Climatology (frae Greek κλίμα, klima, "place, zone"; an -λογία, -logia) or climate science is the study o climate, scienteefically defined as wather condeetions averaged ower a period o time. This modren field o study is regairdit as a branch o the atmospheric sciences an a subfield o pheesical geografie, which is ane o the Yird sciences. Climatology nou includes aspects o oceanografie an biogeochemistry. Basic knawledge o climate can be uised within shorter term wather forecastin uisin analog techniques such as the El Niño–Soothren Oscillation (ENSO), the Madden–Julian oscillation (MJO), the North Atlantic oscillation (NAO), the Northren Annular Mode (NAM) which is an aa kent as the Arctic oscillation (AO), the Northren Paceefic (NP) Index, the Paceefic decadal oscillation (PDO), an the Interdecadal Pacific Oscillation (IPO). Climate models are uised for a variety o purposes frae study o the dynamics o the wather an climate seestem tae projections o futur climate. Wather is kent as the condeetion o the atmosphere ower a period o time. While Climate haes tae dae wi the atmospheric condeetion ower an extendit tae indefinite period o time.