scholarly journals Urbanization-induced land and aerosol impacts on sea-breeze circulation and convective precipitation

2020 ◽  
Vol 20 (22) ◽  
pp. 14163-14182
Author(s):  
Jiwen Fan ◽  
Yuwei Zhang ◽  
Zhanqing Li ◽  
Jiaxi Hu ◽  
Daniel Rosenfeld
Keyword(s):  
Ultrafine Particles ◽  
Sea Breeze ◽  
Urban Land ◽  
Mixed Phase ◽  
Convective Precipitation ◽  
Breeze Circulation ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Convective Clouds ◽  
Aerosol Effect

Abstract. Changes in land cover and aerosols resulting from urbanization may impact convective clouds and precipitation. Here we investigate how Houston urbanization can modify sea-breeze-induced convective cloud and precipitation through the urban land effect and anthropogenic aerosol effect. The simulations are carried out with the Chemistry version of the Weather Research and Forecasting model (WRF-Chem), which is coupled with spectral-bin microphysics (SBM) and the multilayer urban model with a building energy model (BEM-BEP). We find that Houston urbanization (the joint effect of both urban land and anthropogenic aerosols) notably enhances storm intensity (by ∼ 75 % in maximum vertical velocity) and precipitation intensity (up to 45 %), with the anthropogenic aerosol effect more significant than the urban land effect. Urban land effect modifies convective evolution: speed up the transition from the warm cloud to mixed-phase cloud, thus initiating surface rain earlier but slowing down the convective cell dissipation, all of which result from urban heating-induced stronger sea-breeze circulation. The anthropogenic aerosol effect becomes evident after the cloud evolves into the mixed-phase cloud, accelerating the development of storm from the mixed-phase cloud to deep cloud by ∼ 40 min. Through aerosol–cloud interaction (ACI), aerosols boost convective intensity and precipitation mainly by activating numerous ultrafine particles at the mixed-phase and deep cloud stages. This work shows the importance of considering both the urban land and anthropogenic aerosol effects for understanding urbanization effects on convective clouds and precipitation.

scholarly journals Urbanization-induced land and aerosol impacts on sea breeze circulation and convective precipitation

2020 ◽  
Author(s):  
Jiwen Fan ◽  
Yuwei Zhang ◽  
Zhanqing Li ◽  
Jiaxi Hu ◽  
Daniel Rosenfeld
Keyword(s):  
Ultrafine Particles ◽  
Sea Breeze ◽  
Urban Land ◽  
Mixed Phase ◽  
Convective Precipitation ◽  
Breeze Circulation ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Convective Clouds ◽  
Aerosol Effect

Abstract. Changes in land cover and aerosols resulting from urbanization may impact convective clouds and precipitation. Here we investigate how Houston urbanization can modify sea-breeze induced convective cloud and precipitation through urban land effect and anthropogenic aerosol effect. The simulations are carried out with the Chemistry version of the Weather Research and Forecasting model (WRF-Chem), which is coupled with the spectral-bin microphysics (SBM) and the multilayer urban model with a building energy model (BEM-BEP). We find that Houston urbanization (the joint effect of both urban land and anthropogenic aerosols) notably enhances storm intensity (by ~ 15 m s−1 in maximum vertical velocity) and precipitation intensity (up to 45 %), with the anthropogenic aerosol effect more significant than the urban land effect. Urban land effect modifies convective evolution: speed up the transition from the warm cloud to mixed-phase cloud thus initiating surface rain earlier but slowing down the convective cell dissipation, all of which result from urban heating induced stronger sea breeze circulation. The anthropogenic aerosol effect becomes evident after the cloud evolves into the mixed-phase cloud, accelerating the development of storm from the mixed-phase cloud to deep cloud by ~ 40 min. Through aerosol-cloud interaction (ACI), aerosols boost convective intensity and precipitation mainly by activating numerous ultrafine particles at the mixed-phase and deep cloud stages. This work shows the importance of considering both urban land and anthropogenic aerosol effects for understanding urbanization effects on convective clouds and precipitation.

scholarly journals Sensitivity studies of different aerosol indirect effects in mixed-phase clouds

