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In the present study, the seasonal and vertical distributions of key aerosol types and its extinction coefficient (EC) are investigated with an emphasis on the impact of desert dust aerosols on the microphysical properties of cirrus. For this, we obtained near-simultaneous and collocated datasets retrieved from the CALIPSO (Cloud-Aerosol LiDAR and Infrared Pathfinder Satellite Observations), CloudSat, and MODerate-resolution Imaging Spectroradiometer (MODIS) over the Taklimakan Desert (TMD) area situated in Northwest China during 2006–2011. We found that the main aerosol types prevalent over the TMD region are desert dust (DD), polluted dust (PD), and polluted continental/elevated smoke (PC/SE) which accounted for ∼88.38%, ∼10.81%, and ∼0.47%, respectively. The DD type was the most dominant aerosol type during the total observational period due to the nature of the desert underlying surface, and the frequent dust activities occurred over the region. Further, the concentrations of PD and PC/SE were observed larger in winter compared to the other seasons contributing ∼25.66% and 1.42%, respectively. This is likely attributed to increased burning of fossil fuels used for combustion processes in the cold season over Northwest China. On the other hand, the latitudinal distribution total aerosol loading of EC presented the south-to-north gradient with a declined tendency in all seasons due to enhanced amount of dust aerosols transported from the TMD area. Further, the seasonal mean values of total EC over TMD showed a maximum of 0.021 km−1 appeared in spring, with a minimum (0.017 km−1) in autumn. In addition, we also investigated the impact of dust aerosols on the cirrus microphysical properties namely, ice water content (IWC), ice water path (IWP), ice cloud effective radius (IER), ice number concentration (INC), and ice distribution width (IDW). The results showed that dust aerosol can possibly change the microphysical properties of cirrus over the study domain.

The present study elucidates on the evaluation of two versions (V3 and V4.10) of vertical feature mask (VFM) and aerosol sub-types data derived from the Cloud-Aerosol LiDAR and Infrared Pathfinder Satellite Observations (CALIPSO), and its utilization to analyze the impact of dust aerosol on the microphysical properties of cirrus over the Tibetan Plateau (TP). In conjunction to the CALIPSO, we have also used the CloudSat data to study the same during the summer season for the years 2007–2010 over the study area 25–40°N and 75–100°E. Compared to V3 of CALIPSO, V4.10 was found to have undergone substantial changes in the code, algorithm, and data products. Intercomparison of both versions of data products in the selected grid between 30–31°N and 83–84°E within the study area during 2007–2017 revealed that the VFM and aerosol sub-types are in good agreement of ∼95.27% and ∼82.80%, respectively. Dusty cirrus is defined as the clouds mixed with dust aerosols or existing in dust aerosol conditions, while the pure cirrus is that in a dust-free environment. The obtained results illustrated that the various microphysical properties of cirrus, namely ice water content (IWC), ice water path (IWP), ice distribution width (IDW), ice effective radius (IER), and ice number concentration (INC) noticed a decrease of 17%, 18%, 4%, 19%, and 10%, respectively due to the existence of dust aerosol, consistent with the classical “Twomey effect” for liquid clouds. Moreover, the aerosol optical depth (AOD) showed moderate negative correlations between −0.4 and −0.6 with the microphysical characteristics of cirrus. As our future studies, in addition to the present work undertaken, we planned to gain knowledge and interested to explore the impact of a variety of aerosols apart from the dust aerosol on the microphysical properties of cirrus in different regions of China.

The Republic of Kazakhstan, by geographical and climatological conditions, is a key location for the characterization of atmospheric aerosols due to an unprecedented increase of aerosol's concentrations in the recent years. This study presents a 13-year (2003-2015) analysis of the spatiotemporal distributions and trends of aerosol and cloud properties derived from the Moderate Resolution Imaging Spectroradiometer (MODIS)–Aqua (Dark Target–DT) and Ozone Monitoring Instrument (OMI) over Kazakhstan. The spatial patterns of annual mean AOD were generally characterized with low ( 035) AOD centers over Kazakhstan. The respective maximum and minimum values of AOD550 were observed in July (0.22 ± 0.07) and November (0.12 ± 0.03), with an annual mean of 0.18 ± 0.03. The seasonal mean values of AOD was noticed to be maximum (0.21 ± 0.02) during summer and minimum (0.14 ± 0.01) during autumn seasons. The inter-annual variations in AOD showed enhanced AOD values during 2012 (0.23) followed by 2014 (0.21) and low during 2003 (0.15) and 2004 (0.14). The spatial trend analysis revealed an increase in AOD over most parts of the study domain. Also, the most important cloud parameters such as cloud fraction (CF) and cloud effective radius (CER) were investigated to assess their relationship with the AOD over Kazakhstan. It was found that the CF and CER were negatively and positively correlated with AOD over most parts of the study domain attributed to the strong influence of dust and continental background aerosols, respectively. The backward trajectories obtained from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model showed air parcels originating from the Barents Sea, Russia, Europe, China, and the mainland of Kazakhstan. The results derived from the present study gives a sense of aerosol and cloud properties, and form a basis for further research over this unique and unexplored landmass of the Asian Continent.

