A Microphysical Retrieval Scheme for Continental Low-Level Stratiform Clouds: Impacts of the Subadiabatic Character on Microphysical Properties and Radiation Budgets

Chin, H S; Rodriguez, Daniel J.; Cederwall, R.T.; Chuang, Catherine C.; Grossman, Allen; Yio, J. John; Fu, Qiang; Miller, Mark A.

doi:10.1175/1520-0493(2000)128<2511:amrsfc>2.0.co;2

Cited by 26 publications

(25 citation statements)

References 36 publications

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“…Clothiaux et al (1995) discussed how MMCRs might be employed for retrievals of cloud properties. Many subsequent studies explored these and other specific methods to retrieve cloud system properties from radar data and employed these retrieved quantities to focus on cloud structure or climatology [e.g., Frisch et al (1995a);Babb et al (1999); Sassen et al (1999);Chin et al (2000); Kato et al (2001); Dong et al (2005); Kim et al (2005), which is by no means an exhaustive list].…”

Section: Introductionmentioning

confidence: 99%

“…This ensures that the Doppler velocities represent the air motion and not a combination of air motion and precipitation sedimentation. A number of thresholds have been used previously to delineate clouds from precipitation (Chin et al 2000;Kato et al 2001;Kogan et al 2005;Liu et al 2008), and we chose a value of 220 dBZ to screen out most precipitation-sized particles. Only a small fraction of scans were filtered out during the 0600-1200 UTC period of interest.…”

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confidence: 99%

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Large-Eddy Observation of Post-Cold-Frontal Continental Stratocumulus

Schultz¹

2010

Journal of the Atmospheric Sciences

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More studies on the dynamics of marine stratus and stratocumulus clouds have been performed than comparable studies on continental stratocumulus. Therefore, to increase the number of observations of continental stratocumulus and to compare marine and continental stratocumulus to each other, the approach of large-eddy observation (LEO) was applied to a case of nocturnal continental stratocumulus observed over the Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) in the central United States on 8 April 2006. The stratocumulus occurred in cold-air and dry-air advection behind a surface cold front. LEOs were obtained from millimeter-wavelength cloud radar and micropulse lidar, whereas traditional meteorological observations described the synoptic environment. This study focuses on a 9-h period of a predominantly nonprecipitating stratocumulus layer 250-400 m thick. A slight thinning of the cloud layer over time is consistent with dry-air advection. A deep layer of descent overlaid a shallower layer of ascent from the surface up to 800 mb, providing a mechanism for strengthening the inversion at cloud top. Time series of Doppler velocity indicate vertically coherent structures identifiable throughout much of the cloud layer. The magnitude of turbulence, as indicated by the variance of the vertical velocity, was weak relative to typical marine stratocumulus and to the one other case of continental stratocumulus in the literature. Conditional sampling of the eddy structures indicate that strong downdrafts were more prevalent than strong updrafts, and negative skewness of vertical velocity in the cloud implies an in-cloud circulation driven by longwave cooling at cloud top, similar to that in marine stratocumulus.

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Large-Eddy Observation of Post-Cold-Frontal Continental Stratocumulus

Schultz¹

2010

Journal of the Atmospheric Sciences

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“…The LWC profile is based on the study of Chin et al (2000). In this study a weighting function is applied to describe the subadiabatic character of the profile.…”

Section: Simulation Of Cloud Fieldsmentioning

confidence: 99%

“…In the study Chin et al (2000) give two types of weighting functions: one is related to subadiabatic conditions involving cloud top entrainment alone and the other considers both cloud top entrainment and drizzle effects. To ensure the validity of Mie theory for calculation of optical properties the first type was chosen, with the parameterisation of α=1.375 and β=4.…”

Section: Simulation Of Cloud Fieldsmentioning

confidence: 99%

“…To ensure the validity of Mie theory for calculation of optical properties the first type was chosen, with the parameterisation of α=1.375 and β=4. The value of α is recommended by Chin et al (2000) and with β=4 a strong cloud top entrainment is simulated. The weighting function given above weights an adiabatic LWC (LWC ad ) profile to a subadiabatic one (LWC subad ) in the following way…”