2009 ◽  
Vol 9 (4) ◽  
pp. 15045-15081
Author(s):  
U. Lohmann ◽  
C. Hoose
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Mixed Phase ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Activation Effect ◽  
Aerosol Effect ◽  
Sensitivity Studies ◽  
Mixed Phase Clouds

Abstract. Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m−2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

scholarly journals Sensitivity studies of different aerosol indirect effects in mixed-phase clouds

2009 ◽  
Vol 9 (22) ◽  
pp. 8917-8934 ◽  
Author(s):  
U. Lohmann ◽  
C. Hoose
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Mixed Phase ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Activation Effect ◽  
Aerosol Effect ◽  
Sensitivity Studies ◽  
Mixed Phase Clouds

Abstract. Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m−2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

scholarly journals Aerosol–cloud interactions in mixed-phase convective clouds – Part 1: Aerosol perturbations

2018 ◽  
Vol 18 (5) ◽  
pp. 3119-3145 ◽  
Author(s):  
Annette K. Miltenberger ◽  
Paul R. Field ◽  
Adrian A. Hill ◽  
Phil Rosenberg ◽  
Ben J. Shipway ◽  
...  
Keyword(s):  
Structural Changes ◽  
Cloud Droplet ◽  
Sea Breeze ◽  
Mixed Phase ◽  
Convective Precipitation ◽  
Cloud Base ◽  
Latent Heating ◽  
Convective Clouds ◽  
Precipitation Response ◽  
The Uk

Abstract. Changes induced by perturbed aerosol conditions in moderately deep mixed-phase convective clouds (cloud top height ∼ 5 km) developing along sea-breeze convergence lines are investigated with high-resolution numerical model simulations. The simulations utilise the newly developed Cloud–AeroSol Interacting Microphysics (CASIM) module for the Unified Model (UM), which allows for the representation of the two-way interaction between cloud and aerosol fields. Simulations are evaluated against observations collected during the COnvective Precipitation Experiment (COPE) field campaign over the southwestern peninsula of the UK in 2013. The simulations compare favourably with observed thermodynamic profiles, cloud base cloud droplet number concentrations (CDNC), cloud depth, and radar reflectivity statistics. Including the modification of aerosol fields by cloud microphysical processes improves the correspondence with observed CDNC values and spatial variability, but reduces the agreement with observations for average cloud size and cloud top height. Accumulated precipitation is suppressed for higher-aerosol conditions before clouds become organised along the sea-breeze convergence lines. Changes in precipitation are smaller in simulations with aerosol processing. The precipitation suppression is due to less efficient precipitation production by warm-phase microphysics, consistent with parcel model predictions. In contrast, after convective cells organise along the sea-breeze convergence zone, accumulated precipitation increases with aerosol concentrations. Condensate production increases with the aerosol concentrations due to higher vertical velocities in the convective cores and higher cloud top heights. However, for the highest-aerosol scenarios, no further increase in the condensate production occurs, as clouds grow into an upper-level stable layer. In these cases, the reduced precipitation efficiency (PE) dominates the precipitation response and no further precipitation enhancement occurs. Previous studies of deep convective clouds have related larger vertical velocities under high-aerosol conditions to enhanced latent heating from freezing. In the presented simulations changes in latent heating above the 0∘C are negligible, but latent heating from condensation increases with aerosol concentrations. It is hypothesised that this increase is related to changes in the cloud field structure reducing the mixing of environmental air into the convective core. The precipitation response of the deeper mixed-phase clouds along well-established convergence lines can be the opposite of predictions from parcel models. This occurs when clouds interact with a pre-existing thermodynamic environment and cloud field structural changes occur that are not captured by simple parcel model approaches.

scholarly journals Aerosol-cloud interactions in mixed-phase convective clouds. Part 1: Aerosol perturbations

2017 ◽  
Author(s):  
Annette K. Miltenberger ◽  
Paul R. Field ◽  
Adrian A. Hill ◽  
Phil Rosenberg ◽  
Ben J. Shipway ◽  
...  
Keyword(s):  
Cloud Droplet ◽  
Sea Breeze ◽  
Phase Region ◽  
Field Structure ◽  
Mixed Phase ◽  
Cloud Base ◽  
Convergence Zone ◽  
Latent Heating ◽  
Convective Clouds ◽  
The Uk

