Climatic Research Unit : Data

Mediterranean Oscillation Indices (MOI) and Saharan Oscillation Index (SaOI)

NEW (August 2022): Added Saharan Oscillation Index (SaOI)

Please do not ask me to produce monthly MOI data: it is ambiguous, as it can be calculated in different ways. If you need monthly MOI then feel free to calculate it from the daily data presented here.

Note that early NCEP data (1948-1967) has a problem relating to SLP, this will affect derived products such as these MOI indices.

Note that the previous versions (1958 to 2010) did not include leap year days (29/02) for 2004 and 2008 due to a fault in the programs. This has been corrected for the updated files.

The MOI is defined by Palutikof et al. (1996) and Conte et al. (1989) as the normalized pressure difference between Algiers (36.4°N, 3.1°E) and Cairo (30.1°N, 31.4°E) A second version of the index can be calculated from Gibraltar's Northern Frontier (36.1°N, 5.3°W) and Lod Airport in Israel (32.0°N, 34.5°E) (Palutikof et al., 2003). Here data is presented for both variants, using pressure interpolated (16 point Bessel) from NCEP/NCAR reanalysis data.

More information about the Western MOI data (WeMOi) may be found here. Users of WeMOi should also reference:

The Saharan Oscillation Index (SaOI) is defined by Khomsi et al. (2020) as the difference between the normalized pressures at the Azores (37.79° N, -25.5° E) and Niamey (13.51° N, 2.10° E). It is calculated based on the sea level pressure data provided by the ERA5 reanalysis accessible in the Climate Data Store from the European Centre for Medium-Range Weather Forecasts (ECMWF) (CDS;!/search?text=ERA5&type=dataset). We present two sets of the SaOI data: - Daily data as used in (Khomsi et al., 2020) between 2013 and 2016; - Daily data calculated between 1950 and 2021.

New Daily File format (MOI only)
for year = 1948 to 2021
  for month = 1 to 12
    format(F5.0, 2F3.0, F7.3) year, month, day, value
Missing values represented by -99.99 (MOI)

WeMOi format is one line per year, with year plus 12 monthly values (tab-separated). 11 header lines. Missing values represented by -999

SaOI format is one line per day, with year, month, day SaOI (separated by tabs). 1 header line. Missing values represented by -99.99

Filename SizeDescription
moi1.output.dat 506 kilobytesMOI: Algiers and Cairo
moi2.output.dat 506 kilobytesMOI: Israel and Gibraltar
Web_WeMOi-2020.txt 29 kilobytesWeMOi: Padua and Cadiz, monthly
SaOI(1950-2021).txt 29 kilobytesSaOI: Azores and Niamey
SaOI(2013-2016).txt 29 kilobytesSaOI: Azores and Niamey

Previous updates

June 2022: updates to 2021

April 2021: Updated to 2020

July 2020: Updated to 2019

November 2018: Added WeMOi; Updated to 2017

February 2017: Updated to 2016

August 2015: Updated to 2014

November 2014: Updated to 2013

October 2013: Updated to 2012

May 2011: Indices are now daily. Initial data files run from 1958 to 2010

Thanks to Andrew Harding for updating the index. Future updates are planned. Please contact me ( if you wish to access the software routines that calculate the MOI indices from the NCAR Reanalysis Data.

The previous monthly index is still available to allow comparisons to be made:

Old Monthly File format (MOI)
for year = 1958 to 2000
  for month = 1 to 12
    format(i4,i3,f7.2) year, month, value
Missing values represented by -99.99

Filename SizeDescription
moac.dat 8 kilobytesMOI: Algiers and Cairo
moig.dat 8 kilobytesMOI: Israel and Gibraltar

Last updated: August 2022, Ian Harris.

These datasets are made available under the Open Database License.
Any rights in individual contents of the datasets are licensed under the
Database Contents License under the conditions of Attribution and Share-Alike.
Please use the attribution Climatic Research Unit, University of East Anglia