Cloud droplet number concentration (N-c) is retrieved from remotely observed marine stratocumulus cloud liquid water path (LWP), cloud optical depth ((c)), and cloud thickness, using an optical model that assumes liquid water content (LWC) increases linearly from cloud base. Assuming that LWC is vertically uniform would underestimate (c) by 5% and N-c by 14%. Individual retrievals of N-c from 10-min averages vary by orders of magnitude from long-term averages. Surface cloud condensation nuclei (CCN) number concentration N-CCN is weakly but significantly correlated with N-c (R=0.3) for the day leading and 6hr following N-c. Consistent with coalescence and drizzle scavenging cloud droplets, lag correlations show that N-c decreases for 1hr after the peak area-average rain rate. Greater observed LWP for lower N-c [d(log N-c)/d(log LWP)=-2.3] is consistent with enhanced entrainment drying of clouds with greater N-c and consistent with removal of N-c by thicker clouds with more coalescence and drizzle. Stronger precipitation in clouds with greater N-c is the opposite sensitivity as expected were LWP to be controlled by the cloud lifetime indirect aerosol effect. The strong sensitivity of N-c to LWP suggests that cloud dynamic and thermodynamic forcings drive macrophysical variability that controls N-c in southeastern tropical Pacific stratocumulus clouds. Regressions are relatively insensitive to assumptions about the covariance of errors among the sensors.

Simulate 24-hour ocular itching assessments between olopatadine 0.2% and 0.7% treatments, in patients with high baseline itching severity. A differential odds model characterized individual and population olopatadine ocular itching using 2 completed CAC trials. These trials graded itching from 0 (no itching) to 4 (unbearable itching). Both vehicle and olopatadine reduced baseline itching. A one-compartment KPD Emax model was used to model the effect of Olopatadine. The baseline itching severity was significant in the model, affecting both overall itching and magnitude of effect. This model simulated the proportion of patients achieving 24 hour itching control with olopatadine 0.2% and 0.7%, with baseline severities being screened so that 1/6 to 5/6 sampled baseline time-points would have scores of ≤ 2 to ≤ 3.5. The model predicted both mean scores and proportions of patients in itching categories. With increasing baseline severity, % population with 24-hour control for Olopatadine 0.7% increased over Olopatadine 0.2% (from 5% to 14% more control). This prediction was confirmed with retrospective clinical data analysis. The model predicted more patients had 24-hour control with olopatadine 0.7% than olopatadine 0.2% regardless of baseline severity or magnitude of 24-hour control. This validated model can simulate large trials with high baseline itching, to estimate the patient response to itching relief at 24-hour between Olopatadine 0.7% and 0.2%.

In this study, we evaluated 10 months data (September 2009 to June 2010) of atmospheric aerosol particle number size distribution at three atmospheric observation stations along the Baltic Sea coast: Vavihill (upwind, Sweden), Utö (upwind, Finland), and Preila (downwind, Lithuania). Differences in aerosol particle number size distributions between the upwind and downwind stations during situations of connected atmospheric flow, when the air passed each station, were used to assess the contribution of ship emissions to the aerosol number concentration (diameter interval 50–400 nm) in the Lithuanian background coastal environment. A clear increase in particle number concentration could be noticed, by a factor of 1.9 from Utö to Preila (the average total number concentration at Utö was 791 cm−3), and by a factor of 1.6 from Vavihill to Preila (the average total number concentration at Vavihill was 998 cm−3). The simultaneous measurements of absorption Ångström exponents close to unity at Preila supported our conclusion that ship emissions in the Baltic Sea contributed to the increase in particle number concentration at Preila.

During June and July of 2004, airborne measurements of size-resolved aerosol properties were made over the coastal Pacific near Marina, California. Tandem differential mobility analysis was used to determine the hygroscopic properties of these aerosols and, subsequently, to examine the change in soluble mass after the aerosol had been cloud-processed. Three of the eight cases analyzed during the field campaign exhibited increased soluble mass attributable to cloud-processing. The calculated change in soluble mass after cloud-processing, derived from measurements made below and above cloud, ranged from 1.08 Gamma g m(-3) to 1.40 Gamma g m(-3). These values are in agreement with those determined using data collected during previous field studies in the same region. Aerosol size distributions measured throughout the study with a Passive Cavity Aerosol Spectrometer Probe were averaged to create a single representative distribution, which was used to examine the impact of the addition of sulfate to a typical aerosol measured during this project. Mass light-scattering efficiencies were calculated for both the initial and cloud-processed size distributions using Mie-Lorenz theory. These calculations show that the increase in mass light-scattering efficiency following passage through a single non-precipitating cloud to be 14%, which is in agreement with findings of previous studies in the same region. This new technique produces results that are consistent with existing methods for measuring in-cloud sulfate production and has the advantage of intrinsic consistency with the hygroscopicity and CCN activity of the aerosol. (C) 2011 Elsevier Ltd. All rights reserved.

