Aerosol influences on marine atmospheric surface layer optics

被引:1
|
作者
Walker, P [1 ]
机构
[1] USN, Postgrad Sch, Dept Phys, Monterey, CA 93943 USA
来源
PROPAGATION AND IMAGING THROUGH THE ATMOSPHERE II | 1998年 / 3433卷
关键词
D O I
10.1117/12.330208
中图分类号
P4 [大气科学(气象学)];
学科分类号
0706 ; 070601 ;
摘要
Shipboard optical systems are used as passive sensors for threat detection. When a threat is at low altitude part of the optical path from it may lie in the marine surface layer where it is distorted by refractivity gradients caused by large vertical changes in temperature and humidity in the first several meters above the sea surface. In addition, the poorly characterized giant sea salt aerosols in this region not only contribute to scattering but add to atmospheric refractivity by an amount equal to the product of water refractivity and aerosol contribution to atmospheric liquid water content. The added refractivity is about 10 per cent of that due to water vapor, depending on relative humidity. These aerosols are created from bubble fragments and jet droplets caused by air bubbles bursting at the sea surface and can be hundreds of micrometers in size. Their size and number depend on wind speed and turbulent diffusivity. Because of the droplets 'large size the vertical profile of liquid water content decreases more rapidly than exponential leading to correspondingly larger ray bending. As for scattering the large size of the droplets means that Beer's law of extinction does not apply. Part of this work has been presented previously, but the current work will incorporate more up-to-date size distribution data for near sea surface aerosols, obtained from a literature review in progress, into calculations of forward scattering and vertical refractivity profiles using selected wind speeds, relative humidity and air-sea temperature differences.
引用
收藏
页码:102 / 107
页数:6
相关论文
共 50 条