scholarly journals Effects of the Vertical Profiles of Cloud Droplets and Ice Particles on the Visible and Near-Infrared Radiative Properties of Mixed-Phase Stratocumulus Clouds

2005 ◽  
Vol 83 (4) ◽  
pp. 471-480 ◽  
Author(s):  
Yukio YOSHIDA ◽  
Shoji ASANO
Keyword(s):  
Near Infrared ◽  
Mixed Phase ◽  
Radiative Properties ◽  
Vertical Profiles ◽  
Cloud Droplets ◽  
Ice Particles ◽  
Stratocumulus Clouds

scholarly journals The relative impact of cloud condensation nuclei and ice nucleating particle concentrations on phase partitioning in Arctic mixed-phase stratocumulus clouds

2018 ◽  
Vol 18 (23) ◽  
pp. 17047-17059 ◽  
Author(s):  
Amy Solomon ◽  
Gijs de Boer ◽  
Jessie M. Creamean ◽  
Allison McComiskey ◽  
Matthew D. Shupe ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Mixed Phase ◽  
Radiative Properties ◽  
Condensation Nuclei ◽  
Phase Partitioning ◽  
Cloud Dynamics ◽  
Stratocumulus Clouds ◽  
Cloud Ice ◽  
Mixed Phase Clouds ◽  
The Impact

Abstract. This study investigates the interactions between cloud dynamics and aerosols in idealized large-eddy simulations (LES) of Arctic mixed-phase stratocumulus clouds (AMPS) observed at Oliktok Point, Alaska, in April 2015. This case was chosen because it allows the cloud to form in response to radiative cooling starting from a cloud-free state, rather than requiring the cloud ice and liquid to adjust to an initial cloudy state. Sensitivity studies are used to identify whether there are buffering feedbacks that limit the impact of aerosol perturbations. The results of this study indicate that perturbations in ice nucleating particles (INPs) dominate over cloud condensation nuclei (CCN) perturbations; i.e., an equivalent fractional decrease in CCN and INPs results in an increase in the cloud-top longwave cooling rate, even though the droplet effective radius increases and the cloud emissivity decreases. The dominant effect of ice in the simulated mixed-phase cloud is a thinning rather than a glaciation, causing the mixed-phase clouds to radiate as a grey body and the radiative properties of the cloud to be more sensitive to aerosol perturbations. It is demonstrated that allowing prognostic CCN and INPs causes a layering of the aerosols, with increased concentrations of CCN above cloud top and increased concentrations of INPs at the base of the cloud-driven mixed layer. This layering contributes to the maintenance of the cloud liquid, which drives the dynamics of the cloud system.

scholarly journals The relative impact of cloud condensation nuclei and ice nucleating particle concentrations on phase-partitioning in Arctic Mixed-Phase Stratocumulus Clouds

2018 ◽  
Author(s):  
Amy Solomon ◽  
Gijs de Boer ◽  
Jessie M. Creamean ◽  
Allison McComiskey ◽  
Matthew D. Shupe ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Mixed Phase ◽  
Radiative Properties ◽  
Condensation Nuclei ◽  
Phase Partitioning ◽  
Cloud Dynamics ◽  
Stratocumulus Clouds ◽  
Cloud Ice ◽  
Mixed Phase Clouds ◽  
The Impact

Abstract. This study investigates the interactions between cloud dynamics and aerosols in idealized large-eddy simulations of an Arctic mixed-phase stratocumulus cloud observed at Oliktok Point, Alaska in April 2015. This case was chosen because it allows the cloud to form in response to radiative cooling starting from a cloud-free state, rather than requiring the cloud ice and liquid to adjust to an initial cloudy state. Sensitivity studies are used to identify whether there are buffering feedbacks that limit the impact of aerosol perturbations. The results of this study indicate that perturbations in ice nucleating particles (INPs) dominate over cloud condensation nuclei (CCN) perturbations, i.e., an equivalent fractional decrease in CCN and INPs results in an increase in the cloud-top longwave cooling rate, even though the droplet effective radius increases and the cloud emissivity decreases. The dominant effect of ice in the simulated mixed-phase cloud is a thinning rather than a glaciation, causing the mixed-phase clouds to radiate as a grey body and the radiative properties of the cloud to be more sensitive to aerosol perturbations. It is demonstrated that allowing prognostic CCN and INP causes a layering of the aerosols, with increased concentrations of CCN above cloud top and increased concentrations of INP at the base of the cloud-driven mixed-layer. This layering contributes to the maintenance of the cloud liquid, which drives the dynamics of the cloud system.

