Mean Diurnal Variation of Marine Air Temperature Observed on Meteorological Buoys in the Pacific Ocean

Abstract

Mean diurnal variation of marine air temperature has been investigated using observations made on meteorological buoys in the Pacific Ocean. The mean diurnal variation of the air temperature showed minimum temperature around 5 a.m. and maximum temperture around 3-4 p.m. in local time. The range of the diurnal variation is 0.3-0.8 K. In the areas where the atomspheric tide dominates, the temperature rise in the morning is slightly emphasized and the maximum temperature tends to be suppressed in the afternoon. The mean diurnal variation of the air temperature best represents the individual diurnal change in areas where the water is generally calm, such as the eastern and central Equatorial Pacific. Temperature variations due to convective activities and synoptic to intra seasonal variations overwhelm the diurnal variations of the air temperature in the western tropical region and middle to high latitudes. The temperature variation range in these areas is one order of magnitude larger than the range of the mean diurnal cycle. Significant positive biases, estimated as high as 0.1-0.2 K, are suspected to appear in the morning and afternoon on the temperature record obtained on some buoys according to a previous study.