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We have developed a compact instrument called the “COmpact COlor BIofinder”, or CoCoBi, for the standoff detection of biological materials and organics with polyaromatic hydrocarbons (PAHs) using a nondestructive approach in a wide area. The CoCoBi system uses a compact solid state, conductively cooled neodymium-doped yttrium aluminum garnet (Nd:YAG) nanosecond pulsed laser capable of simultaneously providing two excitation wavelengths, 355 and 532 nm, and a compact, sensitive-gated color complementary metal–oxide–semiconductor camera detector. The system is compact, portable, and determines the location of biological materials and organics with PAHs in an area 1590 cm2 wide, from a target distance of 3 m through live video using fast fluorescence signals. The CoCoBi system is highly sensitive and capable of detecting a PAH concentration below 1 part per billion from a distance of 1 m. The color images provide the simultaneous detection of various objects in the target area using shades of color and morphological features. We demonstrate that this unique feature successfully detected the biological remains present in a 150-million-year-old fossil buried in a fluorescent clay matrix. The CoCoBi was also successfully field-tested in Hawaiian ocean water during daylight hours for the detection of natural biological materials present in the ocean. The wide-area and video-speed imaging capabilities of CoCoBi for biodetection may be highly useful in future NASA rover–lander life detection missions.

We report the remote Raman spectra of natural igneous, metamorphic, and sedimentary rock samples at a standoff distance of 5 m. High-quality remote Raman spectra of unprepared rocks are necessary for accurate and realistic analysis of future Raman measurements on planetary surfaces such as Mars. Our results display the ability of a portable compact remote Raman system (CRRS) to effectively detect and isolate various light- and dark-colored mineral phases in natural rocks. The CRRS easily detected plagioclase and potassium feldspar end members, quartz, and calcite in rocks with high fluorescence backgrounds. Intermediate feldspars and quartz, when found in rocks with complex mineralogies, exhibited band shifts and broadening in the ${504{-}510}\,\,{{\rm cm}^{ - 1}}$504−510cm−1 and ${600{-}1200}\,\,{{\rm cm}^{ - 1}}$600−1200cm−1 regions. A good approximation of intermediate plagioclase feldspars was possible by using overall Raman spectral shape and assigning other minor Raman peaks in addition to the $ 504{-}510\,\,{{\rm cm}^{ - 1}}$504−510cm−1 peaks. Detection of olivine and pyroxene in mafic rocks allowed for compositional characterization.

The detection and identification of materials from a distance is highly desirable for applications where accessibility is limited or there are safety concerns. Raman spectroscopy can be performed remotely and provides a very high level of confidence in detection of chemicals through vibrational modes. However, the remote Raman detection of chemicals is challenging because of the very weak nature of Raman signals. Using a remote Raman system, we performed fast remote detection of various solid and liquid chemicals from 1752 m during afternoon hours on a sunny day in Hawaii. Remote Raman systems with kilometer target range could be useful for chemical detection of volcanic gases, methane clathrate icebergs or fire ice, toxic gas clouds and toxic waste, explosives, and hazardous chemicals. With this successful test, we demonstrate the feasibility of developing future mid-size remote Raman systems suitable for long range chemical detection using helicopters and light airplanes.

Remote measurements of sulfur dioxide (SO2) path-concentration and emission rate (mass flux), released by passive volcanic degassing, are a key diagnostic of volcanic behavior. SO2 gas concentrations are also important for public health. Despite the significance of measuring SO2 mass flux at active volcanoes, an accurate method is still very difficult to obtain due largely to uncertainties of plume transport velocities and radiative transfer calculations. Here, we present a new infrared imaging method for deriving SO2 flux at active volcanoes with less than 20% plume transport velocity and radiative transfer uncertainties. The thermal hyperspectral imager (THI) was used for this study. THI is an uncooled remote sensing long-wave thermal infrared (TIR) imaging hyperspectral sensor that can obtain ~ 50 wavelength samples between 8 and 14 μm. Measurements of SO2 at the summit of Kīlauea volcano, collected using THI, are presented, where we obtained (for the periods of July 24–26, 2017, and February 5–6, 2018) a SO2 flux raging between 0 and 20 kg/s with occasional peaks higher than 40 kg/s. The spatial distribution of SO2 path-concentrations was obtained from the THI images by processing them using a newly developed SO2 retrieval algorithm, the SO2 amenable lookup table algorithm (SO2-ALTA). The sampling rate (30 Hz) of the microbolometer camera within THI means raw frames can be used for wind velocity derivation. Volcanic plume motion can be thus inferred by tracking plume features in sequential frames using spatial correlation techniques and knowing the camera angular orientation. Volcanic SO2 flux was estimated from the spatial distribution of SO2 and wind velocity. We evaluated temporal trends of the SO2 flux during the day and the night at the summit of Kīlauea volcano under both clear sky weather with northeasterly trade winds and cloudy sky conditions with low variable wind. These tests showed that the camera and techniques described in this paper provide an effective tool for monitoring SO2 fluxes remotely with less than 20% plume transport velocity and radiative transfer uncertainties and under a variety of background conditions (clear and cloudy sky, cold and hot backgrounds).

