Archives for July 2011

Dr Joshua Wurman - understanding rain and hail in a supercell

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Aira Idris Aira Idris | 08:00 AM, Friday, 29 July 2011

Distance travelled ~ 538'572'800 km

(Dr Joshua Wurman created the Doppler On Wheels (DOW) mobile radars which observe tornadoes, hurricanes, wildfires, and other phenomena from close range. He has been actively chasing storms, for science, since 1995. One of the key objectives of the research carried out by him and his colleagues is to better understand what generates a tornado)

 

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Transcript:

Helen Czerski - So we've got all this data that the truck is measuring, so what can we see?

 

Dr. J

oshua Wurman - Well the radar can measure both winds and precipitation, rain and hail inside the storm. So we can see the red area here, which is precipitation, rain and hail in a super cell, and then these browns and blues here represent different wind speeds, different Doppler wind speeds.

 

And then there are other fields, we can also look at the difference in the return from horizontal and vertical polarised microwaves and we can tell the difference between hail and rain. Rain, big raindrops look kind of like hamburger buns and they return more energy horizontally, and then vertically, so we can tell if it is heavy rain. Hail stones are very irregularly shaped and they are also tumbling, so if we look at a million of them in our radar volume they average out to zero orientation, so we can tell the difference between hail and rain, like in the areas we were just experiencing outside.

"Dry and sunny" has been replaced with "rain and showers"

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Liam Dutton Liam Dutton | 08:00 AM, Wednesday, 27 July 2011

(Liam returned to the BBC Weather Centre in September 2007 and now broadcasts across a wide range of BBC channels. He can be seen regularly on BBC News, BBC World News and BBC Breakfast on BBC One at the weekends, in addition to being an established voice on the Today programme on Radio 4.)

Distance travelled ~ 533'427'200 km

After the driest spring in some parts of the UK for more than 100 years, the switch to more unsettled weather of late has necessitated a change in vocabulary for us weather folk.


bbc weather forecast 27/07/11

Dry and sunny has been replaced with rain and showers, especially during last week with low pressure driving our weather. And there's more rain and showers set for today and tomorrow.

But what exactly is the difference between rain and showers? It sounds like a simple question with an obvious answer, but ponder for a little longer and your thoughts may start to waiver.

Whilst the inevitability of getting caught outdoors in rain or showers without an umbrella is the same - a good soaking, the associated clouds and how they form in each case are quite different!

Rain vs. showers - clouds types, their formation and scale
Rain clouds form when a huge wedge of warm, moist air is forced to gently rise above cooler, denser air over hundreds of miles, in a process known as mass ascent.

As air rises, it condenses to form layers of cloud. Initially the cloud is high, thin, cirrus, but eventually thickens and lowers to nimbostratus producing outbreaks of increasingly persistent and heavy rain.

Shower clouds form when parcels of air just a few miles across rise into the atmosphere having been warmed by the Sun heated ground below, in a process known as convection.

The air rises and condenses to form heaped, cauliflower-like clouds. The smaller, fluffy white cumulus clouds produce few, if any showers, but the bigger, taller towering cumulus or cumulonimbus clouds can give intense downpours.

Rain vs. showers - speed of development
The easiest way to visualise the difference in how rain, showers and their associated
Empire State Building
clouds form, along with the speed at which air rises, is to think of making a journey to the top of the Empire State Building.

Imagine walking to the top of the building on an extremely long, gently sloping ramp. It would take a long time (hours) to reach the top and a great distance would have been covered. This is what happens to air when mass ascent occurs - a slow, gradual development of cloud and rain.

Now imagine instead taking a lift to the top of the building. It would take very little time (minutes) to reach the top and very little distance would have been covered. This is what happens to parcels of air with convection - a relatively quick, sudden development of cloud and showers.

Rain vs. showers - duration and intensity
With the formation of rain clouds being gradual and slow, a spell of rain can last for as long as six hours. Rain tends to start off light, but turns heavier and more persistent as cloud thickens and lowers. Eventually, the rain eases and it becomes dry again, but remains quite cloudy.

Conversely, shower clouds tend to form quickly. As parcels of air rise, energy is transferred upwards into the atmosphere. The higher and quicker the parcel of air rises into the sky (i.e. the greater the rate of energy transfer), the more intense the shower is likely to be.

Showers are often moved along by the wind, hence their short duration, in most cases, of not much more than tens of minutes. However, there are cases when showers form where there is little or no wind. When this happens, the same shower can sit over the same location for a long time and give the impression of rain, when technically it's just a shower that's got stuck!

So there you have it - rain and showers in a nutshell. Now, where did I put my umbrella...?