Abstract. Changes induced by perturbed aerosol conditions in moderately deep (cloud top at about 5 km) mixed-phase convective clouds developing along sea-breeze convergence lines are investigated with high-resolution numerical model simulations (grid spacing of 250 m). The simulations utilise the newly developed Cloud-AeroSol Interacting Microphysics module (CASIM) for the Unified Model, which allows for the representation of the two-way interaction between cloud and aerosol fields. Simulations are evaluated against observations collected during the COPE field campaign over the southwestern peninsula of the UK in 2013. The simulations compare favourably with observed thermodynamic profiles, cloud-base cloud droplet number concentrations (CDNC), cloud depth, and radar reflectivity statistics. Including the modification of aerosol fields by cloud microphysical processes in the simulations improves the match to observed cloud-base CDNC, increases the CDNC variability and leads to a larger decrease of CDNC with height above cloud base. However, it also reduces the average cloud size and cloud top height, which is less compatible with observations. Before clouds become organised along the sea-breeze convergence lines, precipitation is suppressed by increasing aerosol due to less efficient precipitation production by warm-phase microphysics. The precipitation suppression is less evident if aerosol processing is taken into account. After the sea breeze convergence zone is established, accumulated precipitation from the on average deeper and wider clouds increases with aerosol concentrations as long as cloud top heights are not limited by an upper level stable layer. The precipitation enhancement is controlled by changes in condensate production and precipitation efficiency. Enhanced condensate production in high aerosol scenarios is related to higher vertical velocities in the convective cores, i.e., convective invigoration, and stronger latent heating below the 0 °C level, while changes in latent heating in the mixed-phase region are negligible. Perturbed aerosol concentrations alter the cloud field structure with fewer larger cells developing in high aerosol environments, but inducing only small changes in cloud fraction. It is hypothesised that the stronger latent heating from convection is related to the changes in the cloud field structure reducing the mixing of environmental air into the convective core. For very high aerosol concentrations, the translation of convective invigoration into deeper clouds and enhanced precipitation is limited by thermodynamic constraints. The aerosol-induced changes in shallow warm-phase clouds prior to the development of a strong convergence zone is consistent with ideas based on parcel models. However, the precipitation response of the deeper mixed-phase clouds along well-established convergence lines suggest that when clouds begin to interact with the pre-existing thermodynamic environment and modifications to the cloud field structure occur, i.e., processes other than microphysics effect the cloud evolution, and the precipitation behaviour can be opposite to predictions from parcel models.

scholarly journals Global anthropogenic aerosol effects on convective clouds in ECHAM5-HAM

2008 ◽  
Vol 8 (7) ◽  
pp. 2115-2131 ◽  
Author(s):  
U. Lohmann
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Circulation Model ◽  
Cloud Microphysics ◽  
Convective Precipitation ◽  
Anthropogenic Aerosol ◽  
Convective Clouds ◽  
Double Moment ◽  
Aerosol Effects

Abstract. Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei and may have an influence on the hydrological cycle. Here we investigate aerosol effects on convective clouds by extending the double-moment cloud microphysics scheme developed for stratiform clouds, which is coupled to the HAM double-moment aerosol scheme, to convective clouds in the ECHAM5 general circulation model. This enables us to investigate whether more, and smaller cloud droplets suppress the warm rain formation in the lower parts of convective clouds and thus release more latent heat upon freezing, which would then result in more vigorous convection and more precipitation. In ECHAM5, including aerosol effects in large-scale and convective clouds (simulation ECHAM5-conv) reduces the sensitivity of the liquid water path increase with increasing aerosol optical depth in better agreement with observations and large-eddy simulation studies. In simulation ECHAM5-conv with increases in greenhouse gas and aerosol emissions since pre-industrial times, the geographical distribution of the changes in precipitation better matches the observed increase in precipitation than neglecting microphysics in convective clouds. In this simulation the convective precipitation increases the most suggesting that the convection has indeed become more vigorous.

