Observation of aerosol induced ‘lower tropospheric cooling’ over Indian core monsoon region

Abstract Aerosols play a significant role in regional scale pollution that alters the cloud formation process, radiation budget, and climate. Here, using long-term (2003-2019) observations from multi-satellite and ground-based remote sensors, we show robust aerosol-induced instantaneous daytime lower tropospheric cooling during the pre-monsoon season over the Indian core monsoon region (ICMR). Quantitatively, an average cooling of -0.82±0.11 °C to -1.84±0.25 °C is observed in the lower troposphere. The observed cooling is associated with both aerosol-radiation and aerosol-cloud-radiation interactions processes. The elevated dust and polluted-dust layers cause extinction of the incoming solar radiation, thereby decreasing the lower tropospheric temperature. The aerosol-cloud interactions also contribute to enhancement of cloud fraction which further contributes to the lower tropospheric cooling. The observed cooling results in a stable lower tropospheric structure during polluted conditions, which can also feedback to cloud systems. Our findings suggest that aerosol induced lower tropospheric cooling can strongly affect the cloud distribution and circulation dynamics over the ICMR, a region of immense hydroclimatic importance.

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On variability of total ozone derived from TOVS data over peninsular Indian sub-continent and adjoining oceanic area

MAUSAM ◽

10.54302/mausam.v53i4.1665 ◽

2022 ◽

Vol 53 (4) ◽

pp. 503-514

Author(s):

R. SURESH

Keyword(s):

Total Ozone ◽

Monsoon Season ◽

Lower Troposphere ◽

Southwest Monsoon ◽

Retrieval Algorithm ◽

Tropospheric Temperature ◽

Minimum Concentration ◽

Upper Troposphere ◽

Positive Correlation Coefficient ◽

Longitudinal Variability

The total ozone derived from TOVS data from NOAA 12 satellite through one step physical retrieval algorithm of International TOVS Processing Package (ITPP) version 5.0 has been used to identify its diurnal, monthly, latitudinal and longitudinal variability during 1998 over the domain Equator to 26° N / 60-100° E. The linkage of maximum total ozone with warmer tropopause and lower stratosphere has been re-established. The colder upper tropospheric temperature which is normally associated with maximum ozone concentration throughout the year elsewhere in the world has also been identified in this study but the relationship gets reversed during southwest monsoon months(June-September) over the domain considered. The moisture available in abundance in the lower troposphere gets precipitated due to the convective instability prevailing in the atmosphere during monsoon season and very little moisture is only available for vertical transport into the upper troposphere atop 500 hPa. The latent heat released by the precipitation processes warms up the middle and upper atmosphere. The warm and dry upper troposphere could be the reason for less depletion of ozone in the upper troposphere during monsoonal months and this is supported by the positive correlation coefficient prevailing in monsoon season between total ozone and upper tropospheric (aloft 300 hPa) temperature. The warmness in middle and upper troposphere which is associated with less depletion and/or production of more ozone in the upper troposphere may perhaps contribute for the higher total ozone during monsoon months than in other seasons over peninsular Indian region. The minimum concentration is observed during January (226 DU) over 6° N and the maximum (283DU) over 18° N during August. Longitudinal variability is less pronounced than the latitudinal variability.

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Aerosol-cloud interactions: The representation of heterogeneous ice activation in cloud models

10.5194/acp-2021-511 ◽

2021 ◽

Author(s):

Bernd Kärcher ◽

Claudia Marcolli

Keyword(s):

Phase Transitions ◽

Particle Number ◽

Water Phase ◽

Cloud Formation ◽

Ice Formation ◽

Ice Crystal ◽

Nucleation Behavior ◽

Aerosol Cloud ◽

Cloud Models ◽

Aerosol Cloud Interactions

Abstract. The homogeneous nucleation of ice in supercooled liquid water clouds is characterized by time-dependent freezing rates. By contrast, water phase transitions induced heterogeneously by ice nucleating particles (INPs) are described by time-independent ice-active fractions depending on ice supersaturation (s). Laboratory studies report ice-active particle number fractions (AFs) that are cumulative in s. Cloud models budget INP and ice crystal numbers to conserve total particle number during water phase transitions. Here, we show that ice formation from INPs with time-independent nucleation behavior is overpredicted when models budget particle numbers and at the same time derive ice crystal numbers from s-cumulative AFs. This causes a bias towards heterogeneous ice formation in situations where INPs compete with homogeneous droplet freezing during cloud formation. We resolve this issue by introducing differential AFs, moving us one step closer to more robust simulations of aerosol-cloud interactions.

