K1

K1 is the luni-solar declinational diurnal tidal constituent, period 23.9345 hours and speed 15.0411 degrees per hour, the single largest diurnal term. It combines the diurnal effects of lunar and solar declination, so it cannot be separated into purely lunar and solar parts within a single station record short of about a year. K1 and O1 together drive the diurnal tide and define the numerator of the form number F = (K1 plus O1) / (M2 plus S2). The K1 nodal factor varies by roughly plus or minus 11 percent over the 18.61-year cycle, the largest nodal modulation among the main constituents, so its correction matters most in tidal prediction.