scholarly journals Evolution of trace elements in the planetary boundary layer in southern China: Effects of dust storms and aerosol-cloud interactions

2017 ◽  
Vol 122 (6) ◽  
pp. 3492-3506 ◽  
Author(s):  
Tao Li ◽  
Yan Wang ◽  
Jie Zhou ◽  
Tao Wang ◽  
Aijun Ding ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Trace Elements ◽  
Planetary Boundary Layer ◽  
Southern China ◽  
Dust Storms ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions

scholarly journals Sunlight-absorbing aerosol amplifies the seasonal cycle in low cloud fraction over the southeast Atlantic

2021 ◽  
Author(s):  
Jianhao Zhang ◽  
Paquita Zuidema
Keyword(s):  
Boundary Layer ◽  
Seasonal Cycle ◽  
Large Scale ◽  
Cloud Fraction ◽  
Small Scale ◽  
Aerosol Cloud ◽  
Ascension Island ◽  
Tropospheric Aerosol ◽  
Low Cloud ◽  
Aerosol Cloud Interactions

Abstract. Many studies examining shortwave-absorbing aerosol-cloud interactions over the southeast Atlantic apply a seasonal averaging. This disregards a meteorology that raises the mean altitude of the smoke layer from July to October. This study details the month-by-month changes in cloud properties and the large-scale environment as a function of the biomass-burning aerosol loading at Ascension Island from July to October, based on measurements from Ascension Island (8º S, 14.5º W), satellite retrievals and reanalysis. In July and August, variability in the smoke loading predominantly occurs in the boundary layer. During both months, the low-cloud fraction is less and is increasingly cumuliform when more smoke is present, with the exception of a late morning boundary layer deepening that encourages a short-lived cloud development. The meteorology varies little, suggesting aerosol-cloud interactions consistent with a boundary-layer semi-direct effect can explain the cloudiness changes. September marks a transition month during which mid-latitude disturbances can intrude into the Atlantic subtropics, constraining the land-based anticyclonic circulation transporting free-tropospheric aerosol to closer to the coast. Stronger boundary layer winds help deepen, dry, and cool the boundary layer near the main stratocumulus deck compared to that on days with high smoke loadings, with stratocumulus reducing everywhere but at the northern deck edge. Longwave cooling rates generated by a sharp water vapor gradient at the aerosol layer top facilitates small-scale vertical mixing, and could help to maintain a better-mixed September free troposphere. The October meteorology is more singularly dependent on the strength of the free-tropospheric winds advecting aerosol offshore. Free-tropospheric aerosol is less, and moisture variability more, compared to September. Low-level clouds increase and are more stratiform, when the smoke loadings are higher. The increased free-tropospheric moisture can help sustain the clouds through reducing evaporative drying during cloud-top entrainment. Enhanced subsidence above the coastal upwelling region increasing cloud droplet number concentrations may further prolong cloud lifetime through microphysical interactions. Reduced subsidence underneath stronger free-tropospheric winds at Ascension supports slightly higher cloud tops during smokier conditions. Overall the monthly changes in the large-scale aerosol and moisture vertical structure act to amplify the seasonal cycle in low-cloud amount and morphology, raising a climate importance as cloudiness changes dominate changes in the top-of-atmosphere radiation budget.

scholarly journals Observing the timescales of aerosol-cloud interactions in snapshot satellite images

2021 ◽  
Author(s):  
Edward Gryspeerdt ◽  
Tristan Smith ◽  
Tom Goren
Keyword(s):  
Boundary Layer ◽  
Satellite Images ◽  
Time Axis ◽  
Wind Fields ◽  
Geostationary Satellites ◽  
Aerosol Cloud ◽  
The World ◽  
Cloud Development ◽  
Aerosol Cloud Interactions ◽  
Single Snapshot

<div>Cloud processes and their response to perturbations happens at a variety of timescales. These timescales are related to processes such as updrafts and mixing, the formation of precipitation and changes in the background meteorology.</div><div> </div><div>Satellites often give a static picture of the world. A single snapshot from an overpass gives a wide view of the cloud field, but not motion within it. Previous studies have used multiple overpass or geostationary satellites to build up a picture of cloud development. Here we use the aerosol perturbation itself as the time axis. <br><br>Ships emit large amounts of aerosol into the boundary layer, often in comparatively clean locations. This aerosol can modify the properties of these clouds, creating linear cloud formations known as shiptracks. Using ship SO<sub>x</sub> emission information derived from ship transponder data, we link the aerosol perturbation to the properties of the shiptrack. By coupling the ship location to reanalysis wind fields, we determine the time since emission for positions along a shiptrack, providing a time axis in a single snapshot image. <br><br>We use this combined satellite/aerosol perturbation dataset to investigate the timescales for clouds responses to the aerosol perturbation from ships, linking it to the cloud and meteorological states as well as the properties of the aerosol perturbation.</div>