Sensitivity Studies of the Importance of Dust Ice Nuclei for the Indirect Aerosol Effect on Stratiform Mixed-Phase Clouds

2006 ◽  
Vol 63 (3) ◽  
pp. 968-982 ◽  
Author(s):  
U. Lohmann ◽  
K. Diehl
Keyword(s):  
Black Carbon ◽  
General Circulation ◽  
Mixed Phase ◽  
Anthropogenic Aerosols ◽  
Water Path ◽  
Ice Nuclei ◽  
Aerosol Effect ◽  
Ice Water Path ◽  
Mixed Phase Clouds ◽  
Ice Water

Abstract New parameterizations of contact freezing and immersion freezing in stratiform mixed-phase clouds (with temperatures between 0° and −35°C) for black carbon and mineral dust assumed to be composed of either kaolinite (simulation KAO) or montmorillonite (simulation MON) are introduced into the ECHAM4 general circulation model. The effectiveness of black carbon and dust as ice nuclei as a function of temperature is parameterized from a compilation of laboratory studies. This is the first time that freezing parameterizations take the chemical composition of ice nuclei into account. The rather subtle differences between these sensitivity simulations in the present-day climate have significant implications for the anthropogenic indirect aerosol effect. The decrease in net radiation in these sensitivity simulations at the top of the atmosphere varies from 1 ± 0.3 to 2.1 ± 0.1 W m−2 depending on whether dust is assumed to be composed of kaolinite or montmorillonite. In simulation KAO, black carbon has a higher relevancy as an ice nucleus than in simulation MON, because kaolinite is not freezing as effectively as montmorillonite. In simulation KAO, the addition of anthropogenic aerosols results in a larger ice water path, a slightly higher precipitation rate, and a reduced total cloud cover. On the contrary, in simulation MON the increase in ice water path is much smaller and globally the decrease in precipitation is dominated by the reduction in warm-phase precipitation due to the indirect cloud lifetime effect.

Urbanization-induced land and aerosol impacts on storm propagation and hail characteristics

2020 ◽  
Author(s):  
Yun Lin ◽  
Jiwen Fan ◽  
Jong-Hoon Jeong ◽  
Yuwei Zhang ◽  
Cameron R. Homeyer ◽  
...  
Keyword(s):  
Land Surface ◽  
Kansas City ◽  
Joint Effect ◽  
Urban Land ◽  
Convective Cell ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Microphysical Properties ◽  
Individual Effects ◽  
Bin Microphysics

AbstractChanges in land surface and aerosol characteristics from urbanization can affect dynamic and microphysical properties of severe storms, thus affecting hazardous weather events resulting from such storms such as hail and tornados. We examine the joint and individual effects of urban land and anthropogenic aerosols of Kansas City on a severe convective storm observed during the 2015 Plains Elevated Convection At Night (PECAN) field campaign, focusing on storm evolution, convective intensity, and hail characteristics. The simulations are carried out at the cloud-resolving scale (1 km) using a version of WRF-Chem in which the spectral-bin microphysics (SBM) is coupled with the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC). It is found that the urban land effect of Kansas City initiated a much stronger convective cell and the storm got further intensified when interacting with stronger turbulence induced by the urban land. The urban land effect also changed the storm path by diverting the storm toward the city mainly resulting from enhanced urban land-induced convergence in the urban area and around the urban-rural boundaries. The joint effect of urban land and anthropogenic aerosols enhances occurrences of both severe hail and significant severe hail by ~ 20% by enhancing hail formation and growth from riming. Overall the urban land effect on convective intensity and hail is relatively larger than the anthropogenic aerosol effect, but the joint effect is much notable than either of the individual effects, emphasizing the importance of considering both effects in evaluating urbanization effects.

scholarly journals The Atmospheric Aerosol over Western Greece-Six Years of Aerosol Observations at the Navarino Environmental Observatory

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 445
Author(s):  
Hans-Christen Hansson ◽  
Peter Tunved ◽  
Radovan Krejci ◽  
Eyal Freud ◽  
Nikos Kalivitis ◽  
...  
Keyword(s):  
Atmospheric Aerosol ◽  
Large Scale ◽  
Eastern Mediterranean ◽  
Sea Breeze ◽  
Radiation Balance ◽  
Precipitation Pattern ◽  
Anthropogenic Aerosols ◽  
Mesoscale Meteorology ◽  
Anthropogenic Aerosol ◽  
Aerosol Properties