scholarly journals Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements

2013 ◽  
Vol 13 (9) ◽  
pp. 24975-25012 ◽  
Author(s):  
Z. Ulanowski ◽  
P. H. Kaye ◽  
E. Hirst ◽  
R. S. Greenaway ◽  
R. J. Cotton ◽  
...  
Keyword(s):  
Light Scattering ◽  
Large Scale ◽  
Extreme Values ◽  
Mixed Phase ◽  
Radiative Properties ◽  
Small Scale ◽  
In Situ Data ◽  
Ice Particles ◽  
Test Particles

Abstract. The knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed phase clouds. Limitations of current cloud probes to measure these properties can be circumvented by acquiring two-dimensional light scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed phase and cirrus clouds. The patterns are analyzed using several measures of pattern texture, selected to reveal the magnitude of particle roughness or complexity. The retrieved roughness is compared to values obtained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corresponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have similar manifestations in terms of light scattering properties and also similar causes. Overall, the in situ data is consistent with ice particles with highly irregular or rough surfaces being dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cirrus forming in clean oceanic airmasses than in a continental, polluted one. Overall, the roughness and complexity is expected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question suggestions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity.

scholarly journals Supercooled liquid water and secondary ice production in Kelvin–Helmholtz instability as revealed by radar Doppler spectra observations

2021 ◽  
Author(s):  
Haoran Li ◽  
Alexei Korolev ◽  
Dmitri Moisseev
Keyword(s):  
Liquid Water ◽  
Supercooled Liquid ◽  
Mixed Phase ◽  
Ice Crystals ◽  
Radiation Budget ◽  
Doppler Spectrum ◽  
Droplet Growth ◽  
Liquid Droplets ◽  
Cloud Droplets ◽  
Ice Particles

Abstract. Mixed-phase clouds are globally omnipresent and play a major role in the Earth's radiation budget and precipitation formation. The existence of liquid droplets in presence of ice particles is microphysically unstable and depends on a delicate balance of several competing processes. Understanding mechanisms that govern ice initiation and moisture supply are important to understand the life-cycle of such clouds. This study presents observations that reveal the onset of drizzle inside a ∼600 m deep mixed-phase layer embedded in a stratiform precipitation system. Using Doppler spectra analysis, we show how large supercooled liquid droplets are generated in Kelvin-Helmholtz (K-H) instability despite ice particles falling from upper cloud layers. The spectral width of supercooled liquid water mode in radar Doppler spectrum is used to identify a region of increased turbulence. The observations show that large liquid droplets, characterized by reflectivity values larger than −20 dBZ, are generated in this region. In addition to cloud droplets, Doppler spectral analysis reveals the production of the columnar ice crystals in the K-H billows. The modelling study estimates that the concentration of these ice crystals is 3 ∼ 8 L−1, which is at least one order of magnitude higher than that of primary ice nucleating particles. Given the detail of the observations, we show that multiple populations of secondary ice particles are generated in regions where larger cloud droplets are produced and not at some constant level within the cloud. It is therefore hypothesized that K-H instability provides conditions favorable for enhanced droplet growth and formation of secondary ice particles.

scholarly journals Photomineralization mechanism changes the ability of dissolved organic matter to activate cloud droplets and to nucleate ice crystals

2019 ◽  
Author(s):  
Nadine Borduas-Dedekind ◽  
Rachele Ossola ◽  
Robert O. David ◽  
Lin S. Boynton ◽  
Vera Weichlinger ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Hydrological Cycle ◽  
Supercooled Liquid ◽  
Mixed Phase ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Cloud Droplets ◽  
Photochemical Processing ◽  
Mixed Phase Clouds

Abstract. An organic aerosol particle has a lifetime of approximately one week in the atmosphere during which it will be exposed to sunlight. Yet, the effect of photochemistry on the propensity of organic matter to participate in the initial cloud-forming steps is difficult to predict. In this study, we quantify on a molecular scale the effect of photochemical exposure of naturally occurring dissolved organic matter (DOM) and of a fulvic acid standard on its ability to form mixed-phase clouds, by acting as cloud condensation nuclei (CCN) and by acting as ice nucleating particles (INPs). We find that photochemical processing, equivalent to 4.6 days in the atmosphere, of DOM increases its ability to form cloud droplets by up to a factor of 2.5 but decreases its ability to form ice crystals at a loss rate of −0.04°CT50 h−1 of sunlight at ground level. In other words, the ice nucleation activity of photooxidized DOM can require up to 4 degrees colder temperatures for 50 % of the droplets to activate as ice crystals under immersion freezing conditions. This temperature change could impact the ratio of ice to water droplets within a mixed phase cloud by delaying the onset of glaciation and by increasing the supercooled liquid fraction of the cloud, thereby modifying the radiative properties and the lifetime of the cloud. Concurrently, a photomineralization mechanism was quantified by monitoring the loss of organic carbon and the simultaneous production of organic acids, such as formic, acetic, oxalic and pyruvic acids, CO and CO2. This mechanism explains and predicts the observed increase in CCN and decrease in INP efficiencies. Indeed, we show that photochemical processing can be a dominant atmospheric aging process, impacting CCN and INP efficiencies and concentrations. Photomineralization can thus alter the aerosol-cloud radiative effects of organic matter by modifying the supercooled liquid water-to-ice crystal ratio in mixed-phase clouds with implications for cloud lifetime, precipitation patterns and the hydrological cycle.

