Retrieval of Marine Stratus Cloud Droplet Size from NOAA–AVHRR Nighttime Imagery

Pérez, Juan Carlos; Herrera, F.; Rosa, F.; González, Albano; Wetzel, Melanie; Borys, Randolph D.; Lowenthal, Douglas H.

doi:10.1016/s0034-4257(00)00077-8

Cited by 10 publications

(7 citation statements)

References 16 publications

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“…The mean SST (292.0 K) for the whole flight area is also indicated. Perez et al 2000), which itself is a proxy for drizzle (Han et al 1995;Ferek et al 2000). Here ⌬T B values less than 2 K have also been found to be correlated with areas with heavy drizzle during the specific conditions encountered during DYCOMS-II (vanZanten et al 2005).…”

Section: Methodsmentioning

confidence: 79%

Observations of the Structure of Heavily Precipitating Marine Stratocumulus

vanZanten

Stevens

2005

Journal of the Atmospheric Sciences

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The second research flight of the Second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) field study is analyzed. This case attracted attention because it combined the presence of high drizzle rates with the occurrence of clearings in the cloud cover, which previous work has suggested could be due to a drizzle-induced change in cloud structure. Recent work has named the configuration of these open-cell-like features pocket of open cells (POC). A division of the data, based on the difference of brightness temperature of the 11- and 4-μm channels of the Geostationary Operational Environmental Satellite-10 (GOES-10), is used to condition averages over POC and non-POC sections of the data. Based on this division, significant precipitation is observed almost entirely within the POC. Overall, the observed PBL was markedly energetic and well mixed, commensurate with observations of similarly forced nonprecipitating boundary layers. Regions of elevated equivalent potential temperature, Θe, are encountered in association with the POC and are particularly pronounced below cloud in regions of active precipitation. In the same areas, evaporative cooling and moistening of the subcloud layer air and a marked reduction of the vertical velocity variance below cloud is noted. The POC, and in particular the drizzling areas in the POC, have a mean upward velocity, while the non-POC is associated with descending air. In addition to exhibiting more mesoscale variability the POC differs microphysically from the non-POC: in the POC liquid water amount is higher, cloud droplet number concentration lower, and the effective radii larger. Factors maintaining regions of elevated Θe are discussed, and targets for future modeling or observational studies are identified.

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Section: Methodsmentioning

confidence: 79%

Observations of the Structure of Heavily Precipitating Marine Stratocumulus

vanZanten

Stevens

2005

Journal of the Atmospheric Sciences

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“…Strong drizzle seems to be a common feature of open MCC [ Comstock et al , 2005, 2007; Sharon et al , 2006]. Low values of the 11–3.9 μ m brightness temperature difference (BTD) have been observed in and around POCs [ Stevens et al , 2005; Van Zanten et al , 2005] indicating large cloud droplets [ Pérez et al , 2000]. Very low accumulation mode aerosol concentrations have been observed in POCs [ Petters et al , 2006; Sharon et al , 2006].…”

Section: Introductionmentioning

confidence: 99%

Open cellular structure in marine stratocumulus sheets

et al. 2008

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[1] Geostationary and Sun-synchronous satellite data and in situ observations from ship cruises are used to investigate the formation of open cellular structure in marine stratocumulus clouds over the southeast Pacific (SEP). Open cellular convection either forms spontaneously as pockets of open cells (POCs) within overcast stratocumulus, or is advected into the region from midlatitude regions. POC formation occurs most frequently during the latter part of the night, demonstrating that this transition is not caused by solar absorption-driven decoupling. The transition preferentially occurs in clouds with low 11-3.9 mm nighttime brightness temperature difference (BTD) which is found to be well correlated with both in situ measured accumulation mode aerosol concentration and cloud droplet concentration estimates derived from MODIS. Besides indicating that nighttime BTD is an excellent proxy for stratocumulus cloud droplet concentration N d , this also suggests that low aerosol concentrations favor POC formation. Indeed, extremely low accumulation mode aerosol concentrations are found during the passage of open cell events over the ship. Free-tropospheric moisture is not found to be an important factor in POC formation. Significant subseasonal variability occurs in the fractional coverage of open cellular convection over the broader SEP. This coverage is well correlated with a MODIS-derived drizzle proxy (MDP) proportional to the ratio of liquid water path (LWP) to N d for predominantly overcast regions. Both LWP and N d variability influences the MDP. Periods of low MDP have significant positive large-scale N d anomalies and are preceded by offshore winds at 850 hPa, which suggests a potential continental influence upon open cell formation over the SEP. Together, the results suggest important two-way interactions between aerosols and drizzle in marine stratocumulus and a role for drizzle in modulating the large-scale albedo of these cloud systems.

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“…Low values of A TB can be accounted for by a reduction in the cloud optical depth from values of 15 to unity (which is not consistent with the earlymorning visible imagery), or by changes in the effective radius from 6 to 12 /nm for a cloud with a fixed optical depth of 15 (e.g., Fig. 1 of Perez et al 2000). Thus, we conclude that the POCs are favored in regions of the cloud field where the cloud droplets are larger and thus have a greater propensity to form precipitation.…”

mentioning

confidence: 96%