A better understanding of aerosol–cloud interaction processes is important to quantify the role of clouds and aerosols on the climate system. There have been significant efforts to explain the ways aerosols modulate cloud properties. However, from the observational point of view, it is indeed challenging to observe and/or verify some of these processes because no single instrument or platform has been proven to be sufficient. Discrimination between aerosol and cloud is vital for the quantification of aerosol–cloud interaction. With this motivation, a set of observational field campaigns named balloon-borne aerosol–cloud interaction studies (BACIS) is proposed and conducted using balloon-borne in situ measurements in addition to the ground-based (lidar; mesosphere, stratosphere and troposphere (MST) radar; lower atmospheric wind profiler; microwave radiometer; ceilometer) and space-borne (CALIPSO) remote sensing instruments from Gadanki (13.45^∘ N, 79.2^∘ E), India. So far, 15 campaigns have been conducted as a part of BACIS campaigns from 2017 to 2020. This paper presents the concept of the observational approach, lists the major objectives of the campaigns, describes the instruments deployed, and discusses results from selected campaigns. Balloon-borne measurements of aerosol and cloud backscatter ratio and cloud particle count are qualitatively assessed using the range-corrected data from simultaneous observations of ground-based and space-borne lidars. Aerosol and cloud vertical profiles obtained in multi-instrumental observations are found to reasonably agree. Apart from this, balloon-borne profiling is found to provide information on clouds missed by ground-based and/or space-borne lidar. A combination of the Compact Optical Backscatter AerosoL Detector (COBALD) and Cloud Particle Sensor (CPS) sonde is employed for the first time in this study to discriminate cloud and aerosol in an in situ profile. A threshold value of the COBALD colour index (CI) for ice clouds is found to be between 18 and 20, and CI values for coarse-mode aerosol particles range between 11 and 15. Using the data from balloon measurements, the relationship between cloud and aerosol is quantified for the liquid clouds. A statistically significant slope (aerosol–cloud interaction index) of 0.77 found between aerosol backscatter and cloud particle count reveals the role of aerosol in the cloud activation process. In a nutshell, the results presented here demonstrate the observational approach to quantifying aerosol–cloud interactions.

Better understanding of aerosol-cloud interaction processes is an important aspect to quantify the role of clouds and aerosols in the climate system. There have been significant efforts to explain the ways aerosols modulate cloud properties. However, from the observational point of view, it is indeed challenging to observe and/or verify some of these processes because no single instrument or platform is proven sufficient. With this motivation, a unique set of observational field campaigns named Balloon borne Aerosol Cloud Interaction Studies (BACIS) is proposed and conducted using balloon borne in-situ measurements in addition to the ground-based (Lidars, MST radar, LAWP, MWR, Ceilometer) and space borne (CALIPSO) remote sensing instruments from Gadanki (13.45° N, 79.2° E). So far, 15 campaigns have been conducted as a part of BACIS campaigns from 2017 to 2020. This paper presents the concept of observational approach, lists the major objectives of the campaigns, describes the instruments deployed, and discusses results from selected campaigns. Consistency in balloon borne measurements is assessed using the data from simultaneous observations of ground-based, space borne remote sensing instruments. A good agreement is found among multi-instrumental observations. Balloon borne in-situ profiling is found to complement the information provided by ground-based and/or space borne measurements. A combination of the Compact Optical Backscatter AerosoL Detector (COBALD) and Cloud Particle Sensor (CPS) sonde is employed for the first time to discriminate cloud and aerosol in an in-situ profile. A threshold value of COBALD color index (CI) for ice clouds is found to be between 18 and 20 and CI values for coarse mode aerosol particle range between 11 and 15. Using the data from balloon measurements, the relationship between cloud and aerosol is quantified for the liquid clouds. A statistically significant slope (aerosol-cloud interaction index) of 0.77 (0.86) found between aerosol back scatter from 300 m (400 m) below the cloud base and cloud particle count within the cloud indicates the role of aerosol in the cloud activation process. In a nutshell, the results presented here demonstrate the observational approach to quantify aerosol-cloud interactions and paves the way for further investigations using the approach.

From Aug. 1st to Aug. 29th, 2022, 8 ozonesondes were successfully launched at Pengjia Islet, Taiwan (122°04’17” E, 25°37’46” N) to measure vertical ozone profiles up to 35 km. An ozone DIAL lidar was operated at Academia Sinica in Taipei City, Taiwan (25.040°N, 121.614°E, about 80 km southwest of Pengjia Islet) to continuously measure ozone profile up to 12 km. Ozonesondes launched by the CWB, Taiwan during 1992-2011 are also presented for comparison. The lowest ozone concentration usually occurred around cold point tropopause around 17.5km. The ozone concentration observed in Aug. 2022 in general was in the range of ozone observed during 1992-2011. And there is no significant ozone abundance observed in the UT/LS region. On Aug. 1st and 12th, significant low ozone episodes (about 0.5mPa and 0.8mPa) were found at 10km-16km and 9km-12km, respectively. These two ozone deficiencies might be owing to ozone quenching processes and HYSPLIT back-trajectory analysis indicated the air parcels passed northeast of the Philippines on 7/31 and south of Japan on 8/10, respectively. On the other hand, several weak ozone abundant/deficient episodes were noticed by ozonesonde and ozone DIAL measurements in the UTLS and the low troposphere regions. Ozone concentrations are also noticed to tend to be weakly negatively correlated with RH. HYSPLIT analysis shows most of the back-trajectory of air parcels nearby the south of Japan or northeast of the Philippines.