We determined Raman cross-sections of various organic liquids and inorganic polyatomic ions in aqueous solutions with a 532 nm pulsed laser using remote Raman systems developed at the University of Hawaii. Using a calibrated integrating sphere as a light source, we converted the intensity counts in the spectrum of the light from the integrating sphere measured with UH remote Raman instrument to spectral radiance. From these data, a response function of the remote Raman instrument was obtained. With the intensity-calibrated instrument, we collected remote Raman data from a standard 1 mm path length fused silica spectrophotometer cell filled with cyclohexane. The measured value of the differential Raman cross-section for the 801 cm−1 vibrational mode of cyclohexane is 4.55 × 10−30 cm2 sr−1 molecule−1 when excited by a 532 nm laser, in good agreement with the values reported in the literature. Using the measured cyclohexane Raman cross-section as a reference and relative Raman mode intensities of the various ions and organic liquids, we calculated the Raman cross-sections of the strongest Raman lines of nitrate, sulfate, carbonate, phosphate ions, and organic liquids by maintaining same experimental conditions for remote Raman detection. These relative Raman cross-section values will be useful for estimating detection capabilities of remote Raman systems for planetary exploration.

Quantifying sulfur dioxide (SO2) in volcanic plumes is important for eruption predictions and public health. Ground-based remote sensing of spectral radiance of plumes contains information on the path-concentration of SO2. However, reliable inversion algorithms are needed to convert plume spectral radiance measurements into SO2 path-concentrations. Various techniques have been used for this purpose. Recent approaches have employed thermal infrared (TIR) imaging between 8 μm and 14 μm to provide two-dimensional mapping of plume SO2 path-concentration, using what might be described as “dual-view” techniques. In this case, the radiance (or its surrogate brightness temperature) is computed for portions of the image that correspond to the plume and compared with spectral radiance obtained for adjacent regions of the image that do not (i.e., “clear sky”). In this way, the contribution that the plume makes to the measured radiance can be isolated from the background atmospheric contribution, this residual signal being converted to an estimate of gas path-concentration via radiative transfer modeling. These dual-view approaches suffer from several issues, mainly the assumption of clear sky background conditions. At this time, the various inversion algorithms remain poorly validated. This paper makes two contributions. Firstly, it validates the aforementioned dual-view approaches, using hyperspectral TIR imaging data. Secondly, it introduces a new method to derive SO2 path-concentrations, which allows for single point SO2 path-concentration retrievals, suitable for hyperspectral imaging with clear or cloudy background conditions. The SO2 amenable lookup table algorithm (SO2–ALTA) uses the MODTRAN5 radiative transfer model to compute radiance for a variety (millions) of plume and atmospheric conditions. Rather than searching this lookup table to find the best fit for each measured spectrum, the lookup table was used to train a partial least square regression (PLSR) model. The coefficients of this model are used to invert measured radiance spectra to path-concentration on a pixel-by-pixel basis. In order to validate the algorithms, TIR hyperspectral measurements were carried out by measuring sky radiance when looking through gas cells filled with known amounts of SO2. SO2–ALTA was also tested on retrieving SO2 path-concentrations from the Kīlauea volcano, Hawai’i. For cloud-free conditions, all three techniques worked well. In cases where background clouds were present, then only SO2–ALTA was found to provide good results, but only under low atmospheric water vapor column amounts.

A S canning St andoff R aman S pectroscopy (SSTRS) system has been developed to map out the spatial distributions of selected minerals at long distances (10–100 m). The SSTRS is based on a standoff Raman system, which is mounted inside a custom pan and tilt scanner. Computer software is used to control the direction of the pan-tilt scanner and to point the laser beam onto the distant samples. Measurements are made in an x-y grid pattern on a target area defined by the user. The Raman spectra collected at each grid point are processed to identify the distribution of minerals present from their respective Raman fingerprints. In the initial experiment, the Raman spectra of barite (BaSO 4 ), gypsum (CaSO 4 ·2H 2 O), plagioclase feldspar (solid solution of NaAlSi 3 O 8 -CaAl 2 Si 2 O 8 ), α -quartz ( α -SiO 2 ) rocks, and silica glass were measured at 30 m distance. The Raman spectra at the grid points are measured and processed to obtain a Raman mineral image of the distant minerals by selecting respective Raman fingerprints of α -quartz, gypsum and plagioclase feldspar. The ability to provide interpolated Raman images of distant mineral species is illustrated. The new SSTRS system works well and now offers the ability to obtain spatial distribution maps of distant mineral species from their Raman fingerprints.

