finding navigable paths through tidal flats with Synthetic Aperture Radar

Tidal flats are some of the most dynamic coastal environments in the world, where traditional coastal mapping and monitoring provide insufficient temporal resolution to reliably map channels and sand flats. Satellite-based Synthetic Aperture Radar (SAR) enables regular cloud-penetrating detection of water flowing through channels within the tidal flats, referred to as tidal channels. This paper presents a method for detecting a path through tidal channels, using satellite imagery, that supports our understanding and safe exploitation of this valuable coastal environment. This approach is the first proposed to identify navigable paths in all conditions, with SAR images susceptible to variation due to weather and tidal conditions. Tidal channels are known to vary in SAR presentation, and we find that tidal flat presentation is also influenced by conditions. The most influential factor is the wind, with high winds causing an inversion in how both tidal flats and tidal channels present in SAR images. The presented method for the automatic detection of tidal channels accounts for this variability by using previous channel paths as a reference to reliably correct imagery and detect the latest path. The final algorithm produces paths with minor errors in 17.6% of images; the error rate increases to 71.7%, with an almost tenfold increase in errors, when the SAR image and paths are not adjusted to account for conditions. This capability has been used to support the Nith Inshore Rescue in attending call-outs from their base in Glencaple, UK, while the insights from monitoring tidal channels for a year demonstrate how periods of high river flow preceded major changes in the channel path

Deep internal learning for inpainting of cloud-affected regions in satellite imagery

Cloud cover remains a significant limitation to a broad range of applications relying on optical remote sensing imagery, including crop identification/yield prediction, climate monitoring, and land cover classification. A common approach to cloud removal treats the problem as an inpainting task and imputes optical data in the cloud-affected regions employing either mosaicing historical data or making use of sensing modalities not impacted by cloud obstructions, such as SAR. Recently, deep learning approaches have been explored in these applications; however, the majority of reported solutions rely on external learning practices, i.e., models trained on fixed datasets. Although these models perform well within the context of a particular dataset, a significant risk of spatial and temporal overfitting exists when applied in different locations or at different times. Here, cloud removal was implemented within an internal learning regime through an inpainting technique based on the deep image prior. The approach was evaluated on both a synthetic dataset with an exact ground truth, as well as real samples. The ability to inpaint the cloud-affected regions for varying weather conditions across a whole year with no prior training was demonstrated, and the performance of the approach was characterised

Correction: Czerkawski et al. Deep internal learning for inpainting of cloud-affected regions in satellite umagery. Remote Sens. 2022, 14, 1342

Following the publication of the article [1], it was discovered that the computation of the inpainting Structural Similarity Index (SSIM) metric value was incorrect. However, the relationship between method performances remains unchanged upon correction and all of the conclusions made in the original manuscript still stand

Boundary Layer Wind Structure and Ocean Waves in Tropical Cyclones from SAR Imagery

This dissertation examines boundary layer winds and ocean surface waves within tropical cyclones using Synthetic Aperture Radar (SAR) from satellites. The study focuses on the atmospheric boundary layer&#39;s bottom two kilometers, crucial for energy exchange between storms and the ocean surface, influencing tropical cyclone intensity and trajectory. SAR&#39;s capability to penetrate clouds and provide high-resolution, sunlight-independent sea surface measurements enables the retrieval of detailed wind and wave data at 1 km spatial resolution. Utilizing in-situ and model data from the 2010 Impact of Typhoons on the Ocean in the Pacific experiment, this research validates SAR-derived wind and wave products. It compares two SAR images of Typhoon Megi, taken 12 minutes apart with different wavelengths, to assess wind retrieval algorithms. Findings indicate that SAR winds align with in-situ data, though X-Band signals saturate at winds over 30 m/s, suggesting limitations in high-frequency microwave use for extreme wind conditions. The study also inputs SAR winds into a boundary layer model to simulate and validate 3D wind patterns against dropsonde data, investigating roll vortices and supergradient winds. Additionally, it applies an empirical model to SAR winds to estimate significant wave heights under cyclone conditions, identifying the need for model reparameterization to correct wave height estimations. Analysis of 23 days of buoy data on wave height and inertial currents post-tropical cyclone shows significant modulation, highlighting inertial currents&#39; impact. This work underscores SAR&#39;s value in marine and atmospheric research, offering insights into tropical cyclones&#39; complex dynamics and their effects on wind and wave patterns.</p

