scholarly journals A CloudSat Perspective on the Cloud Climatology and Its Association with Aerosol Perturbations in the Vertical over Eastern China

2016 ◽  
Vol 73 (9) ◽  
pp. 3599-3616 ◽  
Author(s):  
Tianmeng Chen ◽  
Jianping Guo ◽  
Zhanqing Li ◽  
Chuanfeng Zhao ◽  
Huan Liu ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Eastern China ◽  
Three Dimensional ◽  
Warm Season ◽  
Radar Reflectivity ◽  
Cumulus Clouds ◽  
Convective Clouds ◽  
Aerosol Effect ◽  
Aerosol Cloud Interactions ◽  
Level 2

Abstract Many efforts have been taken to investigate aerosol–cloud interactions from space, but only a few studies have examined the response of vertical cloud structure to aerosol perturbations. Three-dimensional cloud climatologies of eight different cloud types identified from the CloudSat level-2 cloud product during the warm season (May–September) in 2008–10 over eastern China were first generated and analyzed. Using visibility as a proxy for cloud condensation nuclei, in combination with satellite-observed radar reflectivity, normalized contoured frequency by altitude diagrams of the differences in cloud radar reflectivity Z profiles under polluted and clean conditions were constructed. For shallow cumulus clouds (shallow Cu) Z tends to be inhibited, and it is enhanced in the upper layers for deep cumulus (deep Cu), nimbostratus (Ns), and deep convective clouds (DCC) under polluted conditions. Overall, analyses of the modified center of gravity (MCOG) and cloud-top height (CTH) also point to a similar aerosol effect, except for the nonsignificant changes in MCOGs and CTHs in deep Cu. The impacts of environmental factors such as lower-tropospheric stability and vertical velocity are also discussed for these types of clouds. Although consistent aerosol-induced elevations in MCOGs and CTHs for Ns and DCC clouds are observed, the effect of meteorology cannot be completely ruled out, which merits further analysis.

scholarly journals The incorporation of the Tripleclouds concept into the <i>δ</i>-Eddington two-stream radiation scheme: solver characterization and its application to shallow cumulus clouds

2020 ◽  
Vol 20 (17) ◽  
pp. 10733-10755
Author(s):  
Nina Črnivec ◽  
Bernhard Mayer
Keyword(s):  
Climate Models ◽  
Three Dimensional ◽  
Surface Flux ◽  
Radiation Budget ◽  
Cumulus Clouds ◽  
Convective Clouds ◽  
Plane Parallel ◽  
Shallow Cumulus ◽  
Cloudy Region ◽  
Horizontal Inhomogeneity

Abstract. The treatment of unresolved cloud–radiation interactions in weather and climate models has considerably improved over the recent years, compared to conventional plane-parallel radiation schemes, which previously persisted in these models for multiple decades. One such improvement is the state-of-the-art Tripleclouds radiative solver, which has one cloud-free and two cloudy regions in each vertical model layer and is thereby capable of representing cloud horizontal inhomogeneity. Inspired by the Tripleclouds concept, primarily introduced by Shonk and Hogan (2008), we incorporated a second cloudy region into the widely employed δ-Eddington two-stream method with the maximum-random overlap assumption for partial cloudiness. The inclusion of another cloudy region in the two-stream framework required an extension of vertical overlap rules. While retaining the maximum-random overlap for the entire layer cloudiness, we additionally assumed the maximum overlap of optically thicker cloudy regions in pairs of adjacent layers. This extended overlap formulation implicitly places the optically thicker region towards the interior of the cloud, which is in agreement with the core–shell model for convective clouds. The method was initially applied on a shallow cumulus cloud field, evaluated against a three-dimensional benchmark radiation computation. Different approaches were used to generate a pair of cloud condensates characterizing the two cloudy regions, testing various condensate distribution assumptions along with global cloud variability estimate. Regardless of the exact condensate setup, the radiative bias in the vast majority of Tripleclouds configurations was considerably reduced compared to the conventional plane-parallel calculation. Whereas previous studies employing the Tripleclouds concept focused on researching the top-of-the-atmosphere radiation budget, the present work applies Tripleclouds to atmospheric heating rate and net surface flux. The Tripleclouds scheme was implemented in the comprehensive libRadtran radiative transfer package and can be utilized to further address key scientific issues related to unresolved cloud–radiation interplay in coarse-resolution atmospheric models.

