Monitoring of mixing layer height (MLH) was performed during different measurement campaigns in urban and suburban
area (Hannover, Munich, Budapest, Zürich, Augsburg) by the Vaisala ceilometer LD40. It is an eye-safe
commercial lidar and designed originally to detect cloud base heights and vertical visibility for aviation safety purposes.
Software for routine retrieval of mixing layer height from ceilometer data was developed and improved continuously.
MLH was determined during a one-week-campaign at the airport Mexico City. Air pollutants like NO, NOx, CO and O3
as well as meteorological parameters like wind, temperature and irradiance are measured at the airport in addition to the
air quality monitoring network RAMA in Mexico City. The influence of MLH together with wind, temperature and
cloudiness upon air pollution is investigated. These continuous MLH and meteorological data are correlated with
simultaneous measured air pollutants. The influence of mixing layer height upon air quality is shown.
The scanning infrared gas imaging system (SIGIS-HR) and the quantitative gas analysis software MAPS
(Multicomponent Air Pollution Software) are applied to investigate the spatial distribution of the temperature and gas
concentrations (CO, NO) within the plume of aircraft engines at airports. The system integrates an infrared camera also.
It is used for the localisation of the hot source that additionally suggests the best measurement position of the SIGIS-HR.
The application of emission FTIR spectrometry for the measurement of temperature and gas emission index of CO and
NO is presented for the exhaust of a small turbojet based on a helicopter turbine. In these measurements the emitted
infrared radiation from the exhaust gas stream was collected by the SIGIS-HR at different spectral resolution (56 cm-1
and 0.2 cm-1). The software MAPS includes the Instrumental Line Shape (ILS) of the OPAG- 22 FTIR spectrometer
obtained by active gas cell measurements and ILS modelling.
The rough concept of the system will be presented and operational applications will be discussed. The results of the
investigation of the temperature and gas concentrations (CO, NO) within the aircraft engine plumes will be shown. The
limitations and of the systems will be discussed.
The method of passive remote sensing by Fourier transform spectroscopy allows the retrieval of column densities or concentrations of molecules in gas plumes such as exhaust gas plumes of aircraft or vapor plumes emitted after chemical accidents. State- of-the-art retrieval algorithms require two models: a radiative transfer model and an instrument model, the instrument line shape (ILS). The instrument line shape of real Fourier transform spectrometers (FTS) differs significantly from the instrument line shape of an ideal FTS, in particular if the instrument is optimized for high signal-to-noise ratio, which is achieved by interferometer designs with high optical throughput (etendue). The real instrument line shape may be modeled by convolution of the instrument line shape of the ideal FTS with an inherent instrument line shape describing the deviations. In this work, the inherent instrument line shape is modeled by a function which is dependent on a small number of parameters. In order to determine these parameters automatically, a new method has been developed. Spectra of a well-known gas in a gas cell are measured. The measured spectrum is approximated using a least squares fit with a model that contains the parameters of the instrument line shape. The fitting procedure is performed automatically. The instrument line shape model, the experimental setup of the method for the determination of the instrument line shape, and results of measurements using the instrument line shape are presented. In addition to the analysis of spectra with the ILS determined by the new method, analysis results obtained with an ideal instrument line shape are presented to demonstrate the negative effect of an inaccurate instrument line shape on the retrieved column density.
The Scanning Infrared Gas Imaging System of High Resolution (SIGIS-HR) was used to perform non-intrusive measurements of a Boeing 737 and a diesel powered burned (used as a hot gas producer). During the measurements it was observed that the selection of the optimal measurement positions into the plume, visualised by an infrared image from a real-time infrared camera in which the emission intensity of different field of view (FOV) positions into the plume are plotted in false colours, is possible very precisely. This enhanced considerably the probability of detection of infrared radiation emitted by a hot gas plume (e. g. from an in-service aircraft at the ground) for the objective to determine composition and temperature of the exhausts. Using this improved localization of the optimum measurement position into the hot exhaust plume the temperature and the concentrations of CO and NO were calculated. Additionally, the spatial distribution of gas temperature and concentrations of CO, CO2 and NO into the exhaust plume were determined.
An open-path Fourier Transform Infrared (FTIR) and a Differential Optical Absorption Spectrometer (DOAS) were installed and simultaneously operated along a 426 m optical path in downtown Mexico City. O3 and SO2 were measured by both optical remote sensing techniques and the results from the comparison are presented. The instruments presented comparable sensitivities for O3 and an excellent agreement (R2 > 0.99) in their correlation. Although the sensitivity of the infrared technique for SO2 was limited to concentrations > 20 ppb or so, the agreement of the FTIR response with the more sensitive DOAS technique during the high levels of this pollutant was favorable (R2 = 0.94) and accurate to within experimental error. These episodes (>100 ppb) were found to occur several times per month. Benzene and toluene were measured by the DOAS technique and their concentrations are reported for a 3-month period during 11/2 - 12/5, 2003. The mean and highest concentration registered for benzene was 5.1 and 18.7 ppb, respectively, with an average of daily maxima at 11.5 ppb. Toluene's highest concentration during this period reached 97.3 ppb, with a mean and daily maximum average of 13.4 and 41.7 ppb, respectively. A benzene/toluene ratio of 2.6 was determined for the entire period of study and a decrease of ~20% in the daily ambient concentration of these aromatic hydrocarbons was observed on Sundays relative to weekdays.
Information about the interaction between the exhaust plume of an aircraft jet engine and ambient air is required for the application of small-scale chemistry-transport models to investigate airport air quality. This interaction is not well understood. In order to study the interaction, spatial information about the plume is required. FTIR emission spectroscopy may be applied to analyze the aircraft exhausts. In order to characterize the plumes spatially, a scanning imaging FTIR system (SIGIS) has been improved. SIGIS is comprised of an interferometer (Bruker OPAG), an azimuth-elevation-scanning mirror, a data acquisition and control system with digital signal processors (DSP), an infrared camera and a personal computer. With this instrumentation it is possible to visualise the plume and to obtain information about the temperature distribution within the plume. Measurements are performed at low spectral resolution, because the dynamic environment of these measurements limits the measurement time to about 2 minutes. Measurements of the plume shapes of an APU and of main engines were performed.
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