P1M
Calendar-month mean
Temperature and salinity averaged over the complete UTC calendar month. It removes day-to-day and subdaily structure.
H01W1 hydrophone · coherent RAM transmission loss (TL) · 63 Hz
Finer ocean time steps change the answer, but not in one direction.
Monthly, daily and six-hourly inputs from the same Copernicus system sometimes move the exact endpoint by several decibels. Other paths barely move. The signs reverse from path to path, so these results cannot be turned into one correction.
The useful result is sensitivity, not a verdict that daily or PT6H is always better.
The twelve-path follow-up found daily minus monthly changes from -4.955 to +8.459 dB. PT6H minus daily ranged from -3.368 to +1.050 dB. Each contrast split six positive and six negative.
What the labels mean
Three views of one operational ocean model
P1D
UTC daily mean
A mean from 00:00 to 24:00 UTC. It is not a midnight or noon snapshot.
PT6H
Instantaneous state
The nearest model state on the 00, 06, 12 or 18 UTC grid. It is not a six-hour mean.
The four-path pilot and the twelve-path follow-up answer related questions, but they are separate cohorts. This report never pools them.
First study · four paths
The pilot found large daily versus monthly changes on some paths
Three of four paths changed by at least 1 dB. Two exceeded 3 dB. PT6H versus daily was smaller overall, though two paths still exceeded 1 dB. The two largest daily-minus-monthly cases later reproduced exactly under identical inputs.
Four-path pilot · derived.comparison_table
P1D minus P1M at the exact 63 Hz endpoint
Selected case
P1M monthly TL
P1D daily TL
P1D minus P1M
Definition, matching and source
- Left definition
- P1M monthly TL
- Right definition
- P1D daily TL
- Signed comparison
- P1D minus P1M
- Matched keys
- Candidate row, path to the H01W1 hydrophone, event UTC, 63 Hz, 6 m source depth, endpoint and solver settings
- Case coordinate
- Exact WGS84 source range to the H01W1 hydrophone
- Source table
- /home/rui/ara/ctbto-2026/data/derived/ha01-ocean-temporal-sensitivity/v1/temporal-deltas.csv
| Case | Event UTC | Range (km) | P1M monthly TL (dB) | P1D daily TL (dB) | P1D minus P1M (dB) |
|---|---|---|---|---|---|
| primary_1 | 2025-05-20T15:09:37Z | 91.020 | 109.337 | 106.736 | -2.601 |
| primary_2 | 2025-01-06T10:24:53Z | 55.229 | 85.383 | 89.045 | +3.662 |
| primary_3 | 2026-02-19T06:29:57Z | 100.208 | 103.666 | 106.846 | +3.179 |
| primary_4 | 2026-03-28T09:53:44Z | 59.005 | 111.945 | 111.961 | +0.016 |
Four-path pilot · derived.comparison_table
PT6H minus P1D at the exact 63 Hz endpoint
Selected case
P1D daily TL
PT6H instantaneous TL
PT6H minus P1D
Definition, matching and source
- Left definition
- P1D daily TL
- Right definition
- PT6H instantaneous TL
- Signed comparison
- PT6H minus P1D
- Matched keys
- Candidate row, path to the H01W1 hydrophone, event UTC, 63 Hz, 6 m source depth, endpoint and solver settings
- Case coordinate
- Exact WGS84 source range to the H01W1 hydrophone
- Source table
- /home/rui/ara/ctbto-2026/data/derived/ha01-ocean-temporal-sensitivity/v1/temporal-deltas.csv
| Case | Event UTC | Range (km) | P1D daily TL (dB) | PT6H instantaneous TL (dB) | PT6H minus P1D (dB) |
|---|---|---|---|---|---|
| primary_1 | 2025-05-20T15:09:37Z | 91.020 | 106.736 | 108.517 | +1.781 |
| primary_2 | 2025-01-06T10:24:53Z | 55.229 | 89.045 | 89.456 | +0.411 |
| primary_3 | 2026-02-19T06:29:57Z | 100.208 | 106.846 | 105.553 | -1.292 |
| primary_4 | 2026-03-28T09:53:44Z | 59.005 | 111.961 | 111.891 | -0.070 |
Blind follow-up · twelve paths
The follow-up confirmed that the effect depends on the path
The frozen follow-up selected one primary per calendar month before opening outcomes. Nine of twelve daily-minus-monthly changes reached 1 dB and four reached 3 dB. PT6H-minus-daily was usually smaller, but one path reached -3.368 dB.
