Aerosol–cloud–radiation interactions are widely held to be the largest single source of uncertainty in climate model projections of future radiative forcing due to increasing anthropogenic emissions. The underlying causes of this uncertainty among modeled predictions of climate are the gaps in our fundamental understanding of cloud processes. There has been significant progress with both observations and models in addressing these important questions but quantifying them correctly is nontrivial, thus limiting our ability to represent them in global climate models. The Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) 2011 was a targeted aircraft campaign with embedded modeling studies, using the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft and the research vessel Point Sur in July and August 2011 off the central coast of California, with a full payload of instruments to measure particle and cloud number, mass, composition, and water uptake distributions. EPEACE used three emitted particle sources to separate particle-induced feedbacks from dynamical variability, namely 1) shipboard smoke-generated particles with 0.05–1-μm diameters (which produced tracks measured by satellite and had drop composition characteristic of organic smoke), 2) combustion particles from container ships with 0.05–0.2-μm diameters (which were measured in a variety of conditions with droplets containing both organic and sulfate components), and 3) aircraft-based milled salt particles with 3–5-μm diameters (which showed enhanced drizzle rates in some clouds). The aircraft observations were consistent with past large-eddy simulations of deeper clouds in ship tracks and aerosol– cloud parcel modeling of cloud drop number and composition, providing quantitative constraints on aerosol effects on warm-cloud microphysics.
The seasonal cycles in the distribution of precipitation around the western North Pacific and Atlantic cyclones have been examined by compositing quantitative estimates of the precipitation rate relative to cyclone centers. The precipitation data sources considered include estimates produced by the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) project, the satellite-based daily precipitation estimates produced by the Global Precipitation Climatology Project, and estimates derived based on observed weather reports contained in the Comprehensive Ocean–Atmosphere Data Set (COADS). Results from all three datasets suggest that for Pacific cyclones, substantially more precipitation is found in the warm sector in fall than in winter and less precipitation is found behind the cold front in spring and summer than in winter. The seasonal cycle for Atlantic cyclones is found to be distinctly different. The distribution in precipitation around cyclones in fall and winter are not very different, while in spring and summer less precipitation is found over much of the cyclone. The implications for the observed seasonal cycles are discussed. The seasonal cycle for Pacific cyclones suggests that diabatic contributions to the generation of eddy available potential energy (APE) due to latent heat release should be maximal in fall with a relative minimum in midwinter, while for Atlantic cyclones diabatic generation of eddy APE in fall and winter is nearly the same. This is suggested to be one of the factors that can contribute to the observed midwinter minimum in the Pacific storm track, and the absence of such a minimum in the Atlantic. Possible reasons contributing to the differences in the seasonal cycle between the two basins are discussed. Preliminary analyses suggest that differences in static stability, availability of moisture, as well as dynamical forcing may all be contributing factors. Issues on estimating rates of precipitation based on ship reports are addressed in appendix A. It is argued that it may be a good time to recalibrate existing schemes.
Abstract.To study the effect of giant cloud condensation nuclei (GCCN) on precipitation processes in stratocumulus clouds, 1-10 µm diameter salt particles (salt powder) were released from an aircraft while flying near the cloud top on 3 August 2011 off the central coast of California. The seeded area was subsequently sampled from the aircraft that was equipped with aerosol, cloud, and precipitation probes and an upward-facing cloud radar. During post-seeding sampling, made 30-60 min after seeding, the mean cloud droplet size increased, the droplet number concentration decreased, and large drop (e.g., diameter larger than 10 µm) concentration increased. Average drizzle rates increased from about 0.05 to 0.20 mm h −1 , and the liquid water path decreased from about 52 to 43 g m −2 . Strong radar returns associated with drizzle were observed on the post-seeding cloud-base levelleg flights and were accompanied by a substantial depletion of the cloud liquid water content. The changes were large enough to suggest that the salt particles with concentrations estimated to be 10 −2 to 10 −4 cm −3 resulted in a four-fold increase in the cloud-base rainfall rate and depletion of the cloud water due to rainout. In contrast, a case is shown where the cloud was already precipitating (on 10 August) and the effect of adding GCCN to the cloud was insignificant.
Backgroundent-Sauchinone is a polyphenolic compound found in plants belonging to the lignan family. ent-Sauchinone has been shown to modulate the expression of inflammatory factors through the nuclear factor-kappa B (NF-κB) signaling pathway. It is well known that neuroinflammation is associated with amyloidogenesis. Thus, in the present study, we investigated whether ent-Sauchinone could have anti-amyloidogenic effects through the inhibition of NF-κB pathways via its anti-inflammatory property.MethodsTo investigate the potential effect of ent-Sauchinone on anti-neuroinflammation and anti-amyloidogenesis in in vitro studies, we used microglial BV-2 cells and cultured astrocytes treated with ent-Sauchinone (1, 5, and 10 μM) for 24 hours. For the detection of anti-neuro-inflammatory responses, reative oxygen species (ROS) and Nitric oxide (NO) generation and inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression were measured with assay kits and western blotting. β-secretase and β-secretase activities and β-amyloid levels were determined for measuring the anti-amyloidogenic effects of ent-Sauchinone by enzyme assay kits. NF-κB and STAT3 signals were detected with electromobility shift assay (EMSA) to study the related signaling pathways. The binding of ent-Sauchinone to STAT3 was evaluated by a pull-down assay and by a docking model using Autodock VINA software (Hoover’s Inc., Texas, United states).Resultsent-Sauchinone (1, 5, and 10 μM) effectively decreased lipopolysaccharide (LPS)-(1 μg/ml) induced inflammatory responses through the reduction of ROS and NO generations and iNOS and COX-2 expressions in cultured astrocytes and microglial BV-2 cells. ent-Sauchinone also inhibited LPS-induced amyloidogenesis through the inhibition of β-secretase and β-secretase activity. NF- κB amyloid and STAT3, critical transcriptional factors regulating not only inflammation but also amyloidogenesis, were also inhibited in a concentration dependent manner by ent-Sauchinone by blocking the phosphorylation of I κB and STAT3 in cultured astrocytes and microglial BV-2 cells. The docking model approach showed that ent-Sauchinone binds to STAT3, and the employment of a STAT3 inhibitor and siRNA reversed ent-Sauchinone-induced inhibition NF-κB activation and Aβ generation.ConclusionsThese results indicated that ent-Sauchinone inhibited neuroinflammation and amyloidogenesis through the inhibition of STAT3-mediated NF-κB activity, and thus could be applied in the treatment of neuro-inflammatory diseases, including Alzheimer’s disease.
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