Los medios de comunicación masivos en la enseñanza media chilena: propuestas para su utilización pedagógica

Esta tesis consiste en una investigación de tipo cualitativa sobre la introducción de los Medios de Comunicación Masivos a la enseñanza media, en el área de Lenguaje y Comunicación, y en el contexto de la Reforma Educacional. El objetivo del estudio consiste en explorar cuáles son las falencias que presentan los docentes a la hora de utilizar productos periodísticos en las aulas, y que se supone, tienen que ver con la falta de material didáctico y apoyo especializado en el área de las comunicaciones. Se realizaron tres tipos de entrevistas en profundidad a personeros del área de la Educación y la Reforma. Por parte del Ministerio de Educación se entrevistó a: Sergio Carumán Jorquera (Coordinador Equipo Lengua Castellana y Comunicación, Unidad de Currículum y Evaluación), Cristián Cox (Coordinador Unidad de Currículum y Evaluación) y a Luis Vaisman (Coordinador Lengua Castellana y Comunicación, Enseñanza Media, UCE). En tanto, paralelamente, se conversó con profesores del área y pertenecientes a tres instituciones educacionales de la provincia: Universidad Austral, Windsor School e Intituto Comercial de Valdivia. Finalizando con el análisis teórico -práctico de esta tesis, se presentan 4 propuestas para la utilización de Medios de Comunicación en la enseñanza media, como son el Editorial, Noticia, Reportaje y Entrevista. A modo de conclusión, se pudo inferir que efectivamente falta apoyo en el área de los Medios de Comunicación y específicamente en aspectos como manejo de los mismos, selección de material, carencia de propuestas o modelos de trabajo. Por tanto, se hace imprescindible un trabajo colaborativo entre los docentes y los profesionales de la comunicación a fin de lograr un óptimo uso de los Mass Media en la enseñanza. Esta tesis consiste en una investigación de tipo cualitativa sobre la introducción de los Medios de Comunicación Masivos a la enseñanza media, en el área de Lenguaje y Comunicación, y en el contexto de la Reforma Educacional. El objetivo del estudio consiste en explorar cuáles son las falencias que presentan los docentes a la hora de utilizar productos periodísticos en las aulas, y que se supone, tienen que ver con la falta de material didáctico y apoyo especializado en el área de las comunicaciones. Se realizaron tres tipos de entrevistas en profundidad a personeros del área de la Educación y la Reforma. Por parte del Ministerio de Educación se entrevistó a: Sergio Carumán Jorquera (Coordinador Equipo Lengua Castellana y Comunicación, Unidad de Currículum y Evaluación), Cristián Cox (Coordinador Unidad de Currículum y Evaluación) y a Luis Vaisman (Coordinador Lengua Castellana y Comunicación, Enseñanza Media, UCE). En tanto, paralelamente, se conversó con profesores del área y pertenecientes a tres instituciones educacionales de la provincia: Universidad Austral, Windsor School e Intituto Comercial de Valdivia. Finalizando con el análisis teórico -práctico de esta tesis, se presentan 4 propuestas para la utilización de Medios de Comunicación en la enseñanza media, como son el Editorial, Noticia, Reportaje y Entrevista. A modo de conclusión, se pudo inferir que efectivamente falta apoyo en el área de los Medios de Comunicación y específicamente en aspectos como manejo de los mismos, selección de material, carencia de propuestas o modelos de trabajo. Por tanto, se hace imprescindible un trabajo colaborativo entre los docentes y los profesionales de la comunicación a fin de lograr un óptimo uso de los Mass Media en la enseñanza