Secondary ice production (SIP) is an important physical phenomenon that results in an increase in... more Secondary ice production (SIP) is an important physical phenomenon that results in an increase in the ice particle concentration and can therefore have a significant impact on the evolution of clouds. In this study, idealized simulations of a mesoscale convective system (MCS) were conducted using a high-resolution (250 m horizontal grid spacing) mesoscale model and a detailed bulk microphysics scheme in order to examine the impacts of SIP on the microphysics and dynamics of a simulated tropical MCS. The simulations were compared to airborne in situ and remote sensing observations collected during the "High Altitude Ice Crystals-High Ice Water Content" (HAIC-HIWC) field campaign in 2015. It was found that the observed high ice number concentration can only be simulated by models that include SIP processes. The inclusion of SIP processes in the microphysics scheme is crucial for the production and maintenance of the high ice water content observed in tropical convection. It was shown that SIP can enhance the strength of the existing convective updrafts and result in the initiation of new updrafts above the melting layer. Agreement between the simulations and observations highlights the impacts of SIP on the maintenance of tropical MCSs in nature and the importance of including SIP parameterizations in models.
In this work we report the airborne aerosol optical depth (AOD) from measurements within freshly ... more In this work we report the airborne aerosol optical depth (AOD) from measurements within freshly emitted anthropogenic plumes arising from mining and processing operations in the Athabasca Oil Sands Region (AOSR) in the context of ground-based AERONET climatological daily averaged AODs at Fort McMurray (Alberta, Canada). During two flights on 9 and 18 June 2018, the NASA airborne 4STAR (Spectrometers for Sky-Scanning, Sun-Tracking Atmospheric Research) Sun photometer registered high finemode (FM, < 1 µm) in-plume AODs of up to 0.4 and 0.9, respectively, in the vicinity of the plume source (< 20 km). Particle composition shows that the plumes were associated with elevated concentrations of sulfates and ammonium. These high AODs significantly exceed climatological averages for June and were not captured by the nearby AERONET instrument (mean daily AODs of 0.10±0.01 and 0.07±0.02, maximum AOD of 0.12) due possibly to horizontal inhomogeneity of the plumes, plume dilution and winds which in certain cases were carrying the plume away from the ground-based instrument. The average 4STAR out-of-plume (background) AODs deviated only marginally from AERONET daily averaged values. While 4STAR AOD peaks were generally well correlated in time with peaks in the in situ-measured particle concentrations, we show that differences in particle size are the dominant factor in determining the 4STAR-derived AOD. During the two flights of 24 June and 5 July 2018 when plumes likely travelled distances of 60 km or more, the average 4STAR FM AOD increased by 0.01-0.02 over ∼ 50 km of downwind particle evolution, which was supported by the increases in layer AODs calculated from the in situ extinction measurements. Based on these observations as well as the increases in organic mass, we attribute the observed AOD increase, at least in part, to secondary organic aerosol formation. The in-plume and out-of-plume AODs for this second pair of flights, in contrast to clear differences in in situ optical and other measurements, were practically indistinguishable and compared favourably to AERONET within 0.01-0.02 AOD. This means that AERONET was generally suc-Published by Copernicus Publications on behalf of the European Geosciences Union. 10672 K. Baibakov et al.: Aerosol optical depth measurements of oil sands plumes cessful in capturing the background AODs, but missed some of the spatially constrained high-AOD plumes with sources as close as 30-50 km, which is important to note since the AERONET measurements are generally thought to be representative of the regional AOD loading. The fact that industrial plumes can be associated with significantly higher AODs in the vicinity of the emission sources than previously reported from AERONET can potentially have an effect on estimating the AOSR radiative impact.
Figure S1: 4STAR at Fort McMurray installed on the Convair-580 aircraft; b. 4STAR head and its op... more Figure S1: 4STAR at Fort McMurray installed on the Convair-580 aircraft; b. 4STAR head and its optical cables sitting inside the aircraft during routine maintenance
Organic aerosols are a major component of particulate matter but have a complex and uncertain eff... more Organic aerosols are a major component of particulate matter but have a complex and uncertain effect on climate and health.
The main radome is being constructed as a sandwich structure using materials that have low loss a... more The main radome is being constructed as a sandwich structure using materials that have low loss at X-band and satisfy the mechanical airworthiness requirements. For the W-band, the
Cloud structure and crystal growth in two nimbostratus were examined using in situ and airborne r... more Cloud structure and crystal growth in two nimbostratus were examined using in situ and airborne radar observations. In both cases, structure throughout the cloud depth was modulated by generating cells at about 8 km altitude. Large-scale horizontal homogeneity at altitudes below the generating cells was due to the rapid movement of the generating cells relative to the main cloud mass. In addition, significant horizontal variability was evident on the scale of few hundred meters, principally in the radar reflectivity data but also readily detectable in the particle data. The melting layer was clearly defined in the radar images. Thin dry layers just above the melting layer were also observed in both cases. In agreement with earlier studies, particle spectra in these clouds are adequately described by exponential relationships. There is a strong correlation between the slope (λ) and intercept (No) parameters; this relationship is well characterized by a power law with constants varyin...
