When the Songhua River Grows Winter Branches

Jilin’s rime begins with a stretch of river that keeps moving through winter. A provincial history account describes the Songhua through the city as open when many northern rivers are frozen. A later meteorological explanation links that open water to Fengman Hydropower Station upstream: its operation leaves moisture available above the urban reach, while the basin around Jilin cools after dark. Water, hills and tree-lined banks make a local system; none of them alone produces the white branches.

Moisture rising from moving water meets surfaces that can lose heat quickly after sunset. The river supplies moisture to the air; cold branches provide a place for ice to accumulate. This explains how the winter landscape can remain liquid and frozen at once: the Songhua flows below while trees on the bank acquire a bright crust.

The World Meteorological Organization defines rime as an ice deposit generally formed when supercooled fog or cloud droplets freeze on an object. A droplet carried through the air can strike a twig and freeze; repeated impacts build an uneven coat, often thicker on the side exposed to the moving air. This is different from snow, which falls as ice crystals formed in clouds, and from hoarfrost, which forms when water vapour deposits as ice crystals on a cold surface.

Jilin’s meteorological account describes the local display as mainly crystalline and gives special importance to moisture settling during cold, calm nights. That local description and the international definition point to related but distinct routes by which moisture becomes ice. In either case, the branch is not merely decorated: its shape and exposure affect where ice can attach, how it grows, and when a breeze or warming makes it fall.

The Songhua does not meet the city in a single uniform line. The 2024 account by Jilin’s senior meteorologist stresses strong small-scale differences along the urban river: conditions at the Songjiang Road waterfront, Ashi and Rime Island can produce different displays. Wind, humidity, water temperature and the shelter of a bend or grove change what reaches each set of trees. A forecast for one stretch cannot describe every riverbank.

The city’s study of rime has become an observing practice. Meteorologists began researching its formation and forecasting in 2008. A dedicated rime laboratory opened in 2019, with work on ice formation, airborne particles, fog-droplet spectra and microclimates along the Songhua. Those measurements shift attention from a scenic image to the small conditions that make it possible: moisture in the air, the size of droplets and the speed of the wind close to the ground.

A local history feature gives the rime season a three-part rhythm: moisture gathers at night, branches are found rimed in the morning, and around midday the bright ice can fall like petals. The sequence describes more than a picturesque day. Nighttime cooling helps ice accumulate; with daylight, slight warming and movement loosen the light crystals from twigs. The river continues below the whole cycle, supplying moisture even as the surface of each branch changes.

That rhythm also explains why rime is a short-lived event rather than a permanent coating. A calm night can let crystals build in a sheltered place; sunlight or wind can make the branches shed them later. Jilin’s winter spectacle is made by a working river, a cold basin and a particular atmospheric interval. Its beauty belongs to that changing process, not to a fixed view that appears on command.