Our friend Pierre & Sophie Larmandier tells us of tough conditions in the Champagne region due to spring frost. This post is an outline from their report.
April 6th 2021, buds have benefited from the sun and summery temperatures of this early spring. Around 6pm, a snow shower suddenly brings us back to winter. Then a very cold (about -2°C) night gives very little chance to the delicate small leaves that were only starting to break.
Today, we estimate at least 30% damage but, as the buds have yet to develop, we have to wait for a few weeks to be able to assess our losses.
We are not equipped to fight against frost, our insurance is our 4+ years of stock in the cellar.
FROST : BLACK OR WHITE ?
If such extreme episodes were to happen more often, we will think of protecting ourselves. Indeed we experience white frost almost every year but this year, as in 2003, the frost is a wintery one: a black frost.
This is a type of frost caused by the move of a cold (negative temperature) air mass. Temperature can drop a few degrees in a matter of minutes.
The black frost doesn’t have a specific colour if not the colour of the night and maybe, of the darkness of the damage caused. This moving air mass has very low humidity, the dew point, negative, isn’t reached yet when temperature goes below 0°C. There’s no dew on the ground then, and the cold air layer can become several metres thick.
During a black frost, damage is worsened by the low humidity of the air. Indeed, as the fruit, made of more than 90% water at this young stage, loses water through evaporation in this dry atmosphere. Water changing from its liquid to gas form absorbs a high amount of energy, which produces as much extra cold along the same principle as the refrigerator. This makes the fruit temperature even lower than its surrounding air. The gap can be between 2 to 4 degrees. The fruit then drops to -6°C -8°C when the air temperature is -2°C -4°C.