Outlook for Research on Subtropical Marine Stratification Clouds

Randall, David A.; Coakley, James A.; Lenschow, D. H.; Fairall, C. W.; Kropfli, R. A.

doi:10.1175/1520-0477(1984)065<1290:ofrosm>2.0.co;2

Cited by 257 publications

(177 citation statements)

References 33 publications

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“…Persistent shallow stratocumulus (Sc) cloud decks trapped below the ABL inversion play an important role in cloud-climate feedback processes because of its radiative cooling effect (e.g., Randall et al, 1984;Slingo, 1990;Klein and Hartmann, 1993;Ma et al, 1996;Bony and Dufresne, 2005;Clement et al, 2009). Lack of understanding and observations of complicated ABL processes (e.g., cloud radiative cooling, entrainment, turbulent mixing, ocean-atmosphere coupling) leads to great model uncertainties in weather and climate predictions (e.g., Randall et al, 1998;Zeng et al, 2004;Palm et al, 2005;Jordan et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Advances and limitations of atmospheric boundary layer observations with GPS occultation over southeast Pacific Ocean

Xie

et al. 2012

Atmos. Chem. Phys.

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Abstract. The typical atmospheric boundary layer (ABL) over the southeast (SE) Pacific Ocean is featured with a strong temperature inversion and a sharp moisture gradient across the ABL top. The strong moisture and temperature gradients result in a sharp refractivity gradient that can be precisely detected by the Global Positioning System (GPS) radio occultation (RO) measurements. In this paper, the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) GPS RO soundings, radiosondes and the high-resolution ECMWF analysis over the SE Pacific are analyzed. COSMIC RO is able to detect a wide range of ABL height variations (1-2 km) as observed from the radiosondes. However, the ECMWF analysis systematically underestimates the ABL heights. The sharp refractivity gradient at the ABL top frequently exceeds the critical refraction (e.g., −157 N-unit km −1 ) and becomes the so-called ducting condition, which results in a systematic RO refractivity bias (or called N -bias) inside the ABL. Simulation study based on radiosonde profiles reveals the magnitudes of the N-biases are vertical resolution dependent. The N -bias is also the primary cause of the systematically smaller refractivity gradient (rarely exceeding −110 N-unit km −1 ) at the ABL top from RO measurement. However, the N-bias seems not affect the ABL height detection. Instead, the very large RO bending angle and the sharp refractivity gradient due to ducting allow reliable detection of the ABL height from GPS RO. The seasonal mean climatology of ABL heights derived from a nine-month composite of COSMIC RO soundings over the SE Pacific reveals significant differences from the ECMWF analysis. Both show an increase of ABL height from the shallow stratocumulus near the coast to a much higher trade wind inversion further off the coast. However, COSMIC RO shows an overall deeper ABL and reveals different locations of the minimum and maximum ABL heights as compared to the ECMWF analysis. At low latitudes, despite the decreasing number of COSMIC RO soundings and the lower percentage of soundings that penetrate into the lowest 500-m above the mean-sea-level, there are small sampling errors in the mean ABL height climatology. The difference of ABL height climatology between COSMIC RO and ECMWF analysis over SE Pacific is significant and requires further studies.

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Section: Introductionmentioning

confidence: 99%

Advances and limitations of atmospheric boundary layer observations with GPS occultation over southeast Pacific Ocean

Xie

et al. 2012

Atmos. Chem. Phys.

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“…This is clearly illustrated by the fact that an additional 4% of marine low cloud cover would offset the radiative forcing resulting from CO 2 doubling (Randall et al, 1984). Also land stratus, particularly during high pressure winter situations, remains a notoriously difficult forecasting challenge for numerical weather prediction (NWP) models as well as bench forecasters (Köhler, 2005).…”

Section: Introductionmentioning

confidence: 99%

Unified treatment of dry convective and stratocumulus‐topped boundary layers in the ECMWF model

