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Turbulence in clouds is known to enhance particle collision rates, as widely demonstrated for warm rain formation. A similar impact on ice growth processes is expected but a solid observational basis is missing. A statistical analysis of a 15‐month data set of cloud radar observations allows for the first time to quantify the impact of turbulence on ice aggregation and riming in Arctic low‐level mixed‐phase clouds. Increasing eddy dissipation rate (EDR), from below 10−4 to above 10−3 m2 s−3, yields larger ice aggregates, and higher particle concentration, likely caused by increasing fragmentation. In conditions more favorable to riming, higher EDR is associated with dramatically higher particle fall velocities (by up to 125%), under similar liquid water paths, indicative of markedly higher degrees of riming. Our findings thus reveal the key role of turbulence for cold precipitation formation, and highlight the need for an improved understanding of turbulence‐hydrometeor interactions in cold clouds. Plain Language Summary: Liquid and frozen precipitation mainly forms by collision and subsequent aggregation of small particles. Collisions between cloud particles, such as droplets and ice crystals, are thought to be increased by turbulence. While this effect has been intensively studied for liquid‐only clouds, the impact of turbulence on ice‐ice collisional growth (aggregation) and ice‐liquid collisional growth (riming) is expected but has so far been poorly quantified. We study the effect of turbulence on aggregation and riming based on a long‐term remote‐sensing data set of low‐level clouds containing both ice and liquid particles, recorded at the Arctic site of Ny‐Ålesund, Svalbard. Cloud radar observations are used to retrieve the dissipation rate of turbulent kinetic energy (i.e., the eddy dissipation rate; EDR), which is the relevant quantity driving increases in collision rates, and to characterize ice particle properties. We find evidence that higher EDR regimes enhance the aggregation of particles, and are associated with signatures of increased ice particle concentration, possibly caused by the production of particle fragments upon collision. In temperature regimes more favorable to riming, turbulence dramatically enhances the particles' fall velocity, denoting higher degrees of riming. Our findings thus highlight a key role of turbulence for the formation of precipitable ice. Key Points: Relation between turbulence and ice growth investigated based on long‐term remote sensing data set of Arctic low‐level mixed‐phase cloudsHigher eddy dissipation rate (EDR) correlates with larger ice aggregates, and possibly higher degrees of fragmentationHigh EDR is an essential component needed for the formation of rimed particles [ABSTRACT FROM AUTHOR]

We present a comprehensive quality-controlled 15-month dataset of remote sensing observations of low-level mixed-phase clouds (LLMPCs) taken at the high Arctic site of Ny-Ålesund, Svalbard, Norway. LLMPCs occur frequently in the Arctic region and extensively affect the energy budget. However, our understanding of the ice microphysical processes taking place in these clouds is incomplete. The dual-wavelength and polarimetric Doppler cloud radar observations, which are the cornerstones of the dataset, provide valuable fingerprints of ice microphysical processes, and the high number of cases included allows for the compiling of robust statistics for process studies. The radar data are complemented with thermodynamic retrievals from a microwave radiometer, liquid base height from a ceilometer, and wind fields from large-eddy simulations. All data are quality controlled, especially the cloud radar data, which are accurately calibrated, matched, and corrected for gas and liquid-hydrometeor attenuation, ground clutter, and range folding. We finally present an analysis of the temperature dependence of Doppler, dual-wavelength, and polarimetric radar variables, to illustrate how the dataset can be used for cloud microphysical studies. The dataset has been published in and is freely available at: 10.5281/zenodo.7803064. [ABSTRACT FROM AUTHOR]

Moisture inversions, i.e. layers in the troposphere where specific humidity increases with height, are extremely frequent in the Arctic. They are strongly intertwined with cloud processes, as well as the energy budget, by affecting the downward longwave radiation. In this study, the capability of two benchmark satellite sounders, the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric Infrared Sounder (AIRS), to detect moisture inversions is systematically assessed based on radiosonde data from the Arctic site Ny-Ålesund. In particular for IASI, such an analysis has not been done before. The frequency of occurrence of moisture inversions at Ny-Ålesund based on radiosoundings is above 95 % in all seasons, with multiple inversions in the same profile occurring most of the time (in 82 % of the profiles). We first performed a sensitivity analysis which revealed that the chosen vertical grid of the specific humidity profiles has a distinct impact on the inversion frequency: in general, the lower the grid resolution, the lower also the detected inversion frequency. However, even when reducing the vertical resolution of the radiosonde profiles used in the comparison to match that of the IASI and AIRS retrievals, a large underestimation in both inversion frequency and inversion strength can be found in the satellite products. While observed inversion frequency in any 100-hPa-deep layer between 1000 and 400 hPa is typically between 10 and 20 % (50 and 80 %) in the regridded (original) radiosonde data, inversion frequency in satellite data is in most cases below 10 %. A better agreement has been found for IASI below the 900-hPa level and in particular for winter, while AIRS does not detect any inversions below the 700-hPa level in this season. In addition to satellite data, reanalysis data also have the potential to provide an Arctic-wide view on moisture inversion characteristics. Here, we thus also assessed the capability of the latest reanalysis developed by ECMWF, ERA5, to detect moisture inversions at Ny-Ålesund, by performing a similar comparison with radiosoundings. We found that ERA5 represents Arctic moisture inversion characteristics very well, if the radiosonde profile resolution is reduced to that of the reanalysis. [ABSTRACT FROM AUTHOR]