Skies over Canada turned green by Aurora's last night 25/07/2011

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Stephen Marsh Stephen Marsh | 17:30 PM, Tuesday, 26 July 2011

A high-speed solar wind stream has been buffeting the Earth's magnetic field for a couple of days. Last night it turned the skies over Canada green. Below are photos sent in by Bob Johnson, Saskatoon, Saskatchewan.

Aurora Saskatoon, Saskatchewan

aurora Saskatoon, Saskatchewan

There's chance of more Auroras tonight over North America and possibly north Europe as the solar wind continues to be more powerful than normal. Though the best place to see them will be in the southern hemisphere. If you have no luck, there should be another solar wind stream hitting Earth on July 30th as another coronal hole has opened up on the Sun today, so there may be auroras.

Cool video alert - Monsoon season Arizona 24/07/11 [VIDEO]

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Aira Idris Aira Idris | 14:00 PM, Monday, 25 July 2011

Distance travelled ~ 528'924'800 km

As the 23 Degrees team prepare to return back home after filming the Monsoons in India, a few videos have surfaced of the Arizona Monsoon season. Although not as strong as the Indian Monsoons, Arizona's Monsoon can vary from small dust storms to huge thunderstorms. Here's a cool video from @luxeagent of the Lightning storm in Scottsdale Arizona last night. Although quite dark you get a few interesting views throughout from the lightning strikes!

Storm chase 2011 - Has it been an unusual tornado year? [VIDEO]

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George Kourounis | 14:00 PM, Friday, 22 July 2011

Distance travelled ~ 521'206'400 km

(Following on from Henry Margusity's blog - 'Joplin tornado - one of the 10 deadliest on record?', George Kourounis shares his take on 2011's tornado season. George Kourounis Is the first storm chaser to ever be elected into the prestigious Explorers Club, and each spring he guides tornado chasing tours in the central U.S.)

 

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We all have a weather story... Perhaps lightning struck across the street from you or maybe you have vivid memories of that unexpected storm that rumbled through one afternoon and pelted you with hail while you were on your way to Aunt Susan's house. The weather is the one subject that we can all talk to each other about. It's not political, not religious, it affects us all and plays a role in just about every aspect of our lives. It's no wonder that whenever we try to make small-talk with a stranger on an elevator, we invariably lean towards the topic of the day's weather. "Sure is hot out today isn't it?"

lightning june 18 2011 USA

Image George Kourounis

I just happen to have more weather stories than most. As a storm chaser for the past 14 years, I've seen a lot of very, VERY bad weather. In fact, I've travelled the world, to all 7 continents and over 40 countries, documenting the most extreme forces of nature from tornado outbreaks in Kansas to the eye of landfalling hurricanes, I even got married on the crater's edge of an exploding volcano in the South Pacific.

disaster area joplin tornado

Image © George Kourounis

The 2011 Tornado season in the U.S. has been unlike any I've experienced, not only for the record breaking number of tornadoes, but also the fact that many of these storms have struck densely populated urban areas, resulting in tremendous loss of life and widespread destruction.

In April, the deep south states of Mississippi and Alabama were hit hard by powerful, fast moving tornadoes that did incredible damage in places like Tuscaloosa. The peak of tornado season typically arrives in May and the deadly trend continued with Joplin, Missouri taking a direct hit on May 22nd. I chased that storm and our team arrived on the scene about 2 minutes after the tornado had passed and we had to instantly switch from being storm chasers to being first responders as we assisted with injured motorists on the side of the main highway. Others were not so fortunate and a large part of the city was simply leveled in a display of natural power that I've never seen the likes of before.

As the month progressed, another outbreak of tornadoes raked across Oklahoma, causing more devastation and loss of life. In total over 1,500 tornadoes have touched down so far this year with 5 of them being ranked as EF-5 on the Enhanced Fujita scale, the highest possible rating.

oklahoma tornado 2011

                Image © George Kourounis

So what's to blame? How did this all happen?

Currently there is no direct link between climate change and tornado production, but the waning La Nina ocean pattern in the Pacific has caused the jet stream over North America to persist in an orientation that helps develop supercell storm that produce tornadoes. Couple this with the increasing population density that keeps expanding these regions and then add an unfortunate dose of bad luck to the mix and we end up with a tragic season like 2011 has been.

Tornadoes are a naturally occurring phenomenon but they only make the shift from "natural phenomena" to "natural "disasters" when they have a direct impact on communities of people unfortunate enough to find themselves in the path of these wicked winds. There is still much to learn and many improvements to be made in the warning systems for these communities and that's part of the reason I'll continue to find myself out there, prowling the great Plains for many more years to come.

