Probabilistic approach to cloud and snow detection on Advanced Very High Resolution Radiometer (AVHRR) imagery

Derivation of probability estimates complementary to geophysical data sets has gained special attention over the last years. Information about a confidence level of provided physical quantities is required to construct an error budget of higher-level products and to correctly interpret final results of a particular analysis. Regarding the generation of products based on satellite data a common input consists of a cloud mask which allows discrimination between surface and cloud signals. Further the surface information is divided between snow and snow-free components. At any step of this discrimination process a misclassification in a cloud/snow mask propagates to higher-level products and may alter their usability. Within this scope a novel probabilistic cloud mask (PCM) algorithm suited for the 1 km × 1 km Advanced Very High Resolution Radiometer (AVHRR) data is proposed which provides three types of probability estimates between: cloudy/clear-sky, cloudy/snow and clear-sky/snow conditions. As opposed to the majority of available techniques which are usually based on the decision-tree approach in the PCM algorithm all spectral, angular and ancillary information is used in a single step to retrieve probability estimates from the precomputed look-up tables (LUTs). Moreover, the issue of derivation of a single threshold value for a spectral test was overcome by the concept of multidimensional information space which is divided into small bins by an extensive set of intervals. The discrimination between snow and ice clouds and detection of broken, thin clouds was enhanced by means of the invariant coordinate system (ICS) transformation. The study area covers a wide range of environmental conditions spanning from Iceland through central Europe to northern parts of Africa which exhibit diverse difficulties for cloud/snow masking algorithms. The retrieved PCM cloud classification was compared to the Polar Platform System (PPS) version 2012 and Moderate Resolution Imaging Spectroradiometer (MODIS) collection 6 cloud masks, SYNOP (surface synoptic observations) weather reports, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) vertical feature mask version 3 and to MODIS collection 5 snow mask. The outcomes of conducted analyses proved fine detection skills of the PCM method with results comparable to or better than the reference PPS algorithm.

Application of Imagery Theory to Sport Psychology: Some Preliminary Findings

Bioinformational theory has been proposed by Lang (1979a), who suggests that mental images can be understood as products of the brain's information processing capacity. Imagery involves activation of a network of propositionally coded information stored in long-term memory. Propositions concerning physiological and behavioral responses provide a prototype for overt behavior. Processing of response information is associated with somatovisceral arousal. The theory has implications for imagery rehearsal in sport psychology and can account for a variety of findings in the mental practice literature. Hypotheses drawn from bioinformational theory were tested. College athletes imagined four scenes during which their heart rates were recorded. Subjects tended to show increases in heart rate when imagining scenes with which they had personal experience and which would involve cardiovascular activation if experienced in real life. Nonsignificant heart rate changes were found when the scene involved activation but was one with which subjects did not have personal experience.

Multi-Decadal Record of Ice Dynamics on Daugaard Jensen Gletscher, East Greenland, from Satellite Imagery and Terrestrial Measurements

The history of ice velocity and calving front position of Daugaard Jensen Gletscher, a large outlet glacier in East Greenland, is reconstructed from field measurements, aerial photography and satellite imagery for the period 1950-2001. The calving terminus of the glacier has remained in approximately the same position over the past similar to 50 years. There is no evidence of a change in ice motion between 1968 and 2001, based on a comparison of velocities derived from terrestrial surveying and feature tracking using sequential satellite images. Estimates of flux near the entrance to the fjord vs snow accumulation in the interior catchment show that Daugaard Jensen Gletscher has a small negative mass balance. This result is consistent with other mass-balance estimates for the inland region of the glacier.

A New Velocity Map for Byrd Glacier, East Antarctica, from Sequential Aster Satellite Imagery

New ice-velocity measurements are obtained for the main trunk of Byrd Glacier, East Antarctica, using recently acquired Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery. The velocities are derived from the application of a cross-correlation technique to sequential images acquired in 2000 and 2001. Images were co-registered and ortho-rectified with the aid of a digital elevation model (DEM) generated from ASTER stereo imagery. This paper outlines the process of DEM generation, image co-registration and correction, and the application of the cross-correlation technique to obtain ice velocities. Comparison of the new velocity map with earlier measurements of velocity from 1978 indicates that the glacier has undergone a substantial deceleration between observations. Portions of the glacier flowing at speeds of similar to 850 m a(-1) in 1978/79 were flowing at similar to 650 m a(-1) in 2000/01. The cause of this change in ice dynamics is not known, but the observation shows that East Antarctic outlet glaciers can undergo substantial changes on relatively short timescales.

Rapid Volume Loss from Two East Greenland Outlet Glaciers Quantified Using Repeat Stereo Satellite Imagery

The coastal portions of Kangerdlugssuaq and Helheim glaciers in southeast Greenland lost at least 51 +/- 8 km(-3) yr(-1) of ice between 2001-2006 due to thinning and retreat, according to an analysis of sequential digital elevation models (DEMs) derived from stereo ASTER satellite imagery. The dominant contribution to this ice loss was dynamic thinning caused by the acceleration in flow of both glaciers. Peak rates of change, including thinning rates of similar to 90 m yr(-1), coincided with the rapid increases in flow speed. Extrapolation of the measured data to the ice divides yields an estimated combined catchment volume loss of similar to 122 +/- 30 km(-3) yr(-1), which accounts for half the total mass loss from the ice sheet reported in recent studies. These catchment-wide volume losses contributed similar to 0.31 +/- 0.07 mm yr(-1) to global sea level rise over the 5-year observation period with the coastal regions alone contributing at least 0.1 +/- 0.02 mm yr(-1).

Perceptual learning of motion discrimination by mental imagery.

