Extending Twomey’s Analytical Estimate of Nucleated Cloud Droplet Concentrations from CCN Spectra
Extending Twomey’s Analytical Estimate of Nucleated Cloud Droplet Concentrations from CCN Spectra
复制标题
扩展 Twomey 根据 CCN 光谱对有核云滴浓度的分析估计
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
C. Bedos
中科院分区：
文献类型：
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作者：
J. Cohard;J. Pinty;C. Bedos
A fundamental but approximate formula has been established by Twomey in order to compute the nucleated cloud droplet number concentration as a function of the vertical velocity and the CCN (cloud condensation nuclei) characteristics expressed by the C and k parameters. The derivation of such a relationship employs the widespread power-law dependence NCCN 5 of the total activable CCN number NCCN at a given supersaturation k Csy,w of water vapor over cloud droplets sy,w. In this paper the authors follow Twomey’s theoretical approach but using a more realistic four-parameter CCN activation spectrum as shaped by the physicochemical properties of the accumulation mode in a natural aerosol population. The analytical scheme is shown to improve the estimate of cloud droplet number concentration because it accounts for the limited availability of small-sized CN (condensation nuclei) with increasing supersaturation. A first validation and calibration of the new generic CCN activation spectrum is made by comparison with activation spectra, either produced by growing realistic lognormal distributions of CN or measured by a CCN spectrometer over the mid-Atlantic Ocean.