Köhler

Ahlgrimm

Beljaars

2011

Quart J Royal Meteoro Soc

109

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“…Here, using the new Moderate Resolution Imaging Spectroradiometer (MODIS)-Terra satellite data of aerosol and clouds with resolution of 1 km, we analyze 3 months (JuneAugust 2002) of data covering millions of km 2 of shallow (stratiform and trade cumulus) clouds, and the aerosol in their immediate vicinity, and apply multiple regression to distinguish the aerosol impact on clouds from that of coincidentally changing meteorological conditions. Shallow water clouds have a critical role in the climate system; an increase in shallow cloud cover by only 0.04 is enough to offset 2-3 K of greenhouse warming (24). By reflecting sunlight back to space, stratiform clouds are ''the vast climate refrigerator of the tropics and subtropics'' (ref.…”

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confidence: 99%

The effect of smoke, dust, and pollution aerosol on shallow cloud development over the Atlantic Ocean

Kaufman

Koren

Remer

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

606

480

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Clouds developing in a polluted environment tend to have more numerous but smaller droplets. This property may lead to suppression of precipitation and longer cloud lifetime. Absorption of incoming solar radiation by aerosols, however, can reduce the cloud cover. The net aerosol effect on clouds is currently the largest uncertainty in evaluating climate forcing. Using large statistics of 1-km resolution MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data, we study the aerosol effect on shallow water clouds, separately in four regions of the Atlantic Ocean, for June through August 2002: marine aerosol (30°S-20°S), smoke (20°S-5°N), mineral dust (5°N-25°N), and pollution aerosols (30°N-60°N). All four aerosol types affect the cloud droplet size. We also find that the coverage of shallow clouds increases in all of the cases by 0.2-0.4 from clean to polluted, smoky, or dusty conditions. Covariability analysis with meteorological parameters associates most of this change to aerosol, for each of the four regions and 3 months studied. In our opinion, there is low probability that the net aerosol effect can be explained by coincidental, unresolved, changes in meteorological conditions that also accumulate aerosol, or errors in the data, although further in situ measurements and model developments are needed to fully understand the processes. The radiative effect at the top of the atmosphere incurred by the aerosol effect on the shallow clouds and solar radiation is ؊11 ؎ 3 W͞m 2 for the 3 months studied; 2͞3 of it is due to the aerosolinduced cloud changes, and 1͞3 is due to aerosol direct radiative effect.cloud cover ͉ cloud height ͉ indirect effect ͉ radiative forcing ͉ air quality D uring June through August, the Atlantic Ocean is covered by varying concentrations of several aerosol types, each covering a separate latitude belt (see Fig. 1). The Southern Tropical Atlantic (30°S-20°S) is dominated by clean maritime air. The region between 20°S and 5°N is a relatively well defined region covered by smoke from biomass burning in Africa (1, 2). The Northern Tropical Atlantic (5°N-30°N) is under heavy influx of dust from Africa (3), and the Northern Atlantic (30°N-60°N) is impacted by anthropogenic pollution aerosol from North America and Europe. These aerosols absorb and reflect solar radiation to space (4), thereby affecting the regional atmospheric energy balance. Clouds that form in air laden with high aerosol concentrations tend to contain more numerous but smaller droplets that reflect sunlight and cool the Earth (5). The smaller cloud droplets reduce the efficiency of droplet growth by collision coalescence, which at least under some conditions (6) reduce precipitation formation and increase cloud lifetime (7,8). However, there is a second pathway for aerosols to affect clouds: Smoke, pollution, and dust aerosols absorb solar radiation, heat the atmosphere, and reduce evaporation from the surface (9-11). As a result, smoke over the Amazon or pollution aerosol over the Indian Ocean can inhibit cloud...

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Outlook for Research on Subtropical Marine Stratification Clouds

Cited by 257 publications

References 33 publications

Advances and limitations of atmospheric boundary layer observations with GPS occultation over southeast Pacific Ocean

Advances and limitations of atmospheric boundary layer observations with GPS occultation over southeast Pacific Ocean

Unified treatment of dry convective and stratocumulus‐topped boundary layers in the ECMWF model

The effect of smoke, dust, and pollution aerosol on shallow cloud development over the Atlantic Ocean

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