Books on atmospheric phenomenareviewed by T. Nelson
Reviewed by T. Nelson
In the Introduction, V.A. Rakov says he wrote Fundamentals of Lightning because Lightning: Physics and Effects (LPE), which he co-authored with Martin A. Uman, was too much for students to digest in a single semester. There's some merit to that: when people start describing your book by how much it weighs (LPE weighs in at four pounds) instead of what's inside, it's a clue you need to condense.
Lightning is intrinsically exciting. It's dangerous and beautiful. If your lightning book doesn't make the reader's hair stand on end, you're doing something wrong. LPE is full of fascinating stuff: a whole chapter on Schumann resonances and whistlers, another whole chapter on sprites, and one on lightning on Jupiter! How in the world can you make something like that dull? When there's a will there's a way:
Goodman et al. (1988a, b) and Williams et al. (1989c) found that microbursts in the southeastern United States tended to occur roughly 10 min after the peak in the total lightning flash rate and shortly after, or roughly coincident, with the peak in the ground flash rate. The storm studied by Goodman et al. (1988b) produced a total of 116 flashes, only six of which were discharges to ground. The peak flash rate, 23 min−1, occurred 7 to 8 min after the initial discharge and 4 min prior to the microburst onset, simultaneously with the peaks in the storm mass, vertically integrated liquid water content, echo volume, and cloud height. [LPE, p. 30]
That's from chapter 2, “Characterization of individual storms and storm systems” in LPE. This wasn't a textbook—it was a 687-page, 343,000-word review paper.
Many of the illustrations in LPE were blurry, low-quality grayscale images. The book directed the reader to the publisher's website for a real picture. Once there, you got a PDF with ten overexposed and grainy pictures (though, admittedly, the picture showing a giant red spark and some smoke is impressive). But first you got a bitter reminder of how much you paid for the book, which is quite a bit.
Are we getting the idea about why the kids hated it yet? Rakov and Uman have the field to themselves, and Lightning: Physics and Effects is now out of date, so they had an opportunity to rectify the situation. What's in Fundamentals of Lightning?
Most of all it's a lot easier for students to carry around. And it has lots of cool equations. But a lot of the interesting stuff is also missing.
What's left is topics like incidence of lightning, electrical structure of lightning bolts, and calculation of lightning electromagnetic fields. Rakov's main interest is in mathematical modeling of lightning. That's an important topic: the insurance and electrical power industries need to know what to expect. And the numbers are impressive: the first return stroke can contain 30,000 amperes of current. The temperature of a lightning bolt is over 30,000°C. In Florida, on average one in every 200 houses gets struck by lightning each year.
There's also a section on how to detect, measure, and perform direction-finding on lightning. Not surprisingly, you need a special antenna to measure it properly and prevent arcing.
Computer modeling of a lightning bolt might seem easy, but it's surprisingly difficult: it's a complex, three-dimensional natural phenomenon. Rakov describes a number of different models, and none of them give a particularly good match. It's also a mystery of how there can be lightning at all, since the electric field in a cloud is nowhere close to the dielectric breakdown potential of air. According to the latest theory, this discrepancy explains the existence of stepped leaders. That's the most interesting thing in this book, but it's tucked away in an appendix, as is the fascinating chapter on fulgurites.
Textbooks aren't supposed to be exciting. The goal of this one is to give students an understanding of what lightning research is about. That means commercially important calculations, not pretty pictures. They got rid of the bathwater, but part of the baby is missing.
mar 14, 2017