scholarly journals Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)

2014 ◽  
Vol 14 (2) ◽  
pp. 1123-1139 ◽  
Author(s):  
E. Hammer ◽  
N. Bukowiecki ◽  
M. Gysel ◽  
Z. Jurányi ◽  
C. R. Hoyle ◽  
...  
Keyword(s):  
Climate Models ◽  
Cloud Condensation Nuclei ◽  
Radiation Budget ◽  
Minor Role ◽  
Research Station ◽  
Cumulus Clouds ◽  
Air Masses ◽  
The Difference ◽  
Aerosol Cloud Interactions ◽  
A Minor

Abstract. Aerosols influence the Earth's radiation budget directly through absorption and scattering of solar radiation in the atmosphere but also indirectly by modifying the properties of clouds. However, climate models still suffer from large uncertainties as a result of insufficient understanding of aerosol-cloud interactions. At the high altitude research station Jungfraujoch (JFJ; 3580 m a.s.l., Switzerland) cloud condensation nuclei (CCN) number concentrations at eight different supersaturations (SS) from 0.24% to 1.18% were measured using a CCN counter during Summer 2011. Simultaneously, in-situ aerosol activation properties of the prevailing ambient clouds were investigated by measuring the total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems. Combining all experimental data, a new method was developed to retrieve the so-called effective peak supersaturation SSpeak, as a measure of the SS at which ambient clouds are formed. A 17-month CCN climatology was then used to retrieve the SSpeak values also for four earlier summer campaigns (2000, 2002, 2004 and 2010) where no direct CCN data were available. The SSpeak values varied between 0.01% and 2.0% during all campaigns. An overall median SSpeak of 0.35% and dry activation diameter of 87 nm was observed. It was found that the difference in topography between northwest and southeast plays an important role for the effective peak supersaturation in clouds formed in the vicinity of the JFJ, while differences in the number concentration of potential CCN only play a minor role. Results show that air masses coming from the southeast (with the slowly rising terrain of the Aletsch Glacier) generally experience lower SSpeak values than air masses coming from the northwest (steep slope). The observed overall median values were 0.41% and 0.22% for northwest and southeast wind conditions, respectively, corresponding to literature values for cumulus clouds and shallow-layer clouds. These cloud types are consistent with weather observations routinely performed at the JFJ.

scholarly journals Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)

2013 ◽  
Vol 13 (8) ◽  
pp. 20419-20462 ◽  
Author(s):  
E. Hammer ◽  
N. Bukowiecki ◽  
M. Gysel ◽  
Z. Jurányi ◽  
C. R. Hoyle ◽  
...  
Keyword(s):  
Climate Models ◽  
Cloud Condensation Nuclei ◽  
Radiation Budget ◽  
Minor Role ◽  
Research Station ◽  
Cumulus Clouds ◽  
Air Masses ◽  
The Difference ◽  
Aerosol Cloud Interactions ◽  
A Minor

