Determining the susceptibility of cloud albedo to changes in droplet concentration with the advanced very high resolution radiometer

Journal Article · Tue Mar 01 04:00:00 EST 1994 · Journal of Applied Meteorology

DOI:https://doi.org/10.1175/1520-0450(1994)033<0334:DTSOCA>2.0.CO;2· OSTI ID:105449

Platnick, S ^[1]; Twomey, S

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1. Univ. Arizona, Tucson, AZ (United States)

Combustion processes that produce greenhouse gases also increase cloud condensation nuclei (CCN) concentrations, which in turn increase cloud droplet concentrations and thereby cloud albedo. A calculation of cloud susceptibility, defined in this work as the increase in albedo resulting from the addition of one cloud droplet per cubic centimeter (as cloud liquid water content remains constant), is made through the satellite remote sensing of cloud droplet radius and optical thickness. The remote technique uses spectral channels of the Advanced Very High Resolution Radiometer (AVHRR) instrument on board NOAA polar-orbiting satellites. Radiative transfer calculations of reflectance and effective surface and cloud emissivities are made for applicable sun and satellite viewing angles, including azimuth, at various radii and optical thicknesses for each AVHRR channel. Emission in channel 3 (at 3.75 {mu}m) is removed to give the reflected solar component. These calculations are used to infer the radius and optical thickness that best match the satellite measurements. An approximation for the effect of the atmosphere on the signal received by the AVHRR is included in the analysis. Marine stratus clouds, as well as being important modifiers of climate, are cleaner that continental clouds and so likely to be of higher susceptibility. Analysis of several stratus scenes, including some containing ship tracks, supports this expectation. The retrieved range of susceptibilities for all marine stratus clouds studied varied by about two orders of magnitude. This variation implies that climate studies that include possible marine stratus albedo modification from anthropogenic CCN are incomplete without accounting for existing susceptibilities. 54 refs., 10 figs., 1 tab.

• OSTI ID: 105449
• Journal Information: Journal of Applied Meteorology, Journal Name: Journal of Applied Meteorology Journal Issue: 3 Vol. 33; ISSN 0894-8763; ISSN JOAMEZ
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
99 GENERAL AND MISCELLANEOUS
ALBEDO
CLOUD COVER
COMBUSTION
CONDENSATION NUCLEI
DROPLETS
GENERAL CIRCULATION MODELS
GREENHOUSE EFFECT
RADIATION TRANSPORT
RADIOMETERS
REMOTE SENSING
SATELLITES
WATER VAPOR