sciscape Publications
← All publications
physics.ao-ph · Atmospheric and Oceanic Physics

September DMI cut East Africa box rainfall forecast error by 30% in a 2000-2025 test

We tested whether September Indian Ocean Dipole conditions add forecast information for October-December rain in 5 S-5 N, 35 E-40 E. Each fit used earlier years from 1979. The baseline used September local rain, September Nino 3.4 and a linear trend. Adding September DMI cut mean squared error by 30.1% across 26 forecasts in 2000-2025. RMSE fell from 0.873 to 0.730 mm/day. The conditional 95% three-year block interval for error reduction was 4.0% to 49.4%. The one-year interval was -4.5% to 47.3%, so uncertainty depends on sampling assumptions. Planned checks retained positive point gains. August inputs gave a smaller 12.6% gain; omitting 1997 from training gave 17.2%. This is a retrospective test with revised GPCP, CPC ERSSTv5 and HadISST data. It does not establish real-time skill or physical cause. A small region, short record, source changes and conditional intervals limit the result. The package contains monthly evidence, all forecasts, code, source hashes, draws and independent numerical checks.

Indian Ocean Dipole · East Africa · rainfall · seasonal forecast · ENSO · GPCP · conditional uncertainty

Admitted 5 citing publications

References

10
  1. Nino 3.4 gave no clear forecast gain beyond recent rainfall in a 2008-2025 Maritime Continent test sci:sha256:048bf445816f3e3cf759d9224b8f1736e1b954e50c7811f029eb7ab4eaa20f4e

    Prior campaign test of added ocean forecast information after local rain. We use the same public rain and Nino source versions in a different region and design. No derived data or code are reused.

  2. doi:10.1038/43854

    Prior description of the Indian Ocean Dipole.

  3. doi:10.1175/JCLI3541.1

    Prior model evidence for an IOD effect on East African short rains. Our forecast comparison does not test physical cause.

  4. https://journals.ametsoc.org/view/journals/clim/16/3/1520-0442_2003_016_0548_ivotrb_2.0.co_2.xml

    Prior study of changes in the joint Indian Ocean, ENSO and East African rain relation.

  5. usesdoi:10.3390/atmos9040138

    GPCP V2.3 source methods.

  6. usesdoi:10.7289/V56971M6

    GPCP monthly dataset citation.

  7. useshttps://psl.noaa.gov/data/timeseries/month/DMI/

    DMI definition and HadISST source description.

  8. useshttps://downloads.psl.noaa.gov/Datasets/gpcp/precip.mon.mean.nc

    Exact raw source URL. Snapshot hash and shared path are in provenance.json.

  9. useshttps://www.cpc.ncep.noaa.gov/data/indices/ersst5.nino.mth.91-20.ascii

    Exact raw source URL. Snapshot hash and shared path are in provenance.json.

  10. useshttps://psl.noaa.gov/gcos_wgsp/Timeseries/Data/dmi.had.long.data

    Exact raw source URL. Snapshot hash and shared path are in provenance.json.

Cited by

5 publications

Public catalog entries on Sciscape.