scholarly journals Long-term observation of aerosol–cloud relationships in the Mid-Atlantic of the United States

2014 ◽  
Vol 14 (13) ◽  
pp. 18943-18960 ◽  
Author(s):  
S. Li ◽  
E. Joseph ◽  
Q. Min ◽  
B. Yin
Keyword(s):  
Indirect Effect ◽  
The United States ◽  
Aerosol Size Distribution ◽  
Cloud Droplets ◽  
Field Station ◽  
Aerosol Indirect Effect ◽  
Aerosol Loading ◽  
Cloud Properties ◽  
The Mean

Abstract. Long-term ground-based observations (2006 to 2010) of aerosol and cloud properties derived from passive radiometric sensors deployed at an atmospheric measurement field station in the Baltimore–Washington corridor operated by Howard University were used to examine aerosol indirect effect on cloud optical depth (COD), liquid water path (LWP), cloud droplets effective radius (Re) and cloud droplets number concentration (Nd). A higher frequency of clouds with large COD (> 20) and small Re (< 7 m) was found during summer of 2006 and 2007 along with higher frequency of abundant aerosol loading. The five-year data are screened for summer months only and are separated into clean and polluted cases based on aerosol particulate matter with aerodynamic diameter ≤ 2.5 m (PM2.5) value. Evidence of aerosol indirect effect is found where for polluted cases the mean and median values of COD and Nd distributions were elevated while the mean and median values of Re were decreased. Further reinforcing this conclusion is the result that the mean and median values of LWP distributions did not show prominent difference between clean and polluted cases, this implies that differences between the two cases of influential factors on cloud properties were relatively controlled. Moreover aerosol indirect effects were found insignificant when LWP was small but significant when LWP was large through the analysis of sensitivity of Nd to LWP under different aerosol loading and the measurements of aerosol size distribution.

scholarly journals The importance of interstitial particle scavenging by cloud droplets in shaping the remote aerosol size distribution and global aerosol-climate effects

2015 ◽  
Vol 15 (11) ◽  
pp. 6147-6158 ◽  
Author(s):  
J. R. Pierce ◽  
B. Croft ◽  
J. K. Kodros ◽  
S. D. D'Andrea ◽  
R. V. Martin
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Indirect Effect ◽  
Cloud Droplet ◽  
Aerosol Size Distribution ◽  
Cloud Physics ◽  
Cloud Droplets ◽  
Aerosol Indirect Effect ◽  
Ice Cloud ◽  
Coagulation Process

Abstract. In this paper, we investigate the coagulation of interstitial aerosol particles (particles too small to activate to cloud droplets) with cloud drops, a process often ignored in aerosol-climate models. We use the GEOS-Chem-TOMAS (Goddard Earth Observing System-Chemistry TwO-Moment Aerosol Sectional) global chemical transport model with aerosol microphysics to calculate the changes in the aerosol size distribution, cloud-albedo aerosol indirect effect, and direct aerosol effect due to the interstitial coagulation process. We find that inclusion of interstitial coagulation in clouds lowers total particle number concentrations by 15–21% globally, where the range is due to varying assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The interstitial coagulation process lowers the concentration of particles with dry diameters larger than 80 nm (a proxy for larger CCN) by 10–12%. These 80 nm particles are not directly removed by the interstitial coagulation but are reduced in concentration because fewer smaller particles grow to diameters larger than 80 nm. The global aerosol indirect effect of adding interstitial coagulation varies from +0.4 to +1.3 W m−2 where again the range depends on our cloud assumptions. Thus, the aerosol indirect effect of this process is significant, but the magnitude depends greatly on assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The aerosol direct effect of the interstitial coagulation process is minor (< 0.01 W m−2) due to the shift in the aerosol size distribution at sizes where scattering is most effective being small. We recommend that this interstitial scavenging process be considered in aerosol models when the size distribution and aerosol indirect effects are important.

scholarly journals The importance of interstitial particle scavenging by cloud droplets in shaping the remote aerosol size distribution and global aerosol-climate effects

2015 ◽  
Vol 15 (4) ◽  
pp. 5589-5618
Author(s):  
J. R. Pierce ◽  
B. Croft ◽  
J. K. Kodros ◽  
S. D. D'Andrea ◽  
R. V. Martin
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Indirect Effect ◽  
Cloud Droplet ◽  
Aerosol Size Distribution ◽  
Cloud Physics ◽  
Cloud Droplets ◽  
Aerosol Indirect Effect ◽  
Ice Cloud ◽  
Coagulation Process

