Multiwavelength aerosol Raman lidar in combination with polarization lidar at Praia (14.9°N, 23.5°W), Cape Verde, is used to separate the optical properties of desert dust and biomass burning ...particles as a function of height in the mixed dust and smoke plumes over the tropical North Atlantic west of the African continent. The advanced lidar method furthermore permits the derivation of the single‐scattering albedo and microphysical properties of the African biomass burning smoke. A case study is presented to discuss the potential of the technique. The observations were performed during the Saharan Mineral Dust Experiment (SAMUM) in January and February 2008. The height‐resolved lidar results are compared with column‐integrated products obtained with Aerosol Robotic Network Sun photometer. Good agreement is found. Furthermore, the findings are compared with lidar and aircraft observations recently performed in western Africa and with our previous lidar observations taken in tropical and subtropical regions of southern and eastern Asia. The SAMUM case study represents typical aerosol layering conditions in the tropical outflow regime of western Africa during winter season. Above a dense desert dust layer (with an optical depth of about 0.25 at 532 nm) which reached to 1500 m, a lofted layer consisting of desert dust (0.08 optical depth) and biomass burning smoke (0.24 optical depth) extended from 1500 to 5000 m height. Extinction values were 20 ± 10 Mm−1 (desert dust) and 20–80 Mm−1 (smoke) in the lofted plume. The smoke extinction‐to‐backscatter ratios were rather high, with values up to more than 100 sr, effective radii ranged from 0.15 to 0.35 μm, and the smoke single‐scattering albedo was partly below 0.7.
Three cloud data sets, each covering four months of observations, were recently recorded with a lidar at Punta Arenas (53°S), Chile, at Stellenbosch (34°S, near Cape Town), South Africa, and aboard ...the research vessel Polarstern during three north‐south cruises. By comparing these observations with an 11–year cloud data set measured with a lidar at Leipzig (51°N), Germany, the occurrence of heterogeneous ice formation (as a function of cloud top temperature) for very different aerosol conditions in the northern and southern hemisphere is investigated. Large differences in the heterogeneous freezing behavior in the mostly layered clouds are found. For example, <20%, 30%–40% and around 70% of the cloud layers with cloud top temperatures from −15°C to −20°C, showed ice formation over Punta Arenas, Stellenbosch, and Leipzig, respectively. The observed strong contrast reflects the differences in the free tropospheric aerosol conditions at northern midlatitudes, that are controlled by anthropogenic pollution, mineral dust, forest fire smoke, terrestrial biological material and high southern midlatitudes with clean marine conditions.
Key Points
Heterogeneous freezing in the Northern and Southern Hemisphere
Discussion of sources of natural and anthropogenic ice nuclei
Determination of cloud phase state by depolarization lidar
The formation of the ice phase in tropical altocumulus has been studied with multiwavelength aerosol‐cloud Raman lidar, wind Doppler lidar, and radiosonde, providing information on geometrical and ...optical properties, cloud phase, cloud top temperature, updraft and downdraft velocity, and fall speed of ice crystals. The observations were conducted at Praia (15°N, 23.5°W), Cape Verde, in the tropical North Atlantic in the framework of the Saharan Mineral Dust Experiment (SAMUM) project in January and February 2008. More than 200 different altocumulus layers were analyzed. The coldest liquid cloud had a temperature of −36°C and appeared at a height of 9800 m. Tropical altocumulus is found to be geometrically (262 ± 137 m) and optically thin (0.69 ± 0.61), mostly short‐lived, and horizontally small with extents of less than 50 km in 80% of the cases. A clear relationship between the occurrence of the ice phase in altocumulus and cloud top temperature is observed, even more clear after the removal of effects of cloud seeding, which is found to be an important process of ice production in lower layers of multilayer altocumulus systems. Because almost all altocumulus layers (99%) showed a liquid cloud top (region in which ice nucleation begins), we conclude that deposition and condensation ice nucleation are unimportant processes during the initial phase of altocumulus glaciation. A pronounced impact of aerosols such as mineral particles known to be favorable ice nuclei is not found in this region with strong dust‐smoke outbreaks from Africa. The different phases of an almost complete life cycle of an altocumulus were monitored over 5 hours. The observed processes of droplet and ice formation are discussed based on height‐resolved depolarization‐ratio (cloud phase) and vertical‐velocity time series.
