Search Results

Incorporation of 3D Shortwave Radiative Effects within the Weather Research and Forecasting Model

Description: A principal goal of the Atmospheric Radiation Measurement (ARM) Program is to understand the 3D cloud-radiation problem from scales ranging from the local to the size of global climate model (GCM) grid squares. For climate models using typical cloud overlap schemes, 3D radiative effects are minimal for all but the most complicated cloud fields. However, with the introduction of ''superparameterization'' methods, where sub-grid cloud processes are accounted for by embedding high resolution 2D cloud system resolving models within a GCM grid cell, the impact of 3D radiative effects on the local scale becomes increasingly relevant (Randall et al. 2003). In a recent study, we examined this issue by comparing the heating rates produced from a 3D and 1D shortwave radiative transfer model for a variety of radar derived cloud fields (O'Hirok and Gautier 2005). As demonstrated in Figure 1, the heating rate differences for a large convective field can be significant where 3D effects produce areas o f intense local heating. This finding, however, does not address the more important question of whether 3D radiative effects can alter the dynamics and structure of a cloud field. To investigate that issue we have incorporated a 3D radiative transfer algorithm into the Weather Research and Forecasting (WRF) model. Here, we present very preliminary findings of a comparison between cloud fields generated from a high resolution non-hydrostatic mesoscale numerical weather model using 1D and 3D radiative transfer codes.
Date: March 18, 2005
Creator: O'Hirok, W.; Ricchiazzi, P. & Gautier, C.
Item Type: Article
Partner: UNT Libraries Government Documents Department

Geographic Distribution of HIV/AIDS in Texas

Description: This presentation is part of the faculty lecture series UNT Speaks Out on HIV/AIDS. This presentation discusses the geographic distribution of HIV/AIDS in Texas and the associated factors.
Date: December 1, 2011
Creator: Oppong, Joseph R.
Item Type: Presentation
Partner: UNT College of Arts and Sciences

Tuberculosis Among Hispanics of Tarrant County, Texas

Description: Presentation for the 2009 University Scholars Day at the University of North Texas discussing research on tuberculosis (TB) rates among Hispanics in Tarrant County, Texas.
Date: April 2, 2009
Creator: Huddleston, Jody S. & Oppong, Joseph R.
Item Type: Presentation
Partner: UNT Honors College

Diurnal evapotranspiration estimates in the Walnut River Watershed.

Description: Evapotranspiration is an essential component of the surface hydrological balance, but obtaining accurate estimates of the water vapor flux over large terrestrial areas can be difficult because of the substantial temporal and spatial variability in surface moisture conditions that can occur. This variability is often very large in the Great Plains and other portions of the Mississippi River Basin. Nevertheless, variations in soil moisture content, groundwater levels, and runoff in streams and rivers cannot be fully assessed without some knowledge of evapotranspiration rates. Here, observations made at the Walnut River Watershed (WRW), which is near Wichita, Kansas, and has an area of approximately 5000 km{sup 2}, are used to improve and test a modeling system that estimates long-term evapotranspiration with use of satellite remote sensing data with limited surface measurements. The techniques may be applied to much larger areas. As is shown in Fig. 1, the WRW is located in the Red River Basin and is enclosed by the southern Great Plains Clouds and Radiation Testbed (CART) of the US Department of Energy's Atmospheric Radiation Measurement (ARM) program. The functional relationships involving the satellite data, surface parameters, and associated subgrid-scale fluxes are modeled in this study by the parameterization of subgrid-scale surface (PASS) fluxes scheme (Gao, 1995; Gao et al., 1998), which is used in a modified and improved form (PASS2). The advantage of this modeling system is that it can make effective use of satellite remote sensing data and can be run for large areas for which flux data do not exist and surface meteorological data are available from only a limited number of ground stations. In this study, the normalized difference vegetation index (NDVI) or simple ratio (SR) and surface brightness temperature at each pixel for the WRW were derived from advanced very high resolution radiometers data collected ...
Date: October 5, 1998
Creator: Song, J.
Item Type: Article
Partner: UNT Libraries Government Documents Department

Inference of extractable soil moisture in the plant root zone at the Walnut River Watershed.

Description: Soil moisture content is a crucial variable in studies of hydrology, meteorology, and plant sciences. Soil moisture content influences the ability of land to hold additional water from precipitation and thus affects groundwater levels and runoff. Evapotranspiration rates are strongly influenced by soil moisture content near the surface; evapotranspiration regulates surface air temperature and is a major factor in modifying the water vapor content of the atmosphere. Adequate soil moisture is essential for plant growth; excesses and deficits of soil moisture must be considered in agricultural management practices. Soil moisture can be measured by a variety of in situ techniques, but such techniques often are inadequate for evaluation over large areas because of strong temporal and spatial variations. Here, a technique using standard surface meteorological observations together with remote sensing data from satellites is discussed.
Date: October 5, 1998
Creator: Song, J.
Item Type: Article
Partner: UNT Libraries Government Documents Department

