Background Free‐Tropospheric Ice Nucleating Particle Concentrations at Mixed‐Phase Cloud Conditions
Background Free‐Tropospheric Ice Nucleating Particle Concentrations at Mixed‐Phase Cloud Conditions
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DOI：
10.1029/2018jd028338
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发表时间：
2018-09
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影响因子：
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通讯作者：
L. Lacher;P. DeMott;E. Levin;K. Suski;Y. Boose;A. Zipori;E. Herrmann;N. Bukowiecki;M. Steinbacher-M.
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文献类型：
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作者：
L. Lacher;P. DeMott;E. Levin;K. Suski;Y. Boose;A. Zipori;E. Herrmann;N. Bukowiecki;M. Steinbacher-M.
含有冰的云对降水的形成至关重要，对确定地球的辐射收支也很重要。然而，云中冰的主要形成还没有完全了解。在冰成核颗粒（INPs）的存在下，促进了冰的相变，但在自然环境中INPs的识别和定量仍然具有挑战性，因为它们的数量很少。在本文中，我们量化了2014-2017年冬季，春季和夏季在高海拔研究站Jungfraujoch（JFJ）测量的自由对流层（FT）中的INP数浓度。在T = 241/242 K下，在与混合相云形成相关的条件下测量INPs。到目前为止，这是半定期测量的最长时间轴，类似于该站点和采样条件的在线INP监测。我们发现，背景FT中的INP浓度平均上限为10/stdL（标准条件下的空气升数[T = 273 K和p = 1013 hPa]），四分位数范围为0.4-9.6/stdL，与其他空气质量来源（例如，撒哈拉或海洋边界层）占上风。在2016年的实地活动中测量到浓度升高，这可能是由于撒哈拉沙尘和到达JFJ的海洋边界层空气的影响增强。背景FT中INP浓度的上限得到了在相似条件下进行的测量的支持，但在FT中的不同位置，我们发现INP浓度大多数时间低于13/stdL。
Clouds containing ice are vital for precipitation formation and are important in determining the Earth's radiative budget. However, primary formation of ice in clouds is not fully understood. In the presence of ice nucleating particles (INPs), the phase change to ice is promoted, but identification and quantification of INPs in a natural environment remains challenging because of their low numbers. In this paper, we quantify INP number concentrations in the free troposphere (FT) as measured at the High Altitude Research Station Jungfraujoch (JFJ), during the winter, spring, and summer of the years 2014–2017. INPs were measured at conditions relevant for mixed‐phase cloud formation at T = 241/242 K. To date, this is the longest timeline of semiregular measurements akin to online INP monitoring at this site and sampling conditions. We find that INP concentrations in the background FT are on average capped at 10/stdL (liter of air at standard conditions [T = 273 K and p = 1013 hPa]) with an interquartile range of 0.4–9.6/stdL, as compared to measurements during times when other air mass origins (e.g., Sahara or marine boundary layer) prevailed. Elevated concentrations were measured in the field campaigns of 2016, which might be due to enhanced influence from Saharan dust and marine boundary layer air arriving at the JFJ. The upper limit of INP concentrations in the background FT is supported by measurements performed at similar conditions, but at different locations in the FT, where we find INP concentrations to be below 13/stdL most of the time.