Refractory black carbon (rBC) plays an important role in aerosol-cloud-radiation interactions, yet in situ observations of rBC incorporation into cloud droplets within deep convective monsoon clouds remain limited. Aircraft-based measurements of ambient and in-cloud rBC were conducted during Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX Phase-IV) over the rain-shadow region of peninsular India. Ambient aerosols were sampled using an isokinetic inlet, while cloud droplet residuals were sampled using a counterflow virtual impactor (CVI) inlet. Ambient rBC concentrations peaked below cloud base (similar to 60-200 cm(-3)) and decreased with altitude, with values typically below 5 cm(-3) above 5 km. In contrast, in-cloud rBC concentrations remained low (<10 cm(-3)) and declined from cloud base to similar to 0.1 cm(-3) at cloud top. Size-resolved in-cloud rBC residuals showed unimodal distributions peaking at similar to 0.18-0.22 mu m, with concentrations 1-2 orders of magnitude lower than ambient rBC, indicating limited rBC incorporation into cloud droplets. Estimated coagulation fractions of rBC remained below 1% and our estimations showed that coagulation alone is insufficient to explain the observed in-cloud rBC concentrations. The estimated ratio of in-cloud rBC to cloud droplet number concentration (CDNC) indicated that less than 3% of cloud droplets contained rBC particles. Clustering-based analysis further showed that the relationship between in-cloud rBC and CDNC varied with cloud dynamical and microphysical conditions. No significant correlation was observed in cloud-core parcels, whereas a weak positive correlation was evident within entrainment regions. These observations provide new constraints on rBC behavior within deep convective monsoon clouds.

A droplet closure study was done using the sub-cloud aerosol and cloud condensation nuclei (CCN) spectra measurements and cloud base droplet measurements collected during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) Phase IV. Six cases with varying aerosol and cloud droplet number concentrations were identified for the study. An adiabatic parcel model with kinetic limitations of aerosols and two commonly used droplet nucleation parameterizations were used to predict the cloud base droplet number concentration. The parcel model provided better closure, especially at higher updrafts, which signifies the role of kinetic limitation during cloud formation. The underprediction at higher updrafts by one of the parametrizations was improved to some extent by increasing the Aitken mode aerosol hygroscopicity to 0.25. Further, attempts were made to test whether region specific mean aerosol characteristics can be used to predict the cloud base droplet number concentration instead of individual observations. The regional mean aerosol size distribution and hygroscopicity estimates during low and high aerosol loading conditions were taken from Varghese et al. (2023) and tuned. 50 nm - 3 μm aerosols described as three lognormal modes were sufficient to produce the observed droplet number concentration within measurement uncertainties for the monsoon cases. At the same time, finer aerosols (20-50 nm) were crucial for the two cases with continental airmass back trajectories. This droplet closure study is the first of its kind from the Indian subcontinent. It highlights the need for accurately representing aerosols in cloud-resolving models and demonstrates the potential of utilizing regional aerosol characteristics to achieve this goal.

Three years (2021 - 2023) of in-situ ground-based observations from a high-altitude site in Western Ghats, India, have been utilized to study the cloud condensation nuclei (CCN) activation and closure during the monsoon (JJAS, June to September), including its transition periods (May and October). Aerosol-CCN characteristics showed an apparent temporal variation between monsoon and its transition periods. The estimated aerosol bulk hygroscopicity (x) showed a narrow (broad) distribution during monsoon (transition periods). Aitken mode was dominant during JJAS, while Aitken-accumulation mode was dominant during the transition periods, suggesting that these modes primarily control the bulk hygroscopicity of the total aerosol population. These further indicate the increased wet scavenging of larger aerosol particles during JJAS compared to transition periods. The CCN closure study was performed using different x values. The analysis showed a good closure in JJAS when x = 0.15 was considered, while the transition periods showed a good closure at various x and supersaturation (SS) values. This suggests that the CCN closure is less sensitive to the change in SS or x during JJAS than the transition periods. Hence, the assumption of a single x (e.g., x = 0.15) or a narrow range of x (= 0.15 - 0.20) can be considered during monsoon, while the same assumption cannot be applied during the transition periods for the study region. To the best of our knowledge, this is the first such study using an extensive set of ground-based observations from the Indian region.