In this paper, we present the optical and radiative properties of aerosols for the first time measured at Yogi Vemana University (YVU) campus (14.47°N, 78.82°E, 138 m above sea level), Kadapa, a semi-arid region in southern India during December 2013–February 2015. The collocated measurements of aerosol optical depth (AOD) and black carbon (BC) mass concentration are carried out at Kadapa using the ten channels Multi-Wavelength solar Radiometer (MWR) and seven wavelengths Aethalometer, respectively. This work mainly focused on studying the temporal and spectral behavior of aerosol properties, and their implications to the aerosol direct radiative forcing (ADRF). The respective seasonal mean values of AOD at 500 nm were found to be 0.33 ± 0.01, 0.46 ± 0.05, 0.27 ± 0.02 and 0.37 ± 0.06 during the winter, summer, monsoon and post-monsoon, with an annual mean of 0.38 ± 0.18. It is revealed that the Angstrom exponent (AE or α 380–850 ) value was observed to be maximum (minimum) in March (July) with 1.75 ± 0.19 (0.65 ± 0.14) indicates a predominance of fine (coarse) mode aerosols. Added to this, the diurnal variations of BC mass concentration exhibited two maxima with peaks occurred during 07:00–08:00 h and 20:00–21:00 h local time (LT), and a minimum of the afternoon hours around 13:00–16:00 h LT. Further, the AOD-AE relationship was investigated over Kadapa, and the results conclude that the urban-industrial/biomass burning (UI/BB) type aerosols are more dominated during the study period. The OPAC model retrieved single scattering albedo (SSA) at 500 nm was found to vary between 0.83 and 0.92 with relatively lower values during winter, suggest an increase in absorbing type aerosols produced from anthropogenic activities. The SBDART model computed seasonal averaged ADRF within the atmosphere (ADRF ATM ) was found to be 26.7 ± 2.3, 25.1 ± 1.0, 17.8 ± 3.9 and 18.3 ± 2.6 W m −2 during the summer, winter, monsoon and post-monsoon seasons, respectively at Kadapa. This illustrated that the absorption of solar radiation in the ATM is high which produces a significant amount of heating effect, resulted in a maximum atmospheric heating rate of 0.75 K day −1 .

In the present study, the spatial-temporal distribution and estimation of trends of different aerosol optical properties, and related impact factors were investigated over three countries: Ghana, Togo, and Benin along the Gulf of Guinea Coast in Southern West Africa (SWA). For this purpose, long-term satellite derived aerosol optical properties (aerosol optical depth at 550 nm; AOD550, Angstrom exponent at 470–660 nm; AE470-660, and absorption aerosol index; AAI) retrieved from the Moderate-resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) during January 2005–December 2015 were utilized. The annual mean spatial distribution of AOD550 was found to be high (>0.55) over the southern coastal area, moderate-to-high (0.35–0.55) over the central, and low (

A better understanding of aerosol optical, microphysical and radiative properties is a crucial challenge for climate change studies. In the present study, column-integrated aerosol optical and radiative properties observed at a rural site, Mbita (0.42°S, 34.20 °E, and 1125 m above sea level) located in Kenya, East Africa (EA) are investigated using ground-based Aerosol Robotic Network (AERONET) data retrieved during January, 2007 to December, 2015. The annual mean aerosol optical depth (AOD500 nm), Angstrom exponent (AE440–870 nm), fine mode fraction of AOD500 nm (FMF500 nm), and columnar water vapor (CWV, cm) were found to be 0.23 ± 0.08, 1.01 ± 0.16, 0.60 ± 0.07, and 2.72 ± 0.20, respectively. The aerosol optical properties exhibited a unimodal distribution with substantial seasonal heterogeneity in their peak values being low (high) during the local wet (dry) seasons. The observed data showed that Mbita and its environs are significantly influenced by various types of aerosols, with biomass burning and/or urban-industrial (BUI), mixed (MXD), and desert dust (DDT) aerosol types contributing to 37.72%, 32.81%, and 1.40%, respectively during the local dry season (JJA). The aerosol volume size distribution (VSD) exhibited bimodal lognormal structure with a geometric mean radius of 0.15 μm and 3.86–5.06 μm for fine- and coarse-mode aerosols, respectively. Further, analysis of single scattering albedo (SSA), asymmetry parameter (ASY) and refractive index (RI) revealed dominance of fine-mode absorbing aerosols during JJA. The averaged aerosol direct radiative forcing (ARF) retrieved from the AERONET showed a strong cooling effect at the bottom of the atmosphere (BOA) and significant warming within the atmosphere (ATM), representing the important role of aerosols played in this rural site of Kenya. Finally, the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model revealed that aerosols from distinct sources resulted in enhanced loading during JJA.

