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- Author or Editor: A. Vidal x
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Abstract
High-frequency Doppler radar (HFDR) and acoustic Doppler current profiler (ADCP) time-series observations during the Philippine Straits Dynamics Experiment (PhilEx) were analyzed to describe the mesoscale currents in Panay Strait, Philippines. Low-frequency surface currents inferred from three HFDR (July 2008–July 2009), reveal a clear seasonal signal concurrent with the reversal of the Asian monsoon. A mesoscale cyclonic eddy west of Panay Island is generated during the winter northeast (NE) monsoon. This causes changes in the strength, depth, and width of the intraseasonal Panay coastal (PC) jet as its eastern limb. Winds from QuikSCAT and from a nearby airport indicate that these flow structures correlate with the strength and direction of the prevailing local wind. An intensive survey in 8–9 February 2009 using 24 h of successive cross-shore conductivity–temperature–depth (CTD) sections, which in conjunction with shipboard ADCP measurements, show a well-developed cyclonic eddy characterized by near-surface velocities of 50 cm s−1. This eddy coincides with the intensification of the wind in between Mindoro and Panay Islands, generating a positive wind stress curl in the lee of Panay, which in turn induces divergent surface currents. Water column response from the mean transects show a pronounced signal of upwelling, indicated by the doming of isotherms and isopycnals. A pressure gradient then is set up, resulting in the spin up of a cyclonic eddy in geostrophic balance. Evolution of the vorticity within the vortex core confirms wind stress curl as the dominant forcing.
Abstract
High-frequency Doppler radar (HFDR) and acoustic Doppler current profiler (ADCP) time-series observations during the Philippine Straits Dynamics Experiment (PhilEx) were analyzed to describe the mesoscale currents in Panay Strait, Philippines. Low-frequency surface currents inferred from three HFDR (July 2008–July 2009), reveal a clear seasonal signal concurrent with the reversal of the Asian monsoon. A mesoscale cyclonic eddy west of Panay Island is generated during the winter northeast (NE) monsoon. This causes changes in the strength, depth, and width of the intraseasonal Panay coastal (PC) jet as its eastern limb. Winds from QuikSCAT and from a nearby airport indicate that these flow structures correlate with the strength and direction of the prevailing local wind. An intensive survey in 8–9 February 2009 using 24 h of successive cross-shore conductivity–temperature–depth (CTD) sections, which in conjunction with shipboard ADCP measurements, show a well-developed cyclonic eddy characterized by near-surface velocities of 50 cm s−1. This eddy coincides with the intensification of the wind in between Mindoro and Panay Islands, generating a positive wind stress curl in the lee of Panay, which in turn induces divergent surface currents. Water column response from the mean transects show a pronounced signal of upwelling, indicated by the doming of isotherms and isopycnals. A pressure gradient then is set up, resulting in the spin up of a cyclonic eddy in geostrophic balance. Evolution of the vorticity within the vortex core confirms wind stress curl as the dominant forcing.
Abstract
The occurrence of natural and socially driven catastrophic events has increased in the last few decades in response to global environmental changes. One of the most societally relevant challenges in managing the effects of these events is the establishment of risk management strategies that focus on managing vulnerability, particularly in disfavored countries, and communities among them. Most cases of enhanced vulnerability occur in, but are not limited to, developing countries, where the combination of social inequity, inappropriate use of natural resources, population displacement, and institutional mistrust, among other factors, make risk management particularly challenging. This paper presents a vulnerability-centered risk management framework based on social cohesion and integration principles that, combined with scientific, technical, and popular knowledge, lead to the development of social networks of risk reduction. This framework is intended as a strategy to strengthen early warning systems (EWS), where the human-related factor is among their most challenging components. Using water-related hazards as a case study, this paper describes the experience of the conformation of a social network for environmental monitoring using this model example on vulnerability reduction in the rural areas of the central Andes in Colombia. This experience allowed the effective conformation of a social network for environmental monitoring in 80 municipalities of Colombia, where communities developed a sense of ownership with the instrumentation and the network, strengthening links with local authorities and contributing to more efficient EWS. More generally, the authors highlight the need to develop vulnerability-centered risk management via community-building strategies, particularly for areas where little can be done to decrease the occurrence of catastrophic events.
Abstract
The occurrence of natural and socially driven catastrophic events has increased in the last few decades in response to global environmental changes. One of the most societally relevant challenges in managing the effects of these events is the establishment of risk management strategies that focus on managing vulnerability, particularly in disfavored countries, and communities among them. Most cases of enhanced vulnerability occur in, but are not limited to, developing countries, where the combination of social inequity, inappropriate use of natural resources, population displacement, and institutional mistrust, among other factors, make risk management particularly challenging. This paper presents a vulnerability-centered risk management framework based on social cohesion and integration principles that, combined with scientific, technical, and popular knowledge, lead to the development of social networks of risk reduction. This framework is intended as a strategy to strengthen early warning systems (EWS), where the human-related factor is among their most challenging components. Using water-related hazards as a case study, this paper describes the experience of the conformation of a social network for environmental monitoring using this model example on vulnerability reduction in the rural areas of the central Andes in Colombia. This experience allowed the effective conformation of a social network for environmental monitoring in 80 municipalities of Colombia, where communities developed a sense of ownership with the instrumentation and the network, strengthening links with local authorities and contributing to more efficient EWS. More generally, the authors highlight the need to develop vulnerability-centered risk management via community-building strategies, particularly for areas where little can be done to decrease the occurrence of catastrophic events.