Investigation of inter-annual and seasonal variations of the Martian convective PBL by GCM simulations

2020 ◽  
Author(s):  
Cem Berk Senel ◽  
Orkun Temel ◽  
Sara Porchetta ◽  
Hakan Sert ◽  
Ozgur Karatekin ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Seasonal Variations ◽  
Potential Temperature ◽  
Dust Storms ◽  
Planetary Boundary Layer Height ◽  
Geophysical Research ◽  
Layer Potential ◽  
Layer Height ◽  
Boundary Layer Height

<p>The Martian planetary boundary layer (PBL) is an important component of the Martian climate. It is the lowest portion of the atmosphere where the strong buoyant and shear forces influence the interaction between surface and atmosphere <strong>[1]</strong>. The Martian PBL exhibits extreme events compared to the Earth's PBL, such as global dust storms, local dust devils, turbulent gusts and strong updraughts. Due to the thinner atmosphere of Mars and lower surface thermal inertia, the Martian planetary boundary layer shows stronger diurnal variations compared to its terrestrial counterpart. Moreover, as a result of the thinner atmosphere, radiative heat forcing is stronger, such that the Martian planetary boundary layer height can reach up to 10 km. Radiative forcing on Mars is affected by the atmospheric cycles, i.e. CO<sub>2</sub>, water and dust cycles. In this study, we perform GCM simulations, using dust climatologies corresponding to the last 10 Mars years and present the inter-annual and seasonal variations in the planetary boundary layer height, mixed-layer potential temperature, convective velocity scale, friction velocity and Richardson number. To perform these GCM simulations, the Mars version of planetWRF (MarsWRF) model <strong>[2]</strong> is utilized, that solves the fully-compressible, non-hydrostatic Euler equations in a finite difference framework.</p><p><strong>[1]</strong> Hinson, D. P., Pätzold, M., Tellmann, S., Häusler, B., & Tyler, G. L. (2008). The depth of the convective boundary layer on Mars. Icarus, 198(1), 57-66.</p><p><strong>[2]</strong> Richardson, M. I., Toigo, A. D., & Newman, C. E. (2007). PlanetWRF: A general purpose, local to global numerical model for planetary atmospheric and climate dynamics. Journal of Geophysical Research: Planets, 112(E9).</p>

scholarly journals Deconvolution of boundary layer depth and aerosol constraints on cloud water path in subtropical stratocumulus decks

2020 ◽  
Vol 20 (6) ◽  
pp. 3609-3621
Author(s):  
Anna Possner ◽  
Ryan Eastman ◽  
Frida Bender ◽  
Franziska Glassmeier
Keyword(s):  
Boundary Layer ◽  
Radiative Forcing ◽  
Cloud Droplet ◽  
Process Modelling ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Water Path ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions ◽  
Relative Change

Abstract. The liquid water path (LWP) adjustment due to aerosol–cloud interactions in marine stratocumulus remains a considerable source of uncertainty for climate sensitivity estimates. An unequivocal attribution of LWP adjustments to changes in aerosol concentration from climatology remains difficult due to the considerable covariance between meteorological conditions alongside changes in aerosol concentrations. We utilise the susceptibility framework to quantify the potential change in LWP adjustment with boundary layer (BL) depth in subtropical marine stratocumulus. We show that the LWP susceptibility, i.e. the relative change in LWP scaled by the relative change in cloud droplet number concentration, in marine BLs triples in magnitude from −0.1 to −0.31 as the BL deepens from 300 to 1200 m and deeper. We further find deep BLs to be underrepresented in pollution tracks, process modelling, and in situ studies of aerosol–cloud interactions in marine stratocumulus. Susceptibility estimates based on these approaches are skewed towards shallow BLs of moderate LWP susceptibility. Therefore, extrapolating LWP susceptibility estimates from shallow BLs to the entire cloud climatology may underestimate the true LWP adjustment within subtropical stratocumulus and thus overestimate the effective aerosol radiative forcing in this region. Meanwhile, LWP susceptibility estimates in deep BLs remain poorly constrained. While susceptibility estimates in shallow BLs are found to be consistent with process modelling studies, they overestimate pollution track estimates.