Over the last two decades, a number of space-borne sensors have been used to retrieve aerosol optical depth (AOD). The reliability of these datasets over East Africa (EA), however, is an important issue in the interpretation of regional aerosol variability. This study provides an intercomparison and validation of AOD retrievals from the MODIS-Terra (DT and DB), MISR and OMI sensors against ground-based measurements from the AERONET over three sites (CRPSM_Malindi, Nairobi, and ICIPE_Mbita) in Kenya, EA during the periods 2008–2013, 2005–2009 and 2006–2015, respectively. The analysis revealed that MISR performed better over the three sites with about 82.5% of paired AOD data falling within the error envelope (EE). MODIS-DT showed good agreement against AERONET with 59.05% of paired AOD falling within the sensor EE over terrestrial surfaces with relatively high vegetation cover. The comparison between MODIS-DB and AERONET revealed an overall lower performance with lower Gfraction (48.93%) and lower correlation r = 0.58; while AOD retrieved from OMI showed less correspondence with AERONET data with lower Gfraction (68.89%) and lowest correlation r = 0.31. The monthly evaluation of AODs retrieved from the sensors against AERONET AOD indicates that MODIS-DT has the best performance over the three sites with highest correlation (0.71–0.84), lowest RMSE and spread closer to the AERONET. Regarding seasonal analysis, MISR performed well during most seasons over Nairobi and Mbita; while MODIS-DT performed better than all other sensors during most seasons over Malindi. Furthermore, the best seasonal performance of most sensors relative to AERONET data occurred during June–August (JJA) attributed to modulations induced by a precipitation-vegetation factor to AOD satellite retrieval algorithms. The study revealed the strength and weakness of each of the retrieval algorithm and forms the basis for further research on the validation of satellite retrieved aerosol products over EA.

The CloudSat and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) are the members of satellite observation system of A-train to achieve the quasi-synchronization observation on the same orbit. With the help of active (CALIOP and CPR) and passive payloads from these two satellites, respectively, unprecedented detailed information of microphysical properties of ice cloud can be retrieved. The ice water content (IWC) is regarded as one of the most important microphysical characteristics of cirrus for its prominent role in cloud radiative forcing. In this paper, we proposed a new joint (Combination) retrieval method using the full advantages of different well established retrieval methods, namely the LIDAR method (for the region Lidar-only), the MWCR method (for the region Radar-only), and Wang method (for the region Lidar-Radar) proposed by Wang et al. (2002). In retrieval of cirrus IWC, empirical formulas of the exponential type were used for both thinner cirrus (detected by Lidar-only), thicker cirrus (detected by radar-only), and the part of cirrus detected by both, respectively. In the present study, the comparison of various methods verified that our proposed new joint method is more comprehensive, rational and reliable. Further, the retrieval information of cirrus is complete and accurate for the region that Lidar cannot penetrate and Radar is insensitive. On the whole, the retrieval results of IWC showed certain differences retrieved from the joint method, Ca&Cl, and ICARE which can be interpreted from the different hypothesis of microphysical characteristics and parameters used in the retrieval method. In addition, our joint method only uses the extinction coefficient and the radar reflectivity factor to calculate the IWC, which is simpler and reduces to some extent the accumulative error. In future studies, we will not only compare the value of IWC but also explore the detailed macrophysical and microphysical characteristics of cirrus.

The present study is aimed at analyzing spatial and temporal characteristics of aerosols retrieved from MODerate resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) sensors over East Africa (EA). Data spanning for a period of 15 years during 2001–2015 was used to investigate aerosol optical depth (AOD550), Angstrom exponent (AE470-660) and absorption aerosol Index (AAI) over EA and selected locations within EA. Validation results of MODIS-Terra versus the Aerosol Robotic NETwork (AERONET) AOD550 revealed that the former underestimated aerosol loading over the studied regions due to uncertainties in surface reflectance. The annual mean AOD550, AAI, and AE470-660 were found to be 0.20 ± 0.01, 0.81 ± 0.03, and 1.39 ± 0.01, respectively with peak values observed during the local dry seasons. The spatial seasonal distributions of mean AOD550 suggested high (low) values during the local dry (wet) periods. The high AOD values found along the borders of southwest of Uganda were attributed to smoke particles; while higher (lower) values of AE470-660 (AAI) dominated most parts of the study domain. Low AOD (0.1–0.2) centers were located in high-altitude regions with relatively high vegetation cover over western and central parts of Kenya, and central and northern parts of Tanzania. Furthermore, latitudinal and longitudinal gradients in AOD550 showed a “southern low and northern high” and a “western low and eastern high” profile, respectively during JJA, as other seasons showed heterogeneous variations. Trend analysis revealed a general increase in AOD and AAI and a decrease in AE; while impact factors significantly affected AOD distribution over EA. HYSPLIT back trajectory analyses revealed diverse transport pathways originated from the Arabian Deserts, central Africa, and southwest of Indian Ocean along with locally produced aerosols during different seasons.

Aerosol optical properties are continuously measured at a semi-arid station, Anantapur from June 2012 to May 2013 which describes the impact of surface aerosols on climate change over the region. Scattering coefficient (σ sct ) and absorption coefficient (σ abs ) are obtained from integrating Nephelometer and Aethalometer, respectively. Also, the single scattering albedo (ω 0 ), Scattering/absorption Angstrom exponents were examined during the period of study. Diurnal variations of σ sct and σ abs show a bi-peak pattern with two maxima and one minimum in a day. The largest values of σ sct and σ abs are obtained in winter while the lowest values are measured in monsoon. From the measurements σ sct 550 and σ abs 550 are found to be 110 ± 12.23 Mm − 1 and 33 ± 5.2 Mm − 1 , respectively during the study period. An analysis of the ω 0 suggests that there is a more absorbing fraction in the particle composition over the measurement site. The ω 0 obtained in the surface boundary layer of Anantapur is below the critical value of 0.86 that determines the shift from cooling to warming. A relationship between scattering/absorption coefficients and scattering/absorption Angstrom exponent and single scattering albedo is further examined. In order to understand the origins of the air masses in the study region, we performed seven-day back trajectory analyses based on the NOAA HYSPLIT model. These trajectories were computed at several altitudes (3000 m, 1500 m, and 500 m) for June 2012 and May 2013. These results put in evidence the need of efforts to reduce absorbing particles (black carbon) emissions to avoid the possible warming that would result from the reductions of the cooling aerosol only.

