Abstract
Like the southern oscillation index (SOI) based on the pressure difference between Tahiti (17.5°S, 150°W) and Darwin (12.5°S, 130°E), we propose the new atmospheric electrical index (AEI) taking the difference in the model calculated atmospheric electrical columnar resistance (Rc) which involves planetary boundary layer height (PBLH) and aerosol concentration derived from the satellite measurements. This is the first non-oceanic index capable of differentiating between the conventional and modoki La Niña and El Niño both and may be useful in the future air-sea coupling studies and as a complementary to the oceanic indices. As the PBLH variation over Darwin is within 10% of its long term mean, a strong rise in the Rc over Darwin during the modoki period supports modoki’s connection with aerosol loading. Our correlation results show that the intensity of El Niño (La Niña) event is almost independent (not independent) of its duration and the possibility of ENSO modoki being one of the factors responsible for the warming trend slowdown (WTS).
Highlights
There are various studies in atmospheric electricity showing an ENSO (El Niño and Southern Oscillations/La Niña) signal in global lightning and in the global atmospheric electric circuit (GAEC)[1,2,3,4,5,6,7]
When strong cold anomalies appear near the international dateline along with warm sea surface temperature anomaly (SSTA) in the far Eastern Pacific (EP), it is called as the La Niña modoki or Central Pacific (CP) La Niña[18,19]
Distinguished patterns of La Niña modoki have been obtained in the sea surface height (SSH)[19] and sea surface salinity[21] data analysis and a new SST index EMI2 based on the SSH analysis has been constructed
Summary
Where H is the planetary boundary layer height (PBLH), S is the scale height of conductivity (=10 km/ln10)[31] and λ(∞ ) is the average atmospheric electrical conductivity of the planetary boundary layer which depends upon the environmental aerosol and small ion concentrations. The data of atmospheric circulation patterns (geo-potential height at 500 hPa, sea level pressure (SLP), vertical velocity (ω ) at 500 hPa and upward long wave flux at top of atmosphere) (Supplementary Information) have been downloaded from Giovanni MERRA monthly (2D) data collection (2/3 × 1/2 horizontal grids) for Supplementary Figure S2. We use monthly AOD data for the period 1980–1992 and 1996–2000 generated by Total Ozone Mapping Spectrometer (TOMS) and those for the period 2001–2011 generated by Moderate Resolution Imaging Spectra Radiometer (MODIS) (Level 3, monthly collection 5.1 (051)) from the following web sites respectively: ftp://toms.gsfc.nasa.gov/pub/nimbus7/data/aot/36. We use the monthly SLP data of Tahiti and Darwin[40] for the base period 1980–2011 from the National Centers for Environmental Prediction (NCEP) to calculate the monthly SOI. Where m, y, n are the month, year and the number of years respectively and multiplication by 10 in (2) is a convention
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