Formation of the Wink Sink, A Salt Dissolution and Collapse Feature, Winkler County, Texas

UT Librarie

Use of high-dimensional spectral data to evaluate organic matter, reflectance relationships in soils

Recent breakthroughs in remote sensing technology have led to the development of a spaceborne high spectral resolution imaging sensor, HIRIS, to be launched in the mid-1990s for observation of earth surface features. The effects of organic carbon content on soil reflectance over the spectral range of HIRIS, and to examine the contributions of humic and fulvic acid fractions to soil reflectance was evaluated. Organic matter from four Indiana agricultural soils was extracted, fractionated, and purified, and six individual components of each soil were isolated and prepared for spectral analysis. The four soils, ranging in organic carbon content from 0.99 percent, represented various combinations of genetic parameters such as parent material, age, drainage, and native vegetation. An experimental procedure was developed to measure reflectance of very small soil and organic component samples in the laboratory, simulating the spectral coverage and resolution of the HIRIS sensor. Reflectance in 210 narrow (10 nm) bands was measured using the CARY 17D spectrophotometer over the 400 to 2500 nm wavelength range. Reflectance data were analyzed statistically to determine the regions of the reflective spectrum which provided useful information about soil organic matter content and composition. Wavebands providing significant information about soil organic carbon content were located in all three major regions of the reflective spectrum: visible, near infrared, and middle infrared. The purified humic acid fractions of the four soils were separable in six bands in the 1600 to 2400 nm range, suggesting that longwave middle infrared reflectance may be useful as a non-destructive laboratory technique for humic acid characterization

Aggregating available soil water holding capacity data for crop yield models

The total amount of water available to plants that is held against gravity in a soil is usually estimated as the amount present at -0.03 MPa average water potential minus the amount present at -1.5 MPa water potential. This value, designated available water-holding capacity (AWHC), is a very important soil characteristic that is strongly and positively correlated to the inherent productivity of soils. In various applications, including assessing soil moisture status over large areas, it is necessary to group soil types or series as to their productivity. Current methods to classify AWHC of soils consider only total capacity of soil profiles and thus may group together soils which differ greatly in AWHC as a function of depth in the profile. A general approach for evaluating quantitatively the multidimensional nature of AWHC in soils is described. Data for 902 soil profiles, representing 184 soil series, in Indiana were obtained from the Soil Characterization Laboratory at Purdue University. The AWHC for each of ten 150-mm layers in each soil was established, based on soil texture and parent material. A multivariate clustering procedure was used to classify each soil profile into one of 4, 8, or 12 classes based upon ten-dimensional AWHC values. The optimum number of classes depends on the range of AWHC in the population of oil profiles analyzed and on the sensitivity of a crop to differences in distribution of water within the soil profile

The validity of the kinetic collection equation revisited

The kinetic collection equation (KCE) describes the evolution of the average droplet spectrum due to successive events of collision and coalescence. Fluctuations and non-zero correlations present in the stochastic coalescence process would imply that the size distributions may not be correctly modeled by the KCE. <br><br> In this study we expand the known analytical studies of the coalescence equation with some numerical tools such as Monte Carlo simulations of the coalescence process. The validity time of the KCE was estimated by calculating the maximum of the ratio of the standard deviation for the largest droplet mass over all the realizations to the averaged value. A good correspondence between the analytical and the numerical approaches was found for all the kernels. The expected values from analytical solutions of the KCE, were compared with true expected values of the stochastic collection equation (SCE) estimated with Gillespie's Monte Carlo algorithm and analytical solutions of the SCE, after and before the breakdown time. <br><br> The possible implications for cloud physics are discussed, in particular the possibility of application of these results to kernels modified by turbulence and electrical processes

On the diurnal variability of particle properties related to black carbon in Mexico City

International audienceThe black carbon mass (BCM) of individual, internally mixed aerosol particles was measured with the Single Particle Soot Photometer (SP2) in April of 2003 and 2005. The average BCM, single particle BC mass fraction and BCM equivalent diameter were evaluated with respect to concentrations of carbon monoxide (CO), particle bound polycyclic aromatic hydrocarbons (PPAH) and condensation nuclei (CN). The BCM and CO have matching diurnal trends that are linked to traffic patterns and boundary layer growth. The PPAH reaches a maximum at the same hour as CO and BCM but returns rapidly back to nighttime values within three hours of the peak. The number of particles containing BCM ranges between 10% to 40% of all particles between 200 nm and 700 nm and the BCM is between 4% and 12% of the total mass in this size range. The average BC equivalent mass diameter varies between 300 and 400 nm and reaches its daily minimum value when BCM is a maximum. The BC particles have the thinnest coating of non-light absorbing material during periods of maximum BCM. The scattering and absorption coefficients, Bscat and Babs , derived from the SP2 measurements were compared with direct measurements from a nephelometer and soot photometer. The measured and derived Babs are in close agreement whereas the Bscat comparisons show larger discrepancies in absolute value and daily trends. Even though approximately 40% of the BCM is in particles with diameters smaller than 200 nm, the extinction coefficient is dominated by the BCM in particles larger than this size. The BCM contributes up to 20% of the total extinction in this size range. BCM is emitted at a rate of 1200 metric tons per year in Mexico City, based upon the SP2 measurements and correlations between BCM and CO

