Transport of isoprene and its oxidation products by deep convective clouds in the Amazon

2021 ◽  
Author(s):  
Roman Bardakov ◽  
Joel Thornton ◽  
Ilona Riipinen ◽  
Radovan Krejci ◽  
Annica Ekman
Keyword(s):  
Deep Convection ◽  
Convective Cloud ◽  
Particle Growth ◽  
Lightning Activity ◽  
Oxidation Products ◽  
Gas Uptake ◽  
Convective Clouds ◽  
Ice Particles ◽  
Volatile Oxidation Products ◽  
Deep Convective Clouds

<p>Transport of organic trace gases by deep convective clouds plays an important role for new particle formation (NPF) and particle growth in the upper atmosphere. Isoprene accounts for a major fraction of the global volatile organic vapor emissions and a significant fraction is emitted in the Amazon. We examined transport and chemical processing of isoprene and its oxidation products in a deep convective cloud over the Amazon using a box model. Trajectories of individual air parcels of the cloud derived from a large eddy simulation are used as input to the model. Our results show that there exist two main pathways for NPF from isoprene associated with deep convection. The first one is when the gas transport occurs through a cloud with low lightning activity and with efficient gas uptake of low-volatile oxidation products by ice particles. Some of the isoprene will reach the cloud outflow where it is further aged and produces low volatile species capable of forming and growing new particles. The second way is via transport through clouds with high lightning activity and with low gas uptake by ice. For this case, low volatile oxidation products will reach the immediate outflow in concentrations close to the values observed in the boundary layer. The efficiency of gas condensation on ice particles is still uncertain and further research in this direction is needed.</p>

scholarly journals How do changes in warm-phase microphysics affect deep convective clouds?

2017 ◽  
Vol 17 (15) ◽  
pp. 9585-9598 ◽  
Author(s):  
Qian Chen ◽  
Ilan Koren ◽  
Orit Altaratz ◽  
Reuven H. Heiblum ◽  
Guy Dagan ◽  
...  
Keyword(s):  
Rain Rate ◽  
Convective Cloud ◽  
Cloud Fraction ◽  
Marshall Islands ◽  
Cloud System ◽  
Main Question ◽  
Convective Clouds ◽  
Deep Convective Clouds ◽  
Aerosol Effects ◽  
Deep Convective Cloud

Abstract. Understanding aerosol effects on deep convective clouds and the derived effects on the radiation budget and rain patterns can largely contribute to estimations of climate uncertainties. The challenge is difficult in part because key microphysical processes in the mixed and cold phases are still not well understood. For deep convective clouds with a warm base, understanding aerosol effects on the warm processes is extremely important as they set the initial and boundary conditions for the cold processes. Therefore, the focus of this study is the warm phase, which can be better resolved. The main question is: How do aerosol-derived changes in the warm phase affect the properties of deep convective cloud systems? To explore this question, we used a weather research and forecasting (WRF) model with spectral bin microphysics to simulate a deep convective cloud system over the Marshall Islands during the Kwajalein Experiment (KWAJEX). The model results were validated against observations, showing similarities in the vertical profile of radar reflectivity and the surface rain rate. Simulations with larger aerosol loading resulted in a larger total cloud mass, a larger cloud fraction in the upper levels, and a larger frequency of strong updrafts and rain rates. Enlarged mass both below and above the zero temperature level (ZTL) contributed to the increase in cloud total mass (water and ice) in the polluted runs. Increased condensation efficiency of cloud droplets governed the gain in mass below the ZTL, while both enhanced condensational and depositional growth led to increased mass above it. The enhanced mass loading above the ZTL acted to reduce the cloud buoyancy, while the thermal buoyancy (driven by the enhanced latent heat release) increased in the polluted runs. The overall effect showed an increased upward transport (across the ZTL) of liquid water driven by both larger updrafts and larger droplet mobility. These aerosol effects were reflected in the larger ratio between the masses located above and below the ZTL in the polluted runs. When comparing the net mass flux crossing the ZTL in the clean and polluted runs, the difference was small. However, when comparing the upward and downward fluxes separately, the increase in aerosol concentration was seen to dramatically increase the fluxes in both directions, indicating the aerosol amplification effect of the convection and the affected cloud system properties, such as cloud fraction and rain rate.

scholarly journals Ice Microphysics Observations in Hurricane Humberto: Comparison with Non-Hurricane-Generated Ice Cloud Layers