Abstract. Aerosols influence the Earth's radiation budget directly through absorption and scattering of solar radiation in the atmosphere but also indirectly by modifying the properties of clouds. However, climate models still suffer from large uncertainties as a result of insufficient understanding of aerosol-cloud interactions. At the high altitude research station Jungfraujoch (JFJ; 3580 m a.s.l., Switzerland) cloud condensation nuclei (CCN) number concentrations at eight different supersaturations (SS) from 0.24% to 1.18% were measured using a CCN counter during Summer 2011. Simultaneously, in-situ aerosol activation properties of the prevailing ambient clouds were investigated by measuring the total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems. Combining all experimental data, a new method was developed to retrieve the so-called effective peak supersaturation SSpeak, as a measure of the SS at which ambient clouds are formed. A 17 month CCN climatology was then used to retrieve the SSpeak values also for four earlier summer campaigns (2000, 2002, 2004 and 2010) where no direct CCN data were available. The SSpeak values varied between 0.01% and 2.0% during all campaigns. An overall median SSpeak of 0.35% and dry activation diameter of 87 nm was observed. It was found that the difference in topography between northwest and southeast plays an important role for the effective peak supersaturation in clouds formed in the vicinity of the JFJ, while differences in the number concentration of potential CCN only play a minor role. Results show that air masses coming from the southeast (with the slowly rising terrain of the Aletsch Glacier) generally experience lower SSpeak values than air masses coming from the northwest (steep slope). The observed overall median values were 0.41% and 0.22% for northwest and southeast wind conditions, respectively, corresponding to literature values for cumulus clouds and shallow-layer clouds. These cloud types are consistent with weather observations routinely performed at the JFJ.

scholarly journals Aerosol Effects on the Development of Cumulus Clouds over the Tibetan Plateau

2017 ◽  
Author(s):  
Xu Zhou ◽  
Naifang Bei ◽  
Hongli Liu ◽  
Junji Cao ◽  
Li Xing ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Asian Summer Monsoon ◽  
Cloud Condensation Nuclei ◽  
Convective Available Potential Energy ◽  
Cloud Droplet ◽  
The Tibetan Plateau ◽  
Cumulus Clouds ◽  
Upper Troposphere ◽  
Convective Clouds ◽  
Aerosol Effects

Abstract. The aerosol-cloud interaction over the Tibetan Plateau has been investigated using a cloud-resolving weather research and forecasting model with a two-moment bulk microphysical scheme including aerosol effects on cloud condensation nuclei and ice nuclei. Two types of cumulus clouds with a similar convective available potential energy, occurring over the Tibetan Plateau (Cu-TP) and North China Plain (Cu-NCP) in August 2014, are simulated to explore the response of convective clouds to aerosols. A set of aerosol profiles is used in the simulations, with the surface aerosol number concentration varying from 20 to 9000 cm−3 and the sulfate mass concentration varying from 0.02 to 9.0 µg cm−3. Increasing aerosol concentrations generally enhances the cloud core updraft and maximum updraft, intensifying convections in Cu-TP and Cu-NCP. However, the core updraft is much stronger in Cu-TP than Cu-NCP, because of the early occurrence of the glaciation process in Cu-TP that is triggered at an elevation above 4000 m. The precipitation increases steadily with aerosol concentrations in Cu-NCP, caused by the suppression of the warm rain but efficient mix-phased precipitation due to the reduced cloud droplet size. The precipitation in Cu-TP also increases with aerosol concentrations, but the precipitation enhancement is not substantial compared to that in Cu-NCP with high aerosol concentrations. The aerosol-induced intensification of convections in Cu-TP not only facilitates the precipitation, but also transports more ice-phase hydrometeors into the upper troposphere to decrease the precipitation efficiency. Considering the very clean atmosphere over the Tibetan Plateau, elevated aerosol concentrations can remarkably enhance convections due to its specific topography, which not only warms the middle troposphere to influence the Asian summer monsoon, but also delivers hydrometeors into the upper troposphere to allow more water vapor to travel into the lower stratosphere.

scholarly journals Links between satellite retrieved aerosol and precipitation

2014 ◽  
Vol 14 (5) ◽  
pp. 6821-6861 ◽  
Author(s):  
E. Gryspeerdt ◽  
P. Stier ◽  
D. G. Partridge
Keyword(s):  
Lightning Flash ◽  
Convective Clouds ◽  
Cloud Properties ◽  
Aerosol Effect ◽  
Aerosol Retrieval ◽  
Wet Scavenging ◽  
Aerosol Cloud Interactions ◽  
Cloud Regimes ◽  
Cloud Top Temperature ◽  
Aerosol Type