The ability to image and quantify SO2 path-concentrations in volcanic plumes, either by day or by night, is beneficial to volcanologists. Gas emission rates are affected by the chemical equilibria in rising magmas and a better understanding of this relationship would be useful for short-term eruption prediction. A newly developed remote sensing long-wave thermal InfraRed (IR) imaging hyperspectral sensor – the Thermal Hyperspectral Imager (THI) – was built and tested. The system employs a Sagnac interferometer and an uncooled microbolometer in rapid scanning configuration to collect hyperspectral images of volcanic plumes. Each pixel in the resulting image yields a spectrum with 50 samples between 8 and 14 μm. Images are spectrally and radiometrically calibrated using an IR source with a narrow band filter and two blackbodies. In this paper, the sensitivity of the instrument for the purpose of quantifying SO2 using well constrained laboratory experiments is evaluated, and initial field results from Kīlauea volcano, Hawai’i, are presented. The sensitivity of THI was determined using gas cells filled with known concentrations of SO2 and using NIST-traceable blackbodies to simulate a range of realistic background conditions. Measurements made by THI were then benchmarked against a high spectral resolution off-the-shelf Michelson FTIR instrument. Theoretical thermal IR spectral radiances were computed with MODTRAN5 for the same optical conditions, to evaluate how well the (known) concentration of SO2 in the gas cells could be retrieved from the resulting THI spectra. Finally, THI was recently field-tested at Kīlauea to evaluate its ability to image the concentration of SO2 in a real volcanic plume. A path-concentration of 7150 ppm m was retrieved from measurements made near the Halema’uma’u vent.

A Monte Carlo radiative transfer program (Atmosphere–Ocean 3-Dimensional, AO3D) for modeling the coupled atmosphere–ocean environment has been developed. The code allows for the specification of optical properties for the atmosphere, land and ocean. Light rays are tracked as they pass between the atmosphere and the ocean, reflect off the ocean surface, the ocean floor, and off land, or are absorbed. In this version the polarization of light rays is not considered. The optical properties of each horizontally homogeneous layer within the atmosphere and ocean can be set on a layer-by-layer basis with a choice of phase functions, absorption and scattering coefficients, and index of refraction. A wind-dependent Cox and Munk ocean surface realization (with whitecaps) is implemented to model refraction and reflection from surface waves. Either spherical- or flat-Earth models can be used, and all refraction and reflection are accounted for. The AO3D model has been tested by parts, and as a whole by comparison with single- and total-scattering calculations from other radiative transfer codes. Comparisons with Monte Carlo calculations by Adams and Kattawar (agreement in TOA radiance within the published precision ∼2%), MODTRAN4 (agreement in spherical-shell atmosphere (SSA) sky radiance within about 2%) and Coupled DIScrete Ordinate Radiative Transfer (COART) (agreement in plane-parallel (PP) sky radiance within 2%) are shown. Sun photometer measurements (including large air mass values) at the Mauna Loa Observatory are compared to AO3D simulations (for a spherical Earth) and suggest that a thin aerosol layer was present above the observatory at the time of the measurements.

Handheld sun photometers are typically used to make aerosol optical depth measurements while on the ground. Various investigators, in unrelated efforts, have used handheld sun photometers to make aerosol optical depth measurements from light aircraft, but the strengths and weakness of this approach have not been characterized until now. While the ease and relatively low cost of an aircraft manual sun photometer are attractive, determining if the sun photometer was correctly pointed at the sun for each measurement is the biggest challenge. This problem can be partially addressed by collecting a large number of measurements at each altitude, then manually removing the largest optical depths (misalignment always results in erroneous larger values). Examples of past aircraft manual sun photometer measurements are demonstrating that it is possible to obtain quantitative measurements if sufficient sun photometer measurements are made at each elevation. In order to improve on manual sun photometer measurements, a small webcam was attached to the side of a Microtops sun photometer, and the Microtops sun photometer was triggered by computer control. By detecting the position of the sun in the webcam image, it is possible to determine whether the sun photometer was pointed at the sun correctly when the aerosol optical depth measurement was made. Unfortunately, it was found that the Microtops sun photometer takes ∼1.1 s to scan over the five wavelength channels. This 1.1-s delay proved to be too long, preventing the proposed approach from working as the aircraft was bouncing around.

On 26 June 2003 (approximately 1030 local time) the Helios ultralight aircraft broke apart off the west coast of Kauai Island, Hawaii as it was climbing out of the Kauai wind shadow. Following the aircraft mishap, a study was carried out to understand the conditions on the day of the crash and to better characterize the wind in the lee of Kauai. As part of this effort, both aircraft measurements and numerical modelling studies were carried out. Measurements and models showed the trade wind flow was enhanced around the island creating a region of wind shear surrounding the leeside calm zone. This wind shear region was found to be vertically oriented along the south side but tilted northward with height along the northern side of the calm zone. Several other factors on the day of the crash were investigated including water vapour gradients, diurnal Island heating, and gravity waves but their possible influences on the crash could not be confirmed. While the numerical model captured the general features of the Kauai leeside winds, the orientation of the calm zone was north of the observed one.

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.