The present study aims to investigate spatio-temporal evolution and trend in the aerosol optical properties (aerosol optical depth, AOD; Angstrom exponent, AE), qualitatively identify different types and origin of aerosols over an urban city, Nanjing in the Yangtze River Delta, East China. For this purpose, the Collection 5.1 Level-2 data obtained from the Moderate resolution Imaging Spectroradiometer (MODIS) sensor onboard Terra and Aqua satellites and the Multi-angle Imaging Spectroradiometer (MISR) instrument for the period between 2002 and 2014 have been analyzed. An inter-comparison and validation of AOD were performed against the AOD measurements obtained from the ground-based Aerosol Robotic Network (AERONET) sunphotometer. The MODIS AOD 550 exhibited wide spatial and temporal distributions over East China, while MISR AOD 555 was consistently lower than that of Terra and Aqua AOD 550 values. The temporal variations (monthly and seasonal mean) of MODIS (Terra and Aqua) and MISR AOD values exhibited a similar pattern. The seasonal mean AOD 550 (AE 470–660 ) was found to be maximum with 0.97 ± 0.48 during summer (1.16 ± 0.33 in summer) and a minimum of 0.61 ± 0.28 during the winter season (0.80 ± 0.28 in spring). The annual mean Terra AOD 550 at Nanjing showed a strong decreasing trend (− 0.70% year − 1 ), while the Aqua exhibited a slight increasing trend (+ 0.01 year − 1 ) during the study period. Seasonal air mass back-trajectories obtained from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model were also computed to infer on the transport component over the study region. Different aerosol types were identified via the relationship between AOD 550 and fine mode fraction, which reveals that the biomass burning/urban-industrial type aerosols (desert dust) are abundant over the region in summer (spring), apart from the mixed aerosol type.

To build a long-term database and improve the accuracy of the satellite products used for aerosol studies, there is a need to carry out intercomparison and validation of these satellite observations with ground-based measurements. With this objective, we estimated the long-term inter-annual variations and percentage change in trends of aerosol optical depth (AOD) retrieved from MODerate resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectro-Radiometer (MISR) sensors for a 10-year period during 2004–2013 over two distinct sites namely, Skukuza (SKZ; 24.99°S, 31.58°E) and Richards Bay (RBAY; 28.8°S, 21.1°E) in South Africa. The validation performed over SKZ site shows that MISR was better correlated with AErosol RObotic NETwork (AERONET) when compared to Terra and Aqua satellites of MODIS. Later both the MODIS products (Terra and Aqua) were compared on the annual and seasonal basis to derive the relationship between them through scattering plot. The long-term regression analysis performed at these sites shows that the annual trends were decreasing, with the MODIS products underestimating MISR. This is due to difficulties of the MODIS algorithm when dealing with highly complex surface reflectance conditions and aerosol model assumptions. Also, the temporal variations of AOD derived from the two sensors noticed maximum in spring (September/October) and minimum in winter (June). Further, the Ultra-Violet Aerosol Index (UVAI) retrieved from the Ozone Monitoring Instrument (OMI) at the two locations for 9 years (2005–2013) showed a significant increasing trend with a high value of +0.009 yr −1 at SKZ than +0.006 yr −1 at RBAY during the study period, which is due to the transport of dust and smoke particles.

Cirrus plays an important role in the regulation of the Earth-atmosphere radiation budget. The joint observation using both the LIght Detection And Ranging (LIDAR) and Millimeter-Wave Cloud RADAR (MWCR) was implemented in this study to obtain properties of cirrus at Atmospheric Radiation Measurement (ARM) mobile facility in Shouxian (32.56°N, 116.78°E, 21 m above sea level), China during May–December 2008. We chose the simultaneous measurements of LIDAR and MWCR with effective data days, and the days must with cirrus. Hence, the cirrus properties based on 37 days of data between October 18th and December 13th, 2008 were studied in the present work. By comparing the LIDAR data with the MWCR data, we analyzed the detection capabilities of both instruments quantitatively for measuring the cirrus. The LIDAR cannot penetrate through the thicker cirrus with optical depth (τ) of more than 1.5, while the MWCR cannot sense the clouds with an optical depth of less than 0.3. Statistical analysis showed that the mean cloud base height (CBH) and cloud thickness (CT) of cirrus were 6.5±0.8 km and 2.1±1.1 km, respectively. Furthermore, we investigated three existing inversion methods for deriving the ice water content (IWC) by using the separate LIDAR, MWCR, and the combination of both, respectively. Based on the comparative analysis, a novel joint method was provided to obtain more accurate IWC. In this joint method, cirrus was divided into three different categories according to the optical depth (τ≤0.3, τ≥1.5, and 0.3