Cloud seeding experiments for modifying clouds and precipitation have been underway for nearly a century; yet practically all the attempts to link precipitation enhancement or suppression to the presence of seeding materials within clouds remain elusive. In 2019, the Cloud–Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) investigated residuals of cloud hydrometeors in seeded and non-seeded clouds with an airborne mini aerosol mass spectrometer (mAMS). The mAMS was utilized in conjunction with a counterflow virtual impactor (CVI) inlet with a cutoff diameter size of approximately 7 µm. The evaporated cloud droplets from the CVI inlet as cloud residuals were evaluated through the mAMS. The chlorine (Cl) associated with hygroscopic materials, i.e. calcium chloride (CaCl2) and potassium (K), which serve as the oxidizing agents in the flares, is found in relatively higher concentrations in the seeded clouds compared to the non-seeded clouds. In convective clouds, Cl and K as cloud residuals were found even at a vertical distance of 2.25 km from the cloud base. Major findings from the seeding impact are an increase in the number concentration of small (< 20 µm) droplets and an indication of raindrop formation at 2.25 km above the cloud base. It is demonstrated that the seed particle signature can be traced inside clouds along with the microphysical impacts.

Combination of radiosonde profiles with collocated in-situ ground and aircraft measurements is used for the first time to study the vertical structure and microphysics of clouds during southwest monsoon over the Western Ghats, India. The morphology of clouds is detailed with the help of radiosonde observations and classified as low, mid, and high-level clouds depending on the cloud base height. Radiosonde sounding profiles indicated occur-rences of both single and multi-layered clouds with higher occurrences of single-layered (-35%) clouds during monsoon transition period (June and September) and two-layered (-42%) during core monsoon period (July and August). Dominance of low (-30%) and high-level (-60%) clouds were noticed compared to mid-level clouds over the observational site during the southwest monsoon.Warm cloud microphysics was investigated using collocated ground and airborne in situ measurements. Irrespective of the cloud type, the cloud liquid water content and the effective droplet diameter increased with altitude. One of the key results is the rapid broadening of the cloud droplet size distribution with height. The number concentration of droplets above 25 mu m diameters showed a steep decrease at altitudes above 1800 m, suggesting active collision-coalescence.

The demand for effective methods to augment precipitation over arid regions of India has been increasing over the past several decades as the changing climate brings warmer average temperatures. In the fourth phase of the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX IV), a scientific investigation was conducted over a rain-shadow region of the Western Ghats mountains in India. The primary objective was to investigate the efficacy of hygroscopic seeding in convective clouds and to develop a cloud seeding protocol. CAIPEEX IV followed the World Meteorological Organization (WMO) recommendations in a peer-reviewed report with physical, statistical, and numerical investigations. The initial results of the campaign in the monsoon period of 2018 and 2019 with two instrumented aircraft, a ground-based dual-polarization C-band radar, a network of rain gauges, radiosondes, and surface aerosol measurements are reported here. The hygroscopic seeding material was detected in cloud droplets and key cloud microphysical processes in the seeding hypothesis were tracked. The formidable challenges of assessing seeding impacts in convective clouds and the results from 150 seed and 122 no-seed samples of randomized experiments are illustrated. Over 5,000 cloud passes from the airborne campaign provided details about the convective cloud properties as the key indicators for a seeding strategy and the evaluation protocol. The experimental results suggest that cloud seeding can be approached scientifically to reduce uncertainty. The results from this study should interest the scientific community and policymakers concerned with climate change’s impact on precipitation and how to mitigate rainfall deficiencies.

