Compared to other parts of the Earth, the incidence of climatic factors linked to the presence of continental masses is limited on the vast surfaces of the Pacific, if we exclude Australia, whose large surfaces determine an accentuated continentality (both incidentally and also for as regards hydrography, a development of a certain consistency exists only in Australia, given the extension of this continent-island, and in New Guinea; the island fragmentation of the rest of Oceania therefore prevents a global treatment of watercourses of this continent). The ocean is crossed, along the line of the Equator, by the belt of intertropical convergences, towards which the trade winds converge in the directions determined by the Earth’s rotation: that is, from Northeast in the northern hemisphere, from SE into the southern one. Beyond the equatorial belt you enter the tropical domain, characterized by the formation of vast and mobile anticyclonic areas which in their rotational motion follow the line of the trade winds on the one hand, on the other heading towards the polar areas of low pressures (on the low pressure front Antarctic a barometric “jump” is created which gives rise to violent winds, i Roaring Forties). The general conditions of the atmosphere have seasonal mutations in relation to the zenith displacements of the Sun: thus the belt of the equatorial convergences moves to the South or North of the Equator and consequently also the anticyclonic areas are pushed further to the South or North , rejecting or expanding rhythmically the influences of polar air masses.
To these atmospheric shifts is connected the precipitation regime, which has rhythmic trends also in the equatorial belt, albeit to a lesser extent than in the tropical ones. In the equatorial belt it actually rains almost all year round, with an accentuation of rainfall in the summer months: in the Solomon Islands the quantitatively higher values are reached, even at 6000 mm per year. In general, however, around 3000 mm of rain are recorded, which are reduced towards the edges of the belt, where even the rainfall regime has a sharper seasonal rhythm, with values between 1500 and 1000 mm per year, and with maximum rainfall in summer or winter depending on whether it passes from ‘to each other hemisphere. Annual rainfall is considerably reduced in northern Australia, where, however, the climate is regulated by various mechanisms: from the anticyclone that stays there in the months of the austral winter and from monsoon-like exchanges with the equatorial seas of Indonesia, which however they are felt to a very limited extent in the interior of the continent. AS, as in New Zealand, you enter a zone with a temperate climate, hit, in the months of the austral winter, by humid winds from E. In the Pacific archipelagos, the presence of reliefs emerging from the sea, that is, from a surface open to the natural movement of atmospheric currents, means that there are very different rainfall conditions from one side to the other: very marked differences can be recorded, up to at 1000-1500 mm (as in Tahiti and Hawaii), passing from the leeward to the windward side. In the altitude sense, the differences are notable above all in New Guinea, on whose peaks there is also snowfall (at about 4500 m there is the limit of permanent snow), and in New Zealand, a major country in Oceania according to COUNTRYAAH.
The temperatures of the whole belt between the tropics are relatively constant and this is due to the action exerted by the vast water masses: between 10º S and 10º N there are variations of just one degree, with averages around 27 ºC; in the tropical belt the annual temperature variations increase, reaching up to 4 ºC in Fiji (from 22-25 ºC to 26-28 ºC). In Australia, especially inland, the thermal variations are instead of a distinctly continental type, from 12 ºC to 32 ºC (Alice Springs). The sea currents, linked to the circulation of winds, also exert a significant influence on the climate: the equatorial currents of the S and N, divided by the equatorial countercurrent, move at the height of the Equator, then forming two large circuits (clockwise to North, counterclockwise to S) that lap the coasts of Australia, East Asia (connecting to the Curoscivo) and America (the thermal variations are instead of a distinctly continental type, from 12 ºC to 32 ºC (Alice Springs). The sea currents, linked to the circulation of winds, also exert a significant influence on the climate: the equatorial currents of the South and North, divided by the equatorial countercurrent, move at the height of the Equator, then forming two large circuits (clockwise to North, counterclockwise to South) that lap the coasts of Australia, East Asia (connecting to the Curoscivo) and America (the thermal variations are instead of a distinctly continental type, from 12 ºC to 32 ºC (Alice Springs). The sea currents, linked to the circulation of winds, also exert a significant influence on the climate: the equatorial currents of the S and N, divided by the equatorial countercurrent, move at the height of the Equator, then forming two large circuits (clockwise to North, counterclockwise to S) that lap the coasts of Australia, East Asia (connecting to the Curoscivo) and America (California current to the N, Peru or Humboldt current to the South).
