27.3-day and 13.6-day Atmospheric Tide and Lunar Forcing on Atmospheric Circulation

An analysis of time variations of the earth's length of day (LOD) versus atmospheric geopotential height fields and lunar phase is presented. A strong correlation is found between LOD and geopotential height from which a close relationship is inferred and found between atmospheric circulation and the lunar cycle around the earth. It is found that there is a 27.3-day and 13.6-day east-west oscillation in the atmospheric circulation following the lunar phase change. The lunar revolution around the earth strongly influences the atmospheric circulation. During each lunar cycle around the earth there is, on average, an alternating change of 6.8-day-decrease, 6.8-day-increase, 6.8-day-decrease and 6.8-day-increase in atmospheric zonal wind, atmospheric angular momentum and LOD. The dominant factor producing such an oscillation in atmospheric circulation is the periodic change of lunar declination during the lunar revolution around the earth. The 27.3- day and 13.6-day atmospheric oscillatory phenomenon is akin to a strong atmospheric tide, which is different from the weak atmospheric tides, diurnal and semidiurnal, previously documented in the literature. Also it is different from the tides in the ocean in accordance with their frequency and date of occurrence. Estimation shows that the 27.3-day lunar forcing produces a 1-2 m s-1 change in atmospheric zonal wind. Therefore, it should be considered in models of atmospheric circulation and short and middle term weather forecasting. The physical mechanism and dynamic processes in lunar forcing on atmospheric circulation are discussed.