Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles
Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles
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DOI：
10.5194/acp-15-393-2015
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发表时间：
2015-01-01
影响因子：
6.3
通讯作者：
Kreidenweis, S. M.
中科院分区：
文献类型：
--
作者：
DeMott, P. J.;Prenni, A. J.;Kreidenweis, S. M.
从实验室研究和大气测量的数据被用来开发一个经验参数化的天然矿物粉尘颗粒的浸泡冻结活动。当在相对于水的标称105%相对湿度（RHw）下处理矿物粉尘气溶胶时，采用科罗拉多州立大学（CSU）连续流扩散室（CFDC）进行的测量作为颗粒的浸没冷冻成核活性的量度。冰活跃的冻结分数与温度的代表撒哈拉和亚洲沙漠的沙尘源是一致的大气尘羽的一组有限的比较类似的测量。开发的参数化遵循的形式之一，以前建议的非特定组成的大气颗粒在量化冰成核颗粒浓度作为温度和大于0.5 μ m直径的颗粒的总数浓度的函数。这种方法并没有明确考虑冰成核的表面积和时间依赖性，但充分封装的激活特性，在区域和全球建模模拟的潜在用途，并可能在开发遥感检索冰成核粒子的应用。引入了一个校准因子，以解释在RHw为105%时处理的CSU CFDC数据中矿物尘埃颗粒的浸没冷冻分数明显低估（平均约为3），而在较高RHw时处理的最大分数则为活性。影响CFDC仪器中激活行为与RHw的仪器因素仍有待于在未来的研究中充分探索。尽管如此，使用这个校准因子的支持，从气溶胶相互作用和大气动力学（AIDA）的膨胀室云团实验相同的气溶胶获得的冰活化数据进行比较。进一步比较新的参数化，包括校准校正，预测的浸没冻结表面活性位点密度参数化的矿物尘埃粒子，单独开发的AIDA实验数据，显示出良好的协议，通过撒哈拉气溶胶层下降收集的数据。这些研究支持实验室测量的效用，以获得大气相关的数据的灰尘和其他粒子类型的冰成核特性，并建议考虑所有矿物粉尘作为一个单一类型的冰成核粒子作为一个有用的一阶近似数值模拟调查的适合性。
Data from both laboratory studies and atmospheric measurements are used to develop an empirical parameterization for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RHw) are taken as a measure of the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterization developed follows the form of one suggested previously for atmospheric particles of nonspecific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 mu m diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A calibration factor is introduced to account for the apparent underestimate (by approximately 3, on aver-age) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RHw of 105% vs. maximum fractions active at higher RHw. Instrumental factors that affect activation behavior vs. RHw in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this calibration factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization, including calibration correction, to predictions of the immersion freezing surface active site density parameterization for mineral dust particles, developed separately from AIDA experimental data alone, shows excellent agreement for data collected in a descent through a Saharan aerosol layer. These studies support the utility of laboratory measurements to obtain atmospherically relevant data on the ice nucleation properties of dust and other particle types, and suggest the suitability of considering all mineral dust as a single type of ice nucleating particle as a useful first-order approximation in numerical modeling investigations.