Barry R. Lienert

Monte Carlo simulation of errors in the anisotropy of magnetic susceptibility: A second‐rank symmetric tensor

I have used Monte Carlo perturbations of synthetic tensors to evaluate the Hext/Jelinek elliptical confidence regions for anisotropy of magnetic susceptibility (AMS) eigenvectors. When the perturbations are 33% of the minimum anisotropy, both the shapes and probability densities of the resulting eigenvector distributions agree with the elliptical distributions predicted by the Hext/Jelinek equations. When the perturbation size is increased to 100% of the minimum eigenvalue difference, the major axis of the 95% confidence ellipse under estimates the observed eigenvector dispersion by about 10°. The observed distributions of the principal susceptibilities (eigenvalues) are close to being normal, with standard errors that agree well with the calculated Hext/Jelinek errors. The Hext/Jelinek ellipses are also able to describe the AMS dispersions due to instrumental noise and provide reasonable limits for the AMS dispersions observed in two Hawaiian basaltic dikes. I conclude that the Hext/Jelinek method provides a satisfactory description of the errors in AMS data and should be a standard part of any AMS data analysis.

Sea-Salt Size Distributions from Breaking Waves: Implications for Marine Aerosol Production and Optical Extinction Measurements during SEAS*

The authors’ participation in the Shoreline Environment Aerosol Study (SEAS) involved measurements focused on the coastal aerosol size distribution and related optical measurements, including aerosol light scattering, visibility, and remote sensing of aerosol using lidar backscatter. Aerosol production from shoreline breaking waves and the more distant reef (;1 km) was characterized for dry sizes between 0.01 and 10 mm for both their contribution to the marine aerosol population and their influence on near-surface lidar extinction. Thermal volatility was used to extract the refractory sea-salt particles from the other constituents volatile at 360 8C. At 7 m ASL and 20 m inland from the water’s edge the production of sea-salt nuclei number was often in the range of 50‐100 cm23 above the open-ocean value of ;250 cm23. This number peak was near 0.03-mm dry diameter, while light scattering was dominated by a few particles larger than 1 mm. This indicates that production of sea salt from breaking waves contributes not only to aerosol mass and optical effects but also to nuclei mode particle number in remote regions. Separate studies of optical closure quantified links between the size distribution and optical scattering measurements, visibility, and extinction values for both nearshore breaking waves and openocean conditions. These data confirmed that extinction derived from coastal lidar measurements at 0.530 mm was accurate to better than the 25% uncertainty claimed for the lidar inversion.

Repetitive genetic inversion of optical extinction data

We describe a genetic method of deriving aerosol size distributions from multiwavelength extinction measurements. The genetic inversion searches for log-normal size distribution parameters whose calculated extinctions best fit the data. By repetitively applying the genetic inversion using different random number seeds, we are able to generate multiple solutions that fit the data equally well. When these solutions are similar, they lend confidence to an interpretation, whereas when they vary widely, they demonstrate nonuniqueness. In this way we show that, even in the case of a single log-normal distribution, many different distributions can fit the same set of extinction data unless the misfit is reduced below typical measurement error levels. In the case of a bimodal distribution, we find many dissimilar size distributions that fit the data to within 1% at six wavelengths. To recover the original bimodal distribution satisfactorily, we found that extinctions at ten wavelengths must be fitted to within 0.5%. Our results imply that many size distributions recovered from existing extinction measurements can be highly nonunique and should be treated with caution.

Using Horizontal and Slant Lidar Measurements to Obtain Calibrated Aerosol Scattering Coefficients from a Coastal Lidar in Hawaii

Abstract Sea salt aerosol concentrations in the clean marine boundary layer can be considered spatially homogeneous when averaged over space and time. Using this assumption, horizontal and slant lidar measurements are carried out at a Hawaii coastal site allowing accurate retrieval of the marine aerosol scattering coefficient. It is found that when the lidar calibration or the aerosol phase function is adjusted so that the derived scattering coefficients are constant with range, then the derived aerosol scattering coefficients are correct and agree with nephelometer measurements (within 25%) and sun photometer (within 7%). Examples of this calibration process are given.

Vertical and horizontal aerosol scattering fields over Bellows Beach, Oahu, during the SEAS experiment

Scanning lidar measurements were carried out during the Shoreline Environment Aerosol Study (SEAS) experiment (19‐30 April 2000) to characterize the aerosol scattering fields in the coastal marine boundary layer at Bellows Beach on the southeast side of Oahu, Hawaii. The sea salt was found to be well mixed throughout the mixed layer, although the depth of the trade wind mixed layer was found to vary significantly over short timescales. As expected, the frequency distribution of aerosol scatter had a lognormal distribution, with the exception of regions downwind of breaking waves, where the frequency distribution was bimodal. A spatial statistical study revealed that the island-blocking effects cause low-level clouds to develop as they approach the island, with enhanced drizzle near the coastline reaching all the way to the surface. The spray from waves breaking on an outer reef was found to be intermittent and contained to heights of 20 m (on average) for the average wind speed of 7 m s21. Sea-salt concentrations and fluxes from the breaking waves were estimated from the lidar measurements and found to be within the range of values reported by other investigators.