Abstract. Many theories have been proposed detailing how aerosols might impact precipitation, predicting both increases and decreases depending on the prevailing meteorological conditions and aerosol type. In convective clouds, increased aerosol concentrations have been speculated to invigorate convective activity. Previous studies have shown large increases in precipitation with increasing aerosol optical depth, concluding an aerosol effect on precipitation. Our analysis reveals that these studies may have been influenced by cloud effects on the retrieved aerosol, as well as by meteorological covariations. We use a regime-based approach to separate out different cloud regimes, allowing the study of aerosol-cloud interactions in individual cloud regimes. We account for the influence of cloud properties on the aerosol retrieval and make use of the diurnal sampling of the TRMM satellite and the TRMM merged precipitation product to investigate the precipitation development. We find that whilst there is little effect on precipitation at the time of the aerosol retrieval, there is an increase in precipitation from cloud in high aerosol environments in the 6 h after the aerosol retrieval, consistent with the invigoration hypothesis. Increases in lightning flash count with increased aerosol are also observed in this period. The invigoration effect appears to be dependent on the cloud top temperature, with clouds with tops colder than 0 °C showing increases in precipitation at times after the retrieval as well as increases in wet scavenging. Warm clouds show little change in precipitation development with increasing aerosol, suggesting ice processes are important for the invigoration of precipitation.

scholarly journals Links between satellite-retrieved aerosol and precipitation

2014 ◽  
Vol 14 (18) ◽  
pp. 9677-9694 ◽  
Author(s):  
E. Gryspeerdt ◽  
P. Stier ◽  
D. G. Partridge
Keyword(s):  
Lightning Flash ◽  
Convective Clouds ◽  
Cloud Properties ◽  
Aerosol Effect ◽  
Aerosol Retrieval ◽  
Wet Scavenging ◽  
Aerosol Cloud Interactions ◽  
Cloud Regimes ◽  
Cloud Top Temperature ◽  
Aerosol Type

Abstract. Many theories have been proposed detailing how aerosols might impact precipitation, predicting both increases and decreases depending on the prevailing meteorological conditions and aerosol type. In convective clouds, increased aerosol concentrations have been speculated to invigorate convective activity. Previous studies have shown large increases in precipitation with increasing aerosol optical depth, concluding an aerosol effect on precipitation. Our analysis reveals that these studies may have been influenced by cloud effects on the retrieved aerosol, as well as by meteorological covariations. We use a regime-based approach to separate out different cloud regimes, allowing for the study of aerosol–cloud interactions in individual cloud regimes. We account for the influence of cloud properties on the aerosol retrieval and make use of the diurnal sampling of the TRMM satellite and the TRMM merged precipitation product to investigate the precipitation development. We find that whilst there is little effect on precipitation at the time of the aerosol retrieval, in the 6 h after the aerosol retrieval, there is an increase in precipitation from cloud in high-aerosol environments, consistent with the invigoration hypothesis. Increases in lightning flash count with increased aerosol are also observed in this period. The invigoration effect appears to be dependent on the cloud-top temperature, with clouds with tops colder than 0 °C showing increases in precipitation at times after the retrieval, as well as increases in wet scavenging. Warm clouds show little change in precipitation development with increasing aerosol, suggesting ice processes are important for the invigoration of precipitation.

scholarly journals Aerosol effects on the development of cumulus clouds over the Tibetan Plateau

2017 ◽  
Vol 17 (12) ◽  
pp. 7423-7434 ◽  
Author(s):  
Xu Zhou ◽  
Naifang Bei ◽  
Hongli Liu ◽  
Junji Cao ◽  
Li Xing ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Asian Summer Monsoon ◽  
Cloud Condensation Nuclei ◽  
Convective Available Potential Energy ◽  
Cloud Droplet ◽  
The Tibetan Plateau ◽  
Cumulus Clouds ◽  
Upper Troposphere ◽  
Convective Clouds ◽  
Aerosol Effects

