Increase In Effective Radius Research Articles

Microphysical Simulation of the 2022 Hunga Volcano Eruption Using a Sectional Aerosol Model

AbstractApproximately 150 Tg of water vapor and 0.42 Tg of sulfur dioxide were injected directly into the stratosphere by the January 2022 Hunga volcanic eruption, which represents the largest water vapor injection in the satellite era. A comparison of numerical simulations to balloon‐borne and satellite observations of the water‐rich plume suggests that particle coagulation contributed to the Hunga aerosol's effective dry radius increase from 0.2 μm in February to around 0.4 μm in March. Our model suggests that the stratospheric aerosol effective radius is persistently perturbed for years by moderate and large‐magnitude volcanic events, whereas extreme wildfire events show limited impact on the stratospheric background particle size. Our analysis further suggests that both the particle optical efficiency and the aerosols' stratospheric lifetime explain Hunga's unusually large aerosol optical depth per unit of the SO2 injection, as compared with the Pinatubo eruption.

Radiative effect of thin cirrus clouds in the extratropical lowermost stratosphere and tropopause region

Abstract. Cirrus clouds play an important role in the radiation budget of the Earth; nonetheless, the radiative effect of ultra-thin cirrus clouds in the tropopause region and in the lowermost stratosphere remains poorly constrained. These clouds have a small vertical extent and optical depth and are frequently neither observed even by sensitive sensors nor considered in climate model simulations. In addition, their short-wave (cooling) and long-wave (warming) radiative effects are often in approximate balance, and their net effect strongly depends on the shape and size of the cirrus particles. However, the CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere instrument (CRISTA-2) allows ultra-thin cirrus clouds to be detected. Here we use CRISTA-2 observations in summer 1997 in the Northern Hemisphere midlatitudes together with the Suite Of Community RAdiative Transfer codes based on Edwards and Slingo (SOCRATES) radiative transfer model to calculate the radiative effect of observed ultra-thin cirrus. Using sensitivity simulations with different ice effective particle size and shape, we provide an estimate of the uncertainty in the radiative effect of ultra-thin cirrus in the extratropical lowermost stratosphere and tropopause region during summer and – by extrapolation of the summer results – for winter. Cloud top height and ice water content are based on CRISTA-2 measurements, while the cloud vertical thickness was predefined to be 0.5 or 2 km. Our results indicate that if the ice crystals of these thin cirrus clouds are assumed to be spherical, their net cloud radiative effect is generally positive (warming). In contrast, assuming aggregates or a hexagonal shape, their net radiative effect is generally negative (cooling) during summer months and very likely positive (warming) during winter. The radiative effect is in the order of ±(0.1–0.01) W m−2 for a realistic global cloud coverage of 10 %, similar to the magnitude of the contrail cirrus radiative forcing (of ∼ 0.1 W m−2). The radiative effect is also dependent on the cloud vertical extent and consequently the optically thickness and effective radius of the particle size distribution (e.g. effective radius increase from 5 to 30 µm results in a factor ∼ 6 smaller long- and short-wave effects, respectively). The properties of ultra-thin cirrus clouds in the lowermost stratosphere and tropopause region need to be better observed, and ultra-thin cirrus clouds need to be evaluated in climate model simulations.

Refinement of Docked Protein-Protein Complexes Using Repulsive Scaling Replica Exchange Simulations.

Accurate prediction and evaluation of protein-protein complex structures is of major importance to understand the cellular interactome. Predicted complex structures based on deep learning approaches or traditional docking methods require often structural refinement and rescoring for realistic evaluation. Standard molecular dynamics (MD) simulations are time-consuming and often do not structurally improve docking solutions. Better refinement can be achieved with our recently developed replica-exchange-based scheme employing different levels of repulsive biasing between proteins in each replica simulation (RS-REMD). The bias acts specifically on the intermolecular interactions based on an increase in effective pairwise van der Waals radii without changing interactions within each protein or with the solvent. It allows for an improvement of the predicted protein-protein complex structure and simultaneous realistic free energy scoring of protein-protein complexes. The setup of RS-REMD simulations is described in detail including the application on two examples (all necessary scripts and input files can be obtained from https://gitlab.com/TillCyrill/mmib ).

