Visibility forecast in the phase of pre-condensation

Kasten, Fritz

doi:10.1111/j.2153-3490.1969.tb00469.x

Cited by 123 publications

(93 citation statements)

References 2 publications

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“…f (RH) = c × (1−RH) −g Kasten (1969) proposed an empirical equation f (RH) = c × (1−RH) −g to describe how f (RH) varies with RH, which has been used in previous reports, e.g., by Hobbs (1998), Gassó et al (2000), Carrico et al (2003. Table 5 shows the fitting results from the current work and previous studies.…”

Section: Parameterization With Equationmentioning

confidence: 50%

Observations of relative humidity effects on aerosol light scattering in the Yangtze River Delta of China

et al. 2015

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Abstract. Scattering of solar radiation by aerosol particles is highly dependent on relative humidity (RH) as hygroscopic particles take up water with increasing RH. To achieve a better understanding of the effect of aerosol hygroscopic growth on light scattering properties and radiative forcing, the aerosol scattering coefficients at RH in the range of 40 to ∼ 90 % were measured using a humidified nephelometer system in the Yangtze River Delta of China in March 2013. In addition, the aerosol size distribution and chemical composition were measured. During the observation period, the mean and standard deviation (SD) of enhancement factors at RH = 85 % for the scattering coefficient (f (85 %)), backscattering coefficient (f b (85 %)), and hemispheric backscatter fraction (f β (85 %)) were 1.58 ± 0.12, 1.25 ± 0.07, and 0.79 ± 0.04, respectively, i.e., aerosol scattering coefficient and backscattering coefficient increased by 58 and 25 % as the RH increased from 40 to 85 %. Concurrently, the aerosol hemispheric backscatter fraction decreased by 21 %. The relative amount of organic matter (OM) or inorganics in PM 1 was found to be a main factor determining the magnitude of f (RH). The highest values of f (RH) corresponded to the aerosols with a small fraction of OM, and vice versa. The relative amount of NO − 3 in fine particles was strongly correlated with f (85 %), which suggests that NO − 3 played a vital role in aerosol hygroscopic growth during this study. The mass fraction of nitrate also had a close relationship to the curvature of the humidograms; higher mass fractions of nitrate were associated with humidograms that had the least curvature. Aerosol hygroscopic growth caused a 47 % increase in the calculated aerosol direct radiative forcing at 85 % RH, compared to the forcing at 40 % RH.

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Section: Parameterization With Equationmentioning

confidence: 50%

Observations of relative humidity effects on aerosol light scattering in the Yangtze River Delta of China

et al. 2015

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“…The aerosol scattering was scaled to 530 nm based on the wavelength dependence of the scattering measured at 450 nm and 550 nm. The aerosol sample was dried through ram heating and cabin temperature higher than ambient, with the dry aerosol scattering measured by the nephelometer is corrected to ambient relative humidity using the approximation (Kasten, 1969) given by Eq. (3):…”

Section: Higearmentioning

confidence: 99%

NASA LaRC airborne high spectral resolution lidar aerosol measurements during MILAGRO: observations and validation

et al. 2009

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Abstract. The NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL) measures vertical profiles of aerosol extinction, backscatter, and depolarization at both 532 nm and 1064 nm. In March of 2006 the HSRL participated in the Megacity Initiative: Local and Global Research Observations (MILAGRO) campaign along with several other suites of instruments deployed on both aircraft and ground based platforms. This paper presents high spatial and vertical resolution HSRL measurements of aerosol extinction and optical depth from MILAGRO and comparisons of those measurements with similar measurements from other sensors and model predictions. HSRL measurements coincident with airborne in situ aerosol scattering and absorption measurements from two different instrument suites on the C-130 and G-1 aircraft, airborne aerosol optical depth (AOD) and extinction measurements from an airborne tracking sunphotometer on the J-31 aircraft, and AOD from a network of ground based Aerosol Robotic Network (AERONET) sun photometers are presented as a validation of the HSRL aerosol extinction and optical depth products. Regarding the extinction validation, we find bias differences between HSRL and these instruments to be less than 3% (0.01 km −1 ) at 532 nm, the wavelength at which the HSRL technique is employed. The rms differences at 532 nm were less than 50% (0.015 km −1 ). To our knowledge this is the Correspondence to: R. R. Rogers (raymond.r.rogers@nasa.gov) most comprehensive validation of the HSRL measurement of aerosol extinction and optical depth to date. The observed bias differences in ambient aerosol extinction between HSRL and other measurements is within 15-20% at visible wavelengths, found by previous studies to be the differences observed with current state-of-the-art instrumentation .

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“…To answer this question, a correction factor f(RH) describing the hygroscopic growth of the aerosol particles with increasing RH is calculated, according to the equation f (RH)=a·(1−RH/100) b (Kasten, 1969;Hänel, 1976). The choice of the constants a and b vary for different chemical composition of the aerosols (Day and Malm, 2001).…”

Section: Diurnal Variability Of Aerosol Optical Propertiesmentioning

confidence: 99%

Climatological aspects of aerosol optical properties in Northern Greece

et al. 2003

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Abstract.Measurements of aerosol optical properties (aerosol optical depth, scattering and backscattering coefficients) have been conducted at two groundbased sites in Northern Greece, Ouranoupolis (40 • 23 N, 23 • 57 E, 170 m a.s.l.) and Thessaloniki (40 • 38 N, 22 • 57 E, 80 m a.s.l.), between 1999 and 2002. The frequency distributions of the observed parameters have revealed the presence of individual modes of high and low values, indicating the influence from different sources. At both sites, the mean aerosol optical depth at 500 nm was 0.23. Values increase considerably during summer when they remain persistently between 0.3 and 0.5, going up to 0.7-0.8 during specific cases. The mean value of 65±40 Mm −1 of the particle scattering coefficient at 550 nm reflects the impact of continental pollution in the regional boundary layer. Trajectory analysis has shown that higher values of aerosol optical depth and the scattering coefficient are found in the east sector (former Soviet Union countries, eastern Balkan countries), whereas cleaner conditions are found for the NW direction. The influence of Sahara dust events is clearly reflected in the Angström exponents. About 45-60% of the observed diurnal variation of the optical properties was attributed to the growth of aerosols with humidity, while the rest of the variability is in phase with the evolution of the sea-breeze cell. The contribution of local pollution is estimated to contribute 35±10% to the average aerosol optical depth at the Thessaloniki site during summer. Finally, the aerosol scale height (aerosol optical depth divided by scattering coefficient) was found to be related to the height of the boundary layer with values between 0.5-1 km during winter and up to 2.5-3 km during summer.

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Visibility forecast in the phase of pre-condensation

Cited by 123 publications

References 2 publications

Observations of relative humidity effects on aerosol light scattering in the Yangtze River Delta of China

Observations of relative humidity effects on aerosol light scattering in the Yangtze River Delta of China

NASA LaRC airborne high spectral resolution lidar aerosol measurements during MILAGRO: observations and validation

Climatological aspects of aerosol optical properties in Northern Greece

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