Section: Simulation Of Cloud Fieldsmentioning

confidence: 99%

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The influence of cloud top variability from radar measurements on 3-D radiative transfer

et al. 2007

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Abstract. In radiative transfer simulations the simplification of cloud top structure by homogeneous assumptions can cause mistakes in comparison to realistic heterogeneous cloud top structures. This paper examines the influence of cloud top heterogeneity on the radiation at the top of the atmosphere. The use of cloud top measurements with a high temporal resolution allows the analysis of small spatial cloud top heterogeneities by using the frozen turbulence assumption for the time -space conversion. Radiative observations are often based on satellite measurements, whereas small spatial structures are not considered in such treatments. A spectral analysis of the cloud top measurements showed slopes of power spectra between -1.8 and -2.0, these values are larger than the spectra of -5/3 which is often applied to generate cloud field variability. The comparison of 3-D radiative transfer results from cloud fields with homogeneous and heterogeneous tops has been done for a single wavelength of 0.6 µm. The radiative transfer calculations result in lower albedos for heterogeneous cloud tops. The differences of albedos between heterogeneous and homogeneous cloud top decrease with increasing solar zenith angle. The influence of cloud top variability on radiances is shown. The reflectances for heterogeneous tops are explicitly larger in forward direction, in backward direction lower. The largest difference of the mean reflectances (mean over cloud field) between homogeneous and heterogeneous cloud top is approximately 0.3, which is 30% of illumination.

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Measured Constraints on Cloud-Top Entrainment to Reduce Uncertainty of Non-Precipitating Stratocumulus Shortwave Radiative Forcing in the Southern Ocean

Sanchez

Roberts

Russell

et al. 2020

Preprint

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Stratocumulus cloud top entrainment has a significant effect on cloud properties, but there are few observations quantifying its impact. Using explicit 0-D parcel model simulations, initialized with below-cloud in situ measurements, and validated with in situ measurements of cloud properties, the shortwave cloud radiative forcing (SWCF) was reduced by up to 100 W m −2 by cloud top entrainment in the Southern Ocean. The impact of entrainment-corrected SWCF is between 2 and 20 times that of changes in the aerosol particle concentration or updraft at cloud base. The variability in entrainment-corrected SWCF accounts for up to 50 W m −2 uncertainty in estimating cloud forcing. Measurements necessary for estimating the impact of entrainment on cloud properties can be constrained from existing airborne platforms and provide a first-order approximation for cloud radiative properties of nonprecipitating stratocumulus clouds. These measurement-derived estimates of entrainment can be used to validate and improve parameterizations of entrainment in Global Climate Models.Plain Language Summary Clouds over the ocean have a significant impact on climate because they reflect sunlight that would otherwise be absorbed by the ocean. Understanding and accurately modeling how much sunlight these clouds reflect is important to understand feedbacks between clouds and climate. Using a simple model and cloud measurements, mixing of moist cloud air with warm-dry air from above the cloud was shown to decrease the cloud droplet number concentration and consequently total liquid water, which significantly decreases the overall amount of sunlight reflected by the cloud. Cloud droplets form onto small particles as they enter the base of the cloud through an updraft; in the meantime, warm-dry air from above the cloud mixes downward. In this study, the warm-dry air from above the cloud was shown to be more influential on reflecting sunlight than the concentration of particles and the updraft velocity at cloud base. These results emphasize the importance of accurately accounting for the mixing in of warm-dry air from above the cloud in climate models and can be constrained by existing measurements that are readily available on weather balloons and aircraft.

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A Microphysical Retrieval Scheme for Continental Low-Level Stratiform Clouds: Impacts of the Subadiabatic Character on Microphysical Properties and Radiation Budgets

Cited by 26 publications

References 36 publications

Large-Eddy Observation of Post-Cold-Frontal Continental Stratocumulus

Large-Eddy Observation of Post-Cold-Frontal Continental Stratocumulus

The influence of cloud top variability from radar measurements on 3-D radiative transfer

Measured Constraints on Cloud-Top Entrainment to Reduce Uncertainty of Non-Precipitating Stratocumulus Shortwave Radiative Forcing in the Southern Ocean

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