2006 ◽  
Vol 63 (1) ◽  
pp. 288-308 ◽  
Author(s):  
Andrew J. Heymsfield ◽  
Aaron Bansemer ◽  
Stephen L. Durden ◽  
Robert L. Herman ◽  
T. Paul Bui
Keyword(s):  
Doppler Radar ◽  
Deep Convection ◽  
Particle Growth ◽  
Dual Wavelength ◽  
Size Distributions ◽  
Temperature Growth ◽  
Radar Observations ◽  
Ice Cloud ◽  
Ice Particles ◽  
High Concentrations

Abstract Measurements are presented that were acquired from the National Aeronautics and Space Administration (NASA) DC-8 aircraft during an intensive 3-day study of Tropical Storm/Hurricane Humberto on 22, 23, and 24 September 2001. Particle size distributions, particle image information, vertical velocities, and single- and dual-wavelength Doppler radar observations were obtained during repeated sampling of the eyewall and outer eye regions. Eyewall sampling temperatures ranged from −22° to −57°C and peak updraft velocities from 4 to 15 m s−1. High concentrations of small ice particles, in the order 50 cm−3 and above, were observed within and around the updrafts. Aggregates, some larger than 7 mm, dominated the larger sizes. The slope of the fitted exponential size distributions λ was distinctly different close to the eye than outside of that region. Even at low temperatures, λ was characteristic of warm temperature growth (λ < 30 cm−1) close to the eye and characteristic of low temperature growth outside of it as well (λ > 100 cm−1). The two modes found for λ are shown to be consistent with observations from nonhurricane ice cloud layers formed through deep convection, but differ markedly from ice cloud layers generated in situ. It is shown that the median, mass-weighted, terminal velocities derived for the Humberto data and from the other datasets are primarily a function of λ. Microphysical measurements and dual wavelength radar observations are used together to infer and interpret particle growth processes. Rain in the lower portions of the eyewall extended up to the 6- or 7-km level. In the outer eye regions, aggregation progressed downward from between 8.5 and 11.9 km to the melting layer, with some graupel noted in rainbands. Homogeneous ice nucleation is implicated in the high concentrations of small ice particles observed in the vicinity of the updrafts.

Comments on “Do Ultrafine Cloud Condensation Nuclei Invigorate Deep Convection?”

2021 ◽  
Vol 78 (1) ◽  
pp. 329-339
Author(s):  
Jiwen Fan ◽  
Alexander Khain
Keyword(s):  
Cloud Condensation Nuclei ◽  
Deep Convection ◽  
Diffusional Growth ◽  
Loading Effect ◽  
Convective Clouds ◽  
Nonlinear Responses ◽  
High Acceleration ◽  
Deep Convective Clouds ◽  
Physics Modeling ◽  
Aerosol Effects

AbstractHere we elaborate on the deficiencies associated with the theoretical arguments and model simulations in a paper by Grabowski and Morrison (2020, hereafter GM20) that argued convective invigoration by aerosols does not exist. We show that the invigoration can be supported by both accurate theoretical analysis and explicit physics modeling with prognostic supersaturation and aerosols. Negligible invigoration by aerosols via drop freezing in GM20 was explained by a complete compensation between the heating effect from the freezing of extra liquid water and the extra loading effect during droplet ascending. But the reality is that droplet ascending then freezing occur at different locations and time scales, producing complex nonlinear responses that depend on the duration and location of the forcing. Also, this argument neglects the effect of off-loading of precipitating ice particles, increases in condensation during ascending, and riming and deposition accompanying droplet freezing. Regarding the warm-phase invigoration, the quasi-steady assumption for supersaturation as adopted in GM20 makes condensation independent of droplet number and size, therefore an incorrect interpretation of warm-phase invigoration. We illustrate that the quasi-steady assumption is invalid for updrafts of deep convective clouds in clean conditions because of the high acceleration of vertical velocity and the fast depletion of droplets by raindrop formation and accretion. Any assumption imposed on supersaturation, such as quasi-steady approximation and saturation adjustment, leads to errors in the evaluation of aerosol effects on diffusional growth and related buoyancy. Furthermore, we demonstrate that the piggybacking approach they used cannot prove or disprove the convective invigoration.

scholarly journals Sensitivity of a Large Ensemble of Tropical Convective Systems to Changes in the Thermodynamic and Dynamic Forcings

2008 ◽  
Vol 65 (6) ◽  
pp. 1773-1794 ◽  
Author(s):  
Zachary A. Eitzen ◽  
Kuan-Man Xu
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Radiant Energy ◽  
Convective Cloud ◽  
Energy System ◽  
Scale Model ◽  
Convective Clouds ◽  
Cloud Properties ◽  
Deep Convective Clouds ◽  
Deep Convective Cloud

