scholarly journals A Study of Microphysical Mechanisms for Correlation Patterns between Droplet Radius and Optical Thickness of Warm Clouds with a Spectral Bin Microphysics Cloud Model

2010 ◽  
Vol 67 (4) ◽  
pp. 1126-1141 ◽  
Author(s):  
Kentaroh Suzuki ◽  
Teruyuki Nakajima ◽  
Takashi Y. Nakajima ◽  
Alexander P. Khain
Keyword(s):  
Optical Thickness ◽  
Cloud Model ◽  
Cloud Droplet ◽  
Particle Growth ◽  
Size Distribution Function ◽  
Droplet Radius ◽  
Liquid Water Path ◽  
Correlation Pattern ◽  
Cloud Particle ◽  
Bin Microphysics

Abstract This study investigates the correlation patterns between cloud droplet effective radius (CDR) and cloud optical thickness (COT) of warm clouds with a nonhydrostatic spectral bin microphysics cloud model. Numerical experiments are performed with the model to simulate low-level warm clouds. The results show a positive and negative correlation pattern between CDR and COT for nondrizzling and drizzling stages of cloud development, respectively, consistent with findings of previous observational studies. Only a positive correlation is simulated when the collection process is switched off in the experiment, whereas both the positive and negative correlations are reproduced in the simulation with collection as well as condensation processes. The positive and negative correlations can also be explained in terms of an evolution pattern of the size distribution function due to condensation and collection processes, respectively. Sensitivity experiments are also performed to examine how the CDR–COT correlation patterns are influenced by dynamical and aerosol conditions. The dynamical effect tends to change the amplitude of the CDR–COT plot mainly through changing the liquid water path, whereas the aerosol amount significantly modifies the correlation pattern between CDR and COT mainly through changing the cloud particle number concentration. These results suggest that the satellite-observed relationships between CDR and COT can be interpreted as being formed through microphysical particle growth processes under various dynamical and aerosol conditions in the real atmosphere.

scholarly journals Characteristics of Correlation Statistics between Droplet Radius and Optical Thickness of Warm Clouds Simulated by a Three-Dimensional Regional-Scale Spectral Bin Microphysics Cloud Model

2012 ◽  
Vol 69 (2) ◽  
pp. 484-503 ◽  
Author(s):  
Yousuke Sato ◽  
Kentaroh Suzuki ◽  
Takamichi Iguchi ◽  
In-Jin Choi ◽  
Hiroyuki Kadowaki ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Cloud Model ◽  
Regional Scale ◽  
Atmospheric Stability ◽  
Three Dimensional ◽  
Droplet Radius ◽  
Cloud Particle ◽  
Sbm Model ◽  
Bin Microphysics ◽  
Correlation Statistics

Abstract Three-dimensional downscaling simulations using a spectral bin microphysics (SBM) model were conducted to investigate the effects of aerosol amount and dynamical stabilities of the atmosphere on the correlation statistics between cloud droplet effective radius (RE) and cloud optical thickness (COT) of warm clouds off the coast of California. The regeneration process of aerosols was implemented into the SBM and was found to be necessary for simulating the satellite-observed microphysical properties of warm clouds by the SBM model used in this study. The results showed that the aerosol amount changed the correlation statistics in a way that changes the cloud particle number concentration, whereas the inversion height of the boundary layer, which is related to the atmospheric stability and the cloud-top height, changed the correlation statistics in a way that changes the liquid water path. These results showed that the dominant mechanisms that control the correlation statistics are similar to those suggested by previous modeling studies based on two-dimensional idealized simulations. On the other hand, the present three-dimensional modeling was also able to simulate some realistic patterns of the correlation statistics, namely, mixtures of characteristic patterns and the “high-heeled” pattern as observed by satellite remote sensing.

scholarly journals Conditions for super-adiabatic droplet growth after entrainment mixing

2016 ◽  
Vol 16 (14) ◽  
pp. 9421-9433 ◽  
Author(s):  
Fan Yang ◽  
Raymond Shaw ◽  
Huiwen Xue
Keyword(s):  
Cloud Model ◽  
Cloud Droplet ◽  
Droplet Radius ◽  
Droplet Growth ◽  
Critical Height ◽  
Growth Region ◽  
Cloud Droplets ◽  
Environmental Air ◽  
Bin Microphysics ◽  
Entrainment Mixing