Perceptual learning can occur when stimuli are only imagined, i.e., without proper stimulus presentation. For example, perceptual learning improved bisection discrimination when only the two outer lines of the bisection stimulus were presented and the central line had to be imagined. Performance improved also with other static stimuli. In non-learning imagery experiments, imagining static stimuli is different from imagining motion stimuli. We hypothesized that those differences also affect imagery perceptual learning. Here, we show that imagery training also improves motion direction discrimination. Learning occurs when no stimulus at all is presented during training, whereas no learning occurs when only noise is presented. The interference between noise and mental imagery possibly hinders learning. For static bisection stimuli, the pattern is just the opposite. Learning occurs when presented with the two outer lines of the bisection stimulus, i.e., with only a part of the visual stimulus, while no learning occurs when no stimulus at all is presented.

Imagery of Early Christian Rituals in the Greek Physiologus

The paper focuses on the imagery of early Christian rituals (esp. of the eucharist and baptism) as they are found in allegorical interpretations of beasts in the Greek Physiologus and trace the way of selected motifs from the New Testament to this first Christian interpretation of nature in context of early Christian literature and theology. A special attention is given to the pelican, which is one of the most famous symbols of the eucharist, and to impressive baptismal imageries in the chapter on the eagle, on the snake and in some other chapters. The aim of the analysis is to explore the theological roots of the ritual imagery of Physiologus and to show that this work of early Egyptian Christianity is anything but 'unsakramental' as argued by E. Peterson (1959).

Daytime Low Stratiform Cloud Detection on AVHRR Imagery

The near-real time retrieval of low stratiform cloud (LSC) coverage is of vital interest for such disciplines as meteorology, transport safety, economy and air quality. Within this scope, a novel methodology is proposed which provides the LSC occurrence probability estimates for a satellite scene. The algorithm is suited for the 1 × 1 km Advanced Very High Resolution Radiometer (AVHRR) data and was trained and validated against collocated SYNOP observations. Utilisation of these two combined data sources requires a formulation of constraints in order to discriminate cases where the LSC is overlaid by higher clouds. The LSC classification process is based on six features which are first converted to the integer form by step functions and combined by means of bitwise operations. Consequently, a set of values reflecting a unique combination of those features is derived which is further employed to extract the LSC occurrence probability estimates from the precomputed look-up vectors (LUV). Although the validation analyses confirmed good performance of the algorithm, some inevitable misclassification with other optically thick clouds were reported. Moreover, the comparison against Polar Platform System (PPS) cloud-type product revealed superior classification accuracy. From the temporal perspective, the acquired results reported a presence of diurnal and annual LSC probability cycles over Europe.

From Similes to Allegory: The Deconstruction of Chariot Imagery in Early Buddhist Texts, Analyzed with Cognitive Metaphor Theory

The presentation will start by unfolding the various layers of chariot imagery in early Indian sources, namely, chariots as vehicles of gods such as the sun (sūrya), i.e. as symbol of cosmic stability; chariots as symbols of royal power and social prestige e.g. of Brahmins; and, finally, chariots as metaphors for the “person”, the “mind” and the “way to liberation” (e.g., Kaṭ.-Up. III.3; Maitr.-Up. II. 6). In Buddhist and non-Buddhist sources, chariots are in certain aspects used as a metaphor for the (old) human body (e.g., Caraka-S., Vi.3.37-38; D II.100; D II.107); apart from that, there is, of course, mention of the “real” use of chariots in sports, cults, journey, and combat. The most prominent example of the Buddhist use of chariot imagery is its application as a model for the person (S I.134 f.; Milindapañha, ed. Trenckner, 26), i.e., for highlighting the “non-substantial self”. There are, however, other significant examples of the usage of chariot imagery in early Buddhist texts. Of special interest are those cases in which chariot metaphors were applied in order to explain how the ‘self’ may proceed on the way to salvation – with ‘mindfulness’ or the ‘self’ as charioteer, with ‘wisdom’ and ‘confidence’ as horses etc. (e.g. S I. 33; S V.7; Dhp 94; or the Nārada-Jātaka, No. 545, verses 181-190). One might be tempted to say that these instances reaffirm the traditional soteriology of a substantial “progressing soul”. Taking conceptual metaphor analysis as a tool, I will, in contrast, argue that there is a special Buddhist use of this metaphor. Indeed, at first sight, it seems to presuppose a non-Buddhist understanding (the “self” as charioteer; the chariot as vehicle to liberation, etc.). Yet, it will be argued that in these cases the chariot imagery is no longer fully “functional”. The Buddhist usage may, therefore, best be described as a final allegorical phase of the chariot-imagery, which results in a thorough deconstruction of the “chariot” itself.

Colors in Mind: A Novel Paradigm to Investigate Pure Color Imagery

Mental color imagery abilities are commonly measured using paradigms that involve naming, judging, or comparing the colors of visual mental images of well-known objects (e.g., “Is a sunflower darker yellow than a lemon”?). Although this approach is widely used in patient studies, differences in the ability to perform such color comparisons might simply reflect participants’ general knowledge of object colors rather than their ability to generate accurate visual mental images of the colors of the objects. The aim of the present study was to design a new color imagery paradigm. Participants were asked to visualize a color for 3 s and then to determine a visually presented color by pressing 1 of 6 keys. The authors reasoned that participants would react faster when the imagined and perceived colors were congruent than when they were incongruent. In Experiment 1, participants were slower in incongruent than congruent trials but only when they were instructed to visualize the colors. The results in Experiment 2 demonstrate that the congruency effect reported in Experiment 1 cannot be attributed to verbalization of the color that had to be visualized. Finally, in Experiment 3, the congruency effect evoked by mental imagery correlated with performance in a perceptual version of the task. The authors discuss these findings with respect to the mechanisms that underlie mental imagery and patients suffering from color imagery deficits.