Emissions from the Kilauea volcano pose significant environmental and health risks to the Hawaiian community. This paper describes progress toward simulating the concentration and dispersion of plumes of volcanic aerosol after they emanate from the Pu'u O'o vent of the Kilauea volcano. In order to produce an accurate regional forecast of the concentration and dispersion of volcanic aerosol, the Hybrid Single-Particle Lagrangian Integrated Trajectory (HY-SPLIT) model was used. Wind fields and thermodynamic data from the non-hydrostatic Mesoscale Spectral Model (MSM) were employed as input for the HY-SPLIT model. A combination of satellite remote sensing, aircraft, and ground-based observations collected during a field experiment was used to validate the model simulation of aerosol distribution. The HY-SPLIT model shows skill in reproducing the plume shape, orientation, and concentration gradients as deduced from satellite images of aerosol optical depth. Comparison of the modelled and observed values suggests that the model was able to produce reasonable plume concentrations and spatial gradients downwind of the source. Model concentrations were generally less than those observed on the leeward side of the Island of Hawaii. This deficiency may be explained by a lack of (i) background concentrations, (ii) local sources of pollution and/or (iii) sea-breeze circulation in the prognostic input wind field. These results represent early progress toward the goal of future operational application of the HY-SPLIT model to predict volcanic aerosol concentrations in Hawaii. This may help mitigate their negative impacts of plumes respiratory health, agriculture, and general aviation.

The characteristics of a small, lightweight portable lidar system for measuring aerosol (Mie) scatter at wavelengths of 1064 and 532 nm are described. It uses a 20-Hz Nd:YAG pulsed laser as a source and a 12.7-cm-diameter telescope as a receiver. By using a minimal number of commercially available components, the cost of construction has been reduced. The lidar has a useable range of 60–3000 m for clean marine conditions. Its performance has been demonstrated using measurements of tropospheric aerosols on the island of Hawaii.

A high-speed logarithmic amplifier that has been successfully used to improve the dynamic range of a scanning lidar is described. The amplifier incorporates built-in baseline correction and calibration circuits, allowing for real-time offset and temperature corrections. Using a commercial 12-bit analog-to-digital converter, the equivalent linear input signal can be recovered to an accuracy of ′0.5%, while maintaining a dynamic range of more than four decades.

Precipitable water vapour (PWV) was estimated over Lihue, Kauai, from AVHRR data using split-window techniques. The predicted values using the satellite sensor data were compared to precipitable water vapour amounts obtained from radiosondes and corrected GPS measurements. Compared to the corrected GPS precipitable water, the Dalu and RV satellite methods had rms errors of 7.3 and 3.8 mm, respectively. Typical values of PWV over Hawaii are approximately 27.5 mm, suggesting errors of about 14% in values estimated using the satellite split window technique near Hawaii.

A scanning standoff Raman spectroscopy system has been developed to measure the molecular species of distant samples in two dimensions. Computer software is used to control the scanner pan and tilt angles, and Raman measurementsare collected ofthedistantsampleareainanx–ygridpattern.TheRamanspectraateachgridpointaremeasuredandprocessedtoobtainan image of the distant surface composition. The ability to provide interpolated images of distant molecular species is illustrated. Copyright c � 2011 John Wiley & Sons, Ltd.

The use of hand-held Microtops II sun photometers (built by Solar Light Inc.) on ship platforms is discussed. Their calibration, filter stability, and temperature effects are also described. It is found that under rough conditions, the ship motion causes the largest error, which can result in a bias toward higher optical depths. In order to minimize this bias, a large number of sun photometer measurements (∼25) should be taken in a short period of time, and the higher values should be discarded. Under rough ocean conditions, it is also best to shorten the Microtops sun photometer sampling period (less than 5 s) and save only a single value (no averaging) and remove the high optical depths in postprocessing. It is found that the Microtops should be turned off frequently to correct for zero drift caused by temperature effects. Calibration is maintained by routine Langley plot calibrations at the Mauna Loa Observatory for each unit or through cross calibration.

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.

Meteorological conditions in the Atlantic Stratocumulus Transition Experiment (ASTEX) region favored advection of clean air from the central Atlantic during the early part of the experiment that was replaced by polluted air of European origin during the latter part of the experiment. Marked differences in the aerosol size distribution, composition, and state of mixing existed in these air masses. Pronounced differences in their vertical structure also demonstrated that surface measurements often do not represent average boundary layer or column concentrations. Clean subsiding air from the free troposphere had concentrations of condensation nuclei that significantly exceeded concentrations in the boundary layer and had very low mass concentrations and volatility consistent with homogeneous nucleation aloft, supporting the hypothesis that these nuclei can provide a source for “new” nuclei into the marine surface layer. This finding was in contrast to polluted air characterized by high concentrations of aged aerosol but having no evidence for significant recent nuclei formation. Particles in polluted air consisted of more than 90% volatile mass (mostly sulfate) and a refractory residual remaining at 300°C. The refractory mass varied with the concurrently measured light absorption coefficient, associated with combustion-derived soot. In spite of 2 orders of magnitude more volatile sulfate in polluted air, most of the particle number in polluted air remained after volatilization at 300°C, in contrast to less than 10% in clean air. This finding suggests that the number of particles in polluted air may reflect the combustion process producing the primary soot aerosol more than the SO2 emissions responsible for much of the sulfate aerosol mass. The accumulation mode mass mean diameter was found to increase with total accumulation mode mass, suggesting that a size parameterization based upon the more commonly measured sulfate mass could be included in current aerosol models.