Abstract. Cloud droplet response to entrainment and mixing between a cloud and its environment is considered, accounting for subsequent droplet growth during adiabatic ascent following a mixing event. The vertical profile for liquid water mixing ratio after a mixing event is derived analytically, allowing the reduction to be predicted from the mixing fraction and from the temperature and humidity for both the cloud and environment. It is derived for the limit of homogeneous mixing. The expression leads to a critical height above the mixing level: at the critical height the cloud droplet radius is the same for both mixed and unmixed parcels, and the critical height is independent of the updraft velocity and mixing fraction. Cloud droplets in a mixed parcel are larger than in an unmixed parcel above the critical height, which we refer to as the “super-adiabatic” growth region. Analytical results are confirmed with a bin microphysics cloud model. Using the model, we explore the effects of updraft velocity, aerosol source in the environmental air, and polydisperse cloud droplets. Results show that the mixed parcel is more likely to reach the super-adiabatic growth region when the environmental air is humid and clean. It is also confirmed that the analytical predictions are matched by the volume-mean cloud droplet radius for polydisperse size distributions. The findings have implications for the origin of large cloud droplets that may contribute to onset of collision–coalescence in warm clouds.

scholarly journals Correlation Pattern between Effective Radius and Optical Thickness of Water Clouds Simulated by a Spectral Bin Microphysics Cloud Model

SOLA ◽  
2006 ◽  
Vol 2 ◽  
pp. 116-119 ◽  
Author(s):  
Kentaroh Suzuki ◽  
Teruyuki Nakajima ◽  
Takashi Y. Nakajima ◽  
Alexander Khain
Keyword(s):  
Optical Thickness ◽  
Cloud Model ◽  
Effective Radius ◽  
Correlation Pattern ◽  
Bin Microphysics

scholarly journals Effects of wintertime polluted aerosol on cloud over the Yangtze River Delta: case study

2016 ◽  
Author(s):  
Chen Xu ◽  
Junyan Duan ◽  
Yanyu Wang ◽  
Yifan Wang ◽  
Hailin Zhu ◽  
...  
Keyword(s):  
Yangtze River ◽  
Cloud Droplet ◽  
Yangtze River Delta ◽  
River Delta ◽  
Droplet Radius ◽  
The Yangtze River ◽  
Liquid Water Path ◽  
Cloud Parameters ◽  
Low Clouds ◽  
The Yangtze River Delta

Abstract. The effects of polluted aerosol on cloud are examined over the Yangtze River Delta (YRD) using three-month satellite data during wintertime from December 2013 to January 2014. The relationships between aerosol properties and cloud parameters are analyzed in detail to clarify the differences of cloud development under varying aerosol and meteorology conditions. Complex relationships between aerosol optical depth (AOD) and cloud droplet radius (CDR), liquid water path (LWP) and cloud optical thickness (COT) exists in four sub-regions. High aerosol loading (AOD) does not obviously affect the distributions of cloud LWP and COT. In fact, an inhibiting effect of aerosol occurs in coastal area for low- and medium-low clouds, more pronounced in low clouds (

The Microphysics of Ice and Precipitation Development in Tropical Cumulus Clouds

2015 ◽  
Vol 72 (6) ◽  
pp. 2429-2445 ◽  
Author(s):  
R. Paul Lawson ◽  
Sarah Woods ◽  
Hugh Morrison
Keyword(s):  
High Speed ◽  
Cloud Model ◽  
Supercooled Liquid ◽  
High Speed Photography ◽  
Cumulus Clouds ◽  
Cloud Particle ◽  
Ice Particles ◽  
Aircraft Observations ◽  
Bin Microphysics ◽  
Ice Production

Abstract The rapid glaciation of tropical cumulus clouds has been an enigma and has been debated in the literature for over 60 years. Possible mechanisms responsible for the rapid freezing have been postulated, but until now direct evidence has been lacking. Recent high-speed photography of electrostatically suspended supercooled drops in the laboratory has shown that freezing events produce small secondary ice particles. Aircraft observations from the Ice in Clouds Experiment–Tropical (ICE-T), strongly suggest that the drop-freezing secondary ice production mechanism is operating in strong, tropical cumulus updraft cores. The result is the production of small ice particles colliding with large supercooled drops (hundreds of microns up to millimeters in diameter), producing a cascading process that results in rapid glaciation of water drops in the updraft. The process was analyzed from data collected using state-of-the-art cloud particle probes during 54 Learjet penetrations of strong cumulus updraft cores over open ocean in a temperature range from 5° to −20°C. Repeated Learjet penetrations of an updraft core containing 3–5 g m−3 supercooled liquid showed an order-of-magnitude decrease in liquid mass concentration 3 min later at an elevation 1–1.5 km higher in the cloud. The aircraft observations were simulated using a one-dimensional cloud model with explicit bin microphysics. The model was initialized with drop and ice particle size distributions observed prior to rapid glaciation. Simulations show that the model can explain the observed rapid glaciation by the drop-freezing secondary ice production process and subsequent riming, which results when large supercooled drops collide with ice particles.

