Aristotle University of Thessaloniki, Physics Department, Nuclear Physics Laboratory, Thessaloniki 54124, Greece.
Aristotle University of Thessaloniki, Physics Department, Nuclear Physics Laboratory, Thessaloniki 54124, Greece.
J Environ Radioact. 2014 Mar;129:80-5. doi: 10.1016/j.jenvrad.2013.12.013. Epub 2014 Jan 2.
A strong positive correlation between the seasonal changes of the tropopause height and the concentration of (7)Be in the surface air (R = 0.94, p < 0.0001) was observed at 40°N. Moreover, a strong positive correlation was revealed between the activity concentrations of (7)Be and the temperature T (°C) (R = 0.97, p < 0.001), confirming that the increased rate of vertical transport within the troposphere, especially during warmer months, has as a result the descent to the surface of air masses enriched in (7)Be. The results of the present work suggest that the temperature and the tropopause height are good indicators for transport time of air masses enriched in (7)Be to the surface. Higher values of temperature or tropopause height seem to result to shorter transport times. This is attributed to atmospheric convection which provides an effective mechanism for vertical transport of air masses. Increasing tropospheric temperature has generally as a result that convection penetrates more deeply which in turn leads to an increase in tropopause height. But, the atmospheric procedures do not occur immediately after the fluctuations of correlated factors. Thus, a time lag is expected between the tropopause height and (7)Be activity concentrations on surface air that might be from hours to days or weeks. The result suggests that (7)Be concentrations fully respond within three days after the changes in the tropopause height.
在北纬 40°处，观测到同温层顶高度的季节性变化与地表空气中（7）Be 浓度之间存在很强的正相关关系（R = 0.94，p < 0.0001）。此外，（7）Be 的活度浓度与温度 T（°C）之间也存在很强的正相关关系（R = 0.97，p < 0.001），这证实了同温层中垂直输送的增强速率，特别是在温暖的月份，导致富含（7）Be 的空气团下沉到地表。本工作的结果表明，温度和同温层顶高度是（7）Be 富集空气团到达地表的输运时间的良好指标。较高的温度或同温层顶高度似乎导致较短的输运时间。这归因于大气对流，它为空气团的垂直输送提供了有效的机制。同温层温度的升高通常导致对流穿透更深，从而导致同温层顶高度增加。但是，大气过程不会在相关因素波动后立即发生。因此，同温层顶高度和地表空气（7）Be 活度浓度之间预计会存在时间滞后，可能是数小时到数天或数周。结果表明，（7）Be 浓度在同温层顶高度变化后的三天内完全响应。
