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Abstract
Aerosol size distributions and meteorological parameters measured with altitude in a marine environment off the Southern California coast are presented. Extinction coefficients for a wavelength of 3.75 μm are calculated from Mie theory using the measured distributions and compared with those calculated using empirical models of aerosol size distributions which require as inputs the measured meteorological parameters.
Abstract
Aerosol size distributions and meteorological parameters measured with altitude in a marine environment off the Southern California coast are presented. Extinction coefficients for a wavelength of 3.75 μm are calculated from Mie theory using the measured distributions and compared with those calculated using empirical models of aerosol size distributions which require as inputs the measured meteorological parameters.
Abstract
Airborne measurements of aerosol size distributions are used to determine the vertical profiles of infrared (IR) extinction and absorption coefficients and asymmetry factors in eight different maritime stratus cloud regimes during unstable boundary layer conditions where the sea temperature was greater than the ambient air temperature. The average values of these parameters are determined relative to the level where the air temperature change with elevation was near a moist adiabatic lapse rate. A model to determine the effects of aerosols on IR propagation beneath these types of clouds is presented in terms of multiplying arrays compatible with the input format of the transmittance/radiance computer code MODTRAN. The model is used in a modified version of MODTRAN to test its utility in system performance predictions beneath these types of clouds. The maximum detection range (MDR) of a surface ship by an airborne forward looking infrared (FLIR) system was determined to be a factor of 3 in better agreement with the observed MDR than that determined using the MODTRAN ICLD3 stratus model with the Navy Aerosol Model (NAM) beneath the cloud. The predictions were found to be insensitive to the wave slope model used in the zero-range sea radiance calculations. This is shown to be the result of a compensating effect between increased sea emissions and decreased cloud reflections for the larger wave slope variances associated with unstable boundary layer conditions as compared to those for stable or neutral conditions.
Abstract
Airborne measurements of aerosol size distributions are used to determine the vertical profiles of infrared (IR) extinction and absorption coefficients and asymmetry factors in eight different maritime stratus cloud regimes during unstable boundary layer conditions where the sea temperature was greater than the ambient air temperature. The average values of these parameters are determined relative to the level where the air temperature change with elevation was near a moist adiabatic lapse rate. A model to determine the effects of aerosols on IR propagation beneath these types of clouds is presented in terms of multiplying arrays compatible with the input format of the transmittance/radiance computer code MODTRAN. The model is used in a modified version of MODTRAN to test its utility in system performance predictions beneath these types of clouds. The maximum detection range (MDR) of a surface ship by an airborne forward looking infrared (FLIR) system was determined to be a factor of 3 in better agreement with the observed MDR than that determined using the MODTRAN ICLD3 stratus model with the Navy Aerosol Model (NAM) beneath the cloud. The predictions were found to be insensitive to the wave slope model used in the zero-range sea radiance calculations. This is shown to be the result of a compensating effect between increased sea emissions and decreased cloud reflections for the larger wave slope variances associated with unstable boundary layer conditions as compared to those for stable or neutral conditions.
Abstract
The Lake Michigan Ozone Study 2017 (LMOS 2017) was a collaborative multiagency field study targeting ozone chemistry, meteorology, and air quality observations in the southern Lake Michigan area. The primary objective of LMOS 2017 was to provide measurements to improve air quality modeling of the complex meteorological and chemical environment in the region. LMOS 2017 science questions included spatiotemporal assessment of nitrogen oxides (NO x = NO + NO2) and volatile organic compounds (VOC) emission sources and their influence on ozone episodes; the role of lake breezes; contribution of new remote sensing tools such as GeoTASO, Pandora, and TEMPO to air quality management; and evaluation of photochemical grid models. The observing strategy included GeoTASO on board the NASA UC-12 aircraft capturing NO2 and formaldehyde columns, an in situ profiling aircraft, two ground-based coastal enhanced monitoring locations, continuous NO2 columns from coastal Pandora instruments, and an instrumented research vessel. Local photochemical ozone production was observed on 2 June, 9–12 June, and 14–16 June, providing insights on the processes relevant to state and federal air quality management. The LMOS 2017 aircraft mapped significant spatial and temporal variation of NO2 emissions as well as polluted layers with rapid ozone formation occurring in a shallow layer near the Lake Michigan surface. Meteorological characteristics of the lake breeze were observed in detail and measurements of ozone, NOx, nitric acid, hydrogen peroxide, VOC, oxygenated VOC (OVOC), and fine particulate matter (PM2.5) composition were conducted. This article summarizes the study design, directs readers to the campaign data repository, and presents a summary of findings.
Abstract
The Lake Michigan Ozone Study 2017 (LMOS 2017) was a collaborative multiagency field study targeting ozone chemistry, meteorology, and air quality observations in the southern Lake Michigan area. The primary objective of LMOS 2017 was to provide measurements to improve air quality modeling of the complex meteorological and chemical environment in the region. LMOS 2017 science questions included spatiotemporal assessment of nitrogen oxides (NO x = NO + NO2) and volatile organic compounds (VOC) emission sources and their influence on ozone episodes; the role of lake breezes; contribution of new remote sensing tools such as GeoTASO, Pandora, and TEMPO to air quality management; and evaluation of photochemical grid models. The observing strategy included GeoTASO on board the NASA UC-12 aircraft capturing NO2 and formaldehyde columns, an in situ profiling aircraft, two ground-based coastal enhanced monitoring locations, continuous NO2 columns from coastal Pandora instruments, and an instrumented research vessel. Local photochemical ozone production was observed on 2 June, 9–12 June, and 14–16 June, providing insights on the processes relevant to state and federal air quality management. The LMOS 2017 aircraft mapped significant spatial and temporal variation of NO2 emissions as well as polluted layers with rapid ozone formation occurring in a shallow layer near the Lake Michigan surface. Meteorological characteristics of the lake breeze were observed in detail and measurements of ozone, NOx, nitric acid, hydrogen peroxide, VOC, oxygenated VOC (OVOC), and fine particulate matter (PM2.5) composition were conducted. This article summarizes the study design, directs readers to the campaign data repository, and presents a summary of findings.
