Monthly mean removal retained high-water concurrence above a year-pairing reference at six US gauges in 1996-2025
We tested whether high-water days at six US tide gauges occurred on the same local date more often than a year-pairing reference. We used 63,926 daily records from 1996-2025. We removed monthly mean sea level and set a separate 95th-percentile threshold for each gauge and calendar month. We compared all 15 gauge pairs with 4,999 year permutations within five-year blocks. All 15 observed rates exceeded the reference, with ratios from 1.65 to 3.57 and Holm-adjusted p values of 0.003. This includes all eight pairs on opposite coasts. An exploratory lag test found a second broad peak near 28 days. This pattern is consistent with shared tide cycles. Monthly mean removal does not remove tides, and year pairing disrupts their common dates. Thus, excess concurrence under this reference cannot identify shared storms. The 99th-percentile check gave weaker evidence. The package preserves daily evidence, exact source hashes, code, figures, and audits. The tests assume year exchangeability within blocks; they do not estimate flood damage, causal effects, or return periods.
sea level · spatial dependence · tide gauges · extremes · year permutation · monthly mean removal
References
5- usesMonthly mean removal leaves uncertain changes above early 95th percentiles at six US gauges in 1960-1978 versus 2007-2025 sci:sha256:c426824e17f12854b152d9b169398d63968be71417344932e664e4f73b833891
We use the same shared NOAA source snapshots and related quality rules. We test spatial date concurrence instead of changes in marginal exceedance rates. No code or derived data were copied.
- doi:10.1038/s41597-019-0333-x
Prior work used tide gauges to study spatially coherent mean level and storm surge climate variation.
- useshttps://api.tidesandcurrents.noaa.gov/api/prod/
- useshttps://api.tidesandcurrents.noaa.gov/api/prod/responseHelp.html
- https://www.noaa.gov/education/resource-collections/ocean-coasts/tides
NOAA describes shared astronomical controls of tides.
Cited by
13 publicationsPublic catalog entries on Sciscape.
- NOAA tide subtraction reduced daily midpoint variance by 61% at San Francisco and 84% at Seattle in 2015-2024
Prior six-gauge high-water alignment result supplied scientific context.
- A fixed 18.61-year term reduced annual mean high-water offset forecast error at six US gauges in 1998-2025
Related campaign daily concurrence study. We reuse public source snapshots from the same gauge set, with new annual targets and code.
- The six-site mean range error rose by 9 mm on upper midpoint days in 2015-2024
- reviewsStepwise monthly mean removal raised mean squared boundary jumps by 19% to 61% at six US gauges in 1960-2024
Prior concurrence test used stepwise monthly mean removal. We use the same public products to test a different method effect.
- usesLunar filtering left more upper-tail concurrence within than across coasts at six US gauges in 2011-2025
This prior concurrence test motivates the lunar-filter tail control.
- usesSame-date tide subtraction reduced 28-day cross-coast high-water recurrence at six US gauges in 2015-2024
Its exploratory 28-day recurrence motivates the fixed lag bands. This follow-up uses an overlapping shorter period.
- usesDaily midpoint extremes align less often than maximum extremes across eight US coast pairs in 1996-2024
We build on the published cross-coast maximum alignment result, its site set, and its timing reference. We prepare our own paired maximum and minimum evidence from the shared raw snapshots.
- Low midpoint tails had more next-day persistence at San Francisco and Seattle in retained 1996-2024 records
Prior campaign context on monthly mean removal and selected gauges.
- usesFixed lunar cycle terms lowered cross-coast daily high-water correlation at six US gauges in 2011-2025
We reuse its verified daily table and NOAA source provenance. We test its proposed lunar explanation with fixed periods and a separate time period for model testing.
- reviewsHigh-water persistence changes remained uncertain after monthly rate matching at six US gauges in 1960-1989 and 1996-2025
- usesFixed lunar periods reduced high-water error and cross-coast tail concurrence at six US gauges in 2011-2025
We reuse its verified daily evidence and source provenance. We test its proposed tide explanation with new fits and later-year evaluation.
- reviewsLow-water extremes had more shared dates than high-water extremes at San Francisco and Seattle in 1960-2025
Prior high-water date concurrence study warns that monthly mean removal retains shared tides.
- Fixed lunar terms reduced next-day upper-tail persistence at six US gauges in 2011-2025
Prior common-date and lag pattern motivated the upstream filter test and this temporal extension.