Measurement report: Altitudinal variation of cloud condensation nuclei activation across the Indo-Gangetic Plain prior to monsoon onset and during peak monsoon periods: results from the SWAAMI field campaign

Abstract

Abstract. Vertical distributions (altitude profiles) of condensation nuclei (CN) and cloud condensation nuclei (CCN) and their spatial variations across the Indo-Gangetic Plain (IGP) have been investigated based on airborne measurements carried out during the SWAAMI field campaign (June to July 2016) capturing the contrasting phases of the Indian monsoon activity in 2016 just prior to its onset and during its active phase. Prior to the monsoon onset, high concentrations of CN and CCN prevailed across the IGP, and the profiles revealed frequent occurrence of elevated layers (in the altitude range 1–3 km). Highest concentrations and elevated peaks with high values occurred over the central IGP. The scenario changed dramatically during the active phase of the monsoon, when the CN and CCN concentrations dropped (CN by 20 % to 30 % and CCN by 6 % to 25 %) throughout the IGP with more pronounced changes at altitudes higher than 3 km where decreases as high as > 80 % were observed. These reductions have an east-to-west decreasing gradient, being most remarkable in the eastern IGP and very weak over the western IGP where the CN concentrations above 3 km increased during the monsoon. The activation ratios (ARs) showed contrasting features, increasing with increase in altitude, prior to the onset of monsoon, reversing the trend to decrease with increase in altitude during the active phase of the monsoon. The supersaturation spectrum became flatter during the active phase of the monsoon, indicating an increase in the hygroscopicity of aerosols following the mixing of surface-based emissions with the advected marine air mass.

Particle Number Size Distribution of Wintertime Alpine Aerosols and Their Activation as Cloud Condensation Nuclei in the Guanzhong Plain, Northwest China

“…However, when the SS was 1.0%, the contribution of CCN come from the particles in the full accumulation mode and part of Aitken mode. Thus, the contribution of particles from Aitken mode becomes larger when the SS increased to a high value in the cloud processes (Arub et al., 2020; Manoj et al., 2021; Patel & Jiang, 2021; Rejano et al., 2021; H. Wang et al., 2014).…”

Source Apportionment of Cloud Nuclei at 260 m and Ground Level in Urban Beijing

“…Researches have been carried out on the quantitative evaluation of cloud nuclei formed from aerosol activation on different measurement platforms at various heights. The CCN activation property and vertical profiles at or above the cloud base can be directly observed from in situ airborne instruments (Z. Cai et al., 2022; J. Li et al., 2015; Manoj et al., 2021), or can be retrieved from remotely sensed data from the surface or from satellites (Andreae, 2009; Rosenfeld et al., 2014; R. Zhang et al., 2022). However, the inversion of cloud nuclei from satellites is still with large uncertainties at present.…”

Vertical profiles of cloud condensation nuclei number concentration and its empirical estimate from aerosol optical properties over the North China Plain

“…A commonly used platform to observe vertical distributions of N CCN and CCN activation ability is an aircraft (e.g., J. Li et al, 2015b;Jayachandran et al, 2020a;Manoj et al, 2021;Z. Cai et al, 2022).…”