This paper presents aerosol light absorption measurements using a seven channel Aethalometer (AE-42), recorded during September 2011–November 2012 over a tropical semi-arid site in Kadapa, India. The annual average black carbon (BC) mass concentration ([BC]) during the studied period was 2.20 ± 0.78 μg m − 3 which is in agreement when compared to other sites of similar environment. Strong seasonal variation was observed with high values during winter (2.87 ± 0.81 μg m − 3 ) and low in monsoon (1.30 ± 0.31 μg m − 3 ) season, which could be attributed to regional synoptic meteorology and long range transport. The two peaks in diurnal variations of [BC] were observed during morning between 06:00 and 08:00 h local time (LT) and in the evening around 19:00–21:00 h LT, with a minimum peak in the afternoon (~ 16:00 h LT) which is strongly correlated with the boundary layer dynamics, local and regional sources, and associated meteorology. The relationships between measured [BC] and the corresponding meteorological parameters for the studied region were also analysed. The estimated monthly mean spectral absorption coefficient values range from 0.56 to 1.15 with an average of 0.90, which suggests high BC/OC ratio and possible source of emission of aerosols is fossil fuel burning. Trajectory cluster analysis showed significant impact of long range transport of BC aerosols towards the observational site during the period of study.

Black carbon (BC) aerosols were measured using a seven channel Aethalometer at a suburban site of Nanjing, East China from January 2015 to December 2016 to study its temporal variations and quantify the magnitude of BC from fossil fuel (BCff) and biomass burning (BCbb) sources. The mean BC mass concentration was observed to be 2200 ± 1309 ng/m3 at the sampling site during the entire observation period, with the highest (lowest) concentrations found in the winter (summer and spring). A distinct diurnal variations in BC revealed with two maximum peaks occurred between 06:00 and 09:00 local time (LT) and 19:00 and 22:00 LT in all four seasons, was correlated with source emissions, meteorology, and dynamics of the atmospheric boundary layer. A significant seasonality was observed in the absorption Angstrom exponent (α) with higher in spring and winter seasons, and lower during the summer. Further, it is evident that the contribution of BCff (BCff%) dominated during the observation period with the mean contributions of BCff % and BCbb% to the BC were found to be ~81% and 19%, respectively. Similar to α, BCbb% also exhibited high fractions in spring and winter suggests an enhanced contribution from biomass burning sources, and a low in summer. The results from both the potential source contribution function (PSCF) and concentration weighted trajectory (CWT) models indicated that the air masses originating from the northern Zhejiang and Anhui provinces were the potential source areas responsible for the high BC concentrations attributed from agricultural waste burning in Nanjing.

The present study represents the characteristics of aerosol optical depth (AOD) retrieved from multiple satellite sensors (MODerate resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging SpectroRadiometer (MISR), and Ozone Monitoring Instrument (OMI)) during 2003–2013 over an urban–coastal region, Durban (DBN; 29.88°S, 31.02°E, 46 m°asl), situated on the east coast of South Africa. An intercomparison and validation of AOD is performed against the AOD measurements from ground-based AErosol RObotic NETwork (AERONET) Sunphotometer. The results revealed that MISR-AERONET comparison indicated strong correlation compared to MODIS-AERONET comparison. Also, the comparison between MODIS and MISR AODs noticed significant positive correlation over DBN with the overestimation of latter by former. Highest AOD characterizes during the spring (September–November) followed by summer (December–February) and autumn (March–May) with the lowest AOD observed during the winter (June–August) season. The Angstrom exponent (AE470–600) indicates predominance of fine-mode aerosols during spring and summer and dominance of coarse-mode aerosols in winter. A HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model is used to locate the origin of airmass transport and understand the variability of aerosol source regions. Finally, the relationship between AOD and AE has been examined to classify different aerosol types and showed seasonal heterogeneity in their contribution depending upon variability in sources. This is the first ever attempt to classify aerosols over this environment.

The present study is aimed to analyze the spatial and temporal distributions, and trends and variations in aerosol optical properties during the last decade. For this we used the aerosol optical depth (AOD550), Angstrom exponent (AE, α470–660) and fine mode fraction (FMF) products derived from the Moderate resolution Imaging Spectroradiometer (MODIS) on board Terra satellite during the period December 2003–November 2013 over three different aerosol environments in South Africa (SA). The spatial pattern of annual mean AOD is characterized with high (low) AOD in the north (south) and with a moderate AOD in the central part of SA. A decadal decrease in AOD has been noticed by performing linear trend analysis over the three stations (Pretoria, Bloemfontein and Cape Town). The seasonal and inter-annual variability of AOD values over three locations of SA showed that the higher mean AOD values occurred during spring (September) and summer (January/February) seasons, whereas the lower values were found in the late autumn/early winter periods (June). On seasonal basis, the decadal climatological variations showed a decreasing trend in different seasons except during spring. The HYSPLIT back trajectory model was used to identify airmass transport pathways originated from aerosol source regions during the dry and wet seasons.