 

Behind the scenes at 23 Degrees: getting to grips with time-lapse photography

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Tom Hewitson | 15:00 PM, Wednesday, 20 July 2011

Distance travelled ~ 516'168'000 km

(Tom Hewitson is the Assistant Producer on 23 Degrees currently working on episode two. Tom heads to Northern Norway on Friday - his first shoot on 23 Degrees - to film the Sun setting for the first time since May).

When I joined the 23 Degrees team I encountered a challenge I'd not come across before: filming the weather. Mother Nature is rarely willing to do a second take and she insists on working at her own pace, not ours. This can lead to a problem. Over the series we'll be featuring things like cloud formation, sunsets and ice melting. These events can often take many hours, longer than the duration of the entire series! We get around this problem by using time-lapse photography. It's a technique I haven't used before, so I thought I'd better learn pretty sharp-ish...

The principle is simple. Television is simply a string of images shown very quickly. In the UK we show 25 of these pictures a second and when we see them at this speed we have the illusion of motion. Normally the images are played back at the same rate they were originally taken, but time lapses are different. Pictures are taken over a much longer period of time, perhaps an image every few seconds. If we then play these back at the standard 25 frames per second we will see the action very much sped up. Hey presto, we can show an event that could take many hours in a matter of seconds! It's a great way of observing phenomena that we simply miss at our normal pace of life.

Before heading out on location I thought I should get to grips with time lapses so decided to do a test shoot. I'm fortunate enough to have a balcony right next to my desk, so for my very first attempt I decided to film the clouds going overhead.

 

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For this I've used the Canon 5D camera we have in our office. A tripod was essential, as I wanted the weather to be moving, not the landscape! Finally, to trigger the camera you don't want to be pushing the shutter button by hand (not only would it wobble the camera, it would be very boring). We therefore have what's called an intervalometer; a device that automatically activates the camera's shutter at pre-programmed time intervals.

But before I could set it going it was time for some rough maths. Judging the speed of the clouds, I decided filming for about 10 minutes should be enough to show some good movement. As I wanted the final footage to last for about 10 seconds, I'd need to take 250 frames in total. This means I should take 25 pictures a minute, equating to a shot every 2.4 seconds. Unfortunately I could only dial in whole seconds into the intervalometer, so I decided to take an image every 3 seconds, which gave me 8 seconds of footage for 10 minutes of cloud movement.

Thanks to a phone call over-running I ended up filming for a little over 20 minutes giving me 17 seconds of footage, but it's better to have too much than too little. True, the footage is just of some fairly uninspiring clouds over London, but hopefully with this one done I can be a bit better prepared when I'm faced with that once a year weather event I need to catch on camera!

Day 200: very wet in UK but it seems a dry Indian monsoon for the team on location...

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Stephen Marsh Stephen Marsh | 17:00 PM, Tuesday, 19 July 2011

Distance travelled ~ 513'809'600 km

Today the 23 Degrees team are in India to explore the greatest weather event on Earth - the Monsoon.

They start their journey in Udaipur in the northwestern state of Rajasthan. Sometimes known as the desert state it has been baking in the Sun for months and so the rains should come as a blessed salvation from the heat and dust of summer - although there has been no reports of rain today from the team out on location.

Rajasthan is an agrarian state where over two thirds of the population are reliant on agriculture. But Rajasthan only shares around 1% of the surface water in India so it is very dependent on the annual rains.

In Udaipur Kate Humble is visiting a stunning cliff top palace called the Sajjan Garh. Built at the end of the 19th century by the 72nd Maharana of Udaipur the palace was built not to view the city below but the arrival of the monsoon rains. Sajjan Garh, which means Monsoon Palace, gave the rulers of Udaipur a grandstand view of the most dramatic and most important weather event on the planet.

We in the UK often take rain for granted, and frankly moan about it, particularly with this wet July, but for the people of Rajasthan the rains are quite literally a matter of life and death. I know that's an overused term but the Indian monsoon brings water to nearly 2 billion people, and is critical for the farmers like the maize growers of Rajasthan. Should the rains not arrive their crops will fail and they will face seriously desperate times.

Kate is also visiting the famous Lake Pichola. For those who remember the James Bond film Octopussy many scenes were shot there and in the beautiful Lake Palace in the centre of the lake. It's actually a man-made reservoir, created over 600 years ago to store the monsoon rain so the local community have access to water long after the rains have gone.

While Kate Humble stays up north in Rajasthan, Helen Czerski is thousands of kilometres south on a beach in Kerala. It's no holiday; she's there to discover how the different responses of land and water to solar energy power the monsoon, generating incredibly intense rainfall. I suspect she's in for at least one soaking from the rain.