Numerical analysis of temperature effect on CO2 storage capacity and CH4 production capacity during the CO2-ECBM process

Temperature is a key factor affecting the CO2 injection efficiency and CH4 production efficiency, so it is of great significance to clarify the evolution diagram of temperature change during the CO2-ECBM process. In this study, the crushed soft coal seam with low permeability in Huainan coalfield was taken as the research object. Firstly, the fully coupled mathematical models of CO2-ECBM process were constructed, and the influence of temperature field on CO2-ECBM process was emphasized. Secondly, the evolution law of CO2-ECBM process at different time was revealed. Then, the effects of injection temperature and initial temperature on the CO2-ECBM process were analyzed. Finally, the evolution mechanism of reservoir temperature during the CO2-ECBM process was illustrated, and the effect of temperature on temperature field of CO2-ECBM process was further illustrated. The results show that the longer the displacement time, the CH4 concentration gradually decreased, and the CO2 concentration gradually increased. The area where the temperature changes are more concentrated focuses on the vicinity of CO2 injection well, which are mainly determined by the dominant reaction of adsorption and desorption reactions of binary gas. Reservoir temperature and permeability are positively and negatively correlated with injection temperature, respectively. Both CO2 storage capacity and CH4 production capacity increase with the increase of injection temperature, and the sensitivity of CO2 storage capacity to temperature was greater than that of CH4 production capacity. With the increase of displacement time and injection volume, the effective displacement radius increases, but the increment of influencing radius gradually decreases. The lower the initial temperature of coal reservoir, the larger the influencing radius, and which increases with the increase of displacement time. CO2 storage capacity and CH4 production capacity decrease with the increase of initial temperature. Young's modulus and Poisson's ratio can effectively change the reservoir strength. CO2 storage capacity and CH4 production capacity decrease with the increase of Young's modulus, and increase with the increase of Poisson's ratio. This study can support the engineering landing of CO2-ECBM technology in crushed soft coal seam with low permeability, and promote the realization of China's “Dual Carbon” strategic goal.

Numerical Investigation on Potential Influencing Factors Affecting Drainage Effective Radius of Crossing Borehole

Crossing borehole is an effective means to eliminate the outburst risk of coal and gas. The influence of borehole inclination angle, borehole diameter, and drainage time on the effective radius of gas drainage are studied by numerical simulation and engineering example verification. The study shows that the effective radius changes in a “U” shape with the increase in borehole inclination angle. When the angle α of the borehole and coal seam plane decreases, the effective radius increases. Furthermore, the coal mass around the borehole is broken by shear deformation, which is consistent with the results of the inner peephole. The effective radiuses are different in coal seam dip X and strike Y. When α is small, the effective radius in the X direction is generally wider. When α is large (α ≤ 90°), the effective radiuses in the X and Y directions are close. The effective radius is positively correlated with the borehole diameter and is more significantly influenced by increasing borehole diameter when α is small. The effective radius increases as a negative exponential function with time and eventually converges to a constant. The study has practical implications for the design of crossing borehole in the coal seam floor.

Impact of Cloud Condensation Nuclei Reduction on Cloud Characteristics and Solar Radiation during COVID-19 Lockdown 2020 in Moscow

We used MODIS observations to retrieve number concentration of cloud droplets (Nd) at cloud lower boundary during spring 2018–2020 for the Moscow region. Looking through the similar synoptic situations of the northern clear air advection, we obtained Nd within the limits of 200–300 cm−3. During the lockdown period, with similar northern advection conditions, the reduction of Nd on 40–50 cm−3 (or 14–16%), with the increase in droplet effective radius by 8 ± 1% and cloud optical thickness reduction by 5 ± 2%, was observed in contrast to the values in typical conditions in 2018–2019. We used these values for setting up corresponding parameters in numerical simulations with the COSMO-Ru model. According to the numerical experiments, we showed that the observed reduction in cloud droplet concentration by 50 cm−3 provides a 5–9 W/m2 (or 9–11%) increase in global irradiance at ground in overcast cloud conditions with LWP = 200–400 g/m2.