More than 2300 observed cloud layers were analyzed to investigate the impact of aged Saharan dust on heterogeneous ice formation. The observations were performed with a polarization/Raman lidar at ...the European Aerosol Research Lidar Network site of Leipzig, Germany (51.3°N, 12.4°E) from February 1997 to June 2008. The statistical analysis is based on lidar‐derived information on cloud phase (liquid water, mixed phase, ice cloud) and cloud top height, cloud top temperature, and vertical profiles of dust mass concentration calculated with the Dust Regional Atmospheric Modeling system. Compared to dust‐free air masses, a significantly higher amount of ice‐containing clouds (25%–30% more) was observed for cloud top temperatures from −10°C to −20°C in air masses that contained mineral dust. The midlatitude lidar study is compared with our SAMUM lidar study of tropical stratiform clouds at Cape Verde in the winter of 2008. The comparison reveals that heterogeneous ice formation is much stronger over central Europe and starts at higher temperatures than over the tropical station. Possible reasons for the large difference are discussed.
The ambient aerosol particle extinction coefficient is measured with the Spectral Aerosol Extinction Monitoring System (SÆMS) along a 2.84 km horizontal path at 30–50 m height above ground in the ...urban environment of Leipzig (51.3° N, 12.4° E), Germany, since 2009. The dependence of the particle extinction coefficient (wavelength range from 300 to 1000 nm) on relative humidity up to almost 100 % was investigated. The main results are presented. For the wavelength of 550 nm, the mean extinction enhancement factor was found to be 1.75 ± 0.4 for an increase of relative humidity from 40 to 80 %. The respective 4-year mean extinction enhancement factor is 2.8 ± 0.6 for a relative-humidity increase from 40 to 95 %. A parameterization of the dependency of the urban particle extinction coefficient on relative humidity is presented. A mean hygroscopic exponent of 0.46 for the 2009–2012 period was determined. Based on a backward trajectory cluster analysis, the dependence of several aerosol optical properties for eight air flow regimes was investigated. Large differences were not found, indicating that local pollution sources widely control the aerosol conditions over the urban site. The comparison of the SÆMS extinction coefficient statistics with respective statistics from ambient AERONET sun photometer observations yields good agreement. Also, time series of the particle extinction coefficient computed from in situ-measured dry particle size distributions and humidity-corrected SÆMS extinction values (for 40 % relative humidity) were found in good overall consistency, which verifies the applicability of the developed humidity parameterization scheme. The analysis of the spectral dependence of particle extinction (Ångström exponent) revealed an increase of the 390–881 nm Ångström exponent from, on average, 0.3 (at 30 % relative humidity) to 1.3 (at 95 % relative humidity) for the 4-year period.
This report details the characteristics of a case of bilateral optic neuropathy during treatment with oral lorlatinib for ALK-positive metastatic adenocarcinoma of the lung.
A 57-year-old woman with ...metastatic adenocarcinoma of the lung receiving treatment with lorlatinib presented to the ophthalmology urgent care with bilateral loss of vision that had progressed to no light perception over the previous 2 weeks. She was hospitalized for an extensive autoimmune, infectious, neoplastic, and paraneoplastic workup, which revealed enhancement of both optic nerves extending up to the optic chiasm and an area of restricted diffusion in the splenium of the corpus callosum on MRI. Lorlatinib was discontinued by her oncologist and she received treatment with five days of pulse-dose intravenous solumedrol as well as five days of plasmapheresis with gradual improvement in her vision. In follow-up, her vision had improved to 20/40 and 20/30.
There have been few reports describing vision loss associated with lorlatinib, an ALK/ROS1 targeted tyrosine kinase inhibitor used to treat metastatic lung adenocarcinoma. This report details the characteristics of a case of bilateral retrobulbar optic neuropathy as well as the treatment and recovery of such a case. Further exploration is needed in order to improve our understanding of the pathogenesis of this rare but potentially devastating adverse effect.
Atmospheric lidar measurements were carried out at Elandsfontein measurement station, on the eastern Highveld approximately 150 km east of Johannesburg in South Africa throughout 2010. The height of ...the planetary boundary layer (PBL) top was continuously measured using a Raman lidar, PollyXT (POrtabLe Lidar sYstem eXTended). High atmospheric variability together with a large surface temperature range and significant seasonal changes in precipitation were observed, which had an impact on the vertical mixing of particulate matter, and hence, on the PBL evolution. The results were compared to radiosondes, CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) space-borne lidar measurements and three atmospheric models that followed different approaches to determine the PBL top height. These models included two weather forecast models operated by ECMWF (European Centre for Medium-range Weather Forecasts) and SAWS (South African Weather Service), and one mesoscale prognostic meteorological and air pollution regulatory model TAPM (The Air Pollution Model). The ground-based lidar used in this study was operational for 4935 h during 2010 (49% of the time). The PBL top height was detected 86% of the total measurement time (42% of the total time). Large seasonal and diurnal variations were observed between the different methods utilised. High variation was found when lidar measurements were compared to radiosonde measurements. This could be partially due to the distance between the lidar measurements and the radiosondes, which were 120 km apart. Comparison of lidar measurements to the models indicated that the ECMWF model agreed the best with mean relative difference of 15.4%, while the second best correlation was with the SAWS model with corresponding difference of 20.1%. TAPM was found to have a tendency to underestimate the PBL top height. The wind speeds in the SAWS and TAPM models were strongly underestimated which probably led to underestimation of the vertical wind and turbulence and thus underestimation of the PBL top height. Comparison between ground-based and satellite lidar shows good agreement with a correlation coefficient of 0.88. On average, the daily maximum PBL top height in October (spring) and June (winter) was 2260 m and 1480 m, respectively. To our knowledge, this study is the first long-term study of PBL top heights and PBL growth rates in South Africa.
