Mapping liquid water content in snow at the millimeter scale: an intercomparison of mixed-phase optical property models using hyperspectral imaging and in situ measurements

It is well understood that the distribution and quantity of liquid water in snow is relevant for snow hydrology and avalanche forecasting, yet detecting and quantifying liquid water in snow remains a challenge from the micro- to the macro-scale. Using near-infrared (NIR) spectral reflectance measurements, previous case studies have demonstrated the capability to retrieve surface liquid water content (LWC) of wet snow by leveraging shifts in the complex refractive index between ice and water. However, different models to represent mixed-phase optical properties have been proposed, including (1) internally mixed ice and water spheres, (2) internally mixed water-coated ice spheres, and (3) externally mixed interstitial ice and water spheres. Here, from within a controlled laboratory environment, we determined the optimal mixed-phase optical property model for simulating wet snow reflectance using a combination of NIR hyperspectral imaging, radiative transfer simulations (Discrete Ordinate Radiative Transfer model, DISORT), and an independent dielectric LWC measurement (SLF Snow Sensor). Maps of LWC were produced by finding the lowest residual between measured reflectance and simulated reflectance in spectral libraries, generated for each model with varying LWC and grain size, and assessed against the in situ LWC sensor. Our results show that the externally mixed model performed the best, retrieving LWC with an uncertainty of ∼1 %, while the simultaneously retrieved grain size better represented wet snow relative to the established scaled band area method. Furthermore, the LWC retrieval method was demonstrated in the field by imaging a snowpit sidewall during melt conditions and mapping LWC distribution in unprecedented detail, allowing for visualization of pooling water and flow features.

First principle study and Hirshfeld surface analysis on the effect of type, number, and position of small molecules on the structural stability and optical property of a powerful energetic crystal 6-nitro-7-azido-pyrazol[3,4-d][1,2,3]triazine-2-oxide

The powerful but unstable high energy compound ICM-103 is stabilized and desensitized by small molecules H2O, NH3, and H2S.

Synthesis of novel poly(arylene ether amide) containing aliphatic ring for optical property

In this work, the monomer N, N′-bis(4-fluorobenzamide)dicyclohexyl methane (BFDCM) was synthesized successfully by 4-fluorobenzoylchloride and 4,4′-diaminodicyclohexylmethane through interfacial reaction, and then the monomer BFDCM and 1,4-benzenediol (HQ) or 4.4′-biphenol (BH) were used to prepare the novel poly(arylene ether amide) (HQ-BFDCM and BH-BFDCM) containing an aliphatic ring in the main chain by nucleophilic substitution in NMP solution. These two polymers exhibited the inherent viscosities ranging from 0.828 to 1.044 dL g−1, high glass-transition temperatures (Tg) of 214.1–235.0 °C, and weight-loss temperature (T5%) of 425.2–441.3 °C. The polymers HQ-BFDCM and BH-BFDCM could completely or partly dissolve in some polar solutions, such as NMP, DMF, and so on, and they showed moderate corrosion resistance. Additionally, the obtained polymers HQ-BFDCM and BH-BFDCM exhibited good optical property, and the optical transmittances of HQ-BFDCM and BH-BFDCM were 74% and 80% at 450 nm, respectively, which showed that they could be applied to the heat-resistant optical films.