Apportionment of the Pre‐Industrial to Present‐Day Climate Forcing by Methane Using UKESM1: The Role of the Cloud Radiative Effect

AbstractThe Year 1850 to 2014 increase in methane from 808 to 1831 ppb leads to an effective radiative forcing (ERF) of 0.97 ± 0.04 W m−2 in the United Kingdom's Earth System Model, UKESM1. The direct methane contribution is 0.54 ± 0.04 W m−2. It is better represented in UKESM1 than in its predecessor model HadGEM2 due to shortwave and longwave absorption improvements and the absence of an anomalous dust response in the UKESM1 simulations. An indirect ozone ERF of 0.13–0.20 W m−2 is due to the tropospheric ozone increase outweighing that of the stratospheric decrease. The indirect water vapor ERF of 0.02–0.07 W m−2 is consistent with previous estimates. The methane increase also leads to a cloud radiative effect of 0.12 ± 0.02 W m−2 from thermodynamic adjustments and aerosol‐cloud interactions (aci). Shortwave and longwave contributions of 0.23 and −0.35 W m−2 to the cloud forcing arise from radiative heating and stabilization of the upper troposphere, reducing convection and global cloud cover. The aerosol‐mediated contribution (0.28–0.30 W m−2) is due to changes in oxidants reducing new particle formation (−8%), shifting the aerosol size distribution toward fewer but larger particles. Cloud droplet number concentration decreases and cloud droplet effective radius increases. This reduction in the Twomey effect switches the cloud forcing sign (−0.14 to 0.12 W m−2) and is due to chemistry‐aerosol‐cloud coupling in UKESM1. Despite uncertainties in rapid adjustments and process representation in models, these results highlight the potential importance of chemistry‐aerosol‐cloud interactions and dynamical adjustments in climate forcing.

Lidar and Radar Signal Simulation: Stability Assessment of the Aerosol–Cloud Interaction Index

Aerosol–cloud interactions (ACI) are in the spotlight of atmospheric science since the limited knowledge about these processes produces large uncertainties in climate predictions. These interactions can be quantified by the aerosol–cloud interaction index (ACI index), which establishes a relationship between aerosol and cloud microphysics. The experimental determination of the ACI index through a synergistic combination of lidar and cloud radar is still quite challenging due to the difficulties in disentangling the aerosol influence on cloud formation from other processes and in retrieving aerosol-particle and cloud microphysics from remote sensing measurements. For a better understanding of the ACI and to evaluate the optimal experimental conditions for the measurement of these processes, a Lidar and Radar Signal Simulator (LARSS) is presented. LARSS simulate vertically-resolved lidar and cloud-radar signals during the formation process of a convective cloud, from the aerosol hygroscopic enhancement to the condensation droplet growth. Through LARSS simulations, it is observed a dependence of the ACI index with height, associated with the increase in number (ACINd) and effective radius (ACIreff) of the droplets with altitude. Furthermore, ACINd and ACIreff for several aerosol types (such as ammonium sulfate, biomass burning, and dust) are estimated using LARSS, presenting different values as a function of the aerosol model. Minimum ACINd values are obtained when the activation of new droplets stops, while ACIreff reaches its maximum values several meters above. These simulations are carried out considering standard atmospheric conditions, with a relative humidity of 30% at the surface, reaching the supersaturation of the air mass at 3500 m. To assess the stability of the ACI index, a sensitivity study using LARSS is performed. It is obtained that the dry modal aerosol radius presents a strong influence on the ACI index fluctuations of 18% cause an ACI variability of 30% while the updraft velocity within the cloud and the wet modal aerosol radius have a weaker impact. LARSS ACI index uncertainty is obtained through the Monte Carlo technique, obtaining ACIreff uncertainty below 16% for the uncertainty of all LARSS input parameters of 10%. Finally, a new ACI index is introduced in this study, called the remote-sensing ACI index (ACIRs), to simplify the quantification of the ACI processes with remote sensors. This new index presents a linear relationship with the ACIreff, which depends on the Angstrom exponent. The use of ACIRs to derive ACIreff presents the advantage that it is possible to quantify the aerosol–cloud interaction without the need to perform microphysical inversion retrievals, thus reducing the uncertainty sources.