Long-Autonomy Unmanned Aircraft Vehicle (UAV) for Quick Release of Ocean MinidriftersAbstract
In this work we present an unmanned aircraft vehicle (UAV) designed from off-the-shelf components to release ocean minidrifters. Its endurance (~1 h), payload (~5 kg), offshore range (~30 km), capability of operating into wind conditions of ~10 kt (1 kt ≈ 0.51 m s−1), high-precision autopilot (2–3 m), and flying altitude of ~500 m above sea level, along with its relatively low cost [<$5,000 (U.S. dollars)] enables quick and relatively easy oceanographic applications beyond 10 km offshore. We report here the very first successful ocean drifter releases, performed along the Baja California coast, between Tijuana and Rosarito, Mexico, and the technical details of the UAV. About 50 experiments (flights) allowed us to improve the takeoff and landing, the release tunnel for minidrifters, the cruise speed and altitude to release drifters safely, and to implement a parachute that controls the speed of the freefalling minidrifters. Quick release of up to six drifters (armed with real-time data transfer and web display) between 2 and 12 km offshore were performed at ~500 m above sea level, during a single flight in under 15 min, as opposed to classic techniques using boats or ships that, although can transport much more weight, can take several hours, use more human resources, and increase cost. Here we propose a novel open-source technique that can be used as a simplified method for scientific ocean measurements, as a quick-response emergency tool to map spills or for search and rescue.
Abstract
In this work we present an unmanned aircraft vehicle (UAV) designed from off-the-shelf components to release ocean minidrifters. Its endurance (~1 h), payload (~5 kg), offshore range (~30 km), capability of operating into wind conditions of ~10 kt (1 kt ≈ 0.51 m s−1), high-precision autopilot (2–3 m), and flying altitude of ~500 m above sea level, along with its relatively low cost [<$5,000 (U.S. dollars)] enables quick and relatively easy oceanographic applications beyond 10 km offshore. We report here the very first successful ocean drifter releases, performed along the Baja California coast, between Tijuana and Rosarito, Mexico, and the technical details of the UAV. About 50 experiments (flights) allowed us to improve the takeoff and landing, the release tunnel for minidrifters, the cruise speed and altitude to release drifters safely, and to implement a parachute that controls the speed of the freefalling minidrifters. Quick release of up to six drifters (armed with real-time data transfer and web display) between 2 and 12 km offshore were performed at ~500 m above sea level, during a single flight in under 15 min, as opposed to classic techniques using boats or ships that, although can transport much more weight, can take several hours, use more human resources, and increase cost. Here we propose a novel open-source technique that can be used as a simplified method for scientific ocean measurements, as a quick-response emergency tool to map spills or for search and rescue.
Arid and semiarid rangelands comprise a significant portion of the earth's land surface. Yet little is known about the effects of temporal and spatial changes in surface soil moisture on the hydrologic cycle, energy balance, and the feedbacks to the atmosphere via thermal forcing over such environments. Understanding this interrelationship is crucial for evaluating the role of the hydrologic cycle in surface–atmosphere interactions.
This study focuses on the utility of remote sensing to provide measurements of surface soil moisture, surface albedo, vegetation biomass, and temperature at different spatial and temporal scales. Remote-sensing measurements may provide the only practical means of estimating some of the more important factors controlling land surface processes over large areas. Consequently, the use of remotely sensed information in biophysical and geophysical models greatly enhances their ability to compute fluxes at catchment and regional scales on a routine basis. However, model calculations for different climates and ecosystems need verification. This requires that the remotely sensed data and model computations be evaluated with ground-truth data collected at the same areal scales.
The present study (MONSOON 90) attempts to address this issue for semiarid rangelands. The experimental plan included remotely sensed data in the visible, near-infrared, thermal, and microwave wavelengths from ground and aircraft platforms and, when available, from satellites. Collected concurrently were ground measurements of soil moisture and temperature, energy and water fluxes, and profile data in the atmospheric boundary layer in a hydrologically instrumented semiarid rangeland watershed. Field experiments were conducted in 1990 during the dry and wet or “monsoon season” for the southwestern United States. A detailed description of the field campaigns, including measurements and some preliminary results are given.
Arid and semiarid rangelands comprise a significant portion of the earth's land surface. Yet little is known about the effects of temporal and spatial changes in surface soil moisture on the hydrologic cycle, energy balance, and the feedbacks to the atmosphere via thermal forcing over such environments. Understanding this interrelationship is crucial for evaluating the role of the hydrologic cycle in surface–atmosphere interactions.
This study focuses on the utility of remote sensing to provide measurements of surface soil moisture, surface albedo, vegetation biomass, and temperature at different spatial and temporal scales. Remote-sensing measurements may provide the only practical means of estimating some of the more important factors controlling land surface processes over large areas. Consequently, the use of remotely sensed information in biophysical and geophysical models greatly enhances their ability to compute fluxes at catchment and regional scales on a routine basis. However, model calculations for different climates and ecosystems need verification. This requires that the remotely sensed data and model computations be evaluated with ground-truth data collected at the same areal scales.
The present study (MONSOON 90) attempts to address this issue for semiarid rangelands. The experimental plan included remotely sensed data in the visible, near-infrared, thermal, and microwave wavelengths from ground and aircraft platforms and, when available, from satellites. Collected concurrently were ground measurements of soil moisture and temperature, energy and water fluxes, and profile data in the atmospheric boundary layer in a hydrologically instrumented semiarid rangeland watershed. Field experiments were conducted in 1990 during the dry and wet or “monsoon season” for the southwestern United States. A detailed description of the field campaigns, including measurements and some preliminary results are given.