scholarly journals Increasing the spatial resolution of cloud property retrievals from Meteosat SEVIRI by use of its high–resolution visible channel: Evaluation of candidate approaches with MODIS observations

2019 ◽  
Author(s):  
Frank Werner ◽  
Hartwig Deneke
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
High Frequency ◽  
Cloud Droplet ◽  
Horizontal Resolution ◽  
Droplet Radius ◽  
Liquid Water Path ◽  
Cloud Property ◽  
Standard Resolution ◽  
Narrowband Channels

Abstract. This study presents and evaluates several candidate approaches for downscaling observations from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) in order to increase the horizontal resolution of subsequent cloud optical thickness (τ) and effective droplet radius (reff) retrievals from the native 3 × 3 km2 spatial resolution of the narrowband channels to 1 × 1 km2. These methods make use of SEVIRI’s coincident broadband high–resolution visible (HRV) channel. For four example cloud fields, the reliability of each downscaling algorithm is evaluated by means of collocated 1 × 1 km2 MODIS radiances, which are re-projected to the horizontal grid of the HRV channel, and serve as reference for the evaluation. By using these radiances smoothed with the spatial response function of the native SEVIRI channels as retrieval input, the accuracy at the SEVIRI standard resolution can be evaluated and an objective comparison of the accuracy of the different downscaling algorithms can be made. For the example scenes considered in this study, it is shown that neglecting high-frequency variations below the SEVIRI standard resolution results in significant random absolute deviations of the retrieved τ and reff of up to ≈ 14 and ≈ 6 μm, respectively, as well as biases. By error propagation, this also negatively impacts the reliability of the subsequent calculation of liquid water path (WL) and cloud droplet number concentration (ND), which exhibit deviations of up to ≈ 89 g m−2 and ≈ 177 cm−3, respectively. For τ, these deviations can be almost completely mitigated by the use of the HRV channel as a physical constraint, and by applying most of the presented downscaling schemes. For the accuracy of reff,the choice of downscaling scheme however is important: deviations are generally of similar magnitude or larger than those for retrievals at the SEVIRI standard resolution, indicative of their limited skill at predicting high–frequency spatial variability in reff. A strong degradation of accuracy of reff is observed for some of the approaches, which also affects subsequent WL and ND estimates. As a result, an approach which constrains the reff to the lower–resolution results is recommended. Overall, this study demonstrates that an increase in horizontal resolution of SEVIRI cloud property retrievals can be reliably achieved by use of its HRV channel, yielding cloud properties which are preferable in terms of accuracy to those obtained from SEVIRI’s standard-resolution. This work advances efforts to mitigate impacts of scale mismatches among channels of multi–resolution instruments on cloud retrievals.

scholarly journals Increasing the spatial resolution of cloud property retrievals from Meteosat SEVIRI by use of its high-resolution visible channel: evaluation of candidate approaches with MODIS observations

2020 ◽  
Vol 13 (3) ◽  
pp. 1089-1111
Author(s):  
Frank Werner ◽  
Hartwig Deneke
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Cloud Droplet ◽  
Horizontal Resolution ◽  
Droplet Radius ◽  
Modulation Transfer ◽  
Liquid Water Path ◽  
Standard Resolution ◽  
Narrowband Channels ◽  
The Right

