TY - GEN
AU - Franco Molteni
AU - Anca Brookshaw
AB - In the first part of this report, we summarise the state of the art with the regard to the diagnostics and model simulation of teleconnections originated from the Indian Ocean. From a selection of relevant papers in the scientific literature, we point out that similar problems exist when we look at the problem on a range of time scales, from the sub-seasonal to the interdecadal. While the relevance of teleconnections from the Indian Ocean to the northern extra-tropics has become increasingly evident in the last 10-15 years, thanks to both diagnostic studies and specifically planned numerical experimentation, the ability of global numerical models to simulate such teleconnections when they interact with the full range of climate variability has hardly improved in recent years.<br />
In the second part of the paper, we present a range of statistics focussed on the interannual time scale, computed first from observational data (ERA5 and GPCPv3.2 rainfall) and then from the seasonal re-forecasts generated by five European models contributing to the multi-model ensemble of the Copernicus Climate Change Service (C3S). The comparison between observed and simulated teleconnections indicates that current coupled models used for seasonal forecasting can reproduce reasonably well the connections between Indo-Pacific SST and rainfall during the boreal cold season, but (consistently with earlier results) they can only simulate the connections of Indian Ocean SST and rainfall with the North Atlantic/European circulation with about (at best) half the amplitude of the signal from observational data. We also discuss the statistical significance of the differences between observed and model teleconnections, showing that the results are sensitive to the choice of datasets used in the observational diagnostics.
BT - ECMWF Technical Memoranda
CY - Reading
DA - 12/2024
DO - 10.21957/b7694fe435
M1 - 923
N2 - In the first part of this report, we summarise the state of the art with the regard to the diagnostics and model simulation of teleconnections originated from the Indian Ocean. From a selection of relevant papers in the scientific literature, we point out that similar problems exist when we look at the problem on a range of time scales, from the sub-seasonal to the interdecadal. While the relevance of teleconnections from the Indian Ocean to the northern extra-tropics has become increasingly evident in the last 10-15 years, thanks to both diagnostic studies and specifically planned numerical experimentation, the ability of global numerical models to simulate such teleconnections when they interact with the full range of climate variability has hardly improved in recent years.<br />
In the second part of the paper, we present a range of statistics focussed on the interannual time scale, computed first from observational data (ERA5 and GPCPv3.2 rainfall) and then from the seasonal re-forecasts generated by five European models contributing to the multi-model ensemble of the Copernicus Climate Change Service (C3S). The comparison between observed and simulated teleconnections indicates that current coupled models used for seasonal forecasting can reproduce reasonably well the connections between Indo-Pacific SST and rainfall during the boreal cold season, but (consistently with earlier results) they can only simulate the connections of Indian Ocean SST and rainfall with the North Atlantic/European circulation with about (at best) half the amplitude of the signal from observational data. We also discuss the statistical significance of the differences between observed and model teleconnections, showing that the results are sensitive to the choice of datasets used in the observational diagnostics.
PB - ECMWF
PP - Reading
PY - 2024
T2 - ECMWF Technical Memoranda
TI - Indian Ocean teleconnections to the northern extra-tropics
UR - &nbsp;
ER -