Influence of kelp forests on flow around headlands

Kelp forests affect coastal circulation but their influence on upwelling around headlands is poorly understood. Tidal-cycle surveys off two headlands with contrasting kelp coverage illustrated the influence of kelp forests on headland upwelling. Underway acoustic Doppler current and backscatter profiles were collected simultaneously to surface water temperature. Surveys occurred along three off-headland transects in July 25–29, 2018, off Isla Natividad, located midway on the western coast of the Baja California peninsula. Flows and water temperature distributions off the headland with no kelp coverage were consistent with headland upwelling. In contrast, the kelp around the headland with dense coverage: 1) attenuated the ambient flow; 2) favored an increase in effective radius of flow curvature; 3) promoted flow ducting, which consists of enhancing flow through channels unobstructed by kelp; and 4) suppressed headland upwelling. Kelp suppressed upwelling by channeling the flow away from the headland, keeping nearshore waters warmer than offshore. Plain language abstractThis study documents a way in which biology can affect physics in coastal ocean environments. In particular, the study describes how a kelp forest suppresses the upward pumping of cool subsurface waters that is typically found around headlands. Such suppression of subsurface waters injection occurs via a process that we refer to as ‘flow ducting.’ In flow ducting, coastal flows are channelized through kelp gaps, concentrated in bands <30 m wide, and kept away from the morphological influences of a headland. This ducting is analogous to the tortuous flow through porous media.

Long-Term Impact of Continental and Maritime Airflow on Aerosol Environment and Rain Microstructure Near Land–Sea Boundary

The present study deals with the interplay of multiple atmospheric processes in changing the microphysical properties of precipitation during the pre-monsoon season (March–May) using the long-term experimental data of raindrop size distributions (DSDs) spanning over 15 years (2005–2019) obtained at an urban tropical location, Kolkata (22.57°N, 88.37°E), near the land–sea boundary. The changing pattern of air mass flows from the maritime and continental region, which contribute to the formation of precipitation processes, has been responsible for the varying characteristics of rain. Changes in raindrop sizes are related to aerosol properties, cloud features, temperature, and relative humidity that change mass-weighted mean drop diameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{m}$ </tex-math></inline-formula> ) differently in low and high rain rate regimes. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{m}$ </tex-math></inline-formula> has shown an increasing trend over time for low rain rates (< 15 mm/h), but a decreasing trend for high rain rate regimes (≥15 mm/h). An increase (decrease) in mean temperature (relative humidity) below the atmospheric boundary layer (< 1.6 km) has enhanced the evaporation of small raindrops and altered rain microphysical features. Based on satellite observations, it has been found that the increasing aerosol optical depth (AOD) has been accompanied by an increase in cloud effective radius (CER), resulting in the anti-Twomey effect, which is due to the dominance of maritime influence over continental activities. Because of the predominant maritime activities, sea salt aerosols have a greater presence, causing an increase in CER, which consequently prevents raindrops from becoming large enough before they fall, thereby reducing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{m}$ </tex-math></inline-formula> at high rainfall rates.

A Large‐Scale Analysis of Pockets of Open Cells and Their Radiative Impact

AbstractPockets of open cells sometimes form within closed‐cell stratocumulus cloud decks but little is known about their statistical properties or prevalence. A convolutional neural network was used to detect occurrences of pockets of open cells (POCs). Trained on a small hand‐logged data set and applied to 13 years of satellite imagery the neural network is able to classify 8,491 POCs. This extensive database allows the first robust analysis of the spatial and temporal prevalence of these phenomena, as well as a detailed analysis of their micro‐physical properties. We find a large (30%) increase in cloud effective radius inside POCs as compared to their surroundings and similarly large (20%) decrease in cloud fraction. This also allows their global radiative effect to be determined. Using simple radiative approximations we find that the instantaneous global annual mean top‐of‐atmosphere perturbation by all POCs is only 0.01 W/m2.

