In situ measurements of tropical cloud properties in the West African Monsoon: upper tropospheric ice clouds, Mesoscale Convective System outflow, and subvisual cirrus

In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3 ± 1.6) cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10−4 g m−3. All known in situ measurements of subvisual tropopause cirrus are compared and an exponential fit on the size distributions is established for modelling purposes. A comparison of aerosol to ice crystal number concentrations, in order to obtain an estimate on how many ice particles may result from activation of the present aerosol, yielded low ratios for the subvisual cirrus cases of roughly one cloud particle per 30 000 aerosol particles, while for the MCS outflow cases this resulted in a high ratio of one cloud particle per 300 aerosol particles

Atmospheric radiative effects of an in situ measured Saharan dust plume and the role of large particles

This work will present aerosol size distributions measured in a Saharan dust plume between 0.9 and 12 km altitude during the ACE-2 campaign 1997. The distributions contain a significant fraction of large particles of diameters from 4 to 30 μm. Radiative transfer calculations have been performed using these data as input. Shortwave, longwave as well as total atmospheric radiative effects (AREs) of the dust plume are investigated over ocean and desert within the scope of sensitivity studies considering varied input parameters like solar zenith angle, scaled total dust optical depth, tropospheric standard aerosol profiles and particle complex refractive index. The results indicate that the large particle fraction has a predominant impact on the optical properties of the dust. A single scattering albedo of ω0=0.75–0.96 at 550 nm was simulated in the entire dust column as well as 0.76 within the Saharan dust layer at ~4 km altitude indicating enhanced absorption. The measured dust leads to cooling over the ocean but warming over the desert due to differences in their spectral surface albedo and surface temperature. The large particles absorb strongly and they contribute at least 20% to the ARE in the dusty atmosphere. From the measured size distributions modal parameters of a bimodal lognormal column volume size distribution were deduced, resulting in a coarse median diameter of ~9 μm and a column single scattering albedo of 0.78 at 550 nm. A sensitivity study demonstrates that variabilities in the modal parameters can cause completely different AREs and emphasises the warming effect of the large mineral dust particles

Airborne observations of dry particle absorption and scattering properties over the northern Indian Ocean

[1] Airborne measurements of the absorption and scattering coefficients of dry aerosols, at 525 and 545 nm, respectively, were performed over the northern Indian Ocean during the Indian Ocean Experiment (INDOEX). In the marine boundary layer the dry absorption coefficient decreased from about 25 Mm(-1) close the Indian subcontinent to 2 Mm(-1) close to the Intertropical Convergence Zone (ITCZ), which reflects the removal and dilution of anthropogenically produced aerosols during their transport over the Indian Ocean. The dry scattering coefficient initially decreased with distance from the Indian subcontinent, from 70 Mm(-1) at 8degreesN to 10 Mm(-1) at 2degreesN, resulting in a dry single scattering albedo between 0.6 and 0.8 (0.7-0.9 at ambient relative humidity). At further distance from the Indian subcontinent the scattering coefficient and single scattering albedo increased, indicating the increasing importance of aerosols of natural origin. Using Mie theory, the refractive index of the anthropogenically produced aerosols has been estimated to be 1.50-0.06i.Peer reviewe

Uptake of nitric acid in cirrus clouds and contrails

The uptake of nitric acid (HNO3) in cirrus clouds and contrails in the upper troposphere leads to a reduction of the gas phase NOx (=NO+NO2) concentration, resulting in a perturbation of the ozone budget within this region. During the CIRRUS-III campaign over Northern Germany in November 2006 aircraft-based measurements of gas- and condensed-phase reactive nitrogen species (NOy), water vapour, total water, and ice particle size distribution were performed to investigate the uptake of HNO3 in midlatitude cirrus clouds at altitudes between 8 and 12km. Contrails and cirrus clouds were frequently encountered in the course of this campaign. Contrails were identified by the detection of ice crystals in combination with enhanced gas phase NOy and condensation nuclei concentrations resulting from the aircraft exhaust. This method allows to unambiguously identify contrails and to separate contrails and natural cirrus clouds. The HNO3/H2O molar ratio in ice crystals and the particulate fraction of the total nitric acid (HNO3,part/HNO3,tot) were evaluated to quantify the uptake of nitric acid in ice clouds. We show the dependence of these two parameters on temperature, partial pressure of HNO3, and ice water content in the temperature range of 210 to 231K and at nitric acid partial pressures between about 1x10-8 and 1.2x10-7hPa. Further, we compare our data to previous observations in midlatitude clouds. Finally, differences in the chemical composition and trace gas uptake in natural and aviation-induced ice clouds are discussed

Particle production in the lowermost stratosphere by convective lifting in the tropopause

Aircraft measurements of aerosol particles and trace gases were performed in the upper free troposphere and lower stratosphere during the Stratosphere and Troposphere Experiment by Aircraft Measurements (STREAM-96) campaign from Shannon airport, Ireland. During one measurement flight, ultrafine particle number densities up to 10(4) cm(-3) (STP) were observed in the lowermost stratosphere. Concurrent with these very high number densities of ultrafine particles, high accumulation mode particle number densities were observed over the same geographical location in the free troposphere, which were attributed to convective transport in the troposphere. The observations suggest that adiabatic cooling of the stratospheric air, as a result of the convective transport in the troposphere that lifted the tropopause and the air in the lowermost stratosphere, was responsible for triggering the formation of new particles. However, also aircraft emissions could have contributed to the enhancement in ultrafine particles