Abstract. In this paper, we investigate the coagulation of interstitial aerosol particles (particles too small to activate to cloud droplets) with cloud drops, a process often ignored in aerosol-climate models. We use the GEOS-Chem-TOMAS global chemical transport model with aerosol microphysics to calculate the changes in the aerosol size distribution, cloud-albedo aerosol indirect effect, and direct aerosol effect due to the interstitial coagulation process. We find that inclusion of interstitial coagulation in clouds lowers total particle number concentrations by 15–21% globally, where the range is due to varying assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The interstitial coagulation process lowers the concentration of particles with dry diameters larger than 80 nm (a proxy for larger CCN) by 10–12%. These 80 nm particles are not directly removed by the interstitial coagulation, but are reduced in concentration because fewer smaller particles grow to diameters larger than 80 nm. The global aerosol indirect effect of adding interstitial coagulation varies from +0.4 to +1.3 W m−2 where again the range depends on our cloud assumptions. Thus, the aerosol indirect effect of this process is significant, but the magnitude depends greatly on assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The aerosol direct effect of interstitial coagulation process is minor (<0.01 W m−2) due to the shift in the aerosol size distribution at sizes where scattering is most effective being small. We recommend that this interstitial scavenging process be considered in aerosol models when the size distribution and aerosol indirect effects are important.

scholarly journals Influence of Giant CCN on warm rain processes in the ECHAM5 GCM

2008 ◽  
Vol 8 (14) ◽  
pp. 3769-3788 ◽  
Author(s):  
R. Posselt ◽  
U. Lohmann
Keyword(s):  
Indirect Effect ◽  
General Circulation ◽  
Hydrological Cycle ◽  
Precipitation Amount ◽  
Circulation Model ◽  
Anthropogenic Activity ◽  
Total Water ◽  
Anthropogenic Aerosol ◽  
Aerosol Indirect Effect ◽  
Cloud Properties

Abstract. Increased Cloud Condensation Nuclei (CCN) load due to anthropogenic activity might lead to non-precipitating clouds because the cloud drops become smaller (for a constant liquid water content) and, therefore, less efficient in rain formation (aerosol indirect effect). Adding giant CCN (GCCN) into such a cloud can initiate precipitation (namely, drizzle) and, therefore, might counteract the aerosol indirect effect. The effect of GCCN on global climate on warm clouds and precipitation within the ECHAM5 General Circulation Model (GCM) is investigated. Therefore, the newly introduced prognostic rain scheme (Posselt and Lohmann, 2007) is applied so that GCCN are directly activated into rain drops. The ECHAM5 simulations with incorporated GCCN show that precipitation is affected only locally. On the global scale, the precipitation amount does not change. Cloud properties like total water (liquid + rain water) and cloud drop number show a larger sensitivity to GCCN. Depending on the amount of added GCCN, the reduction of total water and cloud drops account for up to 20% compared to the control run without GCCN. Thus, the incorporation of the GCCN accelerate the hydrological cycle so that clouds precipitate faster (but not more) and less condensed water is accumulated in the atmosphere. An estimate of the anthropogenic aerosol indirect effect on the climate is obtained by comparing simulations for present-day and pre-industrial climate. The introduction of the prognostic rain scheme lowered the anthropogenic aerosol indirect effect significantly compared to the standard ECHAM5 with the diagnostic rain scheme. The incorporation of the GCCN changes the model state, especially the cloud properties like TWP and Nl. The precipitation changes only locally but globally the precipitation is unaffected because it has to equal the global mean evaporation rate. Changing the cloud properties leads to a local reduction of the aerosol indirect effect and, hence, partly compensating for the increased anthropogenic CCN concentrations in that regions. Globally, the aerosol indirect effect is nearly the same for all simulations.

scholarly journals Severity of parkinsonism associated with environmental manganese exposure

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Brad A. Racette ◽  
Gill Nelson ◽  
Wendy W. Dlamini ◽  
Pradeep Prathibha ◽  
Jay R. Turner ◽  
...  
Keyword(s):  
South Africa ◽  
Rating Scale ◽  
The United States ◽  
Population Based ◽  
Dominant Hand ◽  
Manganese Exposure ◽  
Disease Rating ◽  
The Mean ◽  
Mn Concentration

