The prediction of the winter weather over complex terrain is quite challenging due to the highly variable nature of winds, visibility, and snowfall. As a World Meteorological Organization (WMO) World Weather Research Program (WWRP) Research Demonstration Project (RDP) and Forecast Demonstration Project (FDP), ICE-POP 2018 (International Collaborative Experiments for PyeongChang 2018 Olympic and Paralympic winter games) was held in the PyeongChang region from November 2017 to April 2018 with contributions from 29 agencies from 12 countries. The region was quite unique for observing winter weathers that are influenced by cold air and warm ocean interaction, sudden uplifting by steep terrains near the coast, and modulation by complex terrains. The main scientific goal was to understand the precipitation processes in this unique region during the cold season and to evaluate/improve forecasting from numerical models based on intensive observations. Dense observational networks of upper air observation (eight soundings, two wind profilers, shipborne sounding, and dropsonde), remote sensing (three X-Pol radars, one Ku/Ka-Pol radar and three S-Pol, one S-band, two C-band, and three Doppler lidars), microphysical observation (2DVD, MASC, PIP, Parsivel, MRR, POSS, Pluvio), and surface stations (64 stations) were implemented, in particular, to observe the evolution of precipitation along and across atmospheric flows. The field experiment and real-time forecast demonstration ended and the second phase of the experiment has started for better understanding of the microphysical processes, their better representation in the numerical modeling, and further improvement of winter weather prediction through various international collaborations.

The main purposes of the special issue are

1) to document the scientific findings on the winter weather during the forecast demonstration project

2) to share scientific knowledge on processes of winter weathers that have been investigated with unprecedented dense observational networks,

3) to share current status and improved knowledge of forecasting of winter weathers, and

4) to document new retrieval and quality control methods of the operational and advanced instruments.

The special issue will include all manuscripts related to observational data, products, NWP modeling, researches on observational instrumentation, process/mechanism study, reanalysis, integration of observation and numerical modeling, and prediction of the winter weathers.