scholarly journals Global and regional modeling of clouds and aerosols in the marine boundary layer during VOCALS: the VOCA intercomparison

2015 ◽  
Vol 15 (1) ◽  
pp. 153-172 ◽  
Author(s):  
M. C. Wyant ◽  
C. S. Bretherton ◽  
R. Wood ◽  
G. R. Carmichael ◽  
A. Clarke ◽  
...  
Keyword(s):  
Boundary Layer ◽  
General Circulation ◽  
Marine Boundary Layer ◽  
Quantitative Estimation ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
General Circulation Models ◽  
Free Troposphere ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions

Abstract. A diverse collection of models are used to simulate the marine boundary layer in the southeast Pacific region during the period of the October–November 2008 VOCALS REx (VAMOS Ocean Cloud Atmosphere Land Study Regional Experiment) field campaign. Regional models simulate the period continuously in boundary-forced free-running mode, while global forecast models and GCMs (general circulation models) are run in forecast mode. The models are compared to extensive observations along a line at 20° S extending westward from the South American coast. Most of the models simulate cloud and aerosol characteristics and gradients across the region that are recognizably similar to observations, despite the complex interaction of processes involved in the problem, many of which are parameterized or poorly resolved. Some models simulate the regional low cloud cover well, though many models underestimate MBL (marine boundary layer) depth near the coast. Most models qualitatively simulate the observed offshore gradients of SO2, sulfate aerosol, CCN (cloud condensation nuclei) concentration in the MBL as well as differences in concentration between the MBL and the free troposphere. Most models also qualitatively capture the decrease in cloud droplet number away from the coast. However, there are large quantitative intermodel differences in both means and gradients of these quantities. Many models are able to represent episodic offshore increases in cloud droplet number and aerosol concentrations associated with periods of offshore flow. Most models underestimate CCN (at 0.1% supersaturation) in the MBL and free troposphere. The GCMs also have difficulty simulating coastal gradients in CCN and cloud droplet number concentration near the coast. The overall performance of the models demonstrates their potential utility in simulating aerosol–cloud interactions in the MBL, though quantitative estimation of aerosol–cloud interactions and aerosol indirect effects of MBL clouds with these models remains uncertain.

scholarly journals Assessing regional scale predictions of aerosols, marine stratocumulus, and their interactions during VOCALS-REx using WRF-Chem

2011 ◽  
Vol 11 (8) ◽  
pp. 22663-22718 ◽  
Author(s):  
Q. Yang ◽  
J. D. Fast ◽  
H. Wang ◽  
R. C. Easter ◽  
H. Morrison ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Cloud Base ◽  
Model Assessment ◽  
Microphysics Scheme ◽  
Marine Stratocumulus ◽  
Aerosol Cloud ◽  
Southeastern Pacific ◽  
Temperature And Humidity ◽  
Stratocumulus Clouds ◽  
Aerosol Cloud Interactions

Abstract. In the recent chemistry version (v3.3) of the Weather Research and Forecasting (WRF-Chem) model, we have coupled the Morrison double-moment microphysics scheme with interactive aerosols so that two-way aerosol-cloud interactions are included in the simulations. We have used this new WRF-Chem functionality in a study focused on assessing predictions of aerosols, marine stratocumulus clouds, and their interactions over the Southeast Pacific using measurements from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) and satellite retrievals. This study also serves as a detailed analysis of our WRF-Chem simulations contributed to the VOCALS model Assessment (VOCA) project. The WRF-Chem 31-day (15 October–16 November 2008) simulation with aerosol-cloud interactions (AERO hereafter) is also compared to a simulation (MET hereafter) with fixed cloud droplet number concentrations assumed by the default in Morrison microphysics scheme with no interactive aerosols. The well-predicted aerosol properties such as number, mass composition, and optical depth lead to significant improvements in many features of the simulated stratocumulus clouds: cloud optical properties and microphysical properties such as cloud top effective radius, cloud water path, and cloud optical thickness, and cloud macrostructure such as cloud depth and cloud base height. In addition to accounting for the aerosol direct and semi-direct effects, these improvements feed back to the prediction of boundary-layer characteristics and energy budgets. Particularly, inclusion of interactive aerosols in AERO strengthens the temperature and humidity gradients within the capping inversion layer and lowers the marine boundary layer depth by 150 m from that of the MET simulation. Mean top-of-the-atmosphere outgoing shortwave fluxes, surface latent heat, and surface downwelling longwave fluxes are in better agreement with observations in AERO, compared to the MET simulation. Nevertheless, biases in some of the simulated meteorological quantities (e.g., MBL temperature and humidity over the remote ocean) and aerosol quantities (e.g., overestimations of supermicron sea salt mass) might affect simulated stratocumulus and energy fluxes over the southeastern Pacific Ocean, and require further investigations. Although not perfect, the overall performance of the regional model in simulating mesoscale aerosol-cloud interactions is encouraging and suggests that the inclusion of spatially varying aerosol characteristics is important when simulating marine stratocumulus over the southeastern Pacific.