&lt;p&gt;Clouds play a significant role in the dynamics and thermodynamics of the atmosphere. To understand the impact of clouds on climate and for better representation of these in the global models, accurate information about the temporal, spatial and vertical distribution of cloud properties such as microphysical, morphological and types are essential. In the present work, vertical structure and microphysics of clouds during southwest (SW) monsoon has been studied from a high altitude site (Mahabaleshwar (17.92&amp;#176;N, 73.66&amp;#176;E, and 1348 m above mean sea level (MSL)) and within &amp;#177; 0.1 degrees) over Western Ghats, India. Vertical structure of the clouds has been detailed using radiosonde observations. Warm cloud microphysics was investigated using in-situ ground and aircraft cloud measurements. Radiosonde profiles showed the presence of single and multi-layered clouds over the observational site. Higher occurrence frequency for cloud layers below 2 km and above 6 km altitude compared to mid-level clouds (2 to 6 km) during SW monsoon were noticed. Higher occurrences of single layer clouds during June and September (transition period) were noticed whereas frequency of two-layer was higher in July and August (core period). Low (~30%) and high-level (~60%) clouds were dominantly seen compared to mid-level clouds over the observational site during SW monsoon. Warm cloud microphysics was investigated using collocated ground and airborne &lt;em&gt;in situ&lt;/em&gt; measurements. Cloud microphysical properties such as cloud droplet number concentration (CDNC), liquid water content (LWC), droplet effective diameter (ED), droplet mean radius (R&lt;sub&gt;m&lt;/sub&gt;) respectively were analyzed. The cloud liquid water content and the effective droplet diameter showed increase with altitude. Analyzed cloud droplet size distribution (DSD) showed a steep decrease in number concentration of droplets above 25 &amp;#181;m diameters at altitudes above 1800 m, suggesting active collision-coalescence. This is the first such report combining in situ observations from two different platforms to study the vertical structure of monsoon clouds over a complex terrain like the Western Ghats in India.&amp;#160;&amp;#160;&lt;/p&gt;

Vertically constrained observations of aerosol size distribution and hygroscopicity using the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) measurements during the monsoon seasons of 2018 and 2019 over a typical global climate model grid area are presented. Two regimes of aerosol loading - low and high, were identified within the season. Low aerosol loading is associated with active monsoon conditions and strong westerlies, while high aerosol loading occurs when the westerly airmass weakens or becomes continental. Aerosol hygroscopicity was the lowest (∼0.08) during low aerosol loading days in 2019 and the highest (∼0.3) during high aerosol loading days in 2018. Aitken mode aerosols control the bulk hygroscopicity on high aerosol loading days and at high supersaturation. The refractory Black Carbon (rBC) aerosols accounted for nearly 10% of the total aerosol number concentration during the monsoon. The internally mixed rBC aerosols had thicker coatings for smaller rBC cores and vice-versa. The cloud condensation nuclei (CCN) closure at the cloud base is established from the in situ observations. These observations are first-of-its-kind from the Indian region, covering two contrasting monsoon seasons, and are useful for studying aerosol-cloud interactions and constraining models.

This data set is obtained from an aircraft campaign Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) conducted over the Indian subcontinent to measure cloud and aerosol properties. Data presented in the paper Black Carbon as residuals of monsoon clouds can be found. The data consist of in-cloud and ambient atmosphere Black Carbon measurements and cloud properties. The data set consists of the following: 1. Mean Aerosol Size Distribution (#/cm**3 ) below cloud base 2. Temperature (°C ), Total Droplet Concentration (#/cm*3 ), Refrectrory Black Carbon (rBC) concentration (#/cm*3 ) 3. rBC mixing state data 4. Data for Figure1, rBC inside the cloud and ambient atmosphere (#/cm**3 ). 5. Mean Relative Humidity (%) and coating thickness (nm) with standard deviations. 6. Scattering Inacasdence Ratio- Scattering Incasdance Time_ Coating thickness 7. Statistics of small drop, mid and large drop concentrations (#/cm**3 )

The properties of carbonaceous aerosols at the rain-shadow region of the Western Ghats of India are studied as part of the Cloud Aerosol Interaction Precipitation Enhancement Experiment (CAIPEEX) during the Indian summer monsoon using optical and thermal methods. The optically derived black carbon (BC) and thermally derived elemental carbon (EC) correlated well (R = 0.9) with a slope value of 1.02. About 1 μg m−3 of mean BC mass concentration is observed with intra-seasonal variations depending upon the wet scavenging during the monsoon. However, rapid recharging of carbonaceous aerosols was observed indicating the presence of local aerosol sources. An enhancement in the absorption Angstrom exponent and the estimated brown carbon (BrC) contribution to absorption is observed during the forenoon hours. High OC/EC ratios (>5) observed over the region indicated the dominance of organic carbon (OC), which reduced (~3.5) subsequently with the onset of monsoon over the region. Primary and secondary organics are estimated from the OC-EC measurements following the novel minimum R-squared (MRS) method. The OC/EC ratio was higher on the intermittent dry days within the monsoon season, during which the primary organic carbon (POC) showed a strong association with the BC mass, indicating common sources for both. Irrespective of the wet and dry days, POC dominated the total carbon loading resulting in the low effective carbon ratio (0.41).

