Local and regional pollution interact at the interface between the Planetary Boundary Layer and the Free Troposphere. The vertical distributions of ozone, aerosols, and winds must be measured with high temporal and vertical resolution to characterize this interchange and ultimately to accurately forecast ozone and aerosol pollution. To address this critical issue, the Regional Atmospheric Profiling Center for Discovery (RAPCD) was built and instrumented in the National Space Science and Technology Center on the UAH campus. The UV DIAL ozone lidar, Nd:YAG aerosol lidar, and 2-micron Doppler wind lidar, along with balloon-borne ECC ozonesondes, form the core of the RAPCD instrumentation for studying this problem. Instrumentation in the associated Mobile Integrated Profiling (MIPS) laboratory includes a 915Mhz profiler, sodar, and ceilometer. The collocated Applied Micro-particle Optics and Radiometry (AμOR) laboratory hosts the FTIR, MOUDI, and optical particle counter. Using MODELS-3 analysis by colleagues, and cooperative ventures with the co-located National Weather Service Forecasting Office in Huntsville, AL, we are developing a unique facility for advancing the state-of-the-science in pollution forecasting.

The drift time spectra of polycyclic aromatic hydrocarbons (PAH), alkylbenzenes and alkylphenylethers were recorded with a laser-based ion mobility (IM) spectrometer. The ion mobilities of all compounds were determined in helium as drift gas. This allows the calculation of the diffusion cross sections (Ω_calc) on the basis of the exact hard sphere scattering model (EHSSM) and their comparison with the experimentally determined diffusion cross sections (Ω_exp). These Ω_exp/Ω_calc-correlations are presented for molecules with a rigid structure like PAH and prove the reliability of the theoretical model and experimental method. The increase of the selectivity of IM spectrometry is demonstrated using resonance enhanced multiphoton ionisation (REMPI) at atmospheric pressure, realized by tuneable lasers. The REMPI spectra of nine alkylbenzenes and alkylphenylethers are investigated. On the basis of these spectra, the complete qualitative distinction of eight compounds in a mixture is shown. These experiments are extended to alkylbenzene isomer mixtures.

We report the realization of a mid-infrared tunable coherent radiation source based on difference-frequency generation with an output power that achieves, for the first time, a few mW. The signal and pump beams coming from two widely tunable, cw high power rare-earth-doped amplifiers are mixed into a periodically poled LiNbO₃ crystal to produce radiation in the 2.9-3.5 μm spectral interval. The low intensity noise and the good spatial profile of the idler beam are first verified. The suitability of this new spectrometer for high-sensitivity and high-resolution gas detection is then demonstrated by performing saturated absorption spectroscopy of methane. Finally, the future development of a portable, multicomponent gas sensor for environmental monitoring is discussed.

In this paper we present a general methodology for a frequency-modulated ladar/lidar (CW-FM-ladar/lidar) concept based on principles of both CW-FM-range-finding and modulation spectroscopy, together with modern techniques of optical signal transmission using tunable laser diodes, signal detection and heterodyne processing. We develop a mathematical description of trace gas detection using CW-LD ladar developing the relationship between the heterodyne echo-signal amplitudes and frequencies and trace gas concentration for each range. In particular, precise range and gas retrieval resolution limits based on the transmitting signal modulation and absorption line parameters are obtained.

A unique optical configuration of a Gas-Filter Correlation Radiometer (GFCR) is described. This configuration, known as a Simultaneous-View Correlation Radiometer (SVCR), was designed for surface-viewing nadir remote sensing of atmospheric trace gases in the near-infrared. It provides simultaneous measurement of both the gas-filter and correlation channels of the GFCR, minimising noise induced by geo-spatial variations in the surface reflectivity. We analyse the reduction in the sensitivity of the SVCR to noise in input radiance in comparison to a sequential gas-density state GFCR.

The response of a long-period grating coated with the sol-gel derived films on the cladding of the fiber grating region to surrounding medium (gases) was studied in this paper based on coupled-mode theory. A four-layered numerical model is also developed to determine the dependence of the central wavelengths of the attenuation bands on the thin film optical parameters ( thickness d₃ and refractive index n₃). By analyzing the relation between the sensitivity S_n and the thin film optical parameters and the fiber grating parameters (the grating period, the core index change and the grating length ), the optimal optical parameters of thin film layer of the sensor is obtained. Data simulation shows that the sensitivity of this scheme to refractive index of the films is predicted to be more than 10⁷. In the end a gas-sensitive long-period grating sensor is fabricated according to the theoretical optimization results. The preliminary gas-sensing experiment was performed, and a novel LPFG gas sensor special to C₂H₅OH and CH₄ was established.

