Meriilmaston

Meriilmaston is a term used in coastal climatology to describe a climate type in which proximity to the sea moderates air temperatures and shapes humidity and precipitation patterns. The word is of Finnish origin, corresponding to meri-ilmasto, literally "sea climate." In practice, meriilmaston refers to coastal zones where the maritime influence produces milder winters and cooler summers than inland areas at similar latitudes, along with relatively high humidity and precipitation distributed fairly evenly through the year.

The underlying mechanism is the moderating effect of ocean surfaces and the transport of moisture by prevailing westerly or along-coast winds. Sea surface temperatures dampen seasonal extremes, and the proximity to water enhances cloud cover and often leads to fog in more humid conditions. These climates are typically characterized by frequent, light-to-moderate rainfall and a narrow temperature range between seasons.

Geographically, meriilmaston-like zones occur on western coasts of continents in temperate regions, including parts of northwestern Europe, the Pacific Northwest of North America, and coastal areas of southern Chile and New Zealand. Local variations exist depending on ocean currents, altitude, and continental position, leading to a spectrum from mild, maritime climates to cooler, subpolar manifestations.

In climate classification, meriilmaston is often associated with oceanic (Cfb) or subpolar oceanic (Cfc) types in Köppen terms. The concept is relevant for agriculture, forestry, urban planning, and climate adaptation strategies, reflecting the sea’s role in shaping regional climate and ecosystem dynamics.