The vertical structure and microphysics of clouds during the southwest monsoon over Western Ghats, India, is studied by combining radiosonde, in-situ ground and aircraft measurements. Radiosonde sounding profiles over Mahabaleshwar (17.92°N, 73.66°E, 1348 m AMSL) indicated occurrences of both single and multi-layered clouds over the region during the monsoon. Depending on the cloud base height, the identified clouds were categorized into low, mid, and high-level clouds. Cloud microphysics was investigated using collocated ground and airborne in-situ cloud measurements. Irrespective of the cloud type, the cloud liquid water content and the effective droplet diameter increased with altitude. The cloud droplet size distribution at the ground (1348 m) quickly broadened towards larger droplets within 400 - 500 m above ground, indicative of the orographic lifting. The number concentration of droplets above 25 µm diameters showed a steep decrease at altitudes above 1800 m, suggesting active collision coalescence. This is the first such report combining in situ observations from two different platforms to study the vertical structure of monsoon clouds over a complex terrain like the Western Ghats in India.

Hygroscopic growth factor and cloud condensation nuclei (CCN) activation properties of aerosols along with their physical and absorption properties were measured during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) over a rain-shadow region, Solapur, India. The hygroscopicity of aerosols at both sub-and supersaturated regimes and the responsible factors are investigated during the Indian Summer Monsoon (ISM). During the intermittent rainy, wet, and cloudy days the total aerosol (& AP; 966 cm(-3)), CCN (& AP; 587 cm(-3) at 0.4% supersaturation, S) number concentrations, and black carbon (& AP; 482 ng m(-3)) mass concentrations were less, which increased to the mean values of & AP; 3754 cm(-3), & AP; 974 cm(-3), and & AP; 892 ng m(-3), respectively during the dry and clear-sky period. Multiple mode aerosol number size distribution prevailed irrespective of the meteorological conditions, while a prominent nucleation mode was observed during the dry conditions. The nucleation mode was consistent from 09:00 hours local time (IST) during the dry conditions, apart from those associated with the local emissions during the sunset. The nucleation mode associated with the sharp enhancement in absorption Angstrom exponent after the BC peak during the early morning hours of dry days indicated the secondary organic aerosol formation. The hygroscopic growth factor measurements at 50 and 150 nm and the hygroscopicity parameter-& UKappa;(HTDMA) values were spread over a wide range. But the mean and the median values were similar for both wet and dry periods. However, the hygroscopicity derived from CCN measurements-& UKappa;(CCN) at 0.2 and 1.0% Ss were higher than the & UKappa;(HTDMA) values. The high & UKappa;(CCN) (& AP; 0.44) during wet conditions reduced to & AP;0.28 during the dry conditions for 1.0% S (corresponding to ~40 nm). The hygro-scopicity and the CCN efficiency of aerosols were high during daytime and from midnight to sunrise for the dry and the wet periods, respectively.

The cloud droplet size distribution (CDSD) and microphysical properties prior to monsoon rain events is studied using in-situ ground observations over a high altitude site in Western Ghats, India. The cloud microphysical properties, such as cloud droplet number concentration (CDNC), liquid water content (LWC), cloud droplet spectrum, droplet effective diameter (ED), droplet mean radius (Rm), spectral width (σ), and relative dispersion (ε) showed a considerable variation. A detailed analysis of CDSD before rain events showed single and multi-mode patterns which varied from case to case. An apparent variation in cloud microphysical properties is noted for both single and multi-mode cases. Large cloud droplets were found in both single and multi-mode clouds, and analysis revealed the possibility of entrainment of aerosols into these clouds leading to multi modes in the CDSD. Observed rain event duration indirectly suggested higher warm rain depths (D*) when multi-mode cases are observed.

