Bowen ratio determination of sensible and latent heat fluxes in a humid tropical environment at Ile- Ife, Nigeria

The Bowen ratio energy balance (BREB) method is the most widely used for estimating the fluxes of sensible heat and latent heat near the surface largely because of its conceptual simplicity and the robustness of instrumentation required. We have adopted the same technique here to study partitioning of measured available energy (difference of net radiation and soil heat flux) over bare soil at a humid tropical location in Ile-Ife, Nigeria (7° 33' N, 4° 34' E) between 7 and 10 March, 1999. Results obtained of the diurnal variations of the both fluxes in relation to the changing surface conditions (case studies) are quite satisfactory. For dry days, the sensible heat flux is comparatively of the same magnitude as the latent heat flux but it is less, about 10-60% for the wet surface conditions. It is clear from the present study that for the tropical forest zone, evaporation is the next important factor after radiation in the energy balance due to the humid conditions that usually prevail. Except for the few instances when very weak gradients exist, particularly of moisture, during transition periods (at sunrise or sunset), the technique has worked satisfactorily for day as well as night time periods regardless of prevailing weather conditions.

Diagnostic classification of flash drought events reveals distinct classes of forcings and impacts

Recent years have seen growing appreciation that rapidly intensifying “flash droughts” are significant climate hazards with major economic and ecological impacts. This has motivated efforts to inventory, monitor, and forecast flash drought events. Here we consider the question of whether the term “flash drought” comprises multiple distinct classes of event, which would imply that understanding and forecasting flash droughts might require more than one framework. To do this, we first extend and evaluate a soil moisture volatility-based flash drought definition that we introduced in previous work and use it to inventory the onset dates and severity of flash droughts across the Contiguous United States (CONUS) for the period 1979-2018. Using this inventory, we examine meteorological and land surface conditions associated with flash drought onset and recovery. These same meteorological and land surface conditions are then used to classify the flash droughts based on precursor conditions that may represent predictable drivers of the event. We find that distinct classes of flash drought can be diagnosed in the event inventory. Specifically, we describe three classes of flash drought: “dry and demanding” events for which antecedent evaporative demand is high and soil moisture is low, “evaporative” events with more modest antecedent evaporative demand and soil moisture anomalies, but positive antecedent evaporative anomalies, and “stealth” flash droughts, which are different from the other two classes in that precursor meteorological anomalies are modest relative to the other classes. The three classes exhibit somewhat different geographic and seasonal distributions. We conclude that soil moisture “flash droughts” are indeed a composite of distinct types of rapidly intensifying droughts, and that flash drought analyses and forecasts would benefit from approaches that recognize the existence of multiple phenomenological pathways.

Investigation on the Ignition of Self-Regulating Heating Cables due to Overheating

Owing to the self-regulating heating cables installed to prevent freeze-up, hundreds of fires are reported annually. According to the Fire Statistical Yearbook of 2020, provided by the National Fire Agency of Korea, a total of 2,245 fires occurred due to seasonal equipment, of which 240 were caused by heating wires. It is reported that the fires due to the self-regulating heating cables are mainly caused by short circuit, heat storage, poor contact, and electric leakage. Herein, the possibility of ignition in self-regulating heating cables owing to overheating is investigated. Test samples were prepared according to the IEC 60738 standard, and the resistance characteristics and surface conditions were analyzed at varying temperatures. It was found that the self-temperature control function of these cables was lost at a specific temperature. In addition, the ignition of self-regulating heating cables was confirmed through a fire reproduction test at the experimental temperature.

Seasonal predictability of the Indian Summer Monsoon : What role do land surface conditions play?

Anomalous springtime snow amounts over Eurasia may provide long term memory to the climate system by affecting the land surface energy and moisture budgets. In turn the anomalous land surface conditions introduced by snow anomalies may influence monsoon variability. In this paper, results from a programme of seasonal forecast ensembles are used to address, specifically, the influence of western Eurasian land surface conditions on the variability and hence predictability of the Indian summer monsoon. The factors that are important for establishing spring time land surface conditions over western Eurasia, particularly snow amounts are also investigated. The results have shown that high snow amounts over western Eurasia are linked to La Nina, suggesting that the El-Nino/Southern Oscillation (ENSO) has an influence on the wintertime climate of Eurasia. The signature of these snow depth anomalies is carried through to the summer in terms of changes in soil wetness and surface temperature. An ensemble of summer integrations with climatological sea surface temperature (SST) has been used to investigate the impact of these anomalous land surface conditions on monsoon variability. The results have shown that the monsoon circulation is substantially weakened in association with above normal snow amounts over western Eurasia, whilst All India Rainfall is slightly increased. Results from a parallel ensemble with observed SSTs show an opposite response in All India Rainfall, suggesting that the forcing by SST anomalies is potentially dominating the monsoon's inter-annual variability. The results have demonstrated that land surface conditions can have a significant impact on the large scale monsoon circulation and to a lesser extent on Indian Summer Monsoon rainfall, although the mechanisms involved have yet to be identified. It is suggested that interactions between the mid-latitude circulation and the monsoon may hold the key to understanding the link between Eurasian land surface conditions and monsoon variability. If that is the case then predictability of this relationship is likely to be limited, due to the high level of internal variability of the mid-latitude circulation.