We present an aerosol size distribution model summarizing measurements of sulfate, sea salt, and dust aerosol obtained in the marine boundary layer and marine free troposphere. Stratospheric aerosol cases are not included here. Aerosols were sampled in both both clean background conditions and aged anthropogenic aerosol (>3 days) which had advected over the ocean. Model size distributions are developed for the sulfate accumulation mode, sea-salt coarse mode, and dust coarse mode. The data demonstrate that both the accumulation and coarse mode aerosol gradually shift to larger diameters as the aerosol mass increases. Based on this relationship, it is possible to estimate the size distribution based on aerosol mass. Comparisons with other aerosol models show significant differences, which suggest further measuring and modeling efforts are needed.

Two Lagrangian experiments were carried out during the Atlantic Stratocumulus Transition Experiment (ASTEX) with the intent of looking at aerosol evolution in the marine boundary layer (MBL). The second Lagrangian (L2) took place below broken stratus clouds and was more successful since little precipitation reached the surface. Aerosol below the inversion was primarily an aged pollution aerosol from central Europe. Vertical variability in aerosol concentrations was generally characterized by highest concentrations in the moist surface and transition layers. Concentrations were a factor of 2 or more lower in the dry subcloud layer and cloud layer and dropped to less than one tenth of surface values in the free troposphere above cloud. This behavior reflected the decoupled boundary layer below the main inversion and complicated the assessment of Lagrangian aerosol evolution. No evidence for new particle formation was observed during L2, and aerosol evolution proceeded only by mixing, coagulation, and removal mechanisms. An entrainment rate of about 0.6 cm s -1 from the free troposphere into the MBL was a key parameter affecting aerosol evolution and resulted in about a 35% column dilution during the 34-hour L2 measurement period. Aerosol evolution in the decoupled subcloud and surface marine layer is consistent with an entrainment rate of about 0.45 cm s -1 into the surface layer and about 0.25 cm s -1 out of the layer. The ability to resolve the effects of separate processes influencing both gas and aerosol during Lagrangian evolution will depend upon (1) an adequate assessment of the variability in the air mass, (2) the ability to characterize this variability relative to the uncertainties in resampling the air mass, and (3) the extent to which the substantial changes due to entrainment alone can be reliably determined.

The capability to analyze and detect the composition of distant samples (minerals, organics, and chemicals) in real time is of interest for various fields including detecting explosives, geological surveying, and pollution mapping. For the past 10 years, the University of Hawaii has been developing standoff Raman systems suitable for measuring Raman spectra of various chemicals in daytime or nighttime. In this article we present standoff Raman spectra of various minerals and chemicals obtained from a distance of 120 m using single laser pulse excitation during daytime. The standoff Raman system utilizes an 8-inch Meade telescope as collection optics and a frequency-doubled 532 nm Nd: YAG laser with pulse energy of 100 mJ/pulse and pulse width of 10 ns. A gated intensified charge-coupled device (ICCD) detector is used to measure time-resolved Raman spectra in daytime with detection time of 100 ns. A gate delay of 800 ns (equivalent to target placed at 120 m distance) was used to minimize interference from the atmospheric gases along the laser beam path and near-field scattering. Reproducible, good quality single-shot Raman spectra of various inorganic and organic chemicals and minerals such as ammonium nitrate, potassium perchlorate, sulfur, gypsum, calcite, benzene, nitrobenzene, etc., were obtained through sealed glass vials during daytime. The data indicate that various chemicals could easily be identified from their Raman fingerprint spectra from a far standoff distance in real time using single-shot laser excitation.

The University of Hawaii has been developing portable remote Raman systems capable of detecting chemicals in daylight from a safe standoff distance. We present data on standoff detection of chemicals used in the synthesis of homemade explosives (HME) using a portable standoff Raman system utilizing an 8-inch telescope. Data show that good-quality Raman spectra of various hazardous chemicals such as ammonium nitrate, potassium nitrate, potassium perchlorate, sulfur, nitrobenzene, benzene, acetone, various organic and inorganic chemicals etc. could be easily obtained from remote distances, tested up to 120 meters, with a single-pulse laser excitation and with detection time less than 1 μs. The system uses a frequency-doubled Nd:YAG pulsed laser source (532 nm, 100 mJ/pulse, 15 Hz, pulse width 10 ns) capable of firing a single or double pulse. The double-pulse configuration also allows the system to perform standoff LIBS (Laser-Induced Breakdown Spectroscopy) at 50 m range. In the standoff Raman detection, the doublepulse sequence simply doubles the signal to noise ratio. Significant improvement in the quality of Raman spectra is observed when the standoff detection is made with 1s integration time. The system uses a 50-micron slit and has spectral resolution of 8 cm-1. The HME chemicals could be easily detected through clear and brown glass bottles, PP and HDPE plastic bottles, and also through fluorescent plastic water bottles. Standoff Raman detection of HME chemical from a 10 m distance through non-visible concealed bottles in plastic bubble wrap packaging is demonstrated with 1 s integration time. Possible applications of the standoff Raman system for homeland security and environmental monitoring are discussed.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