Unique airborne observations of aerosol size spectral and chemical characteristics over the peninsular Indian region are illustrated in this case study. Multimodal lognormal distributions were required to fit the observed in situ aerosol size distribution. The aerosol composition and mixing state was deduced from the single-particle analyses of aerosols using the transmission electron microscope and soot photometer coupled with satellite retrieved aerosol classification, and back trajectory analyses. Organic carbon was the most prominent aerosol type found at all altitudes. Refractory black carbon aerosols which constituted about 10-12% of the aerosols in the boundary layer were primarily internally mixed with both inorganic and organic coating. Other major aerosol types were dust and sea salt, with the latter primarily found below 2 km. Further, the cloud forming ability of in-situ aerosols is tested through a cloud condensation nuclei closure analysis. The effective hygroscopicity decreased above cloud base due to the absence of sea salt aerosols. The change in large-scale winds with altitude affected the aerosol composition and hygroscopicity. The multimodal aerosol size distribution and hygroscopicity parameter (Kappa = 0.18) obtained for the cloud base aerosols over the rain shadow region are useful for studying aerosol-cloud interactions using regional cloud-resolving models.

Airborne observations conducted during the Northeast Monsoon onset as part of the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX 2011) are used to link the activation properties of aerosols with the observed cloud microphysics. This study illustrates the significant spatial variability in the aerosol spectrum, cloud condensation nuclei (CCN) activation characteristics, and the cloud droplet spectral properties over a coastal and an inland location. High concentrations of Aitken mode and black carbon aerosols were observed in the free troposphere and are attributed to the convectively transported smoke and aerosols from the coastal boundary layer. The assumption of an internally mixed organic and inorganic aerosol composition provided a better CCN closure over assumptions of either purely organic or purely inorganic aerosols. The coastal clouds were equally polluted as the inland clouds with high cloud droplet number concentrations near the cloud base. The vertical distribution of cloud droplet spectral characteristics was similar in both coastal and inland clouds. An increase in droplet number concentration up to 2 km above the cloud base indicated a prominent influence of submicron particles on the cloud microphysical parameters. Evidence for an enhanced concentration of supercooled drops above the freezing level up to temperatures below -12 degrees C is documented. The secondary ice production was evident through observations of graupel and snow particles. Heavy loading of aerosols near the cloud base leads to enhanced mixed-phase processes in these clouds.

In situ measurements of aerosol particle chemistry and cloud microphysics made during the Cloud–Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) in 2015 over the Western Ghats and its rain shadow region are presented in this study. The high ratio of cloud condensation nuclei (CCN) to large sized aerosol (above 0.1 µm) concentrations indicates Aitken mode aerosols as the major contributor towards the observed CCN. Morphology and chemical composition of airborne aerosol samples collected from different altitudes and the warm cloud layers indicated distinct particle chemistry on the dry and wet days. The majority of the particles sampled were heterogeneous and internally mixed with two or more aerosol species indicating multiple sources and atmospheric aging, even during the wet days. Si-rich particles (up to 73%) were the dominant species in samples collected during dry days when the shallow clouds with narrow drop size distribution were observed. A higher concentration of Na-rich particles (up to 50%) was observed on wet days when the clouds were majorly multiple layers of stratus, which had broader cloud droplet spectra. Internally mixed carbonaceous and iron/cobalt-rich aerosols from local pollution sources were found on both wet and dry days suggesting boundary layer venting of aerosols. Large droplets were observed near the cloud base over the Western Ghats compared to those formed over the rain shadow region.

Continuous aerosol and cloud condensation nuclei (CCN) measurements carried out at the ground observational facility situated in the rain-shadow region of the Indian subcontinent are illustrated. These observations were part of the Cloud Aerosol Interaction Precipitation Enhancement Experiment (CAIPEEX) during the Indian summer monsoon season (June to September) of 2018. Observations are classified as dry–continental (monsoon break) and wet–marine (monsoon active) according to the air mass history. CCN concentrations measured for a range of supersaturations (0.2 %–1.2 %) are parameterized using Twomey's empirical relationship. CCN concentrations at low (0.2 %) supersaturation (SS) were high (>1000cm-3) during continental conditions and observed together with high black carbon (BC∼2000ngm-3) and columnar aerosol loading. During the marine air mass conditions, CCN concentrations diminished to ∼350cm-3 at 0.3 % SS and low aerosol loading persisted (BC∼800ngm-3). High CCN activation fraction (AF) of ≅0.55 (at 0.3 % SS) was observed before the monsoon rainfall, which reduced to ≅0.15 during the marine air mass and enhanced to ≅0.32 after that. There was mostly monomodal aerosol number size distribution (NSD) with a mean geometric mean diameter (GMD) of ≅85 nm, with least (≅9 %) contribution from nucleation mode (<30 nm) particles persisted before the monsoon, while multimode NSD with ≅19 % of nucleation mode particles was found during the marine air mass. Critical activation diameters (dcri) for 0.3 % SS were found to be about 72, 169, and 121 nm prior to, during, and after the marine conditions, respectively. The better association of CCN with aerosol absorption, and the concurrent accumulation mode particles during continental conditions, points to the possibility of aged (oxygenated) carbonaceous aerosols enhancing the CCN activity prior to the marine conditions. An enhancement in CCN concentrations and k values during the daytime along with absorption Ångström exponent was observed during the marine conditions. Best closure obtained using measured critical diameter and ammonium sulfate composition during continental conditions emphasizes the role of aged aerosols contributing to the accumulation mode, enhancing the CCN efficiency. The overestimation of CCN and less hygroscopicity of accumulation mode aerosols during the marine air mass indicate the role of size-dependent aerosol composition in CCN activity during the period.

