Partitioning Solid and Liquid Precipitation over the Tibetan Plateau Based on Satellite Radar Observations

Whether precipitation falls in the form of rain or snow is of great importance to glacier accumulation and ablation. Assessments of the phase-aware precipitation have been lacking over the vast area of the Tibetan Plateau (TP) due to the scarcity of surface measurements and the low quality of satellite estimates in this region. In this study, we attempt a satellite radar-based method for this precipitation partition, in which the CloudSat radar is used for snowfall while the Global Precipitation Measurement Mission radar is used for rainfall estimation. Assuming that a 11-year snowfall and a 5-year rainfall estimates represent the mean states of precipitation at each phase, the phase partition characteristics including its annual mean, spatial pattern, seasonal dependence and variation with elevations are then discussed. Averaged over the highland area (over 1 km above sea level) in TP, the annual total precipitation is estimated to be around 400 mm, of which about 40% fall as snow. The snowfall mass fraction is about 45% in the northern and 30% in the southern part of TP, and about 80% in the cold and 30% in the warm half year. Surface elevation is found to be a high-impact factor on total precipitation and its phase partition, generally with total precipitation decreasing but snowfall fraction increasing with the increase of elevation. While there are some shortcomings, the current approach in combining snowfall and rainfall estimates from two satellite radars presents a useful pathway to assessing phase-aware precipitation over the TP region.

Supercooled Liquid Water Detection Capabilities from Ka-Band Doppler Profiling Radars: Moment-Based Algorithm Formulation and Assessment

The occurrence of supercooled liquid water in mixed-phase cloud (MPC) affects their cloud microphysical and radiative properties. The prevalence of MPCs in the mid- and high latitudes translates these effects to significant contributions to Earth’s radiative balance and hydrological cycle. The current study develops and assesses a radar-only, moment-based phase partition technique for the demarcation of supercooled liquid water volumes in arctic, MPC conditions. The study utilizes observations from the Ka band profiling radar, the collocated high spectral resolution lidar, and ambient temperature profiles from radio sounding deployments following a statistical analysis of 5.5 years of data (January 2014–May 2019) from the Atmospheric Radiation Measurement observatory at the North Slope of Alaska. The ice/liquid phase partition occurs via a per-pixel, neighborhood-dependent algorithm based on the premise that the partitioning can be deduced by examining the mean values of locally sampled probability distributions of radar-based observables and then compare those against the means of climatologically derived, per-phase probability distributions. Analyzed radar observables include linear depolarization ratio (LDR), spectral width, and vertical gradients of reflectivity factor and radial velocity corrected for vertical air motion. Results highlight that the optimal supercooled liquid water detection skill levels are realized for the radar variable combination of spectral width and reflectivity vertical gradient, suggesting that radar-based polarimetry, in the absence of full LDR spectra, is not as critical as Doppler capabilities. The cloud phase masking technique is proven particularly reliable when applied to cloud tops with an Equitable Threat Score (ETS) of 65%; the detection of embedded supercooled layers remains much more uncertain (ETS = 27%).

H2O-Induced Hydrophobic Interactions in MS-Guided Counter-Current Chromatography Separation of Anti-Cancer Mollugin from Rubia cordifolia

Counter-current chromatography (CCC) is a unique liquid–liquid partition chromatography and largely relies on the partition interactions of solutes and solvents in two-phase solvents. Usually, the two-phase solvents used in CCC include a lipophilic organic phase and a hydrophilic aqueous phase. Although a large number of partition interactions have been found and used in the CCC separations, there are few studies that address the role of water on solvents and solutes in the two-phase partition. In this study, we presented a new insight that H2O (water) might be an efficient and sensible hydrophobic agent in the n-hexane-methanol-based two-phase partition and CCC separation of lipophilic compounds, i.e., anti-cancer component mollugin from Rubia cordifolia. Although the n-hexane-methanol-based four components solvent systems of n-hexane-ethyl acetate-methanol-water (HEMWat) is one of the most popular CCC solvent systems and widely used for natural products isolation, this is an interesting trial to investigate the water roles in the two-phase solutions. In addition, as an example, the bioactive component mollugin was targeted, separated, and purified by MS-guided CCC with hexane-methanol and minor water as a hydrophobic agent. It might be useful for isolation and purification of lipophilic mollugin and other bioactive compounds complex natural products and traditional Chinese medicines.