Background It has been debated as to whether the polarity of mood disorder (bipolar versus unipolar) has prognostic significance for electroconvulsive therapy (ECT) outcome. In the treatment guidelines, ECT is recommended more readily for unipolar depression and not so for bipolar depression. This study aims to examine efficacy of bipolar and unipolar depression to ECT in a real life naturalistic setting. Method We studied the ECT parameters of all consecutive patients with a diagnosis of unipolar depression (recurrent depressive disorder, ≥2 episodes of depression) and bipolar depression referred for ECT between the months of July 2008 and December 2010 (BP-D: n = 44) and (UP-D: n = 106). Results When bipolar depression was compared to unipolar depression, the average motor seizure duration (mean = 46.9 and 46.7, t = −0.06, p = 0.94), number of ECTs required for improvement (mean = 6.4 and 6.5, t = 0.17, p = 0.86), duration of inpatient stay after ECT initiation in days (mean = 16.2 and 16.6, t = 0.23, p = 0.81) and improvement as assessed using a Likert scale (Mann–Whitney U , Z = −0.09, p = 0.92) were not statistically different between the groups. Conclusions We did not find any difference in efficacy of ECT between the two forms of depression in real life setting. This calls for justification of use of ECT in all patients with depression irrespective of the type of illness polarity and inclusion of ECT as a routine treatment option in bipolar depression guidelines.

Remote sensing of global aerosols has generated a great scientific interest in a variety of applications related to global warming and climate change. The spatial and temporal variations in aerosol particles over Southern India were described in the present study and the impact of these variations on various optical properties of clouds, using Moderate Resolution Imaging Spectroradiometer (MODIS) data retrieved from the Terra satellite. High mean Aerosol Optical Depth (AOD) values were observed in almost all regions during the summer season, whereas in Pune, Visakhapatnam and Hyderabad, high AOD values were noticed during the monsoon season. The Angstrom exponent that increases with AOD is opposite to what would be the case if swelling of particles due to hygroscopic growth near cloudy areas played a major role in the MODIS data. We then analyzed the relationships between AOD and four other cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP). Regional correlation maps and time series plots for aerosol (AOD) and cloud parameters were produced to provide a better understanding of aerosol–cloud interaction. The correlation between AOD and CF was greater than 0.51 in Visakhapatnam, 0.45 in Thiruvanantapuram, 0.42 in Pune and whereas in Bangalore, Hyderabad and Anantapur, it is 0.17, 0.39 and 0.12, respectively. The analyses showed strong positive correlations between AOD and WV for all cities investigated. The correlation between AOD and CF was positive for all selected cities. AOD showed a negative correlation with CTP and CTT in Southern Indian regions.

Collocated measurements of black carbon (BC) and composite aerosol mass concentrations were continuously monitored at Anantapur (14.62°N, 77.65°E, 331 m asl), a tropical semi-arid station in southeastern region of India, using Aethalometer and a ten-channel Quartz Crystal Microbalance (QCM) cascade impactor, respectively during August 2009–July 2010. Diurnal and seasonal variations of BC and near surface aerosols in relation to changes in the regional meteorological conditions, frequency distribution of BC for different seasons, week days and weekend days effect on BC concentration and size distributions of near surface aerosols were observed. Also, using the HYSPLIT model, back-trajectories were studied to assess the sources for transported particles. Diurnal variation of BC showed two peaks, one in the morning and another in the evening, which were mostly related to the daily changes in the local boundary layer. BC concentrations were maximum during the winter (4.76 ± 0.97 μg m−3), and minimum concentrations were observed in the monsoon (1.44 ± 0.26 μg m−3). The total mass concentration exhibits a high value in the summer (48.89 ± 2.57 μg m−3) and it remains low in the monsoon (30.33 ± 1.65 μg m−3) period. The maximum BC mass fraction was found to be 9.4% in the winter and a minimum of 4.6% in the monsoon.

In the present study, collocated and simultaneous data on spectral aerosol optical depth (AOD), mass concentration and size distribution of near-surface composite aerosols and black carbon aerosol mass concentrations were obtained from Microtops-II Sunphotometer, Quartz Crystal Microbalance (QCM) and Aethalometer, respectively, over an urban location, Tirupati (India) in the month of May 2009. The mean AOD at 500 nm and Angstrom parameters (α, β) during this period were obtained as 0.64±0.13 and 0.89±0.24, 0.36±0.10, respectively. The total surface aerosol mass concentration varied from 13 to 60 μg m−3 out of which coarse mode dominated by 39%. The mean value of total mass concentration of aerosols was 23.80±0.25 μg m−3. The Angstrom wavelength exponent (α) showed a positive correlation of 0.60 with the near-surface fine-mode fraction. The total mass concentration showed positive and negative correlations of 0.72 and 0.68 with air temperature and relative humidity, respectively. Along with this, the diurnal variation of black carbon aerosol concentration varied from 2 to 14 μg m−3 and observed prominently a sharp fumigation peak at around 07:00–09:00 h and the nocturnal peak between 20:00 and 22:00 h with a low value in afternoon hours (15:00 h) with a mean BC mass concentration of 3.76±0.23 μg m−3. A scatter plot between BC mass concentration (Mb) and total surface mass concentration (Mt) showed significant positive correlation of 0.73 and was used to estimate mean mass fraction (FBC) for the study period, which was found to be 8.1±0.5%.

