Naval Postgraduate School

About: Naval Postgraduate School is a education organization based out in Monterey, California, United States. It is known for research contribution in the topics: Tropical cyclone & Boundary layer. The organization has 5246 authors who have published 11614 publications receiving 298300 citations. The organization is also known as: NPS & U.S. Naval Postgraduate School.

Sensitivity of Pine Island Glacier to observed ocean forcing

Abstract: We present subannual observations (2009–2014) of a major West Antarctic glacier (Pine Island Glacier) and the neighboring ocean. Ongoing glacier retreat and accelerated ice flow were likely triggered a few decades ago by increased ocean-induced thinning, which may have initiated marine ice-sheet instability. Following a subsequent 60% drop in ocean heat content from early 2012 to late 2013, ice flow slowed, but by < 4%, with flow recovering as the ocean warmed to prior temperatures. During this cold-ocean period, the evolving glacier-bed/ice-shelf system was also in a geometry favorable to stabilization. However, despite a minor, temporary decrease in ice discharge, the basin-wide thinning signal did not change. Thus, as predicted by theory, once marine ice-sheet instability is underway, a single transient high-amplitude ocean cooling has only a relatively minor effect on ice flow. The long-term effects of ocean-temperature variability on ice flow, however, are not yet known.

Modeling the dynamics of human energy regulation and its implications for obesity treatment

Abstract: Obesity has reached epidemic proportions in the United States and is threatening to become a global epidemic. Even more concerning, the incidence of overweight continues to increase. The health consequences and economic costs to individuals and to society are considerable. Obesity is associated with many serious health complications, including coronary heart disease, type 2 diabetes mellitus, hypertension, selected cancers, and musculoskeletal disorders. In the U.S., direct and indirect medical costs attributable to obesity are estimated to approach $100 billion yearly. Obesity develops when a chronic imbalance exists between energy intake, in the form of food and drink, and energy expenditure. To date, the emphasis of treatment has been on the energy intake side of the energy balance equation. This, in part, is because it has been difficult to demonstrate the efficacy of exercise as a treatment strategy. This paper attempts to demonstrate the utility of system dynamics modeling to study and gain insight into the physiology related to weight gain and loss. A simulation model is presented that integrates nutrition, metabolism, hormonal regulation, body composition, and physical activity. These processes are typically fragmented between many different disciplines and conceptual frameworks. This work seeks to bring these ideas together highlighting the interdependence of the various aspects of the complex human weight regulation system. The model was used as an experimentation vehicle to investigate the impacts of physical activity on body weight and composition. The results replicate the “mix” of results reported in the literature, as well as providing causal explanation for their variability. In one experiment, weight loss from a moderate level of daily exercise was comparable to the loss from dieting (when both produced equivalent energy deficits). Perhaps of greater significance, the exercise intervention protected against the loss of fat-free mass, which occurs when weight loss is achieved through dieting alone, and thus promoted favorable changes in body composition. In a second experiment, exercise regimens of moderate to high level of intensity proved counter-productive as weight-reducing strategies for an obese sedentary subject. This was due to the limited energy reserves (specifically, muscle glycogen) available to such individuals. However, when the diet was changed from a balanced composition to one that was highly loaded with carbohydrates, it became possible to sustain the intense exercise regimen over the experimental period, and achieve a significant drop in body weight. The results underscore the significant interaction effects between diet composition and physical activity, and emphasize the critical role that diet composition can have in exercise-based treatment interventions. Copyright © 2002 John Wiley & Sons, Ltd.

