ENSO and IOD: Current Status and Predictions - January 2022

In this page, the current status and prediction of the large-scale climate modes such as El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) that primarily influence the Indian climate are discussed.  The current status is based on the evolution of climate variables during the recent three months and their prediction is based on that issued by various international centres.

The global observed anomalies of Sea surface temperature (degree C) and precipitation (mm/day) for the latest month of January 2022 are given in Figure 1.

Figure 1:  Sea surface temperature (SST) anomaly (C) and Precipitation Anomaly (mm/day) for January 2022. [SST data: NOAA ERSSTv5, Precipitation data: GPCPv2.3, Climatology: 1991-2020]

ENSO (El Niño–Southern Oscillation)

In November 2021, La Niña is present in the Pacific Ocean, where cooler than normal SSTs were observed across central and eastern equatorial Pacific and warmer than normal SSTs were observed over west tropical Pacific Ocean (Fig. 2). The cold SST anomalies over central and equatorial Pacific strengthened in December compared to November. However, in January 2022, the SST anomalies over eastern equatorial Pacific slightly weakened compared to December. At the same time in January, the warm anomalies over western equatorial Pacific were also weakened. The above condition in January 2022 was indicating a slight weakening of ENSO. 

Figure 2: Tropical Pacific Sea surface temperature (SST) anomalies (Left Panel) and changes in the SST anomalies (degree C) from the previous month (Right Panel) during November 2021 (Top), December 2021(Middle) and January 2022 (Bottom). [SST data: NOAA ERSSTv5, Climatology: 1991-2020]

In the month of November 2021, the positive subsurface temperatures anomalies were observed (between 20 C isotherm and thermocline depth) over western Pacific Ocean (135E -165E) (Fig. 3). At the same time, the subsurface temperatures anomalies were negative over the broad area of central and eastern Pacific Ocean below the thermocline depth between 105W to 150W. These subsurface warm anomalies were seen expanding eastward (up to 165W) in the month of December 2021 and further eastward (up to 155W) during January 2022.  It was also seen that the positive subsurface temperatures anomalies narrowing eastward from 135E to 155W. However, the cold subsurface temperatures anomalies over the eastern Pacific Ocean below the thermocline depth were strengthened and expanded westward in the month of December 2021. Later, these cold subsurface anomalies which were seen from ~150m to surface, narrowed eastward in the month of January 2022. So, it was seen during the last three months that the positive subsurface temperature anomalies from western Pacific Ocean expanding towards the east whereas the negative subsurface temperature anomalies from central east Pacific Ocean were shrinking towards the eastern Pacific Ocean. 

Figure 3: Depth-longitude section of ocean temperature anomalies (degree C) in the equatorial Pacific Ocean (5S -5N) during November 2021 (Top), December 2021 (Middle) and January 2022 (Bottom). The solid dark line is the 20 degree C isotherm, and the dashed line is thermocline depth. [Data: INCOIS-GODAS]

The monthly time series of ENSO indices for the last 12 months period from February 2021 to January 2022 is shown in Fig. 4. It was seen that all the ENSO indices are below normal during the last 12 months. As per the Nino3.4 and Nino3 indices, the La Niña conditions were observed during September 2021 - January 2022. The Nino3.4 index was slightly weakened from December 2021 to January 2022, at the same time Nino3 index was strengthened. 

Figure 4: ENSO indices (Nino3.4, Nino3, Nino4, Nino1+2, and Modoki) for the last 12 months period from February 2021 to January 2022. [SST data: NOAA ERSSTv5]

Currently, La Niña conditions are present over the Pacific Ocean. A large majority of the climate models based on the February initial conditions, indicates that La Niña conditions are likely to continue till Mar-May and weaken thereafter, to reach cold ENSO neutral conditions during the second quarter of 2022 (Fig.5). Although, most of the model forecasts agreeing to the ENSO neutral conditions by the middle of the year, only one model predicts El Niño to occur during the coming season, whereas three models predict La Niña to continue till northern hemisphere autumn season.