Abstract A two-dimensional cloud-resolving model (CRM) is used to perform five sets of simulations of 68 deep convective cloud objects identified with Clouds and the Earth’s Radiant Energy System (CERES) data to examine their sensitivity to changes in thermodynamic and dynamic forcings. The control set of simulations uses observed sea surface temperatures (SSTs) and is forced by advective cooling and moistening tendencies derived from a large-scale model analysis matched to the time and location of each cloud object. Cloud properties, such as albedo, effective cloud height, cloud ice and snow path, and cloud radiative forcing (CRF), are analyzed in terms of their frequency distributions rather than their mean values. Two sets of simulations, F+50% and F−50%, use advective tendencies that are 50% greater and 50% smaller than the control tendencies, respectively. The increased cooling and moistening tendencies cause more widespread convection in the F+50% set of simulations, resulting in clouds that are optically thicker and higher than those produced by the control and F−50% sets of simulations. The magnitudes of both longwave and shortwave CRF are skewed toward higher values with the increase in advective forcing. These significant changes in overall cloud properties are associated with a substantial increase in deep convective cloud fraction (from 0.13 for the F−50% simulations to 0.34 for the F+50% simulations) and changes in the properties of non–deep convective clouds, rather than with changes in the properties of deep convective clouds. Two other sets of simulations, SST+2K and SST−2K, use SSTs that are 2 K higher and 2 K lower than those observed, respectively. The updrafts in the SST+2K simulations tend to be slightly stronger than those of the control and SST−2K simulations, which may cause the SST+2K cloud tops to be higher. The changes in cloud properties, though smaller than those due to changes in the dynamic forcings, occur in both deep convective and non–deep convective cloud categories. The overall changes in some cloud properties are moderately significant when the SST is changed by 4 K. The changes in the domain-averaged shortwave and longwave CRFs are larger in the dynamic forcing sensitivity sets than in the SST sensitivity sets. The cloud feedback effects estimated from the SST−2K and SST+2K sets are comparable to prior studies.

An Evaluation of the Proposed Mechanism of the Adaptive Infrared Iris Hypothesis Using TRMM VIRS and PR Measurements

2005 ◽  
Vol 18 (20) ◽  
pp. 4185-4194 ◽  
Author(s):  
Anita D. Rapp ◽  
Christian Kummerow ◽  
Wesley Berg ◽  
Brian Griffith
Keyword(s):  
Surface Temperature ◽  
Deep Convection ◽  
Cloud Amount ◽  
Tropical Rainfall Measuring Mission ◽  
Convective Cloud ◽  
Sea Surface ◽  
Central Pacific ◽  
Convective Clouds ◽  
Brightness Temperatures ◽  
Surface Rainfall

Abstract Significant controversy surrounds the adaptive infrared iris hypothesis put forth by Lindzen et al., whereby tropical anvil cirrus detrainment is hypothesized to decrease with increasing sea surface temperature (SST). This dependence would act as an iris, allowing more infrared radiation to escape into space and inhibiting changes in the surface temperature. This hypothesis assumes that increased precipitation efficiency in regions of higher sea surface temperatures will reduce cirrus detrainment. Tropical Rainfall Measuring Mission (TRMM) satellite measurements are used here to investigate the adaptive infrared iris hypothesis. Pixel-level Visible and Infrared Scanner (VIRS) 10.8-μm brightness temperature data and precipitation radar (PR) rain-rate data from TRMM are collocated and matched to determine individual convective cloud boundaries. Each cloudy pixel is then matched to the underlying SST. This study examines single- and multicore convective clouds separately to directly determine if a relationship exists between the size of convective clouds, their precipitation, and the underlying SSTs. In doing so, this study addresses some of the criticisms of the Lindzen et al. study by eliminating their more controversial method of relating bulk changes of cloud amount and SST across a large domain in the Tropics. The current analysis does not show any significant SST dependence of the ratio of cloud area to surface rainfall for deep convection in the tropical western and central Pacific. Results do, however, suggest that SST plays an important role in the ratio of cloud area and surface rainfall for warm rain processes. For clouds with brightness temperatures between 270 and 280 K, a net decrease in cloud area normalized by rainfall of 5% per degree SST was found.

scholarly journals Secondary Ice Formation in Idealised Deep Convection—Source of Primary Ice and Impact on Glaciation