scholarly journals Online coupled meteorology and chemistry models: history, current status, and outlook

2008 ◽  
Vol 8 (1) ◽  
pp. 1833-1912 ◽  
Author(s):  
Y. Zhang
Keyword(s):  
Boundary Layer ◽  
Current Status ◽  
Coupled Models ◽  
Chemical Treatments ◽  
Aerosol Cloud ◽  
Physical Chemical ◽  
Aerosol Cloud Interactions ◽  
Model Features ◽  
Fully Coupled ◽  
The U.S

Abstract. The climate-chemistry-aerosol-cloud-radiation feedbacks are important processes occurring in the atmosphere. Accurately simulating those feedbacks requires fully-coupled meteorology, climate, and chemistry models and presents significant challenges in terms of both scientific understanding and computational demand. This paper reviews the history and current status of development and application of online coupled models. Several representative online coupled meteorology and chemistry models developed in the U.S. such as GATOR-GCMOM, WRF/Chem, CAM3, MIRAGE, and Caltech unified GCM are included along with case studies. Major model features, physical/chemical treatments, as well as typical applications are compared with a focus on aerosol microphysics treatments, aerosol feedbacks to planetary boundary layer meteorology, and aerosol-cloud interactions. Recommendations for future development and improvement of online coupled models are provided.

scholarly journals Long-term measurements of cloud droplet concentrations and aerosol–cloud interactions in continental boundary layer clouds

Tellus B ◽  
2013 ◽  
Vol 65 (1) ◽  
pp. 20138 ◽  
Author(s):  
Irshad Ahmad ◽  
Tero Mielonen ◽  
Daniel P. Grosvenor ◽  
Harri J. Portin ◽  
Antti Arola ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Cloud Droplet ◽  
Boundary Layer Clouds ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions

scholarly journals Observations of nitryl chloride and modeling its source and effect on ozone in the planetary boundary layer of southern China

2016 ◽  
Vol 121 (5) ◽  
pp. 2476-2489 ◽  
Author(s):  
Tao Wang ◽  
Yee Jun Tham ◽  
Likun Xue ◽  
Qinyi Li ◽  
Qiaozhi Zha ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Southern China ◽  
Nitryl Chloride

scholarly journals Global and regional modeling of clouds and aerosols in the marine boundary layer during VOCALS: the VOCA Intercomparison

2014 ◽  
Vol 14 (5) ◽  
pp. 6537-6587 ◽  
Author(s):  
M. C. Wyant ◽  
C. S. Bretherton ◽  
R. Wood ◽  
G. R. Carmichael ◽  
A. Clarke ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Quantitative Estimation ◽  
Cloud Droplet ◽  
South American ◽  
Aerosol Cloud ◽  
Low Cloud ◽  
Forecast Models ◽  
Low Cloud Cover ◽  
Aerosol Cloud Interactions

Abstract. A diverse collection of models are used to simulate the marine boundary layer in the Southeast Pacific region during the period of the October–November 2008 VOCALS REx field campaign. Regional models simulate the period continuously in boundary-forced free-running mode, while global forecast models and GCMs are run in forecast mode. The models are compared to extensive observations along a line at 20° S extending westward from the South American coast. Most of the models simulate cloud and aerosol characteristics and gradients across the region that are recognizably similar to observations, despite the complex interaction of processes involved in the problem, many of which are parameterized or poorly resolved. Some models simulate the regional low cloud cover well, though many models underestimate MBL depth near the coast. Most models qualitatively simulate the observed offshore gradients of SO2, sulfate aerosol, CCN concentration in the MBL, and the related gradient in cloud droplet concentrations, but there are large quantitative intermodel differences in both means and gradients of these quantities. Most models underestimate large CCN (at 0.1% supersaturation) in the MBL and free troposphere. The GCMs also have difficulty simulating coastal gradients in CCN and cloud droplet number concentration. The overall performance of the models demonstrates their potential utility in simulating aerosol-cloud interactions in the MBL, though quantitative estimation of aerosol-cloud interactions and aerosol indirect effects of MBL clouds with these models remains uncertain.

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