On the diurnal variability of particle properties related to light absorbing carbon in Mexico City

International audienceThe mass of light absorbing carbon (LAC) in individual, internally mixed aerosol particles was measured with the Single Particle Soot Photometer (SP2) in April of 2003 and 2005 and evaluated with respect to concentrations of carbon monoxide (CO), particle bound polycyclic aromatic hydrocarbons (PPAH) and condensation nuclei (CN). The LAC and CO have matching diurnal trends that are linked to traffic patterns and boundary layer growth. The PPAH reaches a maximum at the same time as CO and LAC but returns rapidly back to nighttime values within three hours of the peak. The number of particles containing LAC ranges between 10% to 40% of all particles between 150 nm and 650 nm and the mass is between 5% and 25% of the total mass in this size range. The average LAC equivalent mass diameter varies between 160 and 230 nm and the thinnest coating of non-light absorbing material is observed during periods of maximum LAC mass. The coating varies between 10 nm and 30 nm during the day, but is a strong function of particle size. The mass absorption cross sections, ?abs, derived from the SP2, are 5.0±0.2 m2g?1 and 4.8±0.2 m2g?1, dependent on the optical model used to describe LAC mixtures. The LAC contributes up to 50% of the total light extinction in the size range from 100 nm to 400 nm. The estimated emission rate of LAC is 1200 metric tons per year in Mexico City, based upon the SP2 measurements and correlations between LAC and CO

Agricultural scene understanding

The author has identified the following significant results. The LACIE field measurement data were radiometrically calibrated. Calibration enabled valid comparisons of measurements from different dates, sensors, and/or locations. Thermal band canopy results included: (1) Wind velocity had a significant influence on the overhead radiance temperature and the effect was quantized. Biomass and soil temperatures, temperature gradient, and canopy geometry were altered. (2) Temperature gradient was a function of wind velocity. (3) Temperature gradient of the wheat canopy was relatively constant during the day. (4) The laser technique provided good quality geometric characterization

Aerosol particles in the mexican east pacific part I: processing and vertical redistribution by clouds

International audienceAirborne measurements of aerosol particle size distributions were made in the Mexican Intertropical Convergence Zone. The shape of the spectra at cloud base was compared with those at higher altitudes and near cloud boundaries to identify signatures of cloud processed particles. Of 78 cases analyzed, 71% showed enhancement in volume of super-micron particles, 49% had enhanced volume of sub-micron particles, 28% were homogeneous mixtures with boundary layer air, and 24% had super-micron particles removed by precipitation. Almost 100% of the cases with enhanced volume in sub-micron particles also occurred with enhanced super-micron volume. The enhanced volume in super-micron particles is approximately 10 times larger than the sub-micron enhancement. Cloud processed particles in marine air masses had twice as much enhancement of super-micron mass than found in particles processed by clouds formed from continental sources, likely a result of a more efficient coalescence process in clean, maritime clouds. These results are in qualitative agreement with previous observational and theoretical studies that relate enhancements in particle mass to the uptake by cloud droplets of SO2 and subsequent growth by coalescence

Requirements of a global information system for corn production and distribution

There are no author-identified significant results in this report

Spectral characteristics of normal and nutrient-deficient maize leaves

Reflectance, transmittance and absorbance spectra of normal and six types of mineral-deficient (N,P,K,S,Mg and Ca) maize (Zea mays L.) leaves were analyzed at 30 selected wavelengths along the electromagnetic spectrum from 500 to 2600 nm. Chlorophyll content and percent leaf moisture were also determined. Leaf thermograms were obtained for normal, N- and S- deficient leaves. The results of the analysis of variance showed significant differences in reflectance, transmittance and absorbance in the visible wavelengths among leaf numbers 3, 4, and 5, among the seven nutrient treatments, and among the interactions of leaves and treatments. In the reflective infrared wavelengths only treatments produced significant differences. The chlorophyll content of leaves was reduced in all deficiencies in comparison to controls. Percent moisture was increased in S-, Mg- and N- deficiencies. Positive correlation (r = 0.707) between moisture content and percent absorption at both 1450 and 1930 nm were obtained. Polynomial regression analysis of leaf thickness and leaf moisture content showed that these two variables were significantly and directly related (r = 0.894)