Worldwide Historical Estimates of Leaf Area Index, 1932-2000

Description: Approximately 1000 published estimates of leaf area index (LAI) from nearly 400 unique field sites, covering the period 1932-2000, have been compiled into a single data set. LA1 is a key parameter for global and regional models of biosphere/atmosphere exchange of carbon dioxide, water vapor, and other materials. It also plays an integral role in determining the energy balance of the land surface. This data set provides a benchmark of typical values and ranges of LA1 for a variety of biomes and land cover types, in support of model development and validation of satellite-derived remote sensing estimates of LA1 and other vegetation parameters. The LA1 data are linked to a bibliography of over 300 original source references. These historic LA1 data are mostly from natural and seminatural (managed) ecosystems, although some agricultural estimates are also included. Although methodologies for determining LA1 have changed over the decades, it is useful to represent the inconsistencies (e.g., in maximum value reported for a particular biome) that are actually found in the scientific literature. Needleleaf (coniferous) forests are by far the most commonly measured biome/land cover types in this compilation, with 22% of the measurements from temperate evergreen needleleaf forests, and boreal evergreen needleleaf forests and crops the next most common (about 9% each). About 40% of the records in the data set were published in the past 10 years (1991-2000), with a further 20% collected between 1981 and 1990. Mean LAI ({+-} standard deviation), distributed between 15 biome/land cover classes, ranged from 1.31 {+-} 0.85 for deserts to 8.72 {+-} 4.32 for tree plantations, with evergreen forests (needleleaf and broadleaf) displaying the highest LA1 among the natural terrestrial vegetation classes. We have identified statistical outliers in this data set, both globally and according to the different biome/land cover classes, but despite some decreases ...
Date: February 6, 2002
Creator: Scurlock, JMO
Item Type: Report
Partner: UNT Libraries Government Documents Department

Estimating root-zone moisture and evapotranspiration with AVHRR data[Advanced Very High Resolution Radiometer]

Description: The parameterized subgrid-scale surface fluxes (PASS) model uses satellite data and limited surface observations to infer root-zone available moisture content and evapotranspiration rate with moderate spatial resolution over extended terrestrial areas. The ultimate goal of this work is to produce estimates of water loss by evapotranspiration, for application in hydrological models. The major advantage to the method is that it can be applied to areas having diverse surface characteristics where direct surface flux measurements either do not exist or are not feasible and where meteorological data are available from only a limited number of ground stations. The emphasis of this work with the PASS model is on improving (1) methods of using satellite remote sensing data to derive the essential parameters for individual types of surfaces over large areas, (2) algorithms for describing the interactions of near-surface atmospheric conditions with surface processes, and (3) algorithms for computing surface energy and water vapor flux at a scale close to the size of a satellite-derived image pixel. The PASS approach is being developed and tested further with observations from the 1997 Cooperative Atmosphere-Surface Exchange Study (CASES-97) at the Atmospheric Boundary Layer Experiments (ABLE) site in the Walnut River Watershed (WRW), an area of about 5,000 km{sup 2} in southern Kansas. Here the authors describe some of the progress made since the previous report.
Date: October 8, 1999
Creator: Song, J. & Wesely, M. L.
Item Type: Article
Partner: UNT Libraries Government Documents Department

Comparison of different methods for monitoring glacier changes observed by Landsat images

Description: This paper presents three methods for classifying glacier boundaries, compares the three methods to provide advice on how to choose an appropriate method, and analyzes the relationship between glacier change and the trends of precipitation and temperature.
Date: March 18, 2014
Creator: Man, Qixia; Guo, Huadong; Liu, Guang & Dong, Pinliang
Item Type: Paper
Partner: UNT College of Arts and Sciences

Lignite Deposits and Kidney and Renal Pelvic Cancers in Texas 1980-1998

Description: This paper discusses research on lignite deposits and kidney and renal pelvic cancers in Texas from 1980 to 1998. This study also probes the role of such factors as race, gender, and socioeconomic status on mortality rates for these cancers.
Date: April 3, 2008
Creator: Guthrey, Harvey & Oppong, Joseph R.
Item Type: Paper
Partner: UNT Honors College

The Geography of Viral Hepatitis C in Texas, 1992-1999

Description: This paper discusses research on the geography of viral hepatitis C in Texas from 1992-1999. This study examines the relationship between viral hepatitis C (HCV), race, gender, and population density in Texas counties.
Date: March 3, 2006
Creator: Hedrich, Mara & Oppong, Joseph R.
Item Type: Paper
Partner: UNT Honors College

Geophysical Prospecting for Oil and Gas Well Effluent

Description: This article describes the evaluation of the utility of an earth resistivity system for detecting drilling effluent at a site in the Trinity Group outcrop zone.
Date: December 1997
Creator: Hudak, Paul F. & Maxey, George
Item Type: Article
Partner: UNT College of Arts and Sciences

A machine learning approach to automated construction of knowledge bases for expert systems for remote sensing image analysis with GIS data

Description: Knowledge-based remote sensing image analysis with GIS data is acknowledged as a promising technique. However, the difficulty in knowledge acquisition, a well-known bottleneck in building knowledge-based systems, impedes the adoption of this technique. Automating knowledge acquisition is therefore in demand. This paper presents a machine learning approach to automated construction of knowledge bases for image analysis expert systems integrating remotely sensed and GIS data. The methodology applied in the study is based on inductive learning techniques in machine learning, a subarea of artificial intelligence. It involves training with examples from remote sensing and GIS data, learning using the inductive principles, decision tree generating, rule generating from the decision tree, and knowledge base building for an image analysis expert system. This method was used to construct a knowledge base for wetland classification of Par Pond on the Savannah River Site, SC, using SPOT image data and GIS data. The preliminary results show that this method can provide an effective approach to integration of remotely sensed and GIS data in geographic information processing.
Date: December 31, 1995
Creator: Huang, X.; Jensen, J.R. & Mackey, H.E. Jr.
Item Type: Article
Partner: UNT Libraries Government Documents Department