Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: David Reed x
  • All content x
Clear All Modify Search
David Reed and Mark Lyford

The life science program at the University of Wyoming provides introductory and advanced courses for students throughout the University of Wyoming colleges, including courses for nonscience majors. With the fairly low number of total required science courses for nonscience majors many instructors of courses for nonmajors develop course goals to engage students in learning about science that is relevant to their lives, explore how science works, and demonstrate the connections between science and society. The desired goal is to educate students who are better able to make informed decisions in their general lives, the marketplace, or the voting booth. However, many current relevant issues, such as climate change, are difficult to cover in a traditional discipline based science course because of the interdisciplinary nature of the topics. To address this, an integrated freshmen-level science course was developed at the University of Wyoming and, during each semester, students complete surveys to gauge their attitudes about science and expectations about the course. Survey results from this course show a surprisingly large increase in student comfort in science that persists beyond the end of the course, while at the same time their expectations for their grade in the course dropped. The authors' findings show that one science course can be contentrigorous while also helping to change how nonscience majors think about and interact with science in their lives outside of this course.

Full access
David Halpern and Ronald K. Reed

Abstract

The heat budget of a small region (∼2 km×2 km) near the coast of northwest Africa was investigated during a 3-day period in March 1974 when light winds (∼2 m s−1) occurred. Horizontal advection and diffusion of heat were negligible, and the local change in heat content resulted from the net radiative and evaporative flux at the sea surface. Diurnal heating produced surface temperature ranges of 0.9, 1.1 and 1.4°C for each of the 3 days. The exponential decrease of the diurnal heat wave with depth was used to estimate the vertical eddy thermal conductivity of the upper 10 m; values of approximately 10−3 m−2 s−1 were obtained.

Full access
Yu Zhang, Seann Reed, and David Kitzmiller

Abstract

This paper presents methodologies for mitigating temporally inconsistent biases in National Weather Service (NWS) real-time multisensor quantitative precipitation estimates (MQPEs) through rain gauge–based readjustments, and examines their effects on streamflow simulations. In this study, archived MQPEs over 1997–2006 for the Middle Atlantic River Forecast Center (MARFC) area of responsibility were readjusted at monthly and daily scales using two gridded gauge products. The original and readjusted MQPEs were applied as forcing to the NWS Distributed Hydrologic Model for 12 catchments in the domain of MARFC. The resultant hourly streamflow simulations were compared for two subperiods divided along November 2003, when a software error that gave rise to a low bias in MQPEs was fixed. It was found that readjustment at either time scale improved the consistency in the bias in streamflow simulations. For the earlier period, independent monthly and daily readjustments considerably improved the streamflow simulations for most basins as judged by bias and correlation. By contrast, for the later period the effects were mixed across basins. It was also found that 1) readjustments tended to be more effective in the cool rather than warm season, 2) refining the readjustment resolution to daily had mixed effects on streamflow simulations, and 3) at the daily scale, redistributing gauge rainfall is beneficial for periods with substantial missing MQPEs.

Full access
James M. Gilbert, Reed M. Maxwell, and David J. Gochis

Abstract

The boundary layer, land surface, and subsurface are important coevolving components of hydrologic systems. While previous studies have examined the connections between soil moisture, groundwater, and the atmosphere, the atmospheric response to regional water-table drawdown has received less attention. To address this question, a coupled hydrologic–atmospheric model [Parallel Flow hydrologic model (ParFlow) and WRF] was used to simulate the San Joaquin River watershed of central California. This study focuses specifically on the planetary boundary layer (PBL) in simulations with two imposed water-table configurations: a high water table mimicking natural conditions and a lowered water table reflecting historic groundwater extraction in California’s Central Valley, although effect of irrigation was not simulated. An ensemble of simulations including three boundary layer schemes and six initial conditions was performed for both water-table conditions to assess conceptual and initial condition uncertainty. Results show that increased regional water-table depth is associated with a significant increase in peak PBL height for both initial condition and boundary layer scheme conditions, although the choice of scheme interacts to affect the magnitude of peak PBL height change. Analysis of simulated land surface fluxes shows the change in PBL height can be attributed to decreasing midday evaporative fraction under lowered water-table conditions. Furthermore, the sensitivity of PBL height to changes in water-table depth appears to depend on local water-table variation within 10 m of the land surface and the regional average water-table depth. Finally, soil moisture changes associated with lowered water tables are linked to changes in PBL circulation as indicated by vertical winds and turbulence kinetic energy.

Full access
William W. Kellogg, David Atlas, David S. Johnson, Richard J. Reed, and Kenneth C. Spengler
Full access
Fiona M. Guest, Michael J. Reeder, Crispin J. Marks, and David J. Karoly

Abstract

This study examines the properties of inertia–gravity waves observed in the lower stratosphere over Macquarie Island, how these properties vary with season, and the likely source of the waves. The waves are observed in high-resolution upper-air ozonesonde soundings of wind and temperature released from Macquarie Island during the 1994 ASHOE–MAESA program.

The properties of the inertia–gravity waves observed in the soundings are quantified using hodograph and rotary spectral analyses. The analyzed waves have horizontal wavelengths between 100 and 1000 km, vertical wavelengths between about 1 and 7 km, intrinsic frequencies between f and 2f, and horizontal trace speeds between −50 and 30 m s−1. There appears to be a seasonal cycle in the inertia–gravity wave activity in the lower stratosphere, the minimum being in the austral winter when the background zonal flow is strong and westerly and its vertical shear is positive. In contrast, the variance of the horizontal perturbation winds does not show a similar seasonal cycle.