The study of atmospheric aerosol is fundamental in order to get a best comprehension of the atmospheric system and to comprehend how they affect our environment at the local and global levels. Information about aerosol concentration and radiative properties in their ambient environment are indispensable and, in this respect, lidars represent the most powerful tool because their capability to provide information on atmospheric component and parameters with very high spatial and temporal resolutions. Two lidar systems are operational at Istituto di Metodologie per l’Analisi Ambientale of the National Council of Research (IMAA-CNR), Tito Scalo, Potenza, Italy; the first, used in the framework of EARLINET, is able to provide aerosol backscatter coefficient at two wavelengths (355 nm and 532 nm) and extinction coefficient in the UV in the troposphere, and the other, used in the framework of the validation program of ENVISAT, is devoted to measure both tropospheric and stratospheric aerosol in the UV and water vapor up to the tropopause. We present in this paper results obtained starting from three years of systematic aerosol lidar observations and more than one year of water vapor lidar measurements. Both local aerosol and dust transported from the Sahara regions have been characterized.

The use of multi-wavelength lidar measurements can in principle be used to estimate aerosol extinction and backscatter profiles. From the resultant multi-wavelength profiles, an estimate of particle size distribution parameters can be inferred. At present the standard approach is to assess error by adding noise with given covariance properties and inverting the ensemble of signals. Unfortunately, the inversion is often affected by algorithm convergance issues and poor a-priori guesses. On the other hand, graphical estimation of confidence bounds does not require inversion of the optical data and therefore is more robust and with pre-constructed databases isvery efficient. However, determination of appropriate confidence bounds can be quite difficult since correlated optical data ratios are used and simple Gaussian statistics no longer applies. In this paper, several confidence bound estimates are explored and compared to the results from direct inversion of the signal ensemble. Using the appropriate confidendence bounds, we then apply the graphical technique to multiwavelength elastic and raman lidar. In particular, the improvement of the retrieval from additional extinction data obtained from a Raman Lidar system in comparison with a prototypical three wavelength backscatter lidar is examined

This paper describes a project on automating the interpretation of cloud images recorded during several types of atmospheric observations: (1) dust clouds generated by controlled explosions, (2) chemical releases of infrared-active gases, and (3) lidar measurements of cloud altitude winds. This program began with a basic cloud tracking system for lidar comparisons, which has since been upgraded. We describe automated methods for tracking clouds of relatively constant shape, segmenting time-dependent clouds and plumes from scenic backgrounds, characterizing cloud and plume shapes, and measuring the speed and direction of cloud motion. Dust clouds were created by fireworks, releases of pressurized aerosols and by propane-driven blast tubes. Chemical clouds of organic vapors were created by evaporation or with pressurized balloon releases. Cloud imagery for particle releases was recorded primarily with a pair of visible video cameras. The chemical clouds were imaged with a high framing rate infrared camera in the 2.5 – 3.5 micron region. Current project goals include an end-to-end system for cloud warnings, wind measurement, and dispersion predictions in real time.

Satellite remote sensing data are another source of information to study air quality, supplementing the in situ monitoring networks. Satellite data have primarily been used to study specific events that affect air quality, such as wildfires, biomass burning, dust storms, and volcanoes. In this exploratory analysis we have used the monthly averaged aerosol optical depth (AOD) product of the MODIS sensor data from the Terra satellite platform to study fine particulate matter throughout the contiguous U.S. While most of the previous quantitative work has focused on hourly correlations between in situ monitors and satellite AOD data, we have attempted to quantify monthly, seasonal, and annual correlations. Our analysis of 2001 monthly data found that correlations do exist, but not throughout the entire study period or area. The best correlations were seen in the northeast and industrial Midwest during the summer months.