Abstract Background Exposure to occupational manganese (Mn) is associated with neurotoxic brain injury, manifesting primarily as parkinsonism. The association between environmental Mn exposure and parkinsonism is unclear. To characterize the association between environmental Mn exposure and parkinsonism, we performed population-based sampling of residents older than 40 in Meyerton, South Africa (N = 621) in residential settlements adjacent to a large Mn smelter and in a comparable non-exposed settlement in Ethembalethu, South Africa (N = 95) in 2016–2020. Methods A movement disorders specialist examined all participants using the Unified Parkinson Disease Rating Scale motor subsection part 3 (UPDRS3). Participants also completed an accelerometry-based kinematic test and a grooved pegboard test. We compared performance on the UPDRS3, grooved pegboard, and the accelerometry-based kinematic test between the settlements using linear regression, adjusting for covariates. We also measured airborne PM2.5-Mn in the study settlements. Results Mean PM2.5-Mn concentration at a long-term fixed site in Meyerton was 203 ng/m3 in 2016–2017 – approximately double that measured at two other neighborhoods in Meyerton. The mean Mn concentration in Ethembalethu was ~ 20 times lower than that of the long-term Meyerton site. UPDRS3 scores were 6.6 (CI 5.2, 7.9) points higher in Meyerton than Ethembalethu residents. Mean angular velocity for finger-tapping on the accelerometry-based kinematic test was slower in Meyerton than Ethembalethu residents [dominant hand 74.9 (CI 48.7, 101.2) and non-dominant hand 82.6 (CI 55.2, 110.1) degrees/second slower]. Similarly, Meyerton residents took longer to complete the grooved pegboard, especially for the non-dominant hand (6.9, CI -2.6, 16.3 s longer). Conclusions Environmental airborne Mn exposures at levels substantially lower than current occupational exposure thresholds in the United States may be associated with clinical parkinsonism.

Contribution of Changes in Sea Surface Temperature and Aerosol Loading to the Decreasing Precipitation Trend in Southern China

2005 ◽  
Vol 18 (9) ◽  
pp. 1381-1390 ◽  
Author(s):  
Yanjie Cheng ◽  
Ulrike Lohmann ◽  
Junhua Zhang ◽  
Yunfeng Luo ◽  
Zuoting Liu ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Indirect Effect ◽  
Southern China ◽  
Early Summer ◽  
Sea Surface ◽  
Convective Precipitation ◽  
Horizontal Wind ◽  
Aerosol Indirect Effect ◽  
Aerosol Loading

Abstract The effects of increasing sea surface temperature (SST) and aerosol loading in a drought region in Southern China are studied using aerosol optical depth (AOD), low-level cloud cover (LCC), visibility, and precipitation from observed surface data; wind, temperature, specific humidity, and geopotential height from the NCEP–NCAR reanalysis fields; and SST from the NOAA archive data. The results show a warming of the SST in the South China Sea and the Indian Ocean, and a strengthening of the West Pacific Subtropical High (WPSH) in the early summer during the last 40 yr, with the high pressure system extending farther westward over the continent in Southern China. Because the early summer average temperature contrast between the land and ocean decreased, the southwesterly monsoon from the ocean onto mainland China weakened and a surface horizontal wind divergence anomaly occurred over Southern China stabilizing the boundary layer. Thus, less moisture was transported to Southern China, causing a drying trend. Despite this, surface observations show that AOD and LCC have increased, while visibility has decreased. Precipitation has decreased in this region in the early summer, consistent with both the second aerosol indirect effect (reduction in precipitation efficiency caused by the more numerous and smaller cloud droplets) and dynamically induced changes from convective to more stratiform clouds. The second aerosol indirect effect and increases in SST and greenhouse gases (GHG) were simulated separately with the ECHAM4 general circulation model (GCM). The GCM results suggest that both effects contribute to the changes in LCC and precipitation in the drought region in Southern China. The flooding trend in Eastern China, however, is more likely caused by strengthened convective precipitation associated with increases in SST and GHG.