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A global satellite view of aerosol cloud interactions

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-4-6823-2004 ◽

2004 ◽

Vol 4 (5) ◽

pp. 6823-6836 ◽

Cited By ~ 3

Author(s):

C. Luo

Keyword(s):

North Africa ◽

North Atlantic ◽

Radiative Forcing ◽

General Circulation ◽

Large Scale ◽

Regional Scale ◽

Cloud Amount ◽

General Circulation Models ◽

Aerosol Cloud ◽

Aerosol Cloud Interactions

Abstract. Long-term and large-scale correlations between Advanced Very High-Resolution Radiometer (AVHRR) aerosol optical depth and International Satellite Cloud Climatology Project (ISCCP) monthly cloud amount data show significant regional scale relationships between cloud amount and aerosols, consistent with aerosol-cloud interactions. Positive correlations between aerosols and cloud amount are associated with North American and Asian aerosols in the North Atlantic and Pacific storm tracks, and mineral aerosols in the tropical North Atlantic. Negative correlations are seen near biomass burning regions of North Africa and Indonesia, as well as south of the main mineral aerosol source of North Africa. These results suggest that there are relationships between aerosols and clouds in the observations that can be used by general circulation models to verify the correct forcing mechanisms for both direct and indirect radiative forcing by clouds.

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Aerosol-cloud interactions from combined observations with geostationary and polar-orbiting sensors

10.5194/egusphere-egu2020-2598 ◽

2020 ◽

Author(s):

Matthias Tesche ◽

Torsten Seelig ◽

Fani Alexandri ◽

Peter Bräuer ◽

Goutam Choudhury ◽

...

Keyword(s):

Rain Rate ◽

Cloud Condensation Nuclei ◽

Cloud Formation ◽

Development Phase ◽

Time Resolved ◽

Aerosol Cloud ◽

Cloud Properties ◽

The Pacific ◽

Aerosol Cloud Interactions ◽

Ice Water

Atmospheric aerosol particles are of great importance for cloud formation in the atmosphere because they are needed to act as cloud condensation nuclei (CCN) in liquid-water clouds and as ice nucleating particles (INP) in ice-containing clouds. Changes in aerosol concentration affect the albedo, development, phase, lifetime and rain rate of clouds. These aerosol-cloud interactions (ACI) and the resulting climate effects still cause the largest uncertainty in assessing climate change as they are understood only with medium confidence.The PACIFIC project, which is embedded in the French-German Make Our Planet Great Again (MOPGA) initiative, aims to improve our understanding of ACI by enhancing the representation of those aerosols that are relevant for cloud processes and by quantifying temporal changes in cloud properties throughout the cloud life cycle. PACIFIC uses a three-fold approach for studying ACI based on spaceborne observations by (i) using spaceborne lidar data to obtain unprecedented insight in CCN and INP concentrations at cloud level opposed to using column-integrated parameters, (ii) characterizing the development of clouds by tracking them in time-resolved geostationary observations opposed to resorting to the snap-shot view of polar-orbiting sensors, and (iii) combining the detailed observations from polar-orbiting sensors with the time-resolved observations of geostationary sensors &#8211; for clouds observed by both &#8211; to study the effects of CCN and INP on the albedo, liquid and ice water content, droplet and crystal size, development, phase and rain rate of clouds within different regimes carefully accounting for the meteorological background.This contribution will present the scope of the MOPGA-GRI project PACIFIC and illustrate the first findings.

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Aerosol–cloud interactions: the representation of heterogeneous ice activation in cloud models

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-15213-2021 ◽

2021 ◽

Vol 21 (19) ◽

pp. 15213-15220

Author(s):

Bernd Kärcher ◽

Claudia Marcolli

Keyword(s):

Phase Transitions ◽

Particle Number ◽

Water Phase ◽

Cloud Formation ◽

Ice Formation ◽

Ice Crystal ◽

Nucleation Behavior ◽

Aerosol Cloud ◽

Cloud Models ◽

Aerosol Cloud Interactions

Abstract. The homogeneous nucleation of ice in supercooled liquid-water clouds is characterized by time-dependent freezing rates. By contrast, water phase transitions induced heterogeneously by ice-nucleating particles (INPs) are described by time-independent ice-active fractions depending on ice supersaturation (s). Laboratory studies report ice-active particle number fractions (AFs) that are cumulative in s. Cloud models budget INP and ice crystal numbers to conserve total particle number during water phase transitions. Here, we show that ice formation from INPs with time-independent nucleation behavior is overpredicted when models budget particle numbers and at the same time derive ice crystal numbers from s-cumulative AFs. This causes a bias towards heterogeneous ice formation in situations where INPs compete with homogeneous droplet freezing during cloud formation. We resolve this issue by introducing differential AFs, thereby moving us one step closer to more robust simulations of aerosol–cloud interactions.