Observations and Model Calculations of Trace Gas Scavenging in a Dense Saharan Dust Plume

An intensive field measurement campaign was performed in July / August 2002 at the Izana on Tenerife to study the interaction of mineral dust aerosol and tropospheric chemistry. During an intensive dust event strongly reduced mixing ratios of ROx (HO2, CH3O2 and higher organic peroxy radicals), H2O2, NOx (NO and NO2) and O3 were observed. Box model calculations indicate that the reduced H2O2 mixing rations in the dust polume can be explained by including the heterogeneous removal reaction of HO2 with an uptake coefficient of 0.2, or by assuming heterogeneous removal of H2O2 with an accomodation coefficient of 3x10-4. However, these heterogeneous reactions cannot explain the low ROx mixing rations observed during the dust event. Reduced ROx and NOx mixing rations in the Saharan dust plume likely explain the relatively low ozone mixing rations observed during this event.JRC.H.2-Climate chang

Reduced airway levels of fatty-acid binding protein 4 in COPD: relationship with airway infection and disease severity

Background: For still unclear reasons, chronic airway infection often occurs in patients with Chronic Obstructive Pulmonary Disease (COPD), particularly in those with more severe airflow limitation. Fatty-acid binding protein 4 (FABP4) is an adipokine involved in the innate immune response against infection produced by alveolar macrophages (Mɸ). We hypothesized that airway levels of FABP4 may be altered in COPD patients with chronic airway infection. Methods: In this prospective and controlled study we: (1) compared airway FABP4 levels (ELISA) in induced sputum, bronchoalveolar lavage fluid (BALF) and plasma samples in 52 clinically stable COPD patients (65.2 ± 7.9 years, FEV1 59 ± 16% predicted) and 29 healthy volunteers (55.0 ± 12.3 years, FEV1 97 ± 16% predicted); (2) explored their relationship with the presence of bacterial airway infection, defined by the presence of potentially pathogenic bacteria (PPB) at ≥103 colony-forming units/ml in BALF; (3) investigated their relationship with the quantity and proportion of Mɸ in BALF (flow cytometry); and, (4) studied their relationship with the severity of airflow limitation (FEV1), GOLD grade and level of symptoms (CAT questionnaire). Results: We found that: (1) airway levels of FABP4 (but not plasma ones) were reduced in COPD patients vs. controls [219.2 (96.0-319.6) vs. 273.4 (203.1-426.7) (pg/ml)/protein, p = 0.03 in BALF]; (2) COPD patients with airway infection had lower sputum FABP4 levels [0.73 (0.35-15.3) vs. 15.6 (2.0-29.4) ng/ml, p = 0.02]; (3) in COPD patients, the number and proportion of Mɸ were positively related with FABP4 levels in BALF; (4) BALF and sputum FABP4 levels were positively related with FEV1, negatively with the CAT score, and lowest in GOLD grade D patients. Conclusions: Airway FABP4 levels are reduced in COPD patients, especially in those with airway infection and more severe disease. The relationship observed between Mɸ and airway FABP4 levels supports a role for FABP4 in the pathogenesis of airway infection and disease severity in COPD

Reduced airway levels of fatty-acid binding protein 4 in COPD : relationship with airway infection and disease severity

Altres ajuts: This study is supported by Fundació Ramon Pla i Armengol. RF is recipient of a MS research contract (CP16/000039). OS is supported by PERIS.For still unclear reasons, chronic airway infection often occurs in patients with Chronic Obstructive Pulmonary Disease (COPD), particularly in those with more severe airflow limitation. Fatty-acid binding protein 4 (FABP4) is an adipokine involved in the innate immune response against infection produced by alveolar macrophages (Mɸ). We hypothesized that airway levels of FABP4 may be altered in COPD patients with chronic airway infection. In this prospective and controlled study we: (1) compared airway FABP4 levels (ELISA) in induced sputum, bronchoalveolar lavage fluid (BALF) and plasma samples in 52 clinically stable COPD patients (65.2 ± 7.9 years, FEV 59 ± 16% predicted) and 29 healthy volunteers (55.0 ± 12.3 years, FEV 97 ± 16% predicted); (2) explored their relationship with the presence of bacterial airway infection, defined by the presence of potentially pathogenic bacteria (PPB) at ≥10 3 colony-forming units/ml in BALF; (3) investigated their relationship with the quantity and proportion of Mɸ in BALF (flow cytometry); and, (4) studied their relationship with the severity of airflow limitation (FEV), GOLD grade and level of symptoms (CAT questionnaire). We found that: (1) airway levels of FABP4 (but not plasma ones) were reduced in COPD patients vs. controls [219.2 (96.0-319.6) vs. 273.4 (203.1-426.7) (pg/ml)/protein, p = 0.03 in BALF]; (2) COPD patients with airway infection had lower sputum FABP4 levels [0.73 (0.35-15.3) vs. 15.6 (2.0-29.4) ng/ml, p = 0.02]; (3) in COPD patients, the number and proportion of Mɸ were positively related with FABP4 levels in BALF; (4) BALF and sputum FABP4 levels were positively related with FEV, negatively with the CAT score, and lowest in GOLD grade D patients. Airway FABP4 levels are reduced in COPD patients, especially in those with airway infection and more severe disease. The relationship observed between Mɸ and airway FABP4 levels supports a role for FABP4 in the pathogenesis of airway infection and disease severity in COPD