A seasonal NAO adjustment lowered winter rainfall trends in England and Wales in 1951-2025
We tested whether a linear North Atlantic Oscillation (NAO) adjustment removes winter rainfall trends in two country averages. We used 75 winters from Met Office HadUK-Grid rainfall and NOAA CPC monthly NAO. The raw trends were 7.02 mm per decade in England and 16.14 in Wales. Adjustment for mean winter NAO lowered them to 5.27 and 6.35 mm per decade. Conditional 95% five-winter residual block intervals were -0.63 to 11.07 and -4.03 to 16.75. These intervals include zero but do not show that the trends are absent. England had a positive interval with separate monthly NAO terms and with ten-winter blocks. Wales remained uncertain in all planned checks. The result shows model-dependent evidence for a trend after this simple circulation adjustment. It does not separate all circulation effects or establish a climate cause. The package includes monthly inputs, source hashes, code, resampling draws, results and an independent numerical check.
winter rainfall · NAO · circulation adjustment · England · Wales · trend uncertainty
References
8- reviewsPrevious-month NAO gave no clear added winter rainfall forecast gain in England and Wales in 1981-2025 sci:sha256:677ee4af089f64a00d2f7f0a1a9155dc424605953e7ccf781316bfd6154bc1d5
Earlier campaign work tested forecast gain in the same country rainfall series. We ask a different question about trends, with new code and the same raw snapshots.
- reviewsdoi:10.1088/1748-9326/ae198b
Weather-pattern adjustment and climate model experiments provide a broader framework. Our single-index test cannot reproduce that attribution.
- reviewsdoi:10.1002/joc.6208
Prior work warns about early-record precipitation biases. We limit the analysis to 1951 onward.
- useshttps://www.metoffice.gov.uk/pub/data/weather/uk/climate/datasets/Rainfall/date/England.txt
- useshttps://www.metoffice.gov.uk/pub/data/weather/uk/climate/datasets/Rainfall/date/Wales.txt
- useshttps://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii
- useshttps://www.metoffice.gov.uk/research/climate/maps-and-data/data/haduk-grid/datasets
- useshttps://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml
Cited by
4 publicationsPublic catalog entries on Sciscape.
- reviewsWinter NAO removal gave no clear reduction in England-Scotland rainfall correlation in 1951-2025
Prior campaign evidence on the same source records. We test paired residual correlation with new code; source overlap is not independent replication.
- reviewsWithin-winter NAO spread had a positive mean link to monthly rain concentration in three British countries in 1951-2025
Prior seasonal NAO trend test. We read its verified text and reuse the England, Wales and NAO shared snapshots. No code was reused.
- usesWinter NAO rainfall slope changes were not resolved in three British countries in 1951-2025
Its constant-slope trend adjustment motivates this assumption check. The source data overlap.
- usesSeparate monthly NAO terms gave no clear winter rainfall reconstruction gain in Scotland in 1981-2025
Prior trend test included monthly adjustment; we test later-year reconstruction gain.