We analyze and compare the different sensitivities of aerosol/cloud lidar and 35‐GHz cloud radar to detect ice formation in midlevel clouds in order to harmonize mixed phase cloud observations ...performed with lidar and radar. We found good agreement between spaceborne Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)/CloudSat and ground‐based lidar/radar observations at Leipzig, Germany. However, large differences were found to a previous study with an 11‐year cloud statistics solely based on lidar observations which is caused by significantly higher sensitivity of the cloud radar to detect ice crystals. By introducing a lidar detection threshold for the ice water content of 10−6kgm−3, we find that lidar and radar cloud statistics become increasingly similar.
Key Points
Our observations show good agreement with studies of CloudsatCalipso satellites.
Introduction of detection threshold explains discrepancies to previous studies.
Ice formation can be quantified by combining remote sensing and in-situ.
For the first time, multiwavelength polarization Raman lidar observations of optical and microphysical particle properties over the Amazon Basin are presented. The fully automated advanced Raman ...lidar was deployed 60 km north of Manaus, Brazil (2.5°S, 60°W) in the Amazon rain forest from January to November 2008. The measurements thus cover both the wet season (Dec–June) and the dry or burning season (July–Nov). Two cases studies of young and aged smoke plumes are discussed in terms of spectrally resolved optical properties (355, 532, and 1064 nm) and further lidar products such as particle effective radius and single‐scattering albedo. These measurement examples confirm that biomass burning aerosols show a broad spectrum of optical, microphysical, and chemical properties. The statistical analysis of the entire measurement period revealed strong differences between the pristine wet and the polluted dry season. African smoke and dust advection frequently interrupt the pristine phases during the wet season. Compared to pristine wet season conditions, the particle scattering coefficients in the lowermost 2 km of the atmosphere were found to be enhanced, on average, by a factor of 4 during periods of African aerosol intrusion and by a factor of 6 during the dry (burning) season. Under pristine conditions, the particle extinction coefficients and optical depth for 532 nm wavelength were frequently as low as 10–30 Mm−1 and <0.05, respectively. During the dry season, biomass burning smoke plumes reached to 3–5 km height and caused a mean optical depth at 532 nm of 0.26. On average during that season, particle extinction coefficients (532 nm) were of the order of 100 Mm−1 in the main pollution layer (up to 2 km height). Ångström exponents were mainly between 1.0 and 1.5, and the majority of the observed lidar ratios were between 50–80 sr.
Key Points
First time for continuous aerosol profiling in Amazonia covering all seasons
Documentation of smoke and dust transport from Africa to Amazonia
First optical characterization of Amazonian aerosols at ambient conditions
Saharan dust was observed with shipborne lidar from 60° to 20°W along 14.5°N during a 1‐month transatlantic cruise of the research vessel Meteor. About 4500 km off the coast of Africa, mean ...extinction and backscatter‐related Ångström exponent of 0.1, wavelength‐independent extinction‐to‐backscatter ratios (lidar ratios) of around 45 sr, and particle linear depolarization ratio of 20% were found for aged dust (transport time >10 days). In contrast, dust with a shorter atmospheric residence time of 2–3 days showed Ångström exponents of −0.5 (backscatter coefficient) and 0.1 (extinction coefficient), mean lidar ratios of 64 and 50 sr, and particle linear depolarization ratios of 22 and 26% at 355 and 532 nm wavelength, respectively. Traces of fire smoke were also detected in the observed dust layers. The lidar observations were complemented by Aerosol Robotic Network handheld Sun photometer measurements, which revealed a mean total atmospheric column aerosol optical thickness of 0.05 for pure marine conditions (in the absence of lofted aerosol layers) and roughly 0.9 during a strong Saharan dust outbreak. The achieved data set was compared with first Consortium for Small Scale Modeling‐Multi‐Scale Chemistry Aerosol Transport simulations. The simulated vertical aerosol distribution showed good agreement with the lidar observations.
Key Points
Shipborne lidar observations along the Saharan Air Layer from 60°W to 20°W
Comparing shipborne lidar measurements and results from the model COSMO‐MUSCAT
Properties of the Saharan Air Layer after a travel distance of >10 and 2 days
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