R-3 Repository :: Browsing by Author "Few, Arthur A., Jr."

Browsing by Author "Few, Arthur A., Jr."

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A demonstration and evaluation of trajectory mapping
(1995) Morris, Gary Allen; Few, Arthur A., Jr.
The problem of creating synoptic maps from asynoptically gathered data has prompted the development of a number of schemes. Most notable among these schemes are the Kalman filter, the Salby-Fourier technique, and constituent reconstruction. This thesis presents a new technique, called trajectory mapping. Trajectory mapping employs a simple model of air parcel motion to create synoptic maps from asynoptically gathered data. To assess the applicability of the technique, four sources of trajectory mapping errors were analyzed. The analysis revealed that (1) the computational error is negligible; (2) measurement uncertainties can result in errors which grow with time scales on the order of a week; (3) isentropic approximations lead to errors characterized by time scales of a week; and (4) wind field inaccuracies can cause significant errors in individual parcel trajectories in a matter of hours. All the studies, however, indicated that while individual trajectory errors can grow rapidly, constituent distributions, such as those depicted in trajectory maps, are much more robust, maintaining a high level of accuracy for periods on the order of several weeks. The trajectory mapping technique has been successfully applied to a variety of problems. First, trajectory mapping was employed in the study of dynamical wave-breaking events. Second, trajectory mapping was applied in satellite data validation studies, both for the determination of instrument accuracy and precision. Third, trajectory mapping was used to assess the accuracy of the meteorological wind fields. Such demonstrations imply that trajectory mapping will become an important tool in answering questions of global change, particularly the issue of ozone depletion.
A study of the urban heat island of Houston, Texas
(2003) Streutker, David Richard; Few, Arthur A., Jr.
The magnitude, spatial extent, growth, and seasonal and diurnal behaviors of the urban heat island of Houston, Texas are characterized using both in situ air temperature and remotely sensed surface temperature data. Between 1990 and 2000, the air temperature heat island of Houston had an average magnitude of 1.25 K at night but was largely absent during the day. This behavior is reflected in a survey of extreme temperature events, which reveals a dramatic increase in the number of extremely warm nights relative to the surrounding rural areas. Thermal satellite imagery acquired between 1985 and 2001 demonstrate a surface temperature heat island of approximately 3 K at night and up to 10 K during the day. Climatological analysis reveals an inverse dependence of air temperature heat island magnitude on rural temperature. Conversely, daytime surface temperature heat islands grow with rural temperature, while nighttime surface temperature heat islands show no relationship to rural temperature. Examination of temperature maps reveals an urban heat island area of 1200 km2 at night and 2100 km2 during the day. Comparison of satellite imagery taken twelve years apart exhibits a growth in the nighttime heat island of 0.8 K in magnitude and 650 km2 in area. High-resolution temperature data are also examined and show an urban temperature dependence on population density.
A zonally and annually averaged study of potential early Martian atmospheres
(1993) Schmunk, Robert Bradley; Few, Arthur A., Jr.
Observations of the surface of Mars suggest a high probability of surface water activity in that planet's past. Consequently, many studies of Mars' early atmosphere have attempted to estimate the carbon dioxide level by requiring that surface temperatures be high enough to support surface liquid water. In the main, these studies have employed one-dimensional, radiative-convective climate models capable of considering only a single solar zenith angle, typically chosen to represent a global and annual average. Such models are hence not well suited for considering meridional variations in the temperature profile, which are affected by variations in the orbital obliquity and the meridional redistribution of heat by dynamic processes. I describe modifications to a more complex model, the multi-level energy balance model designed at NASA's Goddard Laboratory for Atmospheric Sciences, which make it suitable for study of an atmosphere with varying carbon dioxide levels. Vertically and meridionally defined, the model includes heating and cooling by radiation, mean meridional circulation, large-scale (baroclinic) and small-scale (convective) eddies, and surface turbulent flux. I present annually-averaged results for an examination of potential atmospheres of early Mars, given that its carbon dioxide level may range from 0 to 500 Pa and the orbital obliquity from 0$\sp\circ$ to 50$\sp\circ.$ These results are compared with those obtained from a radiative-convective model.
Acoustic profiling, a technique for lightning channel reconstruction
(1972) Teer, Thomas Leon; Few, Arthur A., Jr.
By measuring the acoustic profile of lightning-generated thunder at several locations simultaneously, it is possible to reconstruct the lightning channel geometry. The technique allows a ground-based study of the lightning channel structure inside thunderstorm clouds. The maximum spatial resolution at a range of 5 km is + 50 meters, except for the vertical direction where the error is + 200 meters. The maximum range is 5 - 25 km, determined by atmospheric attenuation losses and the degree to which refraction of sound away from the array is observed. These limits apply only to a single station deployment of microphones - multi-station arrays greatly increase effective range and data statistics. At least three microphones are deployed in an equilateral triangular shaped array 100 meters on a side. The acoustic pressure profile of thunder events is recorded on magnetic tape and the time lags between similar events are calculated through a cross-correlation analysis. These time lags, taken from the microphone data, are then used to calculate the incident wave vector of the plane wave at the microphone array. A