Abstract. The aerosol–cloud interaction over the Tibetan Plateau has been investigated using a cloud-resolving weather research and forecasting model with a two-moment bulk microphysical scheme including aerosol effects on cloud condensation nuclei and ice nuclei. Two types of cumulus clouds with a similar convective available potential energy, occurring over the Tibetan Plateau (Cu-TP) and North China Plain (Cu-NCP) in August 2014, are simulated to explore the response of convective clouds to aerosols. A set of aerosol profiles is used in the simulations, with the surface aerosol number concentration varying from 20 to 9000 cm−3 and the sulfate mass concentration varying from 0.02 to 9.0 µg cm−3. Increasing aerosol concentrations generally enhances the cloud core updraft and maximum updraft, intensifying convections in Cu-TP and Cu-NCP. However, the core updraft is much stronger in Cu-TP than Cu-NCP, because of the early occurrence of the glaciation process in Cu-TP that is triggered at an elevation above 4000 m. The precipitation increases steadily with aerosol concentrations in Cu-NCP, caused by the suppression of the warm rain but occurrence of efficient mix-phased precipitation due to the reduced cloud droplet size. The precipitation in Cu-TP also increases with aerosol concentrations, but the precipitation enhancement is not substantial compared to that in Cu-NCP with high aerosol concentrations. The aerosol-induced intensification of convections in Cu-TP not only facilitates the precipitation but also transports more ice-phase hydrometeors into the upper troposphere to decrease the precipitation efficiency. Considering the very clean atmosphere over the Tibetan Plateau, elevated aerosol concentrations can remarkably enhance convections due to its specific topography, which not only warms the middle troposphere to influence the Asian summer monsoon but also delivers hydrometeors into the upper troposphere to allow more water vapor to travel into the lower stratosphere.

scholarly journals Simulation study on the indirect effect of sulfate on the summer climate over the eastern China monsoon region

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dongdong Wang ◽  
Bin Zhu ◽  
Hongbo Wang ◽  
Li Sun
Keyword(s):  
Radiative Forcing ◽  
Asian Summer Monsoon ◽  
Cloud Condensation Nuclei ◽  
Eastern China ◽  
Summer Precipitation ◽  
Cloud Droplet ◽  
Monsoon Region ◽  
Liquid Water Path ◽  
Surface Cooling ◽  
Community Atmosphere Model

AbstractIn this study, we designed a sensitivity test using the half number concentration of sulfate in the nucleation calculation process to study the aerosol-cloud interaction (ACI) of sulfate on clouds, precipitation, and monsoon intensity in the summer over the eastern China monsoon region (ECMR) with the National Center for Atmospheric Research Community Atmosphere Model version 5. Numerical experiments show that the ACI of sulfate led to an approximately 30% and 34% increase in the cloud condensation nuclei and cloud droplet number concentrations, respectively. Cloud droplet effective radius below 850 hPa decreased by approximately 4% in the southern ECMR, while the total liquid water path increased by 11%. The change in the indirect radiative forcing due to sulfate at the top of the atmosphere in the ECMR during summer was − 3.74 W·m−2. The decreased radiative forcing caused a surface cooling of 0.32 K and atmospheric cooling of approximately 0.3 K, as well as a 0.17 hPa increase in sea level pressure. These changes decreased the thermal difference between the land and sea and the gradient of the sea-land pressure, leading to a weakening in the East Asian summer monsoon (EASM) and a decrease in the total precipitation rate in the southern ECMR. The cloud lifetime effect has a relatively weaker contribution to summer precipitation, which is dominated by convection. The results show that the ACI of sulfate was one possible reason for the weakening of the EASM in the late 1970s.

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