Aerosol size distributions from genetic inversion of polar nephelometer data

Abstract It is shown that genetic inversions can be used to recover lognormal aerosol size distributions from multiangle optical scattering cross-section data measured by a polar nephelometer at a wavelength of 0.532 μm. The inversions can also be used to recover the absolute calibration factor of the polar nephelometer. The method is demonstrated by applying it to polar nephelometer data measured during the Shoreline Environment Aerosol Study (SEAS) at Bellows Beach on the island of Oahu, Hawaii. Also, the inverted size distributions are compared with those inferred from direct measurements by particle sizers during SEAS. At 0.532 μm, the polar nephelometer data are dominated by the effect of coarse-mode hydrated sea salt. Although the inversion was unable to place constraints on the accumulation-mode size distribution, the modeled size distribution provides a good description of optical scattering at wavelengths of 0.532 μm and above.

Crustal electrical conductivities along the eastern flank of the Sierra Nevadas

A unique controlled-source experiment utilizing a high-voltage dc transmission line and an array of three-component variometers was used in an extensive low-frequency electromagnetic (EM) survey along the eastern flank of the Sierra Nevada batholith. Complex image theory was used to interpret magnetic field data, obtained at over 90 stations, in terms of one-dimensional (1-D) electrical conductivity models of the lower and upper crust. Electrical conductivities in the upper crust were found to be very high in the area between Mono Lake and the Coso geothermal area. The zones of high conductivity are narrow linear features which may be associated with conductive fluids within highly permeable shatter zones. These shatter zones are caused by extensive north-south trending faults defining the eastern margin of the Sierra Nevada batholith.A profile line extending from the Sierra Nevada Mountains into Indian Wells Valley suggests that the electrical conductivity of the crust increases sharply on the eastern side of the Sierra Nevada fault zone. This may be indicative of processes in the deep crust and upper mantle associated with extension of the Basin and Range province westward to this point.South of the Garlock fault zone, the overall crustal conductivity is low. However, high-conductivity anomalies of shallow origin are seen in many places. These are interpreted as the effects of conductive sediments such as those filling the San Joaquin Valley, combined with complicated current systems flowing within major fault zones.

Real Time Analysis and Display of Scanning Lidar Scattering Data

We describe software for an IBM compatible personal computer (PC) that we have developed and used to collect and analyze backscatter data from a multi-wavelength Mie-Rayleigh scanning lidar system. Both one and two-dimensional distributions of optical scattering coefficients are calculated from the lidar return signals and displayed in real time. Although we are using the software for analyzing marine aerosols, the modular nature of the software and data acquisition drivers make it straightforward to adapt the software to different systems, such as differential absorption lidar (DIAL) and oceanic lidars. We show examples of both horizontal and vertical Mie-Rayleigh lidar scans collected at the Makai Pier and Bellows Beach on the northeast side of the island of Oahu.

Remote Raman Spectra of Benzene Obtained from 217 Meters Using a Single 532 nm Laser Pulse

This report describes a mobile Raman lidar system that has been developed for spectral measurements of samples located remotely at ranges of hundreds of meters. The performance of this system has been quantitatively verified in a lidar calibration experiment using a hard target of standardized reflectance. A new record in detection range was achieved for remote Raman systems using 532 nm laser excitation. Specifically, Raman spectra of liquid benzene were measured with an integration time corresponding to a single 532 nm laser pulse at a distance of 217 meters. The single-shot Raman spectra at 217 meters demonstrated high signal-to-noise ratio and good resolution sufficient for the unambiguous identification of the samples of interest. The transmitter consists of a 20 Hz Nd:YAG laser emitting at 532 nm and 1064 nm and a 178 mm telescope through the use of which allows the system to produce a focused beam at the target location. The receiver consists of a large custom telescope (609 mm aperture) and a Czerny–Turner monochromator equipped with two fast photomultiplier tubes.

An electromagnetic study of Maui’s last active volcano

I have used both d.c. resistivity and time‐varying (0.2–5 Hz) magnetic field soundings to study the Ulupalakua‐Makena area on the island of Maui, the site of the last historic eruption in 1970. Using generalized inversions of the combined data, I have estimated the electrical resistivity structure beneath eight magnetometer sites. The resistivity values I obtained for electrical basement (saltwater‐saturated basalt) are reasonably consistent with a single value of 6 ± 1 Ω ⋅ m at all eight sites, although there is a suggestion of an increase in resistivity away from the coastline. The resolution matrices for the magnetic data indicated that, in addition to resolving the resistivity of electrical basement, the data were significantly affected by a combination of the resistivity of the soil layer and the depth to basement. Use of the Schlumberger data in conjunction with the magnetic data removed this correlation and resulted in good resolution for the resistivity/thickness combinations of the four upper mod...