Thursday, 15 January 2009

We think it's cold here!

I’ve spent this week in Phoenix, Arizona, at the American Meteorological Society Annual Meeting. This meeting is an important one for us, as each year we hold our exhibition promoting our scientific journals, we meet many of our international members at our evening reception and we have our bilateral meeting with the AMS executive team to discuss areas of possible collaboration. And its good to renew old friendships.

We often joke about the weather with our US colleagues as we regularly have very extreme unseasonal weather for the AMS meetings. However we seem to have broken the trend this year. Phoenix itself is used to extreme weather conditions. Average summer temperatures are amongst the hottest in the US. On 26 June 1990 they reached an all-time high of 50°C (some 122°F). Rainfall is pretty sparse but there is a period between July to September where humidity levels are high.

This time of year is seasonally the coldest in Phoenix, with temperatures falling between a maximum of 19°C (67°F) and a minimum of 7°C (45°F). This week it has been up in the high end of the climatology - about 16°C (61°F) with sunny blue skies, as a result of a large high pressure sitting over the lower south west past of the US. To the north, much of the rest of the US has been experiencing some pretty cold weather with heavy snowfalls and some of the coldest parts experiencing temperatures around -42°C (-45°F), which is pretty chilly in anyone’s book.

But it wasn’t just the weather that made this year’s meeting a particularly special one. It was that 23 of the world’s meteorological Societies (the largest ever gathering) met to establish an International Forum for Meteorological Societies, where we can discuss issues of common interest and share best practice. The framework for the new forum was put in place and its first meeting will be in January 2010 at the AMS’s next annual meeting in Atlanta in January 2010.

As usual I managed to get hold of some upper atmosphere data from the Phoenix flight, through the in cabin screen displays that show altitude and temperature. Unfortunately I only got hold of some low level temperatures from the cabin display going into Phoenix. Coming out of Phoenix I managed to get some better data.

Surface temperature was pretty much the same on both days, but it was warmer in the upper air by some 5 to 6°C consistently up through at least the first 2.5 km. What’s interesting in the data from the 15th is the drop in temperature in the lowest 500 m or so showing a cold layer of low level air around the airport – I haven’t really looked into the properly, but possibly some cold air drainage from the surrounding mountains.

Saturday, 3 January 2009

Weather Records and Average Temperatures

I was reading over the Christmas holidays that there are records of the weather that go back as far as 13th Century BC. The records were found amongst the Anyang oracle bones, which give us an historical account of the Shang dynasty in China. But it’s the way in which nature responds to our weather that gives us the long record that we use for studying our climate beyond the more systematic observations we have over the last century or so – the sorts of information that comes from tree rings or trapped air in ice cores, and that is what we call paleoclimatology. It’s these observations together with our complex climate models that help us to understand and give context to how our climate is changing.

Our recent summers haven’t been great in the UK, most likely a response to the effects of a strong La NiƱa – a large pool of cold water of the south-American coast. This natural feature of the earth’s climate has masked the underlying warming of land temperatures to some extend. That being said the climate models are telling us that by all accounts 2009 is set to be a warm year globally, although the seasonal forecasts for the UK are showing that we will have a cold start – with colder than average temperatures in January and an average February.