Abstract. This study presents and evaluates several candidate approaches for downscaling observations from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) in order to increase the horizontal resolution of subsequent cloud optical thickness (τ) and effective droplet radius (reff) retrievals from the native ≈3km×3km spatial resolution of the narrowband channels to ≈1km×1km. These methods make use of SEVIRI's coincident broadband high-resolution visible (HRV) channel. For four example cloud fields, the reliability of each downscaling algorithm is evaluated by means of collocated 1 km×1 km MODIS radiances, which are reprojected to the horizontal grid of the HRV channel and serve as reference for the evaluation. By using these radiances, smoothed with the modulation transfer function of the native SEVIRI channels, as retrieval input, the accuracy at the SEVIRI standard resolution can be evaluated and an objective comparison of the accuracy of the different downscaling algorithms can be made. For the example scenes considered in this study, it is shown that neglecting high-frequency variations below the SEVIRI standard resolution results in significant random absolute deviations of the retrieved τ and reff of up to ≈14 and ≈6 µm, respectively, as well as biases. By error propagation, this also negatively impacts the reliability of the subsequent calculation of liquid water path (WL) and cloud droplet number concentration (ND), which exhibit deviations of up to ≈89gm-2 and ≈177cm-3, respectively. For τ, these deviations can be almost completely mitigated by the use of the HRV channel as a physical constraint and by applying most of the presented downscaling schemes. Uncertainties in retrieved reff at the native SEVIRI resolution are smaller, and the improvements from downscaling the observations are less obvious than for τ. Nonetheless, the right choice of downscaling scheme yields noticeable improvements in the retrieved reff. Furthermore, the improved reliability in retrieved cloud products results in significantly reduced uncertainties in derived WL and ND. In particular, one downscaling approach provides clear improvements for all cloud products compared to those obtained from SEVIRI's standard resolution and is recommended for future downscaling endeavors. This work advances efforts to mitigate impacts of scale mismatches among channels of multiresolution instruments on cloud retrievals.

scholarly journals The semianalytical cloud retrieval algorithm for SCIAMACHY II. The application to MERIS and SCIAMACHY data

2006 ◽  
Vol 6 (2) ◽  
pp. 1813-1840 ◽  
Author(s):  
A. A. Kokhanovsky ◽  
W. von Hoyningen-Huene ◽  
V. V. Rozanov ◽  
S. Noël ◽  
K. Gerilowski ◽  
...  
Keyword(s):  
Cloud Droplet ◽  
Droplet Radius ◽  
Retrieval Algorithm ◽  
Liquid Water Path ◽  
Imaging Spectrometer ◽  
Medium Resolution ◽  
Resolution Imaging ◽  
Cloud Optical Thickness ◽  
Scanning Imaging ◽  
First Time

Abstract. The Semianalytical CloUd Retrieval Algorithm (SACURA) is applied to the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) data. In particular, for the first time we derive simultaneously cloud optical thickness (COT), liquid water path (LWP), cloud top height (CTH), and cloud droplet radius (CDR) using SCIAMACHY measurements in the visible (442 nm, COT), in the oxygen A-band (755–775 nm, CTH) and in the infrared (1550 nm, CDR). Some of the results obtained are compared with those derived from the Medium Resolution Imaging Spectrometer (MERIS), which has better spatial resolution and observe almost the same scene as SCIAMACHY.

scholarly journals Conditions for super-adiabatic droplet growth after entrainment mixing

2016 ◽  
Author(s):  
Fan Yang ◽  
Raymond Shaw ◽  
Huiwen Xue
Keyword(s):  
Cloud Model ◽  
Cloud Droplet ◽  
Droplet Radius ◽  
Droplet Growth ◽  
Critical Height ◽  
Growth Region ◽  
Cloud Droplets ◽  
Cloud Properties ◽  
Environment Temperature ◽  
Environmental Air

Abstract. Cloud droplet response to entrainment and mixing between a cloud and its environment is often considered by itself, without accounting for subsequent growth after the mixing event. Here we consider the change in cloud properties when the mixed parcel rises adiabatically after the mixing event. The vertical profile for liquid water mixing ratio after a mixing event is derived analytically, allowing the reduction due to mixing to be predicted from the mixing fraction and the cloud and environment temperature and humidity. It is derived for the limit of homogeneous mixing. The expression leads to a critical height above the mixing level: At the critical height the cloud droplet radius is the same for both mixed and unmixed parcels, and the critical height is independent of the updraft velocity and mixing fraction. Cloud droplets in a mixed parcel are larger than in an unmixed parcel above the critical height, which we refer to as the "super-adiabatic" growth region. Analytical results are confirmed by a bin microphysics cloud model. Using the model, we explore the effects of updraft velocity, aerosol source in the environmental air, and polydisperse cloud droplets. Results show that the mixing parcel is more likely to reach the super-adiabatic growth region when the environmental air is humid and clean. It is also confirmed that the analytical predictions are matched by the volume-mean cloud droplet radius under polydisperse conditions. The findings have implications for the origin of large cloud droplets that may contribute to onset of collision-coalescence in warm clouds.

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