Black carbon (BC) aerosol mass concentrations measured using an aethalometer at Anantapur, a semi-arid tropical station in the southern part of peninsular India, from August 2006 to July 2007 are analyzed. Seasonal and diurnal variations of BC in relation to changes in the regional meteorological conditions have been studied along with the mass fraction of BC to the total aerosol mass concentration (M-t) and fine particle mass (FPM) concentration in different months. The data collected during the study period shows that the annual average BC mass concentration at Anantapur is 1.97 +/- 0.12 mu g m(-3). Seasonal variations of BC aerosol mass concentration showed high during the dry (winter and summer) seasons and low during the post-monsoon followed by the monsoon seasons. Diurnal variations of BC aerosols attain a gradual build up in BC concentration from morning and a sharp peak occurs between 07:00 and 09:00 h almost an hour after local sunrise and a broad nocturnal peak from 19:00 to 21:00 h with a minimum in noon hours. The ratio of BC to the fine particle mass concentration was high during the dry season and low during the monsoon season. The regression analysis between BC mass concentration and wind speed indicates that, with increase in wind speeds the BC mass concentrations would decrease and vice-versa. Aerosol BC mass concentration shows a significant positive correlation with total mass concentration (M-t) and aerosol optical depth (ACID, tau(p)) at 500 nm. (C) 2010 Elsevier B.V. All rights reserved.

Aerosol measurements over a tropical semi-arid site in Anantapur (14.62°N, 77.65°E, 331 m asl), India, provide the variabilities of aerosol characteristics for the period of January 2007–December 2008. The mean values of aerosol optical depth at 500 nm (AOD500 nm) over 2-year period are found to be 0.37 ± 0.11, 0.39 ± 0.13 and 0.30 ± 0.10 during winter, summer and monsoon seasons, respectively. A rather systematic variation is seen with AOD peaking in the month of March, falling off gradually to the lowest value in June and increasing slowly superposed with some modulations, which show a weak secondary peak in October. The mean and standard values of the Angstrom exponent, α (turbidity coefficient, β), are found to be 1.06 ± 0.33 (0.17 ± 0.05) during winter, 0.97 ± 0.35 (0.22 ± 0.04) during summer and 0.85 ± 0.26 (0.16 ± 0.06) during monsoon. The frequency distribution of α is relatively broad with two modes for dusty (α 1) situations. This frequency distribution of α reveals a great dispersion of a values in all seasons thus denoting variability in the aerosol-size distribution. In this study, spectral AOD and Angstrom exponent data are analyzed to obtain information about the adequacy of the simple use of the Angstrom exponent and its variation for characterizing optical properties of aerosols, and exploring possibilities for a more efficient characterization of them. Using the least-squares fit method, the Angstrom parameter, α, is calculated in the spectral interval 380–850 nm, along with coefficients a1 and a2 of the second-order polynomial fit to the plotted logarithm of AOD versus the logarithm of wavelength. The correlations between the coefficients a1 and a2 with months and α are discussed in the paper.

Comprehensive investigations during the last decade have clearly established that aerosols have a significant impact on the climate. This paper reports the results of the spatial variations in aerosol optical depth (AOD) and fine mode fraction (FMF) characteristics as a function of latitude and longitude over the Bay of Bengal (BoB) and the Northern Indian Ocean (NIO) during ICARB-W cruise period of 27th December 2008–30th January 2009 from onboard Sunphotometer and MODIS (Terra, Aqua) satellite measurements. Very high AOD500 (0.7–0.8) occurred over the north head BoB adjacent to the northeastern Indian coast and the lowest AOD500 (0.1–0.2) occurred in central BoB far away from the coasts, and in a small area in the northeastern part close to Myanmar coast as well as over NIO. The highest values (as high as 1.2) of Angstrom exponent, α occurring over northeast BoB (regions close to Bangladesh and Myanmar) indicate relative abundance of accumulation mode particles and very low values of α (below 0.7) over central part of BoB as well as southern BoB/NIO suggesting dominance of coarse-mode sea spray aerosols. Terra/Aqua MODIS AOD550 and cruise measured AOD500 using Sunphotometer showed good agreement (R2 = 0.92) over the BoB. The total mass concentrations over BoB during cruise period were remarkably high, with a mean value of 28.4 ± 5.7 μg m−3. Aerosol FMF was higher than 0.7 over the BoB, while FMF over NIO was about 0.5. NCEP reanalysis data on winds at 850 hPa, along with 5-days airmass back trajectories via HYSPLIT model, suggested transport of continental aerosols from the central and northern India over the BoB by the strong westerly/northwesterly winds. Regionally averaged clear sky aerosol (net) forcing over BoB during the winter is −28.9 W m−2 at the surface and −10.4 W m−2 at the top of the atmosphere whereas, the ARF values estimated over NIO at TOA, surface and in the atmosphere are −6.4, −18.3 and +11.9 W m−2, respectively.

