Monthly Gridded Met Office Historical Marine Air Temperature (MOHMATN4) anomalies (1856-2006)

MOHMAT, (Met Office Historical Marine Air Temperature) is a gridded dataset of marine air temperature anomalies covering the period 1856-2006. The current version of the dataset is MOHMAT4, which is described in reference below (under Doc tab). MOHMAT is produced by taking in-situ measurements of MAT from ships and buoys, rejecting measurements which fail quality checks, converting the measurements to anomalies by subtracting climatological values from the measurements, and averaging the resulting anomalies on a 5 by 5 degree monthly grid. Note that only night-time data are used, because day-time data are corrupted by heat island effects. Up to 1996 the measurements used are those in the U.K. Marine Data Bank; more recent years use data coming in through the GTS. MOHMAT is no longer updated. After gridding the anomalies, bias corrections are applied to remove spurious trends caused by changes in ship deck heights and various unusual operational practices, and the data are smoothed to reduce noise. The data are provided by the Met Office.