Consistent Dynamical and Stellar Masses with Potential Light IMF in Massive Quiescent Galaxies at 3 &lt; z &lt; 4 Using Velocity Dispersions Measurements with MOSFIRE

Abstract We present the velocity dispersion measurements of four massive ∼1011 M ⊙ quiescent galaxies at 3.2 &lt; z &lt; 3.7 based on deep H and K-band spectra using the Keck/MOSFIRE near-infrared spectrograph. We find high velocity dispersions of order σ e ∼250 km s−1 based on strong Balmer absorption lines, and we combine these with size measurements based on HST/WFC3 F160W imaging to infer dynamical masses. The velocity dispersions are broadly consistent with the high stellar masses and small sizes. Together with evidence for quiescent stellar populations, the spectra confirm the existence of a population of massive galaxies that formed rapidly and quenched in the early universe z &gt; 4. Investigating the evolution at constant velocity dispersion between z ∼3.5 and z ∼2, we find a large increase in effective radius 0.35 ± 0.12 dex and in dynamical-to-stellar mass ratio of 0.33 ± 0.08 dex, with low expected contribution from dark matter. The dynamical masses for our z ∼3.5 sample are consistent with the stellar masses for a Chabrier initial mass function (IMF), with the ratio dex suggesting an IMF lighter than Salpeter may be common for massive quiescent galaxies at z &gt; 3. This is surprising in light of the Salpeter or heavier IMFs found for high velocity dispersion galaxies at z ∼2 and cores of present-day ellipticals, which these galaxies are thought to evolve into. Future imaging and spectroscopic observations with resolved kinematics using the upcoming James Webb Space Telescope could rule out potential systematics from rotation and confirm these results.

Anthropogenic emissions from South Asia reverses the aerosol indirect effect over the northern Indian Ocean

Atmospheric aerosols play an important role in the formation of warm clouds by acting as efficient cloud condensation nuclei (CCN) and their interactions are believed to cool the Earth-Atmosphere system (‘first indirect effect or Twomey effect’) in a highly uncertain manner compared to the other forcing agents. Here we demonstrate using long-term (2003–2016) satellite observations (NASA’s A-train satellite constellations) over the northern Indian Ocean, that enhanced aerosol loading (due to anthropogenic emissions) can reverse the first indirect effect significantly. In contrast to Twomey effect, a statistically significant increase in cloud effective radius (CER, µm) is observed with respect to an increase in aerosol loading for clouds having low liquid water path (LWP < 75 g m−2) and drier cloud tops. Probable physical mechanisms for this effect are the intense competition for available water vapour due to higher concentrations of anthropogenic aerosols and entrainment of dry air on cloud tops. For such clouds, cloud water content showed a negative response to cloud droplet number concentrations and the estimated intrinsic radiative effect suggest a warming at the Top of the Atmosphere. Although uncertainties exist in quantifying aerosol-cloud interactions (ACI) using satellite observations, present study indicates the physical existence of anti-Twomey effect over the northern Indian Ocean during south Asian outflow.

Climatological‐Scale Analysis of Intensive and Semi‐intensive Aerosol Parameters Derived From AERONET Retrievals Over the Arctic

AbstractWe investigated the climatological‐scale, monthly binned, seasonal variation of AERONET/Dubovik retrievals across six stations in the North American and European Arctic (multiyear sampling periods ranging from 8 to 17 years). A robust, spring‐to‐summer (StoS) increase in the radius of the peak of the fine mode (FM) component of the particle size distribution (PSD) was observed for five of the six stations. The FM aerosol optical depth (AOD) and the FM effective radius at the individual stations showed, respectively, a negligible to moderate StoS decrease and a significant increase. This was interpreted as a trade‐off between the waning influence of smaller FM Arctic haze aerosols and the increasing influence of large FM smoke particles. A springtime, pan‐Arctic PSD peak in the 1.3 μm coarse mode (CM) bin was attributed to Asian dust. It was suggested that the increase in amplitude of a second (4–7 μm) CM peak from July to August at the low‐elevation coastal sites was influenced by wind‐induced sea salt. The CM AOD went through a StoS decrease attributed to the decreasing amplitude of the 1.3 μm peak. A significant StoS CM effective radius increase was ascribed to the decreasing influence of the 1.3 μm peak. StoS FM fraction increases were largely due to the decrease of the CM AOD (decreasing influence of springtime Asian dust). This extensive and intensive climatology of remotely sensed, bimodal properties will, we believe, provide an important reference for future measurements and modeling of Arctic aerosols.