[1] In August through September 2004 the United Arab Emirates Unified Aerosol Experiment (UAE2) was conducted in the southern Arabian Gulf region. We present atmospheric thermodynamic and aerosol data collected on 18 flights by the South African Aerocommander aircraft. In the first few kilometers, we observed high concentrations of both regional dust (from 100 to 300 μg m−3 in background, to over 1.5 mg m−3 in events) and ubiquitous sulfate based pollution from the Gulf's prevalent petroleum industry (10–100 μg m−3). Smoke and pollution from Europe and possibly Africa were found at levels between 1.5 and 5 km. Inland, classic deep over desert boundary layer characteristics were found. Over the Arabian Gulf, dust and pollution were most often either trapped below or sequestered above a strong stable boundary. However, there were cases where a well-distributed aerosol layer crossed the inversion uniformly. Data suggest that the observed vertical profiles can be explained by the rapid formation of stable marine boundary layers as air moves offshore. This can decouple aerosol layers from within the boundary layer to those aloft in regions of vertical wind shear. In the case of pollution, the ability of flaring plumes to penetrate the inversion may also in part determine layering. In coastal regions without vertical wind shear, uniform concentrations with height across the inversion are a result of internal boundary layer development. We conclude that the bulk of the observed variability in particle vertical distribution appear to be controlled by mesoscale and microscale processes, such as the sea/land breeze.

We have used two-dimensional correlation on two-dimensional extinction cross-sections measured by a scanning lidar to determine the velocity structure of the salt-spray aerosols. The lidar scans were collected over a reef at Bellows Beach, on the Northeast side of Oahu, Hawaii. The resulting velocity streamlines suggest that lifting of sea-spray aerosols as high as 200 m occurs in the vicinity of opposing horizontal roll vortices. The velocities vary rapidly over distances of less than 500 m and show a complex pattern which is inadequately represented by conventional anemometer measurements.

A small portable lidar system was recently used to derive aerosol optical concentrations from ground and aircraft platforms. The mini lidar uses a telescope setup with a relatively wide field of view allowing for measurements from close in (~60 m range) with no near field correction. In order to account for the large dynamic range, a custom logarithmic amplifier is used. Lidar measurements have been made in Hawaii and examples will be shown. More recently the Lidar was mounted on an aircraft for an experiment in the United Arab Emirates. In this case, the Lidar system was used to looking up, forward and down. The Lidar measurements looking up and down provided vertical profiles of aerosol concentrations. The lidar looking forward were used to derive quantitative aerosol extinction values using an existing and a new approach. Preliminary examples of this UAE data are shown. Being able to model aerosol phase functions is important for both satellite and Lidar aerosol retrievals. Mie theory is adequate for spherical particles but complex aerosols such as dust and organics are more difficult to model. Here we discuss phase function measurements we have made with our ground based polar nephelometer for sea salt and more recently for dust in the United Arab Emirates.

The University of Hawaii routinely collects direct broadcast MODIS images over Hawaii. Using this data set we process real time satellite images of aerosol optical depths around Hawaii using our custom algorithm. MODIS channels 1 and 2 (~ 645 and ~ 858 nm) are used to derive aerosol optical depth spatial and temporal properties. The use of MODIS channels 1 and 2 provides images with 250 m resolution resulting in improved cloud detection. Due to this improvement, background aerosol optical depths values remain low even in regions of many small clouds. Although cloud rejection is not expected to be perfect, using 250 m resolution data provides a significant improvement over 1 km resolution data. In order to correct for surface reflection, meso-scale wind fields from the Regional Spectral Model (from the National Center for Environmental Prediction) and synoptic scale winds (from National Center for Environmental Prediction) are interpolated to the satellite pixel size. The use of meso-scale wind fields is required for the complex wind fields in and around the Hawaiian Islands. Here we will discuss the aerosols encountered in Hawaii, and provide examples of interesting aerosol optical depth images around Hawaii.

There is a need for portable, low-cost lidar systems that can be used for cloud, aerosols and chemical monitoring from a stand-off distance. At the University of Hawaii we have developed lidar systems based on a 12.7-cm diameter telescope and a 20 Hz frequency-doubled Nd:YAG laser source. For stand off Raman detection of organic liquid and vapors, and plastic explosives, we are using a 0.25-m HoloSpec f/2.2 spectrometer equipped with a gated intensified detector (PI Model I-MAX-1024-E). The samples of interest are excited with 532-nm laser light (35 mJ/pulse). The operational range of the Raman system is in 10's of meters and has been tested at distance of 66 m. This system can also be operated as a Raman lidar by using appropriate filters for atmospheric nitrogen, oxygen and other gaseous species of interest. The Mie-Rayleigh lidar system uses the same telescope and laser, but we have three (1064, 532 and 355-nm) wavelengths available for monitoring clouds and aerosols. A small Hamamatsu H6779 photomultiplier tube (PMT) located near the focal point of telescope detects 532-nm backscatter signal. An avalanche photodiode (APD, EG & G C3095) detector equipped with a 2.5-cm diameter aspheric lens is used for detecting 1064-nm backscatter. The Mie-Rayleigh lidar has usable range of 60 - 4000 m. Results obtained with this system for marine aerosols and clouds are discussed.

