AbstractImager of Sprite and Upper Atmospheric Lightning (ISUAL) onboard the FORMOSAT-2 satellite is the first space-borne scientific payload dedicated to the long-term survey of the transient luminous events (TLEs). To monitor the performance change of the ISUAL sensors, the instrumental degradation and the effective detection efficiency is carefully investigated by the routine calibration observations. The chronic variation of TLE event rates show no notable trend between the annual cycles; this result implies that the detection efficiency of ISUAL has maintained at a constant level in the first 5 years of operation and no correction to the current statistics is necessary.
We analyze 3 datasets of atmospheric discharge observations from the space, ISUAL-recorded elve, lightning, and LIS-recorded lightning, covering the average energies from high to low respectively. The ISUAL lightning and the LIS lightning rates show similar trend and remain nearly constant from June 2004 to the present, while the seasonal rates of elve increase gradually. Two El Niño events and two La Niña events have experienced in the past 5 years. A standardized anomaly analysis is adapted to identify the elves and lightning variability in the warm and cold phases of ENSO, which is characterized by the South Oscillation Index. The anomaly elve distributions during these episodes are consistent with the Pacific horseshoe pattern and the ENSO lightning characteristics in the Tahiti region.
The correlation between the atmospheric discharges and the major indices that scientist commonly use to identify ENSO, such as Southern Oscillation Index and Niño 3.4 Oceanic Niño Index, is discussed. The equatorial dateline and the Tahiti regions are chosen as a comparative areas for the elve and lightning as they response to the ENSO episodes. The tight correlation between the atmospheric discharges and ENSO interannual variability provides the concrete evidence that the electricity activity at upper atmosphere can be directly affected by the variation of the ocean and atmosphere conditions.
|Date of Award||2010|
|Supervisor||Bing-Chih Chen (Supervisor)|
- El Niño southern oscillation (ENSO)
- Imager of Sprite and Upper
- Atmospheric Lightning (ISUAL)
- Transient Luminous Events (TLEs)
- Lightning Imaging Sensor (LIS)
- Southern Oscillation Index (SOI)
- Walker circulation