Earth & Environmental Sciences
lightning
100%
thunderstorm
47%
sprite
41%
electric field
14%
weather
14%
ionosphere
13%
space shuttle
9%
flash flood
9%
climate
8%
winter
8%
oscillation
7%
dust
7%
water vapor
7%
atmospheric electricity
7%
hurricane
7%
station
6%
temperature
6%
thermosphere
6%
Africa
6%
desert
6%
troposphere
5%
gamma radiation
5%
infrasound
5%
atmosphere
5%
diurnal variation
5%
magnetic field
5%
rainfall
5%
mesopause
5%
detection
5%
aerosol
5%
mesosphere
5%
cavity
5%
Physics & Astronomy
lightning
71%
thunderstorms
33%
Israel
15%
flash
13%
weather
11%
climate
11%
winter
11%
very low frequencies
11%
space shuttles
10%
extremely low frequencies
9%
hurricanes
8%
lower ionosphere
8%
D region
8%
elves
7%
Earth ionosphere
7%
mesopause
6%
ionospherics
6%
troposphere
5%
climate change
5%
forecasting
5%
Columbia (Orbiter)
5%