Twelve-path frozen follow-up · derived.comparison_table
P1D minus P1M at the exact 63 Hz endpoint
Selected case
P1M monthly TL
P1D daily TL
P1D minus P1M
Definition, matching and source
- Left definition
- P1M monthly TL
- Right definition
- P1D daily TL
- Signed comparison
- P1D minus P1M
- Matched keys
- Candidate row, path to the H01W1 hydrophone, event UTC, 63 Hz, 6 m source depth, endpoint and solver settings
- Case coordinate
- Exact WGS84 source range to the H01W1 hydrophone
- Source table
- /home/rui/ara/ctbto-2026/data/derived/ha01-ocean-temporal-followup/v1/temporal-deltas.csv
| Case | Event UTC | Range (km) | P1M monthly TL (dB) | P1D daily TL (dB) | P1D minus P1M (dB) |
|---|---|---|---|---|---|
| primary_01 | 2025-01-22T02:34:55Z | 11.383 | 79.876 | 80.029 | +0.152 |
| primary_02 | 2026-02-21T01:44:59Z | 19.360 | 85.655 | 84.191 | -1.464 |
| primary_03 | 2025-03-23T04:51:29Z | 89.301 | 104.299 | 103.103 | -1.196 |
| primary_04 | 2026-04-28T00:28:14Z | 99.281 | 107.304 | 107.430 | +0.125 |
| primary_05 | 2026-05-17T09:36:40Z | 100.004 | 113.068 | 112.567 | -0.501 |
| primary_06 | 2026-06-22T08:17:44Z | 13.668 | 87.249 | 84.242 | -3.007 |
| primary_07 | 2025-07-09T21:45:55Z | 66.043 | 99.513 | 100.603 | +1.089 |
| primary_08 | 2025-08-12T09:09:27Z | 13.325 | 91.694 | 87.327 | -4.367 |
| primary_09 | 2025-09-28T12:24:38Z | 41.301 | 100.011 | 103.010 | +3.000 |
| primary_10 | 2025-10-04T13:23:58Z | 59.411 | 102.481 | 97.526 | -4.955 |
| primary_11 | 2025-11-29T20:44:58Z | 69.720 | 92.820 | 101.278 | +8.459 |
| primary_12 | 2025-12-14T17:56:17Z | 98.020 | 103.905 | 106.275 | +2.370 |
Twelve-path frozen follow-up · derived.comparison_table
PT6H minus P1D at the exact 63 Hz endpoint
Selected case
P1D daily TL
PT6H instantaneous TL
PT6H minus P1D
Definition, matching and source
- Left definition
- P1D daily TL
- Right definition
- PT6H instantaneous TL
- Signed comparison
- PT6H minus P1D
- Matched keys
- Candidate row, path to the H01W1 hydrophone, event UTC, 63 Hz, 6 m source depth, endpoint and solver settings
- Case coordinate
- Exact WGS84 source range to the H01W1 hydrophone
- Source table
- /home/rui/ara/ctbto-2026/data/derived/ha01-ocean-temporal-followup/v1/temporal-deltas.csv
| Case | Event UTC | Range (km) | P1D daily TL (dB) | PT6H instantaneous TL (dB) | PT6H minus P1D (dB) |
|---|---|---|---|---|---|
| primary_01 | 2025-01-22T02:34:55Z | 11.383 | 80.029 | 80.048 | +0.019 |
| primary_02 | 2026-02-21T01:44:59Z | 19.360 | 84.191 | 84.461 | +0.270 |
| primary_03 | 2025-03-23T04:51:29Z | 89.301 | 103.103 | 103.031 | -0.072 |
| primary_04 | 2026-04-28T00:28:14Z | 99.281 | 107.430 | 108.480 | +1.050 |
| primary_05 | 2026-05-17T09:36:40Z | 100.004 | 112.567 | 112.779 | +0.212 |
| primary_06 | 2026-06-22T08:17:44Z | 13.668 | 84.242 | 84.244 | +0.003 |
| primary_07 | 2025-07-09T21:45:55Z | 66.043 | 100.603 | 100.551 | -0.052 |
| primary_08 | 2025-08-12T09:09:27Z | 13.325 | 87.327 | 87.100 | -0.227 |
| primary_09 | 2025-09-28T12:24:38Z | 41.301 | 103.010 | 102.978 | -0.032 |
| primary_10 | 2025-10-04T13:23:58Z | 59.411 | 97.526 | 97.103 | -0.423 |
| primary_11 | 2025-11-29T20:44:58Z | 69.720 | 101.278 | 97.911 | -3.368 |
| primary_12 | 2025-12-14T17:56:17Z | 98.020 | 106.275 | 106.691 | +0.416 |
Physical and observational reading
Why a small environmental change can make a large endpoint change
RAM keeps phase. Changing the temperature and salinity field can move refractive structure, modes and interference fringes. A fixed receiver can then move toward or away from a coherent minimum. That mechanism naturally permits either sign and makes an exact endpoint more sensitive than an average over range or frequency.
Plausible
The ocean can vary within a day
Upper-ocean warming, evening mixing, internal waves and regional dynamics make hourly-to-daily structure physically plausible near southwest Australia.
Not demonstrated
No coincident profile identifies the right field
The public observing network does not provide tight subsurface temperature and salinity matches for the decisive paths. Satellite SST can test only the surface representation.
Numerical reading
Coherent endpoint sensitivity is not a scalar bias
The 6/6 sign split in the follow-up rejects the idea that a finer time grid simply adds or removes a fixed number of decibels.
Smallest useful next check
Inspect the two fixed extreme paths
Compare quality-controlled surface temperature around primary_10 and primary_11, then use saved complex fields to inspect local fringe stability. This remains a consistency study unless a qualifying subsurface profile exists.
Claim boundary
What this report does not say
- It does not prove that monthly, daily or PT6H is physically correct for any event.
- It does not provide a global correction, because changes have mixed signs.
- It does not turn transmission loss into source level, received level or measured sound.
- It does not support ship attribution or an automatic rerun of all 678 Juan rows.
- It measures one coherent RAM endpoint at 63 Hz, 6 m source depth and the frozen RAM settings.