FY-4A SATELLITE BASED CLOUD MICROPHYSICAL VARIATION ANALYSIS OF AIRBORNE CLOUD SEEDING OPERATIONS IN SICHUAN BASIN

Abstract. Based on a satellite retrieval methodology, the cloud microphysical properties of two airborne cloud seeding operations in Sichuan Basin of Southwest China are analyzed in this paper. The methodology for the retrieval of the cloud particle effective radius (Re), cloud temperature (T) and microphysical structure is based on the data from the AGRI onboard the Chinese FY-4A satellite. A microphysical red–green–blue (RGB) composite visualization has been devised to qualitatively highlight the cloud composition. This RGB scheme is displayed by compositing visible 0.65 micron channel, near infrared 2.2 micron channel and infrared 11.0 micron channel. And the vertical structure and development status of the clouds are demonstrated by the T-Re profiles. The results show that after the cloud seeding operation on June 11, 2018, the cloud particle effective radius increases, and the ground observed PM10 and PM2.5 pollutants decrease as well. As for the cloud seeding operation on November, 17, 2018, the satellite inversion shows that the medium and low level clouds are rich in super-cooled water with small cloud particle effective radius. After the cloud seeding operation, the effective radius of the cloud droplets increases significantly. Both of these two cloud seeding operation in Sichuan Basin demonstrate obvious precipitation enhancement results in the seeding impact area.

The hidden satellites of massive galaxies and quasars at high redshift

ABSTRACT Using cosmological, radiation-hydrodynamic simulations targeting a rare ${\approx}2 \times 10^{12} \, \rm {\rm M}_{\odot }$ halo at $z = 6$, we show that the number counts and internal properties of satellite galaxies within the massive halo are sensitively regulated by a combination of local stellar radiative feedback and strong tidal forces. Radiative feedback operates before the first supernova explosions erupt and results in less tightly bound galaxies. Satellites are therefore more vulnerable to tidal stripping when they accrete on to the main progenitor and are tidally disrupted on a significantly shorter time-scale. Consequently, the number of satellites with $M_{\rm \star } \gt 10^{7} \, \rm {\rm M}_{\odot }$ within the parent system’s virial radius drops by up to $60 \, {\rm per\, cent}$ with respect to an identical simulation performed without stellar radiative feedback. Radiative feedback also impacts the central galaxy, whose effective radius increases by a factor ≲3 due to the presence of a more extended and diffuse stellar component. We suggest that the number of satellites in the vicinity of massive high-redshift galaxies is an indication of the strength of stellar radiative feedback and can be anomalously low in the extreme cosmic environments of high-redshift quasars.

Theoretical study on trade-off relationships between resolution, line edge roughness, and sensitivity in resist processes for semiconductor manufacturing by extreme ultraviolet lithography

Extreme ultraviolet (EUV) lithography will be soon applied to high-volume production of semiconductor devices. A high numerical aperture tool is planned to extend the use of EUV lithography. The trade-off relationships between resolution, line edge roughness (LER), and sensitivity are a significant concern for the extendability of EUV lithography. In this study, the dependences of chemical gradient (an indicator of LER) on the half-pitch of line-and-space patterns, the sensitizer concentration, and the effective reaction radius for deprotection were investigated using a simulation on the basis of the sensitization and reaction mechanisms of chemically amplified EUV resists. The relationships between resolution, LER, and sensitivity were formulated. In sub-10 nm half-pitch resolution region, the effect of thermalized electrons became clear. The increase of sensitizer concentration and/or effective reaction radius is required for the suppression of the effect of thermalized electrons.

Ice nucleation by aerosols from anthropogenic pollution.

