Observations of Diurnal Variation in a Cloud-capped Marine Boundary Layer

Hignett, P.

doi:10.1175/1520-0469(1991)048<1474:oodvia>2.0.co;2

Cited by 72 publications

(66 citation statements)

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“…(Betts 1990;Hignett 1991). For instance, the mean value and diurnal range of cloud-top height, cloud-base height and LWP are consistent with the ceilometer and sodar measurements (Duynkerke and Hignett 1993) and microwave radiometer estimates (Duynkerke and Teixeira 2001).…”

Section: Experiments 1: Sensitivity To Single-scattering Albedo (A) Exmentioning

confidence: 99%

The semi‐direct aerosol effect: Impact of absorbing aerosols on marine stratocumulus

Johnson

Shine

Forster

2004

Quart J Royal Meteoro Soc

405

429

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SUMMARYAerosols that absorb solar radiation may lead to a decrease of low-cloud cover and liquid-water path (LWP), leading to a positive radiative forcing. A large-eddy model was used to investigate this 'semi-direct effect' for marine stratocumulus and examine the dependency on the vertical distribution of the aerosol. In this study, the aerosols influenced clouds by directly altering the short-wave heating rate (the semi-direct effect), but did not interact with the cloud microphysics (i.e. indirect aerosol effects are excluded). Absorbing aerosols within the boundary layer (BL) decreased LWP by 10 g m −2 , leading to a positive semi-direct forcing. Even for mildly absorbing aerosols (mid-visible single-scattering albedo of 0.96), the semi-direct forcing was three times stronger, and opposite in sign, to the aerosol direct forcing. The semi-direct forcing was found to be proportional to aerosol single-scattering co-albedo (tested to a value of 0.12). Conversely, with the absorbing aerosol layer above the cloud, the LWP increased by 5 to 10 g m −2 , leading to a negative semi-direct forcing. Absorbing aerosols located in the BL heat the cloud layer, enhancing the daytime decoupling and thinning of the stratocumulus layer. Absorbing aerosols immediately above the BL increased the contrast in potential temperature across the inversion, leading to a lower cloud-top entrainment rate. With aerosol both within and above the BL, the semidirect forcing was positive but half the magnitude of that experienced when aerosol was only in the BL. As marine stratocumulus covers about 20% of the globe, the semi-direct effect could significantly influence the radiative forcing by absorbing aerosols.

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Section: Experiments 1: Sensitivity To Single-scattering Albedo (A) Exmentioning

confidence: 99%

The semi‐direct aerosol effect: Impact of absorbing aerosols on marine stratocumulus

Johnson

Shine

Forster

2004

Quart J Royal Meteoro Soc

405

429

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“…RGM increases rapidly at sunrise, peaks at midday, declines through the afternoon, and falls near detection limit at night. Neither deposition nor boundary layer growth can drive this diurnal cycle, since the winds and MBL depth have little diurnal variability (Hignett, 1991). Rather, RGM production due to changing oxidant levels must be responsible.…”

Section: Observed Rgm Diurnal Variabilitymentioning

confidence: 99%

Sources and deposition of reactive gaseous mercury in the marine atmosphere

Holmes

Jacob

Mason

et al. 2009

Atmospheric Environment

177

192

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“…A distinct behaviour of the MABL is that the diurnal variations tend to be weak (Hignett, 1991). Several studies have been carried out to delineate the spatial variability of the MABL over different regions of the globe.…”

Section: Introductionmentioning

confidence: 99%

A robust method to determine global distribution of atmospheric boundary layer top from COSMIC GPS RO measurements

Ratnam

Basha

2010

Atmospheric Science Letters

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In this study, we introduce a robust method for precise determination of atmospheric boundary layer (ABL) top from COSMIC global positioning system radio occultation measurements. We apply a wavelet covariance transform to compute the convolution of COSMIC-observed bending angle/refractivity profile with a Haar function and use the maximum covariance to identify the ABL top, making detection of even small transitions possible. Results obtained were compared with radiosonde N profiles for verification of the ABL top. This procedure developed was used to study the global distribution of ABL top with special reference to the inter-tropical convergence zone.

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Observations of Diurnal Variation in a Cloud-capped Marine Boundary Layer

Cited by 72 publications

References 0 publications

The semi‐direct aerosol effect: Impact of absorbing aerosols on marine stratocumulus

The semi‐direct aerosol effect: Impact of absorbing aerosols on marine stratocumulus

Sources and deposition of reactive gaseous mercury in the marine atmosphere

A robust method to determine global distribution of atmospheric boundary layer top from COSMIC GPS RO measurements

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