Emission rate estimates determined for a large number of volatile organic compounds using airborne measurements for the oil sands facilities in Alberta, Canada
Comparisons of Cloud In-Situ Microphysical Properties of Deep Convective Clouds to Appendix D/P, Using Data from the HAIC-HIWC and HIWC RADAR I Flight Campaigns
Airborne Measurements of Polarized Hyperspectral Microwave Radiances to Increase the Accuracy of Temperature and Water Vapor Retrievals: an Information Content Analysis
Automatic classifications of radar polarimetric measurements into hydrometeor types using fuzzy-l... more Automatic classifications of radar polarimetric measurements into hydrometeor types using fuzzy-logic or other similar algorithms are now routinely done using ground-based cm-wavelength polarimetric radars (e.g., Vivekanandan et al. 1999; Lim. et al. 2005). In most of these algorithms, the polarimetric thresholds for various hydrometeor types are based on computational studies. A comprehensive review of polarimetric thresholds used for hydrometeor identification from cm-wavelength radar is given by Straka et al. (2000). Most of the cm-wavelength based algorithms are focused on large-scale systems and typically lump ice crystals into 2-3 broad categories. However, as both observational and computational studies for mm-radar show (e.g., Wolde and Vali, 2001; Tang and Aydin 1995), ice crystals have diverse polarimetric signatures that depend on crystal shape, size, density and fall patterns. By using near coincident in-situ and airborne radar data, it is possible to refine the threshol...
Research aircraft that are equipped with in-situ cloud microphysics probes and millimeter radars,... more Research aircraft that are equipped with in-situ cloud microphysics probes and millimeter radars, similar to the one used in this study, provide coincident and closely spaced radar and cloud microphysics dataset (e.g., Wolde and Vali 2002), which will be very useful to develop and validate radar based cloud microphysics retrieval methodologies using space and ground based radars. This paper presents a comparison of an airborne radar and in-situ data collected in one of the flights during the second Alliance Icing Research Study (AIRS II) that was conducted between November 2003 and February 2004 over the Mirabel airport near Montreal, Canada and the surrounding regions in Ontario and Quebec. AIRS II was an international collaborative aircraft icing study using arrays of ground-based and airborne in-situ and remote-sensing instruments (Isaac et al. 2005). One of the scientific objectives of AIRS II was to develop techniques for identification of cloud particle compositions using remo...
The atmospheric lifetimes of pollutants determine their impacts on human health, ecosystems and c... more The atmospheric lifetimes of pollutants determine their impacts on human health, ecosystems and climate, and yet, pollutant lifetimes due to dry deposition over large regions have not been determined from measurements. Here, a new methodology based on aircraft observations is used to determine the lifetimes of oxidized sulfur and nitrogen due to dry deposition over (3 − 6) × 10 3 km 2 of boreal forest in Canada. Dry deposition fluxes decreased exponentially with distance from the Athabasca oil sands sources, located in northern Alberta, resulting in lifetimes of 2.2-26 h. Fluxes were 2-14 and 1-18 times higher than model estimates for oxidized sulfur and nitrogen, respectively, indicating dry deposition velocities which were 1.2-5.4 times higher than those computed for models. A Monte Carlo analysis with five commonly used inferential dry deposition algorithms indicates that such model underestimates of dry deposition velocity are typical. These findings indicate that deposition to vegetation surfaces is likely underestimated in regional and global chemical transport models regardless of the model algorithm used. The model-observation gaps may be reduced if surface pH and quasi-laminar and aerodynamic resistances in algorithms are optimized as shown in the Monte Carlo analysis. Assessing the air quality and climate impacts of atmospheric pollutants on regional and global scales requires improved measurement-based understanding of atmospheric lifetimes of these pollutants.
An algorithm based on triple-frequency (X, Ka, W) radar measurements that retrieves the size, wat... more An algorithm based on triple-frequency (X, Ka, W) radar measurements that retrieves the size, water content and degree of riming of ice clouds is presented. This study exploits the potential of multi-frequency radar measurements to provide information on bulk snow density that should underpin better estimates of the snow characteristic size and content within the radar volume. The algorithm is based on Bayes' rule with riming parameterised by the "fill-in" model. The radar reflectivities are simulated with a range of scattering models corresponding to realistic snowflake shapes. The algorithm is tested on multi-frequency radar data collected during the ESA-funded Radar Snow Experiment For Future Precipitation Mission. During this campaign, in situ microphysical probes were mounted on the same aeroplane as the radars. This nearly perfectly co-located dataset of the remote and in situ measurements gives an opportunity to derive a combined multi-instrument estimate of snow microphysical properties that is used for a rigorous validation of the radar retrieval. Results suggest that the triple-frequency retrieval performs well in estimating ice water content (IWC) and mean mass-weighted diameters obtaining root-meansquare errors of 0.13 and 0.15, respectively, for log 10 IWC and log 10 D m. The retrieval of the degree of riming is more challenging, and only the algorithm that uses Doppler information obtains results that are highly correlated with the in situ data.
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Papers by Mengistu Wolde