Understanding Thai Urban Pedestrian Culture During Noon Break: How Sidewalk Users Experience the Walking Infrastructure in Bangkok, Thailand

The noon break or lunch hour in Bangkok’s central business district (CBD) is when pedestrians wander around for various activities and purposes, in addition to having a meal, within a limited time frame. It is the only break from their daily working routines for energy recovery or socializing, which, in turn, increases readiness to continue working in the afternoon. Commercial activities preferred by pedestrians during this break contribute to increased economic activity. Since pedestrian behavior depends on the cultural context, this research aims to understand Thai urban pedestrian culture that benefits the public, both socially and economically, and to investigate pedestrians’ experience of the physical quality of their walking infrastructure, reflecting their preferences. According to the information gained from observation, a field survey of four hundred thirty observations, and descriptive statistics, the urban pedestrian culture in the CBD of Bangkok is a combination of various activities related to a way of life; 69.4% and 44.9% of observed pedestrians have secondary and tertiary purposes. These multi-purpose trips during lunch hours include having meals, shopping, recovery from work, socializing, and taking care of business or running errands. The routine of lunch outings declined only slightly after the start of the pandemic in early 2020 compared to the pre-pandemic level (81.8% compared to 94.9%). Socializing has strong presence in the culture; 90.5% of group outings occur at least once or twice a week. On the physical side, the walking infrastructure, mainly comprising sidewalks, is used for circulation and as a place for social and economic settings. Using hierarchical cluster analysis, pedestrians’ concerns about the physical environment were divided into five groups, as follows: Cluster 1, people concerned about thermal comfort, surface conditions, and sidewalk obstructions. Cluster 2, people concerned about thermal comfort and walking distance. Cluster 3, people concerned about level changes and walking distance. Cluster 4, people concerned about surface conditions and sidewalk obstructions. Lastly, cluster 5, people concerned about sidewalk obstructions, traffic safety, and level changes. In conclusion. significant problems experienced or causing concern to pedestrians include sidewalk obstructions of flow due to insufficient width of the walking space as well as blockages caused by utility infrastructure, or social or economic activities, walking distance, surface conditions of sidewalks, level changes, thermal comfort, and traffic safety, respectively. These experiences and concerns reflect pedestrians’ preference for better quality of walking infrastructure. Therefore, inducing walkability is a promising physical strategy for promoting and sustaining Thai urban pedestrian culture.

Marked and unmarked speed bump detection for autonomous vehicles using stereo vision

A current challenge for autonomous vehicles is the detection of irregularities on road surfaces in order to prevent accidents; in particular, speed bump detection is an important task for safe and comfortable autonomous navigation. There are some techniques that have achieved acceptable speed bump detection under optimal road surface conditions, especially when signs are well-marked. However, in developing countries it is very common to find unmarked speed bumps and existing techniques fail. In this paper a methodology to detect both marked and unmarked speed bumps is proposed, for clearly painted speed bumps we apply local binary patterns technique to extract features from an image dataset. For unmarked speed bump detection, we apply stereo vision where point clouds obtained by the 3D reconstruction are converted to triangular meshes by applying Delaunay triangulation. A selection and extraction of the most relevant features is made to speed bump elevation on surfaces meshes. Results obtained have an important contribution and improve some of the existing techniques since the reconstruction of three-dimensional meshes provides relevant information for the detection of speed bumps by elevations on surfaces even though they are not marked.

Obsolete or Viable? Revision of Lane-Change Manoeuvre Duration Empirical Calculation

This study presents a calculation of the time required to execute a lane-change manoeuvre. Compared with other (and older) calculation methods, an analysis was conducted to determine which approach could yield the most reliable results. This study aimed to present a universal calculation method for different road surfaces, surface conditions (dry and wet road surface), and vehicle types (i.e., from small vehicles to SUVs). A total of 108 comparable manoeuvres with modern vehicles were used as a basis for statistical analysis. A new mathematical constant was found based on a regression analysis, adjusting one of the older calculation methods (so-called Kovařík equation), providing the best match between real and calculated manoeuvre duration.