This study reports on new particle formation (NPF) and characteristic features observed from a rural site falling in the rainshadow of the Western Ghats in peninsular India. A total of 35 NPF events observed during August 2018 January 2019 are classified and analyzed here. The apparent formation rates ranged from 0.2 to 10.0 cm(-3) s(-1), while the growth rates of nucleation mode particles ranged from 1.2 to 13.8 nm h(-1). The frequency of occurrence was least during August (core monsoon) and highest during post-monsoon. The local winds were calm and southeasterly to easterly (from the urban centre) supplying the essential precursor gases during October and November, leading to a frequent occurrence of nucleation events. Observations suggest that an increased condensation sink could limit the NPF while promoting Aitken mode growth. The newly formed particles accounted for about 10-80% of the total aerosol concentration. These newly formed particles were able to act as cloud condensation nuclei after growing to approximately 50 nm with an average activation fraction of 0.4.

Abstract. Continuous aerosol and Cloud Condensation Nuclei (CCN) measurements carried out at the ground observational facility situated in the rain-shadow region of the Indian sub-continent are illustrated. These observations were part of the Cloud-Aerosol Interaction Precipitation Enhancement EXperiment (CAIPEEX) during the Indian Summer Monsoon season (June to September) of 2018. Observations are classified as dry-continental (monsoon break) and wet-marine (monsoon active) according to air mass history. CCN concentrations measured for a range of supersaturations (0.2–1.2 %) are parameterized using Twomey's empirical relationship. CCN concentrations even at low (0.2 %) supersaturation (SS) were high (> 1,000 cm-3) during continental conditions associated with high black carbon (BC~2,000 ng m-3) and columnar aerosol loading. During the marine air mass conditions, CCN concentrations diminished to ~ 350 cm-3 at 0.3 % SS and low aerosol loading persisted (BC~900 ng m-3). High CCN activation fraction (AF) of ~ 0.55 (at 0.3 % SS) were observed before the monsoon rainfall, which reduced to ~ 0.15 during the monsoon and enhanced to ~ 0.32 after that. Mostly mono-modal aerosol number-size distribution (NSD) with a mean geometric mean diameter (GMD) of ~ 85 nm, with least (~ 9 %) contribution from nucleation mode (

Unique airborne observations made congruent to 330 km south of Mt. Everest during the Cloud-Aerosol Interaction Precipitation Enhancement EXperiment (CAIPEEX) 2014 are presented in this case study. These observations provide the vertical profile and elemental composition of aerosols from single particle analysis during the break period. An "aerosol dome" was also documented from the horizontal transect across the Varanasi city. The boundary layer was dominated by light scattering fine mode aerosols mainly a mixture of dust and pollution. The individual particle characterization revealed complex mixing states within the same aerosol aggregate. Externally mixed aerosols were present at the cloud bases. Elemental composition of aerosol particles collected from free atmosphere contained signatures of aged pollution with heavy metals, carbonaceous particles and radioactive elements. Cloud processed aerosols were also noted in the neighborhood of deep convective clouds. Shallow and deep cumulus clouds developing in the haze layer revealed distinct dropsize distributions. Shallow cumulus clouds embedded in the haze layer showed narrow droplet size distribution and were narrower than the ones observed for premonsoon conditions. Deep cumulus tops in the neighborhood of rapidly developing convection showed broad, bimodal droplet size distribution attributing to droplet evaporation and entrainment effects. Aerosol sampling near these cloud tops showed aggregates of particles that are internally mixed.