Continuous measurements of surface ozone (O 3 ) at a semi-arid rural site (14.62°N, 77.65°E) in Anantapur, India during the period from December 2008 to July 2009 are presented. The diurnal variation in O 3 shows high concentrations (in the range of 25–77 ppbv) during daytime and low concentrations during late evening and early morning hours, due to slower titration of ozone by oxides of nitrogen (NO x ). The monthly average high (low) O 3 is 56.09 ± 10.1 ppbv (27.45 ± 2.3 ppbv) at noon in March (July), due to a possible increase in precursor gas concentration by anthropogenic activity and also due to the influence of local meteorological conditions. Furthermore, O 3 concentration has been observed as a function of season, which shows that the highest O 3 concentration is 52.05 ± 10.2 ppbv in the summer and the lowest 30.96 ± 5.7 ppbv in the monsoon season. The rate of the increase of surface ozone is high (2.11 ppbv/h) in March and low (0.32 ppbv/h) in July. Among the meteorological parameters, daily average ozone shows a significantly positive correlation with temperature (R = 0.76) and negative correlation with relative humidity (R = − 0.62). Throughout the study period, high ozone concentrations were mainly associated with the winds from 150.5° to 260.1°. The weekend ozone effect indicates that higher O 3 concentration on weekend compared to weekday suggests that the photochemical production of O 3 is non-linear over this site. The results also show that high aerosol concentration has very strong impact on photochemical activities and ozone formation. The correlation between ozone and aerosol concentrations appears in a non-linear feature. Backward trajectory analysis shows that the increase of ozone concentration and the relatively constant high ozone concentrations during the summer might originate from the transport of ozone rich airmass above the boundary layer especially in Northern India and East Asian regions. On the other hand, the airmasses coming from the south over the Indian Ocean contributes low amount of ozone during the monsoon.

The spectral and temporal variations of aerosol optical depths (AOD) observed over Anantapur (a semi-arid region) located in the Southern part of India are investigated by analyzing the data obtained from a Multiwavelength Solar Radiometer (MWR) during January 2005-December 2006 (a total of 404 clear-sky observations) using the Langley technique. In this paper, we highlighted the studies on monthly, seasonal and spectral variations of aerosol optical depth and their implications. The results showed seasonal variation with higher values during pre-monsoon (March-May) and lower in the monsoon (June-November) season at all wavelengths. The pre-monsoon increase is found to be due to the high wind speed producing larger amounts of wind-driven dust particles. The post-monsoon (December-February) AOD values decrease more at higher wavelengths, indicating a general reduction in the number of bigger particles. Also during the post-monsoon, direction of winds in association with high or low pressure weather systems and the air brings more aerosol content to the region which is surrounded by a number of cement plants, lime kilns, slab polishing and brick making units. The quantity of AOD values in pre-monsoon is higher (low during post-monsoon) for wavelength, such as shortwave infrared (SWIR) or near infrared (NIR), which shows that coarse particles contribute more compare with the sub-micron particles. The composite aerosols near the surface follow suit with the share of the accumulation mode to the total mass concentration decreasing from approximately 70% to 30% from post-monsoon to pre-monsoon. Coarse mode particle loading observed to be high during pre-monsoon and accumulation mode particles observed to be high during post-monsoon. The backward trajectories at three representative altitudes with source point at the observing site indicate a possible transport from the outflow regions into Bay of Bengal, southern peninsular India and Arabian Sea. The temporal variations of AOD, Angstrom wavelength exponent and precipitable water content over Anantapur have also been compared with those reported from selected locations in India.

Thermo-acoustical parameters of liquid mixtures viz., Acetone, Methyl Iodide and Acetone + Methyl Iodide have been evaluated at different temperatures in terms of the coefficient of volume expansion, on the assumption that the Moelwyn–Hughes parameter has been utilized to establish some simple relations between the lattice Gruneisen parameter, Beyer's non-linearity parameter, the Anderson–Gruneisen parameter and the Sharma constant. A relationship among the isobaric, isothermal and isochoric microscopic (lattice) Gruneisen parameters have been studied and analysed in the case of liquid mixtures. The Sharma's parameter S 0 remains invariant with the temperature over a wide range of temperatures and retains its characteristics value i.e., 1.11 ± 0.01 as observed in case of liquid systems. The present treatment has the distinct advantage of calculating available volume ( V a ) and intermolecular free-length ( L f ) through Moelwyn–Hughes parameter mainly. Analysis of such type is not found so far in literature.

Northern regions of India experience severe fog conditions during the winter period (December–January) each year. In the present study, concurrent measurements of black carbon aerosols (BC), Carbon monoxide (CO), Surface Ozone (O 3 ) and oxides of Nitrgen (NO x ) have been carried out in Allahabad, located in northern India in order to understand the impact on pollutant concentrations during fog periods. The results of the present study show higher concentrations of BC, NO x and CO during morning and late night hours in the study area. Diurnal variations of ozone concentrations varied from 14 ppbv to 35 ppbv and were observed to increase gradually after sunrise attaining a maximum value by evening time and to decrease gradually thereafter. Concentrations of BC, NO x , O 3 and CO were found to be very low during fog periods over the study area. BC showed a positive correlation with CO and a negative correlation with surface ozone concentrations. The slope between black carbon aerosols and ground level ozone suggests that every 1 μg m − 3 increase in black carbon aerosol mass concentration causes a reduction of 0.7 μg m − 3 surface ozone.