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Relationships between mineral dust and cloud properties in the West African Sahel

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-6901-2010 ◽

2010 ◽

Vol 10 (14) ◽

pp. 6901-6915 ◽

Cited By ~ 26

Author(s):

L. Klüser ◽

T. Holzer-Popp

Keyword(s):

Mineral Dust ◽

Monsoon Season ◽

West African ◽

Dust Aerosol ◽

The West ◽

Aerosol Cloud ◽

Cloud Properties ◽

Aerosol Cloud Interactions ◽

West African Sahel ◽

African Sahel

Abstract. Aerosol cloud interactions are known to be of great importance to many parts of the climate system. Five years of observations from three different satellites (Aqua, ENVISAT and Meteosat Second Generation) are used to statistically analyse the relationship of mineral dust aerosol, separated from other aerosol species, with monsoon season cloud state in the West African Sahel domain. Additionally, observations of the Tropical Rainfall Measuring Mission are used for discrimination of dry and wet seasons. The aerosol-cloud-interactions are analysed separately by season and air mass in order to minimise spurious correlations with meteorological conditions. The detailed analysis uncovers different counteracting relationships of the mineral dust aerosol with the cloud state, which is also evident from an analysis of the spatial distribution patterns of cloud properties changes with dust activity. The aerosol-cloud relationships found from the analysis of this multiple year dataset are mainly consistent with the hypothesis of a suppression of convective activity, but also indications of lifetime enhancement and thus increased cloud cover and convective intensity are found in some subsets.

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Understanding aerosol-cloud interactions in the development of orographic cumulus congestus during IPHEx

10.5194/acp-2017-396 ◽

2017 ◽

Cited By ~ 2

Author(s):

Yajuan Duan ◽

Markus D. Petters ◽

Ana P. Barros

Keyword(s):

Cloud Droplet ◽

Cloud Microphysics ◽

Cloud Formation ◽

Physical Parameters ◽

Aerosol Cloud ◽

Thermodynamic Conditions ◽

Cloud Droplet Number Concentration ◽

Microphysical Processes ◽

Aerosol Cloud Interactions ◽

Cumulus Congestus

Abstract. A new cloud parcel model (CPM) including activation, condensation, collision-coalescence, and lateral entrainment processes is presented here to investigate aerosol-cloud interactions (ACI) in cumulus development prior to rainfall onset. The CPM was employed along with ground based radar and surface aerosol measurements to predict the vertical structure of cloud formation at early stages and evaluated against airborne observations of cloud microphysics and thermodynamic conditions during the Integrated Precipitation and Hydrology Experiment (IPHEx) over the Southern Appalachian Mountains. Further, the CPM was applied to explore the space of ACI physical parameters controlling cumulus congestus growth not available from measurements, and to examine how variations in aerosol properties and microphysical processes influence the evolution and thermodynamic state of clouds over complex terrain via sensitivity analysis. Modelling results indicate that aerosol-cloud droplet number concentration (CDNC) closure is achieved optimally to ~ 1.3 % of the observations for condensation coefficient (ac) = 0.01 and within 5 % for 0.01

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Drivers of cloud droplet number variability in the summertime in the southeastern United States

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-12163-2020 ◽

2020 ◽

Vol 20 (20) ◽

pp. 12163-12176 ◽

Cited By ~ 1

Author(s):

Aikaterini Bougiatioti ◽

Athanasios Nenes ◽

Jack J. Lin ◽

Charles A. Brock ◽

Joost A. de Gouw ◽

...

Keyword(s):

Chemical Composition ◽

Vertical Velocity ◽

Regional Scale ◽

Cloud Droplet ◽

Diurnal Variability ◽

Aerosol Cloud ◽

Climate Interactions ◽

Characteristic Concentration ◽

Aerosol Cloud Interactions ◽

The One

Abstract. Here we analyze regional-scale data collected on board the NOAA WP-3D aircraft during the 2013 Southeast Nexus (SENEX) campaign to study the aerosol–cloud droplet link and quantify the sensitivity of droplet number to aerosol number, chemical composition, and vertical velocity. For this, the observed aerosol size distributions, chemical composition, and vertical-velocity distribution are introduced into a state-of-the-art cloud droplet parameterization to show that cloud maximum supersaturations in the region range from 0.02 % to 0.52 %, with an average of 0.14±0.05 %. Based on these low values of supersaturation, the majority of activated droplets correspond to particles with a dry diameter of 90 nm and above. An important finding is that the standard deviation of the vertical velocity (σw) exhibits considerable diurnal variability (ranging from 0.16 m s−1 during nighttime to over 1.2 m s−1 during day), and it tends to covary with total aerosol number (Na). This σw–Na covariance amplifies the predicted response in cloud droplet number (Nd) to Na increases by 3 to 5 times compared to expectations based on Na changes alone. This amplified response is important given that droplet formation is often velocity-limited and therefore should normally be insensitive to aerosol changes. We also find that Nd cannot exceed a characteristic concentration that depends solely on σw. Correct consideration of σw and its covariance with time and Na is important for fully understanding aerosol–cloud interactions and the magnitude of the aerosol indirect effect. Given that model assessments of aerosol–cloud–climate interactions do not routinely evaluate for overall turbulence or its covariance with other parameters, datasets and analyses such as the one presented here are of the highest priority to address unresolved sources of hydrometeor variability, bias, and the response of droplet number to aerosol perturbations.