model atmosphere is chosen and the incident wave vector is tracked back in time through the atmosphere to its source location. However, interference phenomena due to sources extended in both space and time introduce random, non-stationary effects into the thunder data, we show how to identify these sources of variability in the data. in many cases, we show how to extract this variability from the data to produce more meaningful results, although approximately 60% of the cross-correlations must be disregarded because of the absence of well-defined peaks in the correlograms. By effectively digitizing the lightning source into a "point” source 50 meters in extent, we are usually able to generate 20 to 40 sets of space coordinates that we use to map the lightning channels. Data taken near Tucson, Arizona in August 1970, with photographic support provided by the University of Arizona, is presented in which we match acoustic reconstructions to photographs of the source lightning events.
An analysis of lightning and the limitations it imposes on a global model of thunderstorm electricity
(1990) Geis, Paul B.; Few, Arthur A., Jr.
I report here on preliminary work incorporating transient effects from lightning into a global thunderstorm electricity model. First, E, the electric field produced by a lightning return stroke, is analytically derived. Second, a determination is made of the model's ability to handle the quickly varying fields produced by lightning. In solving for the conduction current and other quantities of interest in the atmosphere the contribution to E from the vector potential is ignored. This approximation is most likely to be invalidated by the electric fields associated with lightning. We calculate the electric field component due to the vector potential, and the conduction current this electric field drives. The conduction current driven by the lightning flash is small compared to the other currents present for the time scales of importance in the model, and can be ignored. Therefore the model is able to include the effect of lightning on the global electric circuit even though the radiation component of the lightning is explicitly absent. A test of the model's accuracy, the continuity of current test, shows the model's results are self-consistent to within 9%-17%, depending upon the region being studied.
Background and early results for the Atmospheric Electrical Current Sensor Project
(1992) Morris, Gary Allen; Few, Arthur A., Jr.
This thesis describes the background behind and early results from an instrument designed to measure atmospheric electrical currents. Preliminary data presented herein (including the marked similarity in the signals from the two arrays, the noticeable Carnegie curve, and the correlation between the measured electric field and current at the same site) demonstrate the proper functioning of the instrument. A description of global circuit theory and Antarctic climate illuminate the deployment decisions. Also presented are a preliminary study suggesting that the instrument is affected by the presence of an electrode layer, and some of the mathematical and theoretical relationships required to determine physical variables from the raw data.
Carbon sequestration in the forests of East Texas
(2003) Almaguer-Reisdorf, Joyce Lynn; Harcombe, Paul A.; Few, Arthur A., Jr.
Increasing levels of atmospheric CO2 threaten to change the earth's climate and diversity in numerous adverse ways. This thesis explores aspects of two potential types of terrestrial sinks in East Texas, plantation rotation management and reforestation. I used a simple method of employing government GIS and tabular data for calculating and visualizing the size of those sinks, which could store an additional 2.3 to 98 million Mg C aboveground. The uncertainty of these values is high because of data inadequacies and also uncertainty about future land use trends. The mitigative powers of these sinks are discussed, as is their potential application in newly forming carbon credit programs such as the Chicago Climate Exchange.
Statistics and trends of global atmospheric electricity measurements
(1995) Cleary, Erika Noel; Few, Arthur A., Jr.
Globally representative atmospheric electric field and current data have been obtained from two sites at Amudsen-Scott South Pole Station at ground level (3 m) with 1 Hz time resolution. The average diurnal variation has been calculated for individual months and seasons, and well known features of the Carnegie curve observed. Amplitude ratios for seasonal curves range between 30-43%, in agreement with other studies. The Northern hemisphere winter is found to be a minimum for global convective-electrical activity and summer a maximum, in contradiction to the original 1929 Carnegie results. Seasonal phase shifts observed in previous studies of the diurnal variation of deep convective activity (DCA) in the tropics also appear in the results of this study. Good correlations between low amplitude peaks suggest our data are highly accurate and could be useful in detecting changes in weather patterns as might occur with global warming.
The electrical environment of thunderstorm models and measurements
(1994) Geis, Paul B.; Few, Arthur A., Jr.
A model describing a thunderstorm's interaction with the global electric circuit is presented. The model includes a thunderstorm, the surrounding atmospheric and ionospheric region, and the magnetically conjugate atmospheric and ionospheric region. The model is time-dependent, and includes lightning and thundercloud evolution. A method of using experimental data to more accurately simulate observed thunderstorms has been developed. Of the upward current generated by a thunderstorm, about 50% flows through the Earth's magnetosphere to the conjugate hemisphere. This percentage is fairly constant over the storm's active life, and varies little with storm size or structure. Infrequent lightning activity (less than one flash/minute) within a thunderstorm does not appear to greatly affect the thunderstorm's efficiency in transferring separated charge to the global circuit. Lightning does limit the magnitude of the electric fields and resulting currents within and below the storm.

Browsing by Author "Few, Arthur A., Jr."

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