scholarly journals Supercooled liquid water and secondary ice production in Kelvin–Helmholtz instability as revealed by radar Doppler spectra observations

2021 ◽  
Vol 21 (17) ◽  
pp. 13593-13608
Author(s):  
Haoran Li ◽  
Alexei Korolev ◽  
Dmitri Moisseev
Keyword(s):  
Spectral Analysis ◽  
Liquid Water ◽  
Supercooled Liquid ◽  
Mixed Phase ◽  
Ice Crystals ◽  
Doppler Spectrum ◽  
Liquid Droplets ◽  
Cloud Droplets ◽  
Ice Particles ◽  
Doppler Spectral Analysis

Abstract. Mixed-phase clouds are globally omnipresent and play a major role in the Earth's radiation budget and precipitation formation. The existence of liquid droplets in the presence of ice particles is microphysically unstable and depends on a delicate balance of several competing processes. Understanding mechanisms that govern ice initiation and moisture supply are important to understand the life cycle of such clouds. This study presents observations that reveal the onset of drizzle inside a ∼ 600 m deep mixed-phase layer embedded in a stratiform precipitation system. Using Doppler spectral analysis, we show how large supercooled liquid droplets are generated in Kelvin–Helmholtz (K–H) instability despite ice particles falling from upper cloud layers. The spectral width of the supercooled liquid water mode in the radar Doppler spectrum is used to identify a region of increased turbulence. The observations show that large liquid droplets, characterized by reflectivity values larger than −20 dBZ, are generated in this region. In addition to cloud droplets, Doppler spectral analysis reveals the production of columnar ice crystals in the K–H billows. The modeling study estimates that the concentration of these ice crystals is 3–8 L−1, which is at least 1 order of magnitude higher than that of primary ice-nucleating particles. Given the detail of the observations, we show that multiple populations of secondary ice particles are generated in regions where larger cloud droplets are produced and not at some constant level within the cloud. It is, therefore, hypothesized that K–H instability provides conditions favorable for enhanced droplet growth and formation of secondary ice particles.

scholarly journals Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements

2014 ◽  
Vol 14 (3) ◽  
pp. 1649-1662 ◽  
Author(s):  
Z. Ulanowski ◽  
P. H. Kaye ◽  
E. Hirst ◽  
R. S. Greenaway ◽  
R. J. Cotton ◽  
...  
Keyword(s):  
Light Scattering ◽  
Large Scale ◽  
Extreme Values ◽  
Mixed Phase ◽  
Radiative Properties ◽  
Small Scale ◽  
In Situ Data ◽  
Ice Particles ◽  
Test Particles

Abstract. The knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed-phase clouds. Limitations of current cloud probes to measure these properties can be circumvented by acquiring two-dimensional light-scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed-phase and cirrus clouds. The patterns are analysed using several measures of pattern texture, selected to reveal the magnitude of particle roughness or complexity. The retrieved roughness is compared to values obtained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corresponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have similar manifestations in terms of light-scattering properties and also similar causes. Overall, the in situ data are consistent, with ice particles with highly irregular or rough surfaces being dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cirrus forming in clean oceanic air masses than in a continental, polluted one. Overall, the roughness and complexity are expected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question suggestions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity.

scholarly journals Characterization of Arctic mixed-phase cloud properties at small scale and coupling with satellite remote sensing

2017 ◽  
Author(s):  
Guillaume Mioche ◽  
Olivier Jourdan ◽  
Julien Delanoë ◽  
Christophe Gourbeyre ◽  
Guy Febvre ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Crystal Size ◽  
Mixed Phase ◽  
Ice Crystals ◽  
Small Scale ◽  
Vertical Profiles ◽  
Liquid Droplets ◽  
Ice Crystal ◽  
High Concentration ◽  
Ice Crystal Size