Inertia–gravity waves are detected over Macquarie Island on days with a common synoptic pattern. Two features define this synoptic pattern: 1) an upper-level jet and associated surface front lying upstream of Macquarie Island, and 2) a 300-hPa height field with Macquarie Island located between the inflection axis and the downstream ridge. This common synoptic pattern is observed on 16 of the 21 days on which inertia–gravity waves were detected. Moreover, the pattern is not observed on 15 of the 21 days in which inertia–gravity waves are not identified. This common synoptic pattern shows a seasonal cycle similar to that found for the inertia–gravity wave activity. Analyses of the ozonesonde soundings suggest also that the source of the inertia–gravity waves is in the troposphere. Using GROGRAT, the ray-tracing model developed by Marks and Eckermann, a cone of rays is released 21 km above Macquarie Island and traced backward in time. These rays suggest that the inertia–gravity waves are generated in the jet–front system southwest of Macquarie Island.

Full access
David E. Reed, Ankur R. Desai, Emily C. Whitaker, and Henry Nuckles

Abstract

Climate change is expected to decrease ice coverage and thickness globally while increasing the variability of ice coverage and thickness on midlatitude lakes. Ice thickness affects physical, biological, and chemical processes as well as safety conditions for scientists and the general public. Measurements of ice thickness that are both temporally frequent and spatially extensive remain a technical challenge. Here new observational methods using repurposed soil moisture sensors that facilitate high spatial–temporal sampling of ice thickness are field tested on Lake Mendota in Wisconsin during the winter 2015/16 season. Spatial variability in ice thickness was high, with differences of 10 cm of ice column thickness over 1.05 km of horizontal distance. When observational data were compared with manual measurements and model output from both the Freshwater Lake (FLake) model and General Lake Model (GLM), ice thickness from sensors matches manual measurements, whereas GLM and FLake results showed a thinner and thicker ice layer, respectively. The FLake-modeled ice column temperature effectively remained at 0°C, not matching observations. We also show that daily ice dynamics follows the expected linear function of ice thickness growth/melt, improving confidence in sensor accuracy under field conditions. We have demonstrated a new method that allows low-cost and high-frequency measurements of ice thickness, which will be needed both to advance winter limnology and to improve on-ice safety.

Full access
David Lobell, Govindasamy Bala, Art Mirin, Thomas Phillips, Reed Maxwell, and Doug Rotman

Abstract

A global climate model experiment is performed to evaluate the effect of irrigation on temperatures in several major irrigated regions of the world. The Community Atmosphere Model, version 3.3, was modified to represent irrigation for the fraction of each grid cell equipped for irrigation according to datasets from the Food and Agriculture Organization. Results indicate substantial regional differences in the magnitude of irrigation-induced cooling, which are attributed to three primary factors: differences in extent of the irrigated area, differences in the simulated soil moisture for the control simulation (without irrigation), and the nature of cloud response to irrigation. The last factor appeared especially important for the dry season in India, although further analysis with other models and observations are needed to verify this feedback. Comparison with observed temperatures revealed substantially lower biases in several regions for the simulation with irrigation than for the control, suggesting that the lack of irrigation may be an important component of temperature bias in this model or that irrigation compensates for other biases. The results of this study should help to translate the results from past regional efforts, which have largely focused on the United States, to regions in the developing world that in many cases continue to experience significant expansion of irrigated land.

Full access
Richard J. Reed, Robert M. White, Edward S. Epstein, Richard A. Craig, Harry Hamilton, Robert E. Livezey, David Houghton, and Frederick Carr
Full access
Gabriele Villarini, David A. Lavers, Enrico Scoccimarro, Ming Zhao, Michael F. Wehner, Gabriel A. Vecchi, Thomas R. Knutson, and Kevin A. Reed

Abstract

Heavy rainfall and flooding associated with tropical cyclones (TCs) are responsible for a large number of fatalities and economic damage worldwide. Despite their large socioeconomic impacts, research into heavy rainfall and flooding associated with TCs has received limited attention to date and still represents a major challenge. The capability to adapt to future changes in heavy rainfall and flooding associated with TCs is inextricably linked to and informed by understanding of the sensitivity of TC rainfall to likely future forcing mechanisms. Here a set of idealized high-resolution atmospheric model experiments produced as part of the U.S. Climate Variability and Predictability (CLIVAR) Hurricane Working Group activity is used to examine TC response to idealized global-scale perturbations: the doubling of CO2, uniform 2-K increases in global sea surface temperature (SST), and their combined impact. As a preliminary but key step, daily rainfall patterns of composite TCs within climate model outputs are first compared and contrasted to the observational records. To assess similarities and differences across different regions in response to the warming scenarios, analyses are performed at the global and hemispheric scales and in six global TC ocean basins. The results indicate a reduction in TC daily precipitation rates in the doubling CO2 scenario (on the order of 5% globally) and an increase in TC rainfall rates associated with a uniform increase of 2 K in SST (both alone and in combination with CO2 doubling; on the order of 10%–20% globally).

Full access