The Eastern Mediterranean is a highly populated area with air quality problems. It is also where climate change is already noticed by higher temperatures and s changing precipitation pattern. The anthropogenic aerosol affects health and changing concentrations and properties of the atmospheric aerosol affect radiation balance and clouds. Continuous long-term observations are essential in assessing the influence of anthropogenic aerosols on climate and health. We present six years of observations from Navarino Environmental Observatory (NEO), a new station located at the south west tip of Peloponnese, Greece. The two sites at NEO, were evaluated to show the influence of the local meteorology and to assess the general background aerosol possible. It was found that the background aerosol was originated from aged European aerosols and was strongly influenced by biomass burning, fossil fuel combustion, and industry. When subsiding into the boundary layer, local sources contributed in the air masses moving south. Mesoscale meteorology determined the diurnal variation of aerosol properties such as mass and number by means of typical sea breeze circulation, giving rise to pronounced morning and evening peaks in pollutant levels. While synoptic scale meteorology, mainly large-scale air mass transport and precipitation, strongly influenced the seasonality of the aerosol properties.

scholarly journals Intercomparison of aerosol-cloud-precipitation interactions in stratiform orographic mixed-phase clouds

2010 ◽  
Vol 10 (4) ◽  
pp. 10487-10550 ◽  
Author(s):  
A. Muhlbauer ◽  
T. Hashino ◽  
L. Xue ◽  
A. Teller ◽  
U. Lohmann ◽  
...  
Keyword(s):  
Cloud Droplet ◽  
Mixed Phase ◽  
Small Scale ◽  
Orographic Precipitation ◽  
Model Intercomparison ◽  
Anthropogenic Aerosols ◽  
Aerosol Cloud ◽  
Aerosol Effect ◽  
Precipitation Decrease ◽  
Mixed Phase Clouds

Abstract. Anthropogenic aerosols serve as a source of both cloud condensation nuclei (CCN) and ice nuclei (IN) and affect microphysical properties of clouds. Increasing aerosol number concentrations is hypothesized to retard the cloud droplet collision/coalescence and the riming in mixed-phase clouds, thereby decreasing orographic precipitation. This study presents results from a model intercomparison of 2-D simulations of aerosol-cloud-precipitation interactions in stratiform orographic mixed-phase clouds. The sensitivity of orographic precipitation to changes in the aerosol number concentrations is analyzed and compared for various dynamical and thermodynamical situations. Furthermore, the sensitivities of microphysical processes such as collision/coalescence, aggregation and riming to changes in the aerosol number concentrations are evaluated and compared. The participating models are the Consortium for Small-Scale Modeling's (COSMO) model with bulk-microphysics, the Weather Research and Forecasting (WRF) model with bin-microphysics and the University of Wisconsin modeling system (UWNMS) with a spectral ice-habit prediction microphysics scheme. All models are operated on a cloud-resolving scale with 2 km horizontal grid spacing. The results of the model intercomparison suggest that the sensitivity of orographic precipitation to aerosol modifications varies greatly from case to case and from model to model. Neither a precipitation decrease nor a precipitation increase is found robustly in all simulations. Qualitative robust results can only be found for a subset of the simulations but even then quantitative agreement is scarce. Estimates of the second indirect aerosol effect on orographic precipitation are found to range from –19% to 0% depending on the simulated case and the model. Similarly, riming is shown to decrease in some cases and models whereas it increases in others which implies that a decrease in riming with increasing aerosol load is not a robust result. Furthermore, it is found that neither a decrease in cloud droplet coalescence nor a decrease in riming necessarily implies a decrease in precipitation due to compensation effects by other microphysical pathways. The simulations suggest that mixed-phase conditions play an important role in reducing the overall susceptibility of clouds and precipitation with respect to changes in the aerosols number concentrations. As a consequence the indirect aerosol effect on precipitation is suggested to be less pronounced or even inverted in regions with high terrain (e.g., the Alps or Rocky Mountains) or in regions where mixed-phase microphysics climatologically plays an important role for orographic precipitation.

Sign in / Sign up

Export Citation Format

Share Document