The relationship between cloud droplet number concentrations and anthropogenic pollution : observations and climatic implications
The relationship between cloud droplet number concentrations and anthropogenic pollution : observations and climatic implications
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DOI：
10.1029/91jd02739
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发表时间：
1992-02
影响因子：
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通讯作者：
W. Leaitch;G. Isaac;J. Strapp;C. Banic;H. Wiebe
中科院分区：
文献类型：
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作者：
W. Leaitch;G. Isaac;J. Strapp;C. Banic;H. Wiebe
在1982年以来进行的四次实地研究中收集的大约400个云水样品中硫酸盐和硝酸盐浓度的测量值与云滴数浓度（CDNC）和液态水含量（LWC）的同步测量值一起使用，以检查CDNC与人为污染之间的关系，其中硫酸盐浓度用作后者的测量值。在任何特定飞行中，通过平均重复和相似高度的多个样本，样本数量被压缩到92个，其中85个包括CDNC测量。对于层状云和积雨云，log （CDNC）和log（云水硫酸盐浓度）之间存在正线性回归。由于影响CDNC的因素较多，不同云型的决定系数仅为0.30和0.49。LWC与云水硫酸盐浓度相对不变。研究区层状云的CDNC观测范围为20 ~ 600 cm−3(59次观测的中位数为210 cm−3)，积雨云的CDNC观测范围为170 ~ 1100 cm−3（26次观测的中位数为400 cm−3）。所有采样云的中位数CDNC为250 cm−3。CDNC也被确定为“清洁空气”条件。后者被定义为云水硫酸盐和云水硝酸盐浓度分别与全球偏远地区报告的气溶胶硫酸盐浓度和气溶胶硝酸盐加硝酸浓度相当的情况。对于洁净空气云，研究区层状云的CDNC观测范围为20 ~ 250 cm−3(12次观测的中位数为120 cm−3)，积雨云的CDNC观测范围为170 ~ 370 cm−3（4次观测的中位数为240 cm−3）。所有清洁空气云的中位数CDNC为160 cm−3。整个人群的中位数CDNC比清洁空气的CDNC高56%；清洁空气CDNC与中位数CDNC没有差异的假设在>99.5%的置信水平上被拒绝。根据北美东部在- 2wm - 2和- 3wm - 2之间的基本模式估计了由CDNC增加引起的云反照率变化引起的当今气候强迫。
Measurements of the concentrations of sulfate and nitrate in approximately 400 cloud water samples collected during four field studies carried out since 1982 are used with coincident measurements of cloud droplet number concentrations (CDNC) and liquid water content (LWC) to examine the relationship between CDNC and anthropogenic pollution, where sulfate concentration is used as the measure of the latter. The number of samples is compressed to 92 by averaging duplicates and multiple samples at similar altitudes during any particular flight, with 85 including CDNC measurements. Positive linear regressions between log (CDNC) and log (cloud water sulfate concentration) are determined for both stratiform and cumuliform cloud. Because of the number of factors affecting the CDNC, the coefficients of determination are only 0.30 and 0.49 for the respective cloud types. The LWC is relatively invariant with the cloud water sulfate concentration. The observed range of CDNC for the study region is 20–600 cm−3 (median of 59 observations is 210 cm−3) for stratiform clouds and 170–1100 cm−3 (median of 26 observations is 400 cm−3) for cumuliform clouds. The median CDNC for all sampled clouds is 250 cm−3. CDNC are also determined for “clean-air” conditions. The latter is defined as cases for which the concentrations of both cloud water sulfate and cloud water nitrate are comparable to aerosol sulfate concentrations and aerosol nitrate plus HNO3 concentrations, respectively, as reported for remote regions of the globe. For the clean-air clouds the observed range of CDNC for the study region is 20–250 cm−3 (median of 12 observations is 120 cm−3) for stratiform clouds and 170–370 cm−3 (median of four observations is 240 cm−3) for cumuliform clouds. The median CDNC for all clean-air clouds is 160 cm−3. The median CDNC for the complete population is 56% greater than the clean-air CDNC; the hypothesis that the clean-air CDNC is not different from the median CDNC is rejected at a confidence level of >99.5%. The present-day climatic forcing due to cloud albedo change arising from increased CDNC is estimated from a rudimentary model at between −2 W m−2 and −3 W m−2 for eastern North America.