Abstract. This study aims to characterize the microphysical and optical properties of ice crystals and supercooled liquid droplets within low-level Arctic mixed-phase clouds (MPC). We compiled and analyzed cloud in situ measurements from 4 airborne campaigns (18 flights, 71 vertical profiles in MPC) over the Greenland Sea and the Svalbard region. Cloud phase discrimination and representative vertical profiles of number, size, mass and shapes of ice crystals and liquid droplets are assessed. The results show that the liquid phase dominates the upper part of the MPC with high concentration of small droplets (120 cm−3, 15&tinsp;μm), and averaged LWC around 0.2 g m−3. The ice phase is found everywhere within the MPC layers, but dominates the properties in the lower part of the cloud and below where ice crystals precipitate down to the surface. The analysis of the ice crystal morphology highlights that irregulars and rimed are the main particle habit followed by stellars and plates. We hypothesize that riming and condensational growth processes (including the Wegener-Bergeron-Findeisein mechanism) are the main growth mechanisms involved in MPC. The differences observed in the vertical profiles of MPC properties from one campaign to another highlight that large values of LWC and high concentration of smaller droplets are possibly linked to polluted situations which lead to very low values of ice crystal size and IWC. On the contrary, clean situations with low temperatures exhibit larger values of ice crystal size and IWC. Several parameterizations relevant for remote sensing or modeling are also determined, such as IWC (and LWC) – extinction relationship, ice and liquid integrated water paths, ice concentration and liquid water fraction according to temperature. Finally, 4 flights collocated with active remote sensing observations from CALIPSO and CloudSat satellites are specifically analyzed to evaluate the cloud detection and cloud thermodynamical phase DARDAR retrievals. This comparison is valuable to assess the sub-pixel variability of the satellite measurements as well as their shortcomings/performance near the ground.

scholarly journals Quantifying lower tropospheric methane concentrations using GOSAT near-IR and TES thermal IR measurements

2015 ◽  
Vol 8 (8) ◽  
pp. 3433-3445 ◽  
Author(s):  
J. R. Worden ◽  
A. J. Turner ◽  
A. Bloom ◽  
S. S. Kulawik ◽  
J. Liu ◽  
...  
Keyword(s):  
Near Infrared ◽  
Surface Fluxes ◽  
Vertical Profiles ◽  
Monthly Average ◽  
Near Ir ◽  
Surface Measurements ◽  
Increased Sensitivity ◽  
The Impact ◽  
Total Column ◽  
Methane Concentrations

Abstract. Evaluating surface fluxes of CH4 using total column data requires models to accurately account for the transport and chemistry of methane in the free troposphere and stratosphere, thus reducing sensitivity to the underlying fluxes. Vertical profiles of methane have increased sensitivity to surface fluxes because lower tropospheric methane is more sensitive to surface fluxes than a total column, and quantifying free-tropospheric CH4 concentrations helps to evaluate the impact of transport and chemistry uncertainties on estimated surface fluxes. Here we demonstrate the potential for estimating lower tropospheric CH4 concentrations through the combination of free-tropospheric methane measurements from the Aura Tropospheric Emission Spectrometer (TES) and XCH4 (dry-mole air fraction of methane) from the Greenhouse gases Observing SATellite – Thermal And Near-infrared for carbon Observation (GOSAT TANSO, herein GOSAT for brevity). The calculated precision of these estimates ranges from 10 to 30 ppb for a monthly average on a 4° × 5° latitude/longitude grid making these data suitable for evaluating lower-tropospheric methane concentrations. Smoothing error is approximately 10 ppb or less. Comparisons between these data and the GEOS-Chem model demonstrate that these lower-tropospheric CH4 estimates can resolve enhanced concentrations over flux regions that are challenging to resolve with total column measurements. We also use the GEOS-Chem model and surface measurements in background regions across a range of latitudes to determine that these lower-tropospheric estimates are biased low by approximately 65 ppb, with an accuracy of approximately 6 ppb (after removal of the bias) and an actual precision of approximately 30 ppb. This 6 ppb accuracy is consistent with the accuracy of TES and GOSAT methane retrievals.

scholarly journals Cloud droplets to drizzle: Contribution of transition drops to microphysical and optical properties of marine stratocumulus clouds

2017 ◽  
Vol 44 (15) ◽  
pp. 8002-8010 ◽  
Author(s):  
S. Glienke ◽  
A. Kostinski ◽  
J. Fugal ◽  
R. A. Shaw ◽  
S. Borrmann ◽  
...  
Keyword(s):  
Optical Properties ◽  
Cloud Droplets ◽  
Marine Stratocumulus ◽  
Stratocumulus Clouds
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