Friday, July 13, 2012

Rainfall in British Summers


In discussing the western US drought the other day, several people noted that Britain has been experiencing record wet conditions in June.  The data for June are above - indeed June 2012 is a record for Junes since 1910.

One might be tempted to look at that point, in conjunction with the 2007 point, and conclude that there is a recent climate-change induced increase in British summer raininess.  However, if we look at similar data for May, there is no such pattern - the data are more-or-less flat:


Similarly, July shows a different pattern again:


And August also show no evidence of a particular recent rise:


I'd be hesitant to conclude too much from this data beyond the fact that the British summer has always been a very hit-or-miss affair and there happen to have been a few big misses in recent years.

8 comments:

ob said...

well, not sure, whether a june-trend has to be mirrored in other extended summer trends. early summer climatology could be special due the climatological seasonal change of the jet in response to the climatological seasonal changes in insolation and lagged responses. but that's pretty much groping in the dark.

rjs said...

got an email from my brother (property NW of houston) this morning; after a drought that killed most of their trees last year, they got 13 inches of rain overnight; he made it home but his wife's car is stuck at the walmart parking lot...

last year my corner of ohio had 10 inches of rain each month february to may & it resumed that pace in the fall...this year, we've had a minor drought, with less than 2 inches each month since march...

so you really cant read anything into one month or one year..

Michael R said...

I don't think anyone would argue a long-term trend of Britain getting wetter:

http://metofficenews.wordpress.com/2012/03/13/why-are-we-in-drought/

In March, all the headlines were about Britain running out of water, and how farmers were going to be wiped out:

http://www.dailymail.co.uk/news/article-1387801/Drought-Britain-Dry-spell-drags-crop-failures-lead-higher-food-prices.html

Literally, the same day as hosepipe bans went into effect across the country, the Met Office issued flash flood warnings, and ever since, there has been unusually high rainfall, and flooding is the biggest threat to agriculture.

http://www.telegraph.co.uk/topics/weather/9389966/Graphic-How-the-UK-went-from-drought-to-floods-in-only-a-few-months.html

I think the question is whether deviations from climate averages are becoming more common, more severe and more sustained, as a possible outcome of slowing Rossby waves.

Whether there's enough data to answer that yet? Probably not. But there's probably enough data to warrant a closer look.

The Arthurian said...

The problem with the weather seems to be turbulence rather than a particular skew.

galacticsurfer said...

I happened to see the news this morning and in Japan there is massive flooding and in China. At wunderground they have a list of the global extreme weather for June with a nice picture of UK showing double the rain of last 40 years for June.

I think if one were to take a look at precipitaion globally per location and date, then measure how far it was from the average per day in terms of standard deviations then you would get something worth showing, i.e. a rising change in deviation over time from norm. In other words too dry or too wet all the time instead of +/- a few mm rain from normal.

http://www.wunderground.com/blog/weatherhistorian/article.html

local climate change graphics globally per day and month:
http://www.wunderground.com/climate/local.html?id=USC00448737&var=PRCP

http://en.wikipedia.org/wiki/Climate_of_the_United_Kingdom

http://epa.gov/climatechange/science/future.html general article on all aspects with good pictures on changes expected till end of century.

a good site I found looking for precipitation infos is
http://gpcc.dwd.de

deutche wetter dienst

they show precipitation anomaly maps and have lots of data

I am glad that The UK catches all the rain before it comes through to us in Northern Germany at any rate.

Michael R said...

Here is something to think about:

"What condition might potentially lead to this scenario? Experts predict that the ORCS might fail if the snowfall between Saskatchewan and New York exceeds that of the winter of 1972-73."

http://www.americaswetlandresources.com/background_facts/detailedstory/LouisianaRiverControl.html

When was the last time that almost happened?

Last year: http://en.wikipedia.org/wiki/2011_Mississippi_River_floods

And what about this year?

http://www.washingtonpost.com/business/industries/a-year-after-near-record-floods-shippers-face-a-low-mississippi-river-amid-dry-conditions/2012/07/16/gJQAhqh3nW_story.html

Seems Rossby waves may be of more than academic interest to the residents of the Louisiana Gulf Coast.

Michael R said...

Something interesting...build your own jet stream animation:

http://squall.sfsu.edu/scripts/nhemjetstream_model.html

Michael R said...

Fatter climate tails are here, now, says James Hansen:

"When we plotted the world’s changing temperatures on a bell curve, the extremes of unusually cool and, even more, the extremes of unusually hot are being altered so they are becoming both more common and more severe."

http://www.washingtonpost.com/opinions/climate-change-is-here--and-worse-than-we-thought/2012/08/03/6ae604c2-dd90-11e1-8e43-4a3c4375504a_story.html