LPI radar: fact or fiction

Abstract: LPI radar is a system that consists of a radar and ES system. Its performance depends on both components. An LPI performance factor is derived and applied to several examples. Operational LPI radars are described. A digital LPI radar detector is described and test results presented. A recent book on LPI radar received a number of somewhat critical reviews that were published in Systems magazine. Although these reviews made a number of excellent points, several questioned the existence of LPI radar. The objectives of this article are to provide a sound technical basis for determining LPI properties of radar, examine several radars that have LPI qualities, and then to describe digital LPI radar detector designed and tested against the PILOT Mk2 radar. LPI radar is a system that represents a confluence between radar and electronic support (ES) technology. The objective of LPI radar is clear; that is, to escape detection by the ES receiver. However, the capability of the LPI radar system depends upon the characteristics of both the radar and ES receiver. To understand LPI radar one must first understand the nature of ES receivers. The functions performed by tactical ES receivers are immediate interception, identification, and location of both friendly and hostile emitters. Location requires interception in the emitter's sidelobes. Identification is performed by comparing the intercepted signature against the signatures contained within its threat library (Schelher, 1999). The metric that establishes the quality of interception is called the probability of intercept (POI) and is generally included in its specifications (Schleher, 1999). From the above discussion it is evident that radar might have LPI properties with respect to one type, but not to another type of ES system. This situation can be clarified if the claim of radar being LPI radar is accompanied by a description of the various types of ES systems for which this claim applies. However the LPI radar can never completely escape detection since there is always a minimum range (R/sub ES/) between the ES system and radar where the interception receiver detection threshold is exceeded.

Ocean-to-ice heat flux at the North Pole environmental observatory

Abstract: [1] Data from drifting buoys deployed in April, 2002, as part of the North Pole Environmental Observatory project have been analysed to estimate ocean heat flux in the time period from 1 May 2002 to 11 Mar 2003. Prior to late January, the observatory remained in deep water, but subsequently drifted directly over the Yermak Plateau, a relatively shallow feature north of Svalbard. While over deep water, heat flux was dominated by storage and release of solar energy in the ocean boundary layer during summer. The most likely annual average value for 2002 was 2.6 W m−2, less than previous determinations in the western Arctic. Over Yermak Plateau, heat flux at the interface came from mixing of warmer water into the boundary layer from below. When the observatory was in water with depths less than 1200 m, the average heat flux was around 22 W m−2.

CCN measurements during ACE‐2 and their relationship to cloud microphysical properties

Abstract: Measurements of cloud condensation nuclei (CCN) concentration at 0.1% supersaturation were made onboard the CIRPAS Pelican over the northeast Atlantic during June and July, 1997, in the vicinity of Tenerife, Spain, as part of the second Aerosol Characterization Experiment (ACE-2). The average CCN concentration (Nccn) in the marine boundary layer for clean air masses was 27±8 and 42±14 cm−3 for cloudy and clear conditions, respectively, consistent with measurements made near the British Isles and close to Tasmania, Australia, during ACE-1 for similar conditions. A local CCN closure experiment was conducted. Measured Nccn is compared with predictions based on aerosol number size distributions and size-resolved chemical composition profiles determined from measurements and the literature. A sublinear relationship between measured and predicted Nccn, Nccn∼N0.51ccn,predicted, was found. This result is consistent with some previous studies, but others have obtained results much closer to the expected 1 : 1 relationship between measured and predicted Nccn . A large variability between measured and predicted Nccn was also observed, leading to the conclusion that, for 95% of the data, the predictions agree with measurements to within a factor of 11. Relationships between below-cloud Nccn and aerosol accumulation mode concentration, and in-cloud cloud droplet number concentration, measured onboard the Pelican and the Meteo-France Merlin-IV, respectively, are calculated for periods while the 2 aircraft were in close proximity at approximately the same time. Measured relationships are reproduced by an adiabatic parcel model, and are also consistent with some previous studies. However, the shape of the CCN spectrum, or the aerosol size distribution, and the updraft velocity are predicted by the model to affect these relationships to a significant extent. Therefore, parameterizations of cloud microphysical properties need to include these variables to accurately predict cloud droplet number concentration. A relationship between Nccn and cloud droplet effective diameter is also calculated and shown to be consistent both with the literature and with the parameterization of effective diameter proposed by Martin et al.