Figure 5: IRI/CPC model-based probabilistic ENSO forecasts (Left Panel) and plume of forecasts of the Nino3.4 SST anomaly from dynamical and statistical models (Right Panel) as provided by IRI. [Source: https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/]

Indian Ocean Dipole (IOD)

In the month of November 2021, the neutral IOD conditions were prevailing over Indian Ocean. In the north Indian Ocean, normal SSTs were observed over the most parts of Arabian Sea and Bay of Bengal (Fig. 6), although the SST anomaly was slightly warmer over the Bay of Bengal. During the following months of December, positive SST anomalies were observed over most parts of the tropical Indian Ocean which was further warmed in the month of January 2022. Compared to previous months, the January SST anomalies were warmer over north Bay of Bengal, eastern equatorial Indian Ocean, and south-central Indian Ocean.

Figure 6: Indian Ocean Sea surface temperature (SST) anomalies (Left Panel) and changes in the SST anomalies (degree C) from the previous month (Right Panel) during November 2021 (Top), December 2021(Middle) and January 2022 (Bottom). [SST data: NOAA ERSSTv5, Climatology: 1991-2020]

In the month of November 2021, the positive subsurface temperature anomalies (Fig. 7) were seen over east equatorial Indian Ocean (between 20C isotherm and thermocline depth) with a stronger magnitude spread over 95E and 105E. At the same time, a small region of negative subsurface anomalies was seen over the central equatorial Indian Ocean around the thermocline depth. During December 2021, the maximum strength of warm anomalies was seen around 105E over eastern equatorial Indian Ocean and the negative anomalies around the thermocline depth were seen over western and central equatorial Indian Ocean. The warm subsurface anomalies over eastern equatorial Indian Ocean were weakened in the month of January 2022. However, a small region of negative subsurface anomalies was seen over the eastern and western equatorial Indian Ocean below the thermocline depth.

Figure 7: Depth-longitude section of ocean temperature anomalies (degree C) in the tropical Indian Ocean (10S - Equator) during November 2021 (Top), December 2021 (Middle) and January 2022 (Bottom). The solid dark line is the 20 degree C isotherm, and the dashed line is thermocline depth. [Data: INCOIS-GODAS]

The monthly time series of Dipole Mode Index (DMI), West Equatorial Indian Ocean (WEIO) index, East Equatorial Indian Ocean (EEIO) index for the last 12 months from February 2021 to January 2022 is shown in Fig.8. During May-July 2021, a weak negative IOD conditions were observed over the Indian Ocean which slightly weakened in the month of August. During September, the negative IOD was weakened further and turned into neutral IOD conditions.

Figure 8: IOD indices (DMI, WEIO, and EEIO) for 12 months period from February 2021 to January 2022. [Dipole Mode Index (DMI), West Equatorial Indian Ocean (WEIO), East Equatorial Indian Ocean (EEIO), [SST data: NOAA ERSSTv5]

Currently, neutral IOD conditions are present over the Indian Ocean and the latest Monsoon Mission Climate Forecasting System (MMCFS) model forecast indicates that the neutral IOD conditions are likely to continue during the forecast period in Figure 9. The probability forecast for IOD also indicates the enhanced probability for neutral IOD conditions during most of the forecast period. 

Figure 9:   Monsoon Mission Climate Forecasting System (MMCFS) model based probabilistic IOD forecasts (Top) and plume of forecasts of the IOD index (Bottom) as provided by India Meteorological Department (IMD). [Source: http://rcc.imdpune.gov.in/Products.html]

References

Ratna, S. B., A. Cherchi, T. J. Osborn, M. Joshi, and U. Uppara, 2021: The Extreme Positive Indian Ocean Dipole of 2019 and Associated Indian Summer Monsoon Rainfall Response, Geophysical Research Letters, https://doi.org/10.1029/2020GL091497

http://rcc.imdpune.gov.in/Products.html

https://incois.gov.in/portal/ElNino

https://incois.gov.in/portal/IOD

https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/