Indirect Impact of Atmospheric Aerosols in Idealized Simulations of Convective–Radiative Quasi Equilibrium

2006 ◽  
Vol 19 (18) ◽  
pp. 4664-4682 ◽  
Author(s):  
Wojciech W. Grabowski
Keyword(s):  
Solar Energy ◽  
Indirect Effect ◽  
Cloud Microphysics ◽  
Effective Radius ◽  
Future Research ◽  
Quasi Equilibrium ◽  
Shallow Convection ◽  
Cloud Droplets ◽  
The Mean ◽  
The Impact

Abstract This paper discusses a cloud-resolving modeling study concerning the impact of warm-rain microphysics on convective–radiative quasi equilibrium with fixed surface characteristics and prescribed solar input, both mimicking the mean conditions on earth. Two limits of the concentration of cloud droplets, either 100 cm−3 (referred to as “pristine”) or 1000 cm−3 (referred to as “polluted”), are considered. In addition, three formulations of the effective radius of water droplets in diluted cloudy volumes are used, corresponding to the homogeneous, intermediate, and extremely inhomogeneous mixing scenarios. The assumed concentration of cloud droplets, together with the assumed mixing scenario, affects the local value of the effective radius of cloud droplets (the first indirect aerosol effect, also known as the Twomey effect) and the transfer of cloud water into drizzle and rain, which can affect the mean cloudiness and the hydrologic cycle (the second indirect effect). The convective–radiative quasi equilibrium mimics the estimates of globally and annually averaged water and energy fluxes across the earth’s atmosphere to within less than 10 W m−2. As on earth, the model cloudiness is dominated by shallow convection. It is found that the impact of warm microphysics is dominated by the first indirect effect, whereas the second indirect effect has a smaller impact. The assumed droplet concentration and mixing scenario impact the mean “planetary” albedo and, thus, the amount of solar energy reaching the surface, with all other components of atmospheric energy and water budgets virtually the same in all simulations. The weak second indirect effect highlights the difference between the impact of cloud microphysics on a single cloud and the impact on an ensemble of clouds, with only the latter including the feedbacks between clouds and their environment. The formulation of the effective radius in the diluted cloudy volumes turns out to be of critical importance, with the amount of solar energy reaching the surface being the same in the pristine case assuming the homogeneous mixing scenario and in the polluted case with the extremely inhomogeneous mixing. This result emphasizes the essential role of poorly understood microphysical transformations within diluted convective clouds, which strongly impact the magnitude of the first indirect (Twomey) effect. Implications for future research in this area are discussed.

scholarly journals Influence of Giant CCN on warm rain processes in the ECHAM5 GCM

2007 ◽  
Vol 7 (5) ◽  
pp. 14767-14811 ◽  
Author(s):  
R. Posselt ◽  
U. Lohmann
Keyword(s):  
Wind Speed ◽  
Liquid Water ◽  
Indirect Effect ◽  
Water Mass ◽  
Cloud Condensation Nuclei ◽  
Sea Salt ◽  
Rain Water ◽  
Anthropogenic Aerosol ◽  
Aerosol Indirect Effect ◽  
Cloud Properties

Abstract. Increased Cloud Condensation Nuclei (CCN) load due to anthropogenic activity might lead to non-precipitating clouds because the cloud drops become smaller (for a constant liquid water content) and, therefore, less efficient in rain formation (aerosol indirect effect). Adding giant CCN (GCCN) into such a cloud can initiate precipitation (namely, drizzle) and, therefore, might counteract the aerosol indirect effect. The effect of GCCN on global climate, especially on clouds and precipitation, within a General Circulation Model (GCM) is investigated. GCCN are aerosol particles larger than 5–10 μm in radius that can act as cloud condensation nuclei. One prominent GCCN species is sea salt. Sea salt concentrations depend mainly on wind speed but also on relative humidity, stability and precipitation history. Natural variability is much larger than the simulated one because sea salt emissions within ECHAM5 are a function of wind speed only. Giant sea salt concentrations in ECHAM5 are determined by using the tail of the coarse mode aerosol distribution with cutoff radii of 5 μm or 10 μm. It is assumed that activated GCCN particles directly form rain drops (of 25 μm size). Thereby, the added rain water mass and number stems from the redistribution of the condensed water into cloud and rain water according to the number of activated GCCN. As the formed precipitation is most likely drizzle with rather small drops a prognostic rain scheme is applied to account for the lower fall speeds and, therefore, slower sedimentation of the drizzle drops. The ECHAM5 simulations with incorporated GCCN show that precipitation is affected only locally. Cloud properties like liquid water and cloud drop number show a larger sensitivity to GCCN. On the one hand, the increased rain water mass causes an increase in the accretion rate and, therefore, in the rain production. On the other hand, very high GCCN concentrations can lead to an artificially exaggerated transfer of cloud water to the rain class which then results in a strong decrease of the conversion rate and the rain production. The introduction of the GCCN reduces the anthropogenic increase of liquid water in the atmosphere from pre-industrial to present day because clouds are precipitating faster in the presence of the GCCN. Hence, the accumulation of liquid water in the atmosphere is reduced. According to those changes in the cloud properties, the radiative budget is also changing. The GCCN cause a reduction of the anthropogenic aerosol indirect effect of about 0.1–0.25 W m−2 which corresponds to 5–10% of the total effect. Thus, the GCCN in ECHAM5 partly offset the anthropogenic aerosol indirect effect.

