Date of Award
2019
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Atmospheric Science
Committee Chair
Larry Carey
Committee Member
Daniel J. Cecil
Committee Member
Phillip Bitzer
Subject(s)
Lightning, El Niño Current, Southern oscillation, Climatology--Observations
Abstract
This study used the Low Resolution Time Series (LRTS) climatological lightning record from the space-based Tropical Rainfall Measuring Mission Lightning Imaging Sensor (TRMM, LIS) to compare individual years of lightning activity for all locations in the tropics and some in the subtropics. As a first guess from previous literature, the El-Ni ̃no/Southern Oscillation (ENSO) was chosen as the most likely cause of inter-annual variability within the TRMM LIS domain. Individual years from the lightning record beginning in 1998 and ending in 2014 were thus classified based on their corresponding phase of ENSO, i.e., warm, cold, or neutral, using the Oceanic Niño Index (ONI). In doing so, 20 locations were identified where consistent inter-annual lightning variability existed over a broad area during the study period, over half of which had apparent ENSO sensitivity. However, ENSO did not explain the lightning variability at all locations in the study. Six of these locations were chosen for a ‘deep-dive’ analysis into the lightning variability, where the lightning patterns were compared to NCEP/NCAR reanalysis data and rainfall observations from TRMM in an attempt to explain the lightning variability. Results indicated that ENSO’s strongest relationships with lightning were generally in locations where atmospheric stability differs between phases, most notably in South America and Africa. The largest magnitude anomalies were also located in these areas with the warm phase, where anomalies of ≥ 6 Fl km−2 Y r−1 were observed in central Africa and Argentina. The most consistent ENSO phase variability was observed in southeastern Africa and the Horn of Africa with more lightning in the cold phase, as well as in southern Mexico where more lightning was observed in the warm phase. Large magnitude anomalies and locations with inter-annual variability were also observed within the LRTS that were not related to ENSO, with examples near Panama, Bhutan, Pakistan, and in the southwestern Atlantic. The implications of the LIS sampling shortfalls made it harder to directly describe the lightning variability in these locations or relate it to the reanalysis variables.
Recommended Citation
Clark, Austin G., "Inter-annual variability of tropical and subtropical lightning activity from the full TRMM LIS lightning climatology-locations, magnitudes, and mechanisms" (2019). Theses. 274.
https://louis.uah.edu/uah-theses/274