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Overview: The CLoud-Aerosol-Radiation Interaction and Forcing: Year-2017 (CLARIFY-2017) measurement campaign

10.5194/acp-2020-729 ◽

2020 ◽

Cited By ~ 2

Author(s):

Jim M. Haywood ◽

Steven J. Abel ◽

Paul A. Barrett ◽

Nicolas Bellouin ◽

Alan Blyth ◽

...

Keyword(s):

Temporal Resolution ◽

Climate Models ◽

Numerical Models ◽

Weather Prediction ◽

Full Range ◽

Radiative Properties ◽

Radiation Budget ◽

Atmospheric Measurements ◽

Aerosol Cloud ◽

Aerosol Cloud Interactions

Abstract. The representation of clouds, aerosols and cloud-aerosol-radiation impacts remain some of the largest uncertainties in climate change, limiting our ability to accurately reconstruct and predict future climate. The south-east Atlantic is a region where high atmospheric aerosol loadings and semi-permanent stratocumulus clouds are co-located, providing a natural laboratory for studying the full range of aerosol-radiation and aerosol-cloud interactions and their perturbations of the Earth’s radiation budget. While satellite measurements have provided some useful insights into aerosol-radiation and aerosol cloud interactions over the region, these observations do not have the spatial and temporal resolution, nor the required level of precision to allow for a process level assessment. Detailed measurements from high spatial and temporal resolution airborne atmospheric measurements in the region are very sparse, limiting their use in assessing the performance of aerosol modelling in numerical weather prediction and climate models. CLARIFY-2017 was a major consortium programme consisting of 5 principal UK universities with project partners from the UK Met Office and European and USA-based universities and research centres involved in the complementary ORACLES, LASIC and AEROCLO-sA projects. The aims of CLARIFY-2017 were four-fold; (1) to improve the representation and reduce uncertainty in model estimates of the direct, semi-direct and indirect radiative effect of absorbing biomass burning aerosols; (2) improve our knowledge and representation of the processes determining stratocumulus cloud microphysical and radiative properties and their transition to cumulus regimes; (3) challenge, validate and improve satellite retrievals of cloud and aerosol properties and their radiative impacts; (4) improve numerical models of cloud and aerosol and their impacts on radiation, weather and climate. This paper describes the modelling and measurement strategies central to the CLARIFY-2017 deployment of the FAAM BAe146 instrumented aircraft campaign, summarises the flight objectives and flight patterns, and highlights some key results from our initial analyses.

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Analysis of polarimetric satellite measurements suggests stronger cooling due to aerosol-cloud interactions

Nature Communications ◽

10.1038/s41467-019-13372-2 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 9

Author(s):

Otto P. Hasekamp ◽

Edward Gryspeerdt ◽

Johannes Quaas

Keyword(s):

Radiative Forcing ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Cloud Formation ◽

Anthropogenic Aerosol ◽

Intergovernmental Panel ◽

Aerosol Cloud ◽

Cloud Properties ◽

Aerosol Cloud Interactions ◽

Aerosol Emissions

AbstractAnthropogenic aerosol emissions lead to an increase in the amount of cloud condensation nuclei and consequently an increase in cloud droplet number concentration and cloud albedo. The corresponding negative radiative forcing due to aerosol cloud interactions (RF$${}_{{\rm{aci}}}$$aci) is one of the most uncertain radiative forcing terms as reported in the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Here we show that previous observation-based studies underestimate aerosol-cloud interactions because they used measurements of aerosol optical properties that are not directly related to cloud formation and are hampered by measurement uncertainties. We have overcome this problem by the use of new polarimetric satellite retrievals of the relevant aerosol properties (aerosol number, size, shape). The resulting estimate of RF$${}_{{\rm{aci}}}$$aci = −1.14 Wm$${}^{{\rm{-2}}}$$-2 (range between −0.84 and −1.72 Wm$${}^{{\rm{-2}}}$$-2) is more than a factor 2 stronger than the IPCC estimate that includes also other aerosol induced changes in cloud properties.

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