In the run-up to the 2008 Olympic Games in Beijing, Chinese government officials at both the central and municipal levels are keenly aware that they must transform Beijing into a world-class city. According to the Beijing Municipal Environmental Protection Bureau (BJEPB) to improve its air quality some actions are adopting, including taking steps to increase the forested area surrounding the city preventing dust storms, reducing the automotive vehicles, moving polluting factories now inside the fourth ring road ringing the inner city to locations outside of the fourth ring road, and switching the fuel of public buses and taxis from diesel to natural gas, etc. Will they eliminate most serious environmental problems in Beijing? MODIS aerosol products are helping us to answer this kind of questions. A long-term validation has been finished by sun-photometer observations, and the results proved the relative error of MODIS level 2 products was slightly larger than the estimation of Chu et al. (2002) from the results in most AERONET sites. However, the comparison between the products and moisture-corrected air pollution index (API) data, which were daily released to public by EPB, showed a high correlation coefficient. An air pollution episode in 2003 was investigated by the usage of satellite products. Our conclusion for the air pollution control strategy in Beijing is that only reducing the pollution sources from inner city can't fully solve the pollution problems in Beijing and the regional transports from the nearby southern provinces are contributing a lot to the pollution situation in Beijing.

Determination of aerosol optical depth from satellite remote sensing measurements is extremely complex due to the large variability of aerosol optical properties. Significant simplification occurs when measurements are taken over water since the ocean reflection signal can be taken as negligible in the NIR.. Unfortunately, over land, most of the signal can be attributed to ground reflectance. While conventional approaches look for “dark” pixels in an image to isolate aerosols, these pixels are subjected to increased noise. In this paper, we explore the feasibility of a regression approach utilizing correlations between the VNIR and MIR channels to extract the aerosol reflection signal over urban areas. This approach is applied to hyperspectral high resolution Hyperion data where the aerosol reflectance signal is shown to agree very well with coincident Aeronet derived reflectance spectra. Comparisons between the regression technique and dark pixel thresholding clearly exhibit the improvement using regression methods. Finally, practical spatial resolution concerns are explored and specifications of the GOES-R imager are assessed.

Remote sensing products of aerosol from MODIS have been released by NASA for a long time, and the Level 2 products showed to be very useful in monitoring regional aerosol pollution pattern and tracing pollutant transports. However, for a city, with an area of several hundreds square-kilometers and complicated terrain, the products with 10 km resolution are not enough especially in depicting the detail particulate matter (PM) distribution in the urban area. Recently, the aerosol optical depth (AOD) retrieval method proposed by NASA has been used to obtain the 1km resolution products in Hong Kong. Aerosol model was improved by sun-photometer observations and the calculation of a radiation transfer model, and finally looking up tables were created for real time aerosol products retrieval. The AOD products were validated by the sun-photometer observations at the HKUST. It was found the relative bias between the satellite products and the ground observations was within the range of about 20%, which was mostly equal to the estimation of NASA for their 10km level 2 products in most AERONET sites. The good results are mainly because of the most regions of Hong Kong are covered by dense dark vegetations (DDV) with very low surface reflectance in visual and near-infrared satellite channels. This high-resolution product was used in the study of air pollution in Hong Kong, and it was found the 1km products were more useful to describe the local urban PM pollutant distribution than the 10 km Level 2 products.

An integrated system approach has been adopted at the Advanced Environment Monitoring Research Center (ADEMRC), Kwangju Institute Science and Technology (KJIST), Korea for the effective monitoring of atmospheric environment utilizing various optical remote sensing methods. A multi-channel LIDAR system has been used since December 2002 to monitor the vertical profile of atmospheric aerosol. Vertical profiles of extinction coefficient, depolarization ratio, and color ratio of atmospheric aerosols are determined from the simultaneous detection of three elastic-backscatter signals and one Raman signal backscattered by atmospheric nitrogen molecules. Ground based sunphotometer measurement provides LIDAR validation and information on the column integrated aerosol optical depth at seven different wavelengths. Optical atmospheric environment monitoring over horizontal path is also made with a Long-path DOAS system and a transmissometer. The GIST long-path DOAS system has been used to measure concentration of trace gases as well as atmospheric extinction at 550 nm. Results of aerosol optical depth determination based on satellite data retrieval are compared with the results of LIDAR and sunphotometer measurements. This paper presents the results of integrated measurements of atmospheric aerosol at Gwangju (35°10`N, 126°53`E), Korea.