The context of this little mishap was that apparently (Kazil et al., 2007), aerosol in cirrus cloud was defined by a size distribution with a geometric mean of 62.5 nm (diameter) and a geometric standard deviation of 1.45 nm. So I figured that since the lognormal distribution is defined:
f(x) = 1 / ( x sigma sqrt[2 pi] ) * exp ( - [ ln x - mu ]^2 / [ 2 sigma^2 ] ) ,
that it was a simple case of using
mu = 62.5 and
sigma = 1.45 and I would have defined f(x). This was giving very weird results though, until I realised that
mu is
not the geometric mean and
sigma is not the geometric standard deviation. Instead:
geometric mu = exp(mu)geometric sigma = exp(sigma) .
Peter Hitchens’ blog (The Mail Online) has a book review on The Death Of Mao, which, apart from its eponymous subject, illuminates the little known but disastrous Tangshan earthquake, which happened in the same year as Mao’s death (1976). Hitchens takes the opportunity to lament our ignorance of Chinese history generally, ancient and modern, and slips in a mention of my favourite Flashman novel: Flashman and the Dragon which is praised as thoughtful, contextual and magnificent (if bawdy).