In order to improve the Community Multiscale Air Quality modeling system (CMAQ) performance for ultrafine particle concentrations in the Pacific Northwest, CMAQ v4.4 was modified so that particles are input to the model with an appropriate size distribution. CMAQ's default emission size distributions are based on outdated measurements which underrepresent ultrafine particles. At the same time, the size distribution must represent the results of all processes between the point of emission and the smallest resolvable spatial scale of the model. As a computationally efficient and simple solution, size distributions were compiled from published modern observations for traffic‐dominated urban areas, power plants, and marine sources at the typical mesoscale air quality model spatial resolution of 4–15 km. CMAQ was modified so that all chemical species are input according to the emission size distribution of traffic‐dominated urban areas because this source emits the majority of each aerosol species in the Pacific Northwest. For a summer 2001 case study based around field measurements, CMAQ v4.4 underpredicts the observable aerosol number concentrations by 1–2 orders of magnitude, while CMAQ with new emission size distributions underpredicts by ∼1 order of magnitude. The modeled size distributions have improved properties in terms of more distinct Aitken and accumulation modes and a more prominent Aitken mode. Errors remain, especially in the accumulation mode.

This paper evaluates aerosol number and mass concentrations from the Community Multiscale Air Quality (CMAQ) modeling system at the 4 km scale against detailed airborne and surface measurements from the coordinated Pacific Northwest 2001 and Pacific 2001 field campaigns. Several investigators have tested CMAQ's prediction of PM2.5 mass, but relatively little attention has been paid to its representation of other subranges of the particulate size distribution. In addition, few have examined CMAQ aerosol performance in the unique Pacific Northwest emission and meteorological conditions. Airborne measurements show an underprediction of aerosol number by a factor of 10–100, especially in the Aitken mode (i.e., ultrafine, <100 nm diameter). This result cannot simply be explained by errors in gas‐phase constituents. Errors in modeled ozone, NO, NOy, and SO2 exist, but the aerosol number underprediction is relatively constant while the gas‐phase errors fluctuate in time and location. For the period of aircraft measurements, the surface PM2.5 mass normalized mean bias is 2%, −33%, and –38%. Speciated aerosol measurements reveal a large but intermittent positive bias in aerosol nitrate and organic mass. Errors in aerosol mass and composition are not consistent or large enough to explain the negative bias factor of 5–10 in accumulation mode particle number concentration and of 10–100 in total particle number concentration. The few other studies of CMAQ size distributions have found similar performance, the root of which has many potential causes and is worthy of future investigation.

Abstract : The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the HOT program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements by successive mooring turnarounds. These observations will be used to investigate air-sea interaction processes related to climate variability. This report documents recovery of the WHOTS-4 mooring and deployment of the fifth mooring (WHOTS-5). Both moorings used Surlyn foam buoys as the surface element and were outfitted with two Air-Sea Interaction Meteorology (ASIMET) systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air-sea fluxes of heat, moisture and momentum. The upper 155 m of the moorings were outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity. A pCO2 system was installed on the WHOTS-5 buoy. The WHOTS mooring turnaround was done between 3 and 11 June 2008. Operations began with deployment of the WHOTS-5 mooring. This was followed by meteorological intercomparisons and CTDs at the WHOTS-4 site. A period of calmer weather was taken advantage of to recover WHOTS-4 on 6 June 2008. The Kilo Moana then returned to the WHOTS-5 mooring for CTD operations and meteorological intercomparisons. This report describes these cruise operations, as well as some of the in-port operations and pre-cruise buoy preparations.

The relative humidity (RH) dependence of light absorption for a Saharan dust‐dominated air mass transported to the Gulf of Mexico was measured during the 2006 TexAQS/GoMACCS study using a photo‐acoustic absorption spectrometer (PAS). Aerosol absorption was measured at low (25%) and high (73%) RH indicating a 1.5(±0.3) absorption enhancement [f(RHAbs)] under high RH conditions. f(RHAbs) estimates, based on air‐mass physical and optical properties and Mie theory modeling, were between 1.2–1.4. Reasons for differences between the measured and modeled f(RHAbs) are discussed. The mass absorption coefficient of the long‐range transported dust was calculated to be 0.04(±0.02) m2g−1.

