On the Use of Pyrgeometers in Cloud

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  • 1 Division of Cloud Physics, CSIRO, Sydney, Australia
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Abstract

Laboratory and airborne observations show that the protective hemispheres of aircraft pyrgeometers are partly covered by water when used in cloud. This cover can reduce the incident longwave flux by as much as 60%. Improved agreement between observations and theory is obtained when a parameterization of water cover in terms of cloud liquid water content is used to correct flux divergence and cooling rate data. It is suggested that all previous in-cloud pyrgeometer measurements may suffer cloud-water contamination.

Abstract

Laboratory and airborne observations show that the protective hemispheres of aircraft pyrgeometers are partly covered by water when used in cloud. This cover can reduce the incident longwave flux by as much as 60%. Improved agreement between observations and theory is obtained when a parameterization of water cover in terms of cloud liquid water content is used to correct flux divergence and cooling rate data. It is suggested that all previous in-cloud pyrgeometer measurements may suffer cloud-water contamination.

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