The formation of ice particles in the atmosphere strongly affects cloud properties and the climate. While mineral dust is known to be an effective ice nucleating particle, the role of aerosols from anthropogenic pollution in ice nucleation is still under debate. Here we probe the ice nucleation ability of different aerosol types by combining 11-year observations from multiple satellites and cloud-resolving model simulations. We find that, for strong convective systems, ice particle effective radius near cloud top decreases with increasing loading of polluted continental aerosols, because the ice formation is dominated by homogeneous freezing of cloud droplets that are smaller under more polluted conditions. In contrast, an increase in ice particle effective radius with polluted continental aerosols is found for moderate convection. Our model simulations suggest that this positive correlation is explained by enhanced heterogeneous ice nucleation and prolonged ice particle growth at larger aerosol loading, indicating that polluted continental aerosols contain a significant fraction of ice nucleating particles. Similar aerosol-ice relationships are observed for dust aerosols, further corroborating the ice nucleation ability of polluted continental aerosols. By catalyzing ice formation, aerosols from anthropogenic pollution could have profound impacts on cloud lifetime and radiative effect as well as precipitation efficiency.

Comparative Analyses of Vertical Structure of Deep Convective Clouds Retrieved from Satellites and Ground-Based Radars at Naqu over the Tibetan Plateau

In order to improve understanding of deep convective clouds over the Tibetan Plateau, characteristics of vertical structure of a deep strong convective cloud over Naqu station and a deep weak convective cloud approximately 100 km to the west of Naqu station, which occurred over 1300–1600 Beijing Time (BT) 9 July 2014 during the Third Tibetan Plateau Atmospheric Science Experiment (TIPEX-III), are analyzed, based on multi-source satellite data from TRMM, CloudSat, and Aqua, and radar data from ground-based vertically pointing radars (C-band frequency-modulated continuous-wave radar and KA-band millimeter wave cloud radar). The results are as follows. (1) The horizontal scales of both the deep strong and deep weak convective clouds were small (10–20 km), and their tops were high [15–16 km above sea level (ASL)]. Across the level of 0°C isotherm in the deep strong convective cloud, the reflectivity increased rapidly, suggesting that the melting process of solid precipitation particles through the 0°C level played an important role. A bright band located at 5.5 km ASL (i.e., 1 km above ground level) appeared during the period of convection weakening. (2) The reflectivity values from TRMM precipitation radar below 11 km were found to be overestimated compared to those derived from the C-band frequency-modulated continuous-wave radar. (3) Deep convective clouds were mainly ice clouds, and there were rich small ice particles above 10 km, while few large ice particles were found below 10 km. The microphysical processes of deep strong and deep weak convective clouds mainly included mixed-phase process and glaciated process, and the mixed-phase process can be divided into two types: one was the rimming process below the level of –25℃ (deep strong convective cloud) or –29℃ (deep weak convective cloud) and the other was aggregation and deposition process above that level. The latter process was accompanied with fast increase in ice particle effective radius. The above evidence from space-based and ground-based observational data further clarify the characteristics of vertical structure of deep convective clouds over the Tibetan Plateau, and provide a basis for the evaluation of simulation results of deep convective clouds by cloud models.

Simulation of the depolarization ratio of adiabatic water clouds by lidar

We have simulated the depolarization signal in adiabatic water clouds due to the occurrence of multiple scattering when measuring the microphysics characteristics using depolarization lidar. The number density of the adiabatic water clouds is constant in the vertical direction. The liquid water content and the effective radius increase nonlinearly with the height, and the varying rule is controlled by the barometric pressure, temperature, and the thermodynamic formulas. The wavelength of the lidar is chosen as 0.355 µm. From the computed results, we can see that the depolarization ratio of the adiabatic clouds increases with the penetration depth of the clouds, and increases with the increase in the receiving field of view angle (FOV). There are great differences between the adiabatic water clouds and the homogeneous clouds in the varying rules of the depolarization ratio. The effective radius of the clouds with a higher cloud base height is less than that of the clouds with a lower cloud base, and the depolarization ratio is also small with the same number density and observation conditions.