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 542
Author(s):  
Annette K. Miltenberger ◽  
Tim Lüttmer ◽  
Christoph Siewert
Keyword(s):  
Deep Convection ◽  
Three Dimensional ◽  
Convective Cloud ◽  
Cloud Formation ◽  
Ice Formation ◽  
Ice Crystal ◽  
Lagrangian Analysis ◽  
Vertical Coupling ◽  
Convective Clouds ◽  
Ice Production

Secondary ice production via rime-splintering is considered to be an important process for rapid glaciation and high ice crystal numbers observed in mixed-phase convective clouds. An open question is how rime-splintering is triggered in the relatively short time between cloud formation and observations of high ice crystal numbers. We use idealised simulations of a deep convective cloud system to investigate the thermodynamic and cloud microphysical evolution of air parcels, in which the model predicts secondary ice formation. The Lagrangian analysis suggests that the “in-situ” formation of rimers either by growth of primary ice or rain freezing does not play a major role in triggering secondary ice formation. Instead, rimers are predominantly imported into air parcels through sedimentation form higher altitudes. While ice nucleating particles (INPs) initiating heterogeneous freezing of cloud droplets at temperatures warmer than −10 °C have no discernible impact of the occurrence of secondary ice formation, in a scenario with rain freezing secondary ice production is initiated slightly earlier in the cloud evolution and at slightly different places, although with no major impact on the abundance or spatial distribution of secondary ice in the cloud as a whole. These results suggest that for interpreting and analysing observational data and model experiments regarding cloud glaciation and ice formation it is vital to consider the complex vertical coupling of cloud microphysical processes in deep convective clouds via three-dimensional transport and sedimentation.

scholarly journals Observing relationships between lightning and cloud profiles by means of a satellite-borne cloud radar

2017 ◽  
Vol 10 (1) ◽  
pp. 221-230 ◽  
Author(s):  
Martina Buiat ◽  
Federico Porcù ◽  
Stefano Dietrich
Keyword(s):  
Vertical Distribution ◽  
Lightning Activity ◽  
Convective Clouds ◽  
Ice Particles ◽  
Ice Water Content ◽  
Ice Content ◽  
Cloud Ice ◽  
Ice Water ◽  
The Vertical Distribution ◽  
Polar Satellite

Abstract. Cloud electrification and related lightning activity in thunderstorms have their origin in the charge separation and resulting distribution of charged iced particles within the cloud. So far, the ice distribution within convective clouds has been investigated mainly by means of ground-based meteorological radars. In this paper we show how the products from Cloud Profiling Radar (CPR) on board CloudSat, a polar satellite of NASA's Earth System Science Pathfinder (ESSP), can be used to obtain information from space on the vertical distribution of ice particles and ice content and relate them to the lightning activity. The analysis has been carried out, focusing on 12 convective events over Italy that crossed CloudSat overpasses during significant lightning activity. The CPR products considered here are the vertical profiles of cloud ice water content (IWC) and the effective radius (ER) of ice particles, which are compared with the number of strokes as measured by a ground lightning network (LINET). Results show a strong correlation between the number of strokes and the vertical distribution of ice particles as depicted by the 94 GHz CPR products: in particular, cloud upper and middle levels, high IWC content and relatively high ER seem to be favourable contributory causes for CG (cloud to ground) stroke occurrence.

scholarly journals The response of precipitation to aerosol through riming and melting in deep convective clouds

2010 ◽  
Vol 10 (11) ◽  
pp. 29007-29050
Author(s):  
Z. Cui ◽  
S. Davies ◽  
K. S. Carslaw ◽  
A. M. Blyth
Keyword(s):  
Cloud Model ◽  
Cloud Microphysics ◽  
Mixed Phase ◽  
Cloud Base ◽  
Spatial And Temporal Variability ◽  
Convective Clouds ◽  
Ice Particles ◽  
Wide Range ◽  
Deep Convective Clouds ◽  
The Impact

