Potential for salt damage from sodium chloride crystallisation. (a) Median number of sodium chloride transitions per year are displayed as closed and open diamonds for thirty year observational periods from MIDAS observations those in the future using the output from UKCP09. (b) The probability density functions of the relative humidity difference between subsequent days (RH
- RHt-1) for the two estimates of the frequency of transitions in the 1975 data; arbitrary scale. (c) The probability distribution of relative humidity values from Heathrow 1949–2011; arbitrary scale. (d) Estimated median of sodium chloride transitions (open circles) per year estimated using the tails of the probability density function compared with the number of transitions counted in the UKCP09 output.