1. Astronomical Tide and Storm Surge Non-Linearity Arielle Alpert

2. Astronomical Tide Gravity-induced Diurnal, semi-diurnal, and mixed semi-diurnal

3. Storm Surge vs. Storm Tide Storm tide (water level) = storm surge + astronomical tide non-linearity

4. Tide-Surge Interaction Not necessarily a linear supposition of the two Reduces water level below that obtained by linearly adding simulated tide and surge Not necessary in observational data Bernier 2007

5. If the tide-surge interaction is linear, the probability of an extreme will be approximately equal for each tidal stage. Tide-surge interaction will only contribute significantly to the total sea level when the surges are large enough to interact. In NYC area, storm surge tends to be reduced when it happens at the high tide or during the rising tide, while it tends to be increased at the low tide or during the receding tide. Analysis  High Tide: within 1.5 hours of tidal maximum  Low Tide: within 1.5 hours of tidal minimum  Receding Tide: from the high to low tidal stage  Rising Tide: from the low to high tidal stage

6. Lin et al., 2012 Low Tide High Tide

7. References Bernier, N. B., and K. R. Thompson (2007), Tide-surge interaction off the east coast of Canada and northeastern United States, J. Geophys. Res., 112, C06008, doi:10.1029/2006JC003793. Tang, Y. M., R. Grimshaw, B. Sanderson, and G. Holland (1995), A Numerical Study of Storm Surges and Tides, with Application to the North Queensland Coast, J. Phys. Oceanography, 26, 2700–2711. Lin, N., K Emanuel, M Oppenheimer, and E. Vanmarcke (2012), Physically Based Assessment of Hurricane Surge Threat Under Climate Change, Nature Clim. Change, 462–467.