Our long-term goal is to improve our understanding of dynamics of marine aerosols and water vapor fields in the coastal marine boundary layer using a scanning lidar and meteorological parameters. Our scientific objectives are to collect lidar data sets that can be used to improve and develop models of the aerosol optical properties in the coastal marine boundary layer (MBL). Various aerosol models exist (e.g., Fitzgerald, 1989; Edson et al., 1999), but few are appropriate for coastal regions. We are studying the vertical aerosol structure in the lowest part of the atmosphere directly above the ocean surface.

We present the results of our multi-wavelength scanning lidar investigations of time dependent 3-D marine aerosol fields as a function of meteorological parameters at a coastal site in Hawaii. We describe our measurements of salt-aerosol plumes generated at a reef >1.3 km from the lidar and their effect on the aerosol extinction coefficient. At typical trade wind speeds of ~7 m/s, plumes of salt spray have been observed to rise to heights of about 50 m above the reef. A time sequence of vertical scans at three wavelengths (355, 532, 1064 nm) was taken under light (1.9 m/s) wind conditions over the same reef. Large salt plumes more than 600 m high were found to develop under these conditions. The much greater height of light-wind plumes suggests that they are being dispersed less rapidly, allowing them to rise to greater heights because of the presence of thermals. Earlier data collected at Bellows showed reef plumes rising to 120 m in winds of 5 m/s, indicating a consistent trend of increasing plume height with decreasing wind speed.

Atmospheric aerosols scatter and absorb solar and terrestrial radiation. These aerosol optical properties affect the solar radiation budget and the ability to see through the atmosphere. In order to model these effects the aerosol phase function, single scatter albedo and optical depth are needed at a range of wavelengths. Satellites are the logical choice to measure these aerosol optical properties but algorithms are often poorly constrained and careful validation efforts are needed.

The Hawaii Kilauea volcano has been active for over 10 years. The trajectory and concentration of the acidic aerosol is currently poorly monitored. The authors report on a new effort to alert the public of the vog concentrations using satellite and model products. Satellite aerosol products are derived from the AVHRR and GOES satellite sensors in near real time. The satellite derived aerosol concentrations will be combined with results from a meso-scale dispersion model to better predict the height and extent of the vog plume.

Due to the complexity of atmospheric aerosol, validation efforts are required to test satellite retrievals. Here we give an overview of our aircraft and ship validation measurements near Hawaii. Some examples of the measurements are shown which illustrate some of the variability we have encountered. This effort is ongoing and can provide important background measurements for satellite validation as well as radiation studies.

On the windward side of Oahu, a multi-wavelength Mie-Rayleigh (MR) scanning lidar is used on a regular basis for measuring aerosol attenuation in the marine boundaiy layer. The lidar data are being used for investigathg dynamic effects of marine aerosol fields on electro-optical (EO) properties. The lidar has been operated mostly at 532 and 1064 nm, and recently at 355 nm. We have observed that the vertical aerosol distribution can be very non-uniform. Under certain atmospheric conditions, ascending and descending streaks of aerosols with high extinction (2x 1O-4 per meter) have been observed, indicating that both the surface and cloud drizzle effects are important. Horizontal lidar scans at 6 meters above the sea surface indicate that aerosol is fairly uniform on a large scale but can exhibit significant variability on small scales particularly close to protruding reefs and shorelines. Above the reefthe enhanced aerosol fields have been observed to rise as high as 100 meters. As expected there is a strong correlation between wind speed and sea salt extinction values. The temporal and spatial distribution ofthese aerosol fields and their dependence meteorological parameters and wave height are discussed.

Lidars are ideal for mapping the spatial distribution ofaerosol concentrations, however efforts to convertthe lidar measurements into estimates of the aerosol extinction or scattering coefficient are usually complicated. The difficulties arise from the uncertainty in the aerosol backscatter-to-extinction ratio and the lidar calibration. In marine conditions with little absorption, the aerosol backscatter-to-extinction ratio is identical to the aerosol phase function/4? at 1 80 degrees (backscatter) . Uncertainty in the lidar calibration is another source ofuncertainty, which can change with time depending on the state ofthe optics (clean or dirty). Here we investigate several techniques to obtain calibrated aerosol extinction coefficient values. The first approach uses horizontal lidar measurements over the open ocean where the atmosphere is horizontally homogeneous. The lidar calibration or aerosol phase function is adjusted until the derived aerosol extinction coefficients are flat with distance. Modeling shows that this provides correct aerosol extinction values. A second approach uses a target to reflect the lidar beam at different distances. The aerosol extinction is derived from the differential transmission measurements. As an independent measurement, the aerosol phase function and scattering coefficients can be measured with a polar nephelometer.

Our long-term goal is to improve our understanding of dynamics of marine aerosols and water vapor fields in the coastal marine boundary layer using a scanning lidar and meteorological parameters.

Upwelling radiance measurements were made on the Cirpas aircraft during the TARFOX experiment. Measurements were made from .375 to 1050nm wavelengths.