Abstract. We have used a 2-D axisymmetric, non-hydrostatic, bin-resolved cloud model to examine the impact of aerosol changes on the development of mixed-phase convective clouds. We have simulated convective clouds from four different sites (three continental and one tropical marine) with a wide range of realistic aerosol loadings and initial thermodynamic conditions (a total of 93 different clouds). It is found that the accumulated precipitation responds very differently to changing aerosol in the marine and continental environments. For the continental clouds, the scaled total precipitation reaches a maximum for aerosol that produce drop numbers at cloud base between 180–430 cm−3 when other conditions are the same. In contrast, all the tropical marine clouds show an increase in accumulated precipitation and deeper convection with increasing aerosol loading. For continental clouds, drops are rapidly depleted by ice particles shortly after the onset of precipitation. The precipitation is dominantly produced by melting ice particles. The riming rate increases with aerosol when the loading is very low, and decreases when the loading is high. Peak precipitation intensities tend to increase with aerosol up to drop concentrations (at cloud base) of ~500 cm−3 then decrease with further aerosol increases. This behaviour is caused by the initial transition from warm to mixed-phase rain followed by reduced efficiency of mixed-phase rain at very high drop concentrations. The response of tropical marine clouds to increasing aerosol is different to, and larger than, that of continental clouds. In the more humid tropical marine environment with low cloud bases we find that accumulated precipitation increases with increasing aerosol. The increase is driven by the transition from warm to mixed-phase rain. Our study suggests that the response of deep convective clouds to aerosol will be an important contribution to the spatial and temporal variability in cloud microphysics and precipitation.

scholarly journals Evaluation and Improvement of Turbulence Parameterization inside Deep Convective Clouds at Kilometer-Scale Resolution

2017 ◽  
Vol 145 (10) ◽  
pp. 3947-3967 ◽  
Author(s):  
Antoine Verrelle ◽  
Didier Ricard ◽  
Christine Lac
Keyword(s):  
Thermal Effects ◽  
Convective Cloud ◽  
Coarse Graining ◽  
Eddy Diffusivity ◽  
Convective Clouds ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Deep Convective Clouds ◽  
The Difference ◽  
Horizontal Grid

A challenge for cloud-resolving models is to make subgrid schemes suitable for deep convective clouds. A benchmark large-eddy simulation (LES) was conducted on a deep convective cloud with 50-m grid spacing. The reference turbulence fields for horizontal grid spacings of 500 m, 1 km, and 2 km were deduced by coarse graining the 50-m LES outputs, allowing subgrid fields to be characterized. The highest values of reference subgrid turbulent kinetic energy (TKE) were localized in the updraft core, and the production of subgrid TKE was dominated by thermal effects at coarser resolution (2 and 1 km) and by dynamical effects at finer resolution than 500 m. Countergradient areas due to nonlocal mixing appeared on the subgrid vertical thermodynamical fluxes in the updraft core and near the cloud top. The subgrid dynamical variances were anisotropic but the difference between vertical and horizontal variances diminished with increasing resolution. Then offline and online evaluations were conducted for this deep convective case with two different parameterization approaches at kilometer-scale resolution and gave the same results. A commonly used eddy-diffusivity turbulence scheme underestimated the thermal production of subgrid TKE and did not enable the countergradient structures to be reproduced. In contrast, the approach proposed by Moeng, parameterizing the subgrid vertical thermodynamical fluxes in terms of horizontal gradients of resolved variables, reproduced these characteristics and limited the overestimation of vertical velocity.

scholarly journals Preconditioning, aerosols, and radiation control the temperature of glaciation in Amazonian clouds

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Alexandre L. Correia ◽  
Elisa T. Sena ◽  
Maria A. F. Silva Dias ◽  
Ilan Koren
Keyword(s):  
Water Cycle ◽  
Deep Convection ◽  
Convective Cloud ◽  
Convective Clouds ◽  
Radiation Control ◽  
Cloud Models ◽  
Radiation Fluxes ◽  
Cloud Development ◽  
Fundamental Phenomenon ◽  
Heat Budgets

AbstractGlaciation in clouds is a fundamental phenomenon in determining Earth’s radiation fluxes, sensible and latent heat budgets in the atmosphere, the water cycle, cloud development and lifetime. Nevertheless, the main mechanisms that govern the temperature of glaciation in clouds have not been fully identified. Here we present an analysis of 15 years (2000-2014) of satellite, sunphotometer, and reanalysis datasets over the Amazon. We find that the temperature of glaciation in convective clouds is controlled by preconditioning dynamics, natural and anthropic aerosols, and radiation. In a moist atmospheric column, prone to deep convection, increasing the amount of aerosols leads to a delay in the onset of glaciation, reducing the glaciation temperature. For a dry column, radiative extinction by biomass burning smoke leads to atmospheric stabilization and an increase in the glaciation temperature. Our results offer observational benchmarks that can help a more precise description of glaciation in convective cloud models.

Sign in / Sign up

Export Citation Format

Share Document