In order to test Community Multiscale Air Quality (CMAQ) model performance for ultrafine particle concentrations in the Pacific Northwest, CMAQ v4.4 was modified for ternary NH3‐H2SO4‐H2O nucleation and for atmospheric processing of ultrafine particles. Sulfuric acid from sulfur dioxide oxidation is iteratively partitioned into gaseous sulfuric acid, newly condensed aerosol sulfate, and aerosol sulfuric acid contained in new 1 nm particles. Freshly nucleated particles are either coagulated to larger particles or grown by sulfuric acid condensation to 10 nm at which point they are included in CMAQ's existing Aitken mode. Multiple nucleation parameterizations were implemented into CMAQ, and one other was investigated in a sensitivity analysis. For a case study in the Pacific Northwest where aerosol number concentration and size distributions were measured, standard binary nucleation in CMAQ produces nearly no particles for this case study. Ternary nucleation can produce millions of 1 nm particles per cm3, but few of these particles survive coagulation loss and grow to 10 nm and into the Aitken mode. There are occasions when the additions to CMAQ increase the number of particles to within an order of magnitude of observations, but it is more common for number concentrations to remain underpredicted by, on average, one order of magnitude. Significant particle nucleation in CMAQ successfully produces a distinct Aitken and accumulation mode and an Aitken mode that is more prominent than the accumulation mode, although errors in the size distribution remain. A more recent ternary nucleation scheme including ammonium bisulfate clusters does not nucleate an appreciable number of particles.

The nephelometer, the primary instrument used for accurate in-situ scattering measurements, suffers from small errors due to truncation and angular nonidealities in the light source. Because that error depends on particle size, it has been traditionally estimated from the wavelength dependence of scattering, which also depends on particle size. Absorption by particles alters the scattering wavelength dependence, so the traditional correction is in error by 1–5% for absorbing particles, particularly when that absorption is wavelength-dependent. Single-scattering albedos under 0.9 and absorption Ångström exponents above 2 can have errors of over 2%. This problem will occur only very near sources, including laboratory measurements of combustion aerosol. For these situations, we suggest the correction should be calculated using Mie theory and an assumed refractive index, resulting in less than a 2% error. Scattering wavelength dependence for absorbing particles should not be used as a measurement of particle size.

Submicron particles collected on Teflon filters aboard the R/V Ronald Brown during the Texas Air Quality Study and Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS/GoMACCS) 2006 in and around the port of Houston, Texas, were measured by Fourier transform infrared (FTIR) and X‐ray fluorescence for organic functional groups and elemental composition. Organic mass (OM) concentrations (1–25 μg m−3) for ambient particle samples measured by FTIR showed good agreement with measurements made with an aerosol mass spectrometer. The fractions of organic mass identified as alkane and carboxylic acid groups were 47% and 32%, respectively. Three different types of air masses were identified on the basis of the air mass origin and the radon concentration, with significantly higher carboxylic acid group mass fractions in air masses from the north (35%) than the south (29%) or Gulf of Mexico (26%). Positive matrix factorization analysis attributed carboxylic acid fractions of 30–35% to factors with mild or strong correlations (r > 0.5) to elemental signatures of oil combustion and 9–24% to wood smoke, indicating that part of the carboxylic acid fraction of OM was formed by the same sources that controlled the metal emissions, namely the oil and wood combustion activities. The implication is that a substantial part of the measured carboxylic acid contribution was formed independently of traditionally “secondary” processes, which would be affected by atmospheric (both photochemical and meteorological) conditions and other emission sources. The carboxylic acid group fractions in the Gulf of Mexico and south air masses (GAM and SAM, respectively) were largely oil combustion emissions from ships as well as background marine sources, with only limited recent land influences (based on radon concentrations). Alcohol groups accounted for 14% of OM (mostly associated with oil combustion emissions and background sources), and amine groups accounted for 4% of OM in all air masses. Organosulfate groups were found in GAM and SAM, accounting for 1% and 3% of OM, respectively. Two thirds of the OM and oxygen‐to‐carbon (O/C) measured could be attributed to oil and wood combustion sources on the basis of mild or strong correlations to coemitted, nonvolatile trace metals, with the remaining one third being associated with atmospherically processed organic aerosol. The cloud condensation nuclei (CCN) fraction (normalized by total condensation nuclei) had weak correlations to the alcohol and amine group fractions and mild correlation with O/C, also varying inversely with alkane group fraction. The chemical components that influenced f(RH) were sulfate, organic, and nitrate fraction, but this contrast is consistent with the size‐distribution dependence of CCN counters and nephelometers.