scholarly journals Effect of aerosols on different regime of clouds and their precipitation over Tehran city

2017 ◽  
Vol 19 (4) ◽  
pp. 666-673
Keyword(s):  
Critical Factor ◽  
Tropical Rainfall Measuring Mission ◽  
Ambient Air ◽  
Cloud Droplets ◽  
Cloud Properties ◽  
Moderate Resolution ◽  
The Mean ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Convective Cells ◽  
The Impact

In this study we investigate the impact of aerosols on different cloud regimes and amount of their precipitation over Tehran for the period of 2003-2014, utilizing data from Moderate-Resolution Imaging Spectroradiometer (MODIS), Tropical Rainfall Measuring Mission (TRMM) and surface data from local synoptic stations. The regimes were determined using a k-means clustering method on retrieved cloud properties. The results indicate that in mixed clouds, increase in aerosols has led to increase in the mean cloud effective radius (CER), cloud height as well as lighting and precipitation amounts of weak and moderate convective cells which may be attributed to more freezing of cloud droplets above the 0 °C isotherm and its associated latent heat releases. Vice versa, warm clouds intensity in polluted air condition are weeker than clean air condition. The results also showed that, nimbostratus clouds thickness and their precipitation increase under high aerosol index (AI). Both TRMM and rain gauges data, however, showed that the average amount of precipitation has decreased during polluted episodes in comparison with clean episodes during the period of study. Elaborating on the observed overall changes in the amount of precipitation, it may be concluded that over Seeding was a critical factor in reducing the mean precipitation over Tehran. Also, observed differences on clouds microphysics over different parts of the city may be related to local pollutions, type of ambient air aerosols and topography conditions.

scholarly journals The effectiveness of diabetes education in rural clinical practice

2020 ◽  
Vol 10 (10) ◽  
pp. 7
Author(s):  
Trejon Anshelle Brignac ◽  
Ruby Sheree Miller ◽  
Dell Mars
Keyword(s):  
Glycemic Control ◽  
Nursing Staff ◽  
Statistical Significance ◽  
Diabetes Education ◽  
The United States ◽  
Implementation Period ◽  
Post Test ◽  
The Mean ◽  
Post Hoc

Objective: Type 2 Diabetes affects approximately 10% of the population in the United States. Diabetes is associated with acute and long-term complications are more severe. Studies are providing a correlation between better self-care actions and a reduction of undesired diabetes outcomes. The purpose of this study was to evaluate the implementation of a diabetes self-management education (DSME) program on glycemic control that was expected to improve staff knowledge and diabetes outcomes.Methods: This study conducted a quality improvement design. Providers and nursing staff in three primary care clinics were recruited. Diabetes Knowledge Test (DKT) and HbA1c were measured pre and post intervention.Results: Data from 15 staff participants were analyzed. The mean score for the pre-test was 81% while the mean score for the post-test was 87%. A paired t-test revealed t = 1.533, df = 3.998 and p = .160. The HbA1c percentage mean over 6 months decreased by 0.02% and subsequently in 3 months by 0.17%. The Friedman rank sum test was used to compare the differences, χ2(2) = 14.79, p < .001. Post-hoc analysis identified a statistical significance in the HbA1c from implementation to post implementation.Conclusions: There was an increase in the percent score in the provider and nursing staff knowledge after implementation of the DSME program. A decrease in percent change of the HbA1c was identified over the three- month implementation period. This study demonstrated that the implementation of a DSME program may contribute to improved glycemic control.

Sign in / Sign up

Export Citation Format

Share Document