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Bryan's Blog 2009/01/06
european summer drying
OK, I confess, I'm clearly reading my abstract summaries this morning ...
Briffa, van der Schrier and Jones: Wet and dry summers in Europe since 1750: evidence of increasing drought (International Journal of Climatology, 2009):
Moisture availability across Europe is calculated based on 22 stations that have long instrumental records for precipitation and temperature. The metric used is the self-calibrating Palmer Drought Severity Index which is based on soil moisture content. This quantity is calculated using a simplified water budget model, forced by historic records of precipitation and temperature data, where the latter are used in a simple parameterization for potential evaporation.
The Kew record shows a significant clustering of dry summers in the most recent decade. When all the records are considered together, recent widespread drying is clearly apparent and highly significant in this long-term context. By substituting the 1961-1990 climatological monthly mean temperatures for the actual monthly means in the parameterization for potential evaporation, an estimate is made of the direct effect of temperature on drought. This analysis shows that a major influence on the trend toward drier summer conditions is the observed increase in temperatures. This effect is particularly strong in central Europe.
Reading in 2009, 1: Six Degrees
So clearly in the last few weeks I've not been working and I've had half as many kids to look after ... so in between tears I've been dealing with fears .... the sort that abound if you make it much past the first chapter of Mark Lynas' book: Six Degrees: Our Future on a Hotter Planet.
Inspired by Aaaron Schwartz, albeit recognising reality (although heavily modified by recent events), I've decided to try and blog my years reading. Don't expect it to be too erudite, when I've got time I read pretty eclectically, and often choose mindless crap just to eat up time with as few brain cells as possible involved.
Anyway, back to the book of the day. The basic thesis is that there are six chapters describing the likely outcomes should our planet heat by between one and six degrees as a result of anthropogenic CO2 climate change.
It's a pretty well written book, with what looks to me like a reasonable coverage of the apocalyptic end of the literature. Clearly it's got a journalistic tone, with a fair dose of hyperbole, but he does temper it with a some qualification from time to time. While we all hope the six degree end is pretty unlikely, the possible consequences of even (!) the 2-3 degree changes make scary reading.
It'd be pretty easy, I think, to find the "ifs buts and maybes" in the original literature, and not much of it was "news" to me, but the thing about reading it all in one place was that it brought home to me that if even some of the predictions come home to roost, the world (both geographically and socially) is going to be a pretty different place in just a few decades, let alone a few centuries. Again, maybe that wasn't news, but there's something about having it rammed home all in one volume ...
So it's inspired me in two ways: I'm going to get back to the entire IPCC report and read the bits I don't normally (i.e. WG2 and WG3 stuff), and I'm going to try much harder to avoid business travel (you may well ask about personal travel, but we'll save the answer for another day). As regular readers will know, I've been avoiding business travel this last year anyway, in favour of virtual conferencing. You now know why, Evan having been pretty sick for a long time, and while looking after Evan is no longer an excuse for not travelling, I think given my profession, and given what we now believe about the future, it'd be wrong not to continue to try. Which brings me to my new years resolution: to try and convince my colleagues, especially the senior ones, to try harder to avoid physical meetings - particularly where the meetings are part of a regular sequence.
Update later same day: One of the things Lynas worries about is declining growth of corals: Ka ching!
blimey! solar wind and tropical cyclones
Here are a couple of papers that I'm going to have to find time to read properly:
Prikryl, P., Ru?in, V., and Rybansk\'y, M.: The influence of solar wind on extratropical cyclones ? Part 1: Wilcox effect revisited, Ann. Geophys., 27, 1-30, 2009, and
Prikryl, P., Muldrew, D. B., and Sofko, G. J.: The influence of solar wind on extratropical cyclones ? Part 2: A link mediated by auroral atmospheric gravity waves?, Ann. Geophys., 27, 31-57, 2009.
Some choice excerpts from the abstracts:
A sun-weather correlation, namely the link between solar magnetic sector boundary passage (SBP) by the Earth and upper-level tropospheric vorticity area index (VAI), that was found by Wilcox et al. (1974) and shown to be statistically significant by Hines and Halevy (1977) is revisited. A minimum in the VAI one day after SBP followed by an increase a few days later was observed. Using the ECMWF ERA-40 re-analysis dataset for the original period from 1963 to 1973 and extending it to 2002, we have verified what has become known as the "Wilcox effect" for the Northern as well as the Southern Hemisphere winters.
Cases of mesoscale cloud bands in extratropical cyclones are observed a few hours after atmospheric gravity waves (AGWs) are launched from the auroral ionosphere. It is suggested that the solar-wind-generated auroral AGWs contribute to processes that release instabilities and initiate slantwise convection thus leading to cloud bands and growth of extratropical cyclones.
It is also observed that severe extratropical storms, explosive cyclogenesis and significant sea level pressure deepenings of extratropical storms tend to occur within a few days of the arrival of high-speed solar wind.
Do I believe in this?
Well, I haven't read the papers, but I'm on record as believing that upper boundary affects can reach the troposphere, so it's feasible, particularly in that the basic thesis seems to revolve around small scale waves driving systems across instability boundaries, a non-linear affect that is more than feasible.