Climate classifications are systems that categorize the world's climates. A climate classification may correlate closely with a biome classification, as climate is a major influence on life in a region. One of the most used is the Köppen climate classification scheme first developed in 1884. There are several ways to classify climates into similar regimes. Originally, climes were defined in Ancient Greece to describe the weather depending upon a location's latitude. Modern climate classification methods can be broadly divided into genetic methods, which focus on the causes of climate, and empiric methods, which focus on the effects of climate. Examples of genetic classification include methods based on the relative frequency of different air mass types or locations within synoptic weather disturbances. Examples of empiric classifications include climate zones defined by plant hardiness, evapotranspiration, or more generally the Köppen climate classification which was originally designed to identify the climates associated with certain biomes. A common shortcoming of these classification schemes is that they produce distinct boundaries between the zones they define, rather than the gradual transition of climate properties more common in nature. Types of climate Alpine climate Desert climate or arid climate Humid continental climate Humid subtropical climate Ice cap climate Oceanic climate Subarctic climate Semi-arid climate Mediterranean climate Tropical monsoon climate Tropical rainforest climate Tropical savanna climate Tundra climate Polar climate Systems Climate classification systems include: Aridity index – part of many systems Alisov climate classification (ru) Berg climate classification Köppen climate classification – most widely used in the 1954 Köppen–Geiger variant Holdridge life zone classification – relatively simple Lauer climate classification Strahler climate classification Trewartha climate classification – 1967 modification of Köppen to fit real-world conditions Troll climate classification Vahl climate classification Bergeron and Spatial Synoptic The simplest classification is that involving air masses. The Bergeron classification is the most widely accepted form of air mass classification. Air mass classification involves three letters. The first letter describes its moisture properties, with c used for continental air masses (dry) and m for maritime air masses (moist). The second letter describes the thermal characteristic of its source region: T for tropical, P for polar, A for Arctic or Antarctic, M for monsoon, E for equatorial, and S for superior air (dry air formed by significant downward motion in the atmosphere). The third letter is used to designate the stability of the atmosphere. If the air mass is colder than the