Statistics on the macrophysical properties of trade wind cumuli over the tropical western Atlantic

Zhao, Guangyu; Girolamo, Larry Di

doi:10.1029/2006jd007371

Cited by 115 publications

(192 citation statements)

References 25 publications

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“…A power law fit to the sampled cloud chord lengths gives a dimension of 2.45, with 85% having lengths 1 km. Our observed cloud altitude and size distribution are consistent with previous observations of trade wind cumuli in this region [Zhao and Di Girolamo, 2007].…”

Section: Methodssupporting

confidence: 82%

“…Meanwhile, lateral mixing with dry air adjacent to cloud causes descending motion due to evaporative cooling [Heus et al, 2008], which may transport larger aerosols near cloud top to mid-cloud levels, enhancing backscatter. The backscatter enhancement maximum at lower altitudes (0.5 km to 0.75 km) is adjacent to cloud bases, most of which are from small and shallow cumuli [Zhao and Di Girolamo, 2007], and is possibly due to vertical advection of humid air below cloud base [Perry and Hobbs, 1996] causing aerosol hygroscopic growth. Median color ratio c 0 = b 0 1064 /b 0 532 in Figure 1c also exhibits enhancement near cloud edge with maxima at similar altitudes as b 0 532 maxima.…”

Section: Resultsmentioning

confidence: 99%

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Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite‐based lidar

Tackett¹,

Girolamo²

2009

Geophysical Research Letters

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[1] There have been many proposed processes by which clouds modify aerosol properties, suggesting that aerosol properties near clouds are different than far from clouds. We provide the first satellite-based lidar observations of backscatter and color ratio, quantities directly related to aerosol properties, as a function of distance to cloud edge for boundary layer clouds over the western tropical Atlantic. We show backscatter and color ratio are enhanced adjacent to cloud edge, particularly near cloud top and cloud base. Specifically, layer integrated median backscatter increases by 31 ± 3% and 42 ± 2%, at wavelengths of 532 nm, and 1,064 nm, respectively, and layer averaged color ratio increases by 15 ± 5%. Backscatter calculations suggest our observations adjacent to cloud are best explained by an aerosol size distribution with reduced number concentration, increased median radius, and decreased width compared to far from cloud.

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Section: Methodssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite‐based lidar

Tackett¹,

Girolamo²

2009

Geophysical Research Letters

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“…Here we use the aircraft (in situ) derived cloud amounts to choose the most representative threshold. The resulting cloud amount is slightly larger than satellite-derived trade-wind cloud amount in the same location (Zhao and Di Girolamo 2007). Cloud amounts from in situ measurements at other heights are not representative, as the decision as to how high to fly above cloud- Fig.…”

Section: Zoom In On Rico Conditionsmentioning

confidence: 93%

Revealing differences in GCM representations of low clouds

2009

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Aquaplanet configurations of four atmospheric general circulation models (GCMs) are compared with standard, Earth-like configurations and observations. The focus here is on tropical, low-level clouds, which have been identified as important for estimates of climate sensitivity. Investigating the distribution of the monthly mean vertical velocity and lower-tropospheric stability, the aquaplanets are seen to capture the core of the distribution of the more Earth-like configurations, whose distributions are, in turn, similar to that of reanalysis data. By conditionally sampling over these distributions, low-cloud regimes are defined, separating shallow cumulus convection from stratocumulus. Within each regime, the GCMs produce similar large-scale environments, yet disparate depictions of the clouds. Aquaplanets lack stratocumulus because of their zonally symmetric boundary conditions, but produce extensive trade-wind regions populated by shallow cumulus clouds just like those in the Earth-like setting. The analysis shows that aquaplanets can be compared with observations, just as well as the Earth-like configuration, with the added ability to focus on particular regimes without complications from geographical or temporal biases.

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“…3.1 are sufficient. The scenes sampled in the tropical western Atlantic (Zhao and Di Girolamo, 2006) were populated entirely by trade wind cumuli with a peak in the cloud fraction distribution at 400-500 m in cloud equivalent diameters (see Zhao and Di Girolamo, 2007) Table 2 lists the case numbers (C1-C48), as well as the sample date of each scene. A wide range of different scene characteristics are covered, with estimated domain-averaged cloud covers C M , based on MODIS cloud flags "0" and "1" (i.e., "confidently" and "probably cloudy" pixels), between C M = 0.01 and 1.00.…”

Section: Data Setmentioning

confidence: 99%

Marine boundary layer cloud property retrievals from high-resolution ASTER observations: case studies and comparison with Terra MODIS

et al. 2016

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Abstract.A research-level retrieval algorithm for cloud optical and microphysical properties is developed for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard the Terra satellite. It is based on the operational MODIS algorithm. This paper documents the technical details of this algorithm and evaluates the retrievals for selected marine boundary layer cloud scenes through comparisons with the operational MODIS Data Collection 6 (C6) cloud product. The newly developed, ASTERspecific cloud masking algorithm is evaluated through comparison with an independent algorithm reported in Zhao and Di Girolamo (2006). To validate and evaluate the cloud optical thickness (τ ) and cloud effective radius (r eff ) from ASTER, the high-spatial-resolution ASTER observations are first aggregated to the same 1000 m resolution as MODIS. Subsequently, τ aA and r eff, aA retrieved from the aggregated ASTER radiances are compared with the collocated MODIS retrievals. For overcast pixels, the two data sets agree very well with Pearson's product-moment correlation coefficients of R > 0.970. However, for partially cloudy pixels there are significant differences between r eff, aA and the MODIS results which can exceed 10 µm. Moreover, it is shown that the numerous delicate cloud structures in the example marine boundary layer scenes, resolved by the high-resolution ASTER retrievals, are smoothed by the MODIS observations. The overall good agreement between the research-level ASTER results and the operational MODIS C6 products proves the feasibility of MODIS-like retrievals from ASTER reflectance measurements and provides the basis for future studies concerning the scale dependency of satellite observations and three-dimensional radiative effects.

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Statistics on the macrophysical properties of trade wind cumuli over the tropical western Atlantic

Cited by 115 publications

References 25 publications

Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite‐based lidar

Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite‐based lidar

Revealing differences in GCM representations of low clouds

Marine boundary layer cloud property retrievals from high-resolution ASTER observations: case studies and comparison with Terra MODIS

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