A ship radiometer is currently being constructed which will make sun, sky and ocean surface multi-wavelength radiance measurements. The measurements will be used to derive aerosol and ocean surface optical properties. This paper describes the basic design of this radiometer.

A knowledge of aerosol optical properties and concentrations is required for modeling their impact on radiative transfer. These aerosol properties are often derived from passive radiation measurements at several wavelengths. In doing this, one encounters the problem that the multi-wavelength information is not sufficient to address the various unknown aerosol properties including concentration, aerosol size distribution, phase function, single scatter albedo and index of refraction. In order to address this problem, a new aerosol model was developed from in-situ aerosol measurements which were carried out in the Pacific, Atlantic and Indian Ocean. After sorting each aerosol distribution by their dry mass they were combined and a double lognormal curve was used to fit the resulting distributions. A example of the model sulfate accumulation mode and sea salt coarse mode is shown in figures 1 and 2.

The ability to derive aerosol properties from satellites is important for climate change studies and atmospheric corrections in studying surface properties. Although aerosols have been measured over land from satellite, it is more feasible to measure them over low surface albedos such as the ocean. One of the uncertainties that must be dealt with is the aerosol phase function, which depends on the aerosol size distribution and the observing wavelength.

[1] Aerosol optical depths and lidar measurements were obtained under the plume of Hawaii Kilauea Volcano on August 17, 2001, ∼9 km downwind from the erupting Pu'u O'o vent. Measured aerosol optical depths (at 500 nm) were between 0.2–0.4. Aerosol size distributions inverted from the spectral sun photometer measurements suggest the volcanic aerosol is present in the accumulation mode (0.1–0.5 micron diameter), which is consistent with past in situ optical counter measurements. The aerosol dry mass flux rate was calculated to be 53 Mg d−1. The estimated SO2 emission rate during the aerosol measurements was ∼1450 Mg d−1. Assuming the sulfur emissions at Pu'u O'o vent are mainly SO2 (not aerosol), this corresponds to a SO2 half-life of 6.0 hours in the atmosphere.

In recent years aerosol optical depths have been estimated from AVHRR satellite images on a regular basis. One of the primary uncertainties of these methods is in the choice of the aerosol phase function. In this paper the possibility of using the ratio of AVHRR channel 1 and channel 2 to infer the value of the aerosol phase function is studied. For this purpose a large number of marine aerosol measurements are employed to study the response of NOAA AVHRR satellites for various aerosol cases.

Upper-level wind fields are obtained by tracking the motion of cloud features as seen in calibrated ground-based stereo cameras. By tracking many cloud features, it is possible to obtain horizontal wind speed and direction over a cone area throughout the troposphere. Preliminary measurements were made at the Mauna Loa Observatory, and resulting wind measurements are compared with winds from the Hilo, Hawaii radiosondes.

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.

In February and March 1990, measurements of aerosol physicochemistry were made during five transects across the equator between 15{degrees}N and 10{degrees}S. Marked equatorial gradients in both the aerosol NH{sub 4}{sup +}/SO{sub 4}{sup 2{minus}} ratio and the strong surface water chlorophyll were associated with boundaries separating oligotrophic waters and regions of equatorial upwelling. Highest aerosol ammonium concentrations appeared to be unrelated to continental signatures but corresponded to regions of highest chlorophyll concentrations. Favorable aerosol chemistry, wind directions, and cruise tracks in conjunction with rapid aerosol sampling made it possible to estimate the flux of ammonia from in surface in these transition regions at about 10 {mu}mol m{sup {minus}2} d{sup {minus}1} with possibly greater values in regions where higher chlorophyll concentrations exceeded about 0.25 mg m{sup {minus}3}. Low NH{sub 4}{sup +}/SO{sub 4}{sup 2{minus}} values in aerosol over oligotrophic regions with chlorophyll concentrations below 0.1 mg m{sup {minus}3} suggest the flux in these regions was about an order of magnitude lower. Aerosol sulfate concentrations were also generally elevated over the upwelling region but showed a less pronounced relationship to chlorophyll abundance, suggesting independent source mechanisms for ammonium and sulfate. Rapid variability in mass and number concentrations were evident in convective regions. Both depletionmore » of larger aerosol (mass) through precipitation scavenging and an increase in the number of smaller aerosol in region of subsidence indicate the complex relationship among CN, CCN, and aerosol mass in the remote marine boundary layer. 37 refs., 11 figs., 1 tab.« less

The aerosol size distribution, composition, and CO2 backscatter at 10.6 microns (beta-CO2) were measured continuosly at the Mauna Loa Observatory (Hawaii) during January-March and November-December, 1988 periods to compare the characteristics of periods associated with appreciable Asian dust transport to that site (January-March) with those of periods characterized by low-dust condition. The aerosol size distribution in the range 0.15 micron to 7.6 microns was measured at temperatures of 40, 150, and 340 C to differentiate between volatile and nonvolatile aerosols. Large ranges of variability was found in measurements of aerosol size distribution during both periods, but the average distributions were similar for both the high-dust and the low-dust periods. However, values for beta-CO2 were more elevated (by about six times) during periods associated with active Asian dust transport to the observatory site than during the low-dust periods.