23 Degrees observers: Pictures of the week 15 July

Aira Idris Aira Idris | 17:00 PM, Friday, 15 July 2011

Distance travelled ~ 503'518'400 km

harvest time
Harvest Time. Photo taken by John Parish, UK

 

Clouds east of Laramie
Clouds east of Laramie. Photo taken by Wayne Karberg, UK

 

blue,white,green
Green,White,Green. Photo taken by Percie Beddoe, UK

 

VIV_4686.jpg
Sunset over Duddon Estuary, Cumbria, Photo taken by Bob Cusworth, UK

 

Akureyri culturhouse and art of nature.
Art of Nature. Photo taken by Jón Ingi Cæsarsson, Iceland

Different types of Sandwich - The weather is key at this week's Open

Alex Deakin Alex Deakin | 12:30 PM, Friday, 15 July 2011

Distance travelled ~ 503'036'000 km: day 196 in Earth's orbit

Mid July, the Open Championship; if we had steady, predictable summers it would be sunny skies and light winds every year, like it seems to be at Augusta, but this is the UK and it is never that simple.

This year we will be fortunate, although the players may see it differently, to see different weather conditions on each of the 4 days at Royal St Georges. The 2011 champion will be the player who is best at manipulating the ball through a very active lower atmosphere.

I am a fair weather golfer and detest playing in the rain but for the pro's who regularly have to play soggy rounds the rain is a mere distraction, it is the wind that is the most crucial of the elements, simply because it is so fickle.

A strong wind can easily make 3 clubs difference, hit a 4 iron into a green one day, or even one hour, and the next you may only need a 7 iron, if the wind is now behind you.

But of course changing the club not only changes the length of shot but also the trajectory and the higher a ball goes the stronger the winds are likely to be. The variation of wind with height, or wind sheer, is caused by the friction of the land.

Gauging the wind as a golfer is an art and why the winner is more likely to be an older, wiser more experienced player and one that has knowledge of playing links golf.

We've all seen players throw a few blades of grass in the air on the tee, but the wind on that tee (possibly sheltered by a sand dune) can be very different both in strength and direction than the wind 200 yards down the fairway and 100 yards up in the atmosphere.

The 'stability' of the lower atmosphere is another variable, when the pressure is low (as it will be this week at Sandwich) the air is said to be unstable. This allows quick movement of air vertically, creating up and downdraughts, which when they hit the ground produce unpredictable sideways gusts.

Even if the weather is relatively calm, because the Open is always on a links course (one by the sea) the winds will always be switching around and provide the biggest problem for the golfers.

Sea breezes develop during the day in the summer months as the land warms up. This means in the cool morning the winds can be light for the early starters. Yet for the later tee off times the sea breeze can scupper their hopes of lifting The Claret Jug.

Sea breezes won't be a factor this year but is a good reason why the Open is always held by the sea, so when we do get a fine mid July the golfers never get it easy at the oldest major of them all.

Watch the BBC's Live coverage of the Open championship

Abundance in UK summer fruits an indicator to past British weather?

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Peter Gibbs Peter Gibbs | 12:00 PM, Thursday, 14 July 2011

Distance travelled ~ 500'409'600 km: day 195 in Earth's orbit

There's been a strange groaning sound emanating from gardens across the country this summer. It's not coming from the creaking limbs of aged gardeners, but from the strained boughs of fruit trees laden down with a bumper crop of steadily swelling apples and pears.
Temptation

Lots of people remarked on the stunning display of blossom this spring and this has translated into one of the most prolific fruit crops in years. Not just tree fruit either, blackcurrants and other berries seem to have done equally well.
IMG_0735

This can all be put down to the combination of a cold winter followed by a warm spring. Most plants that we grow in the UK go into a period of hibernation during the winter, before bursting back into growth as temperatures rise in spring. If they don't get a cold enough spell of weather during the winter they never go into full dormancy, which means they have less energy left over for spring growth.

Once the blossom appears, it's vulnerable to frost damage if there's a late cold snap. Cold weather also means that pollinating insects stay at home. This all means that the fruit doesn't set and you end up with a poor crop.

So why is this year so good? Well, the coldest December in a century was just the thing to push fruit trees and berry shrubs into a good dormant spell, followed by the extravagant display of blossom as temperatures soared through March and a record-breaking April. Late frosts held off until May, by which time the fruit had set.

So all this suggests that an abundance of berries in the hedgerow is more reliable as an indicator of past weather, rather than a prediction of a hard winter to come as weather lore would have it.

But then again, it was a meandering jetstream and the resulting blocked weather pattern that brought us two cold winters in succession. There is some evidence that North Atlantic weather may occasionally get stuck in a blocked pattern for a few years at a time.

So maybe the berries are trying to tell us something. As ever with weather lore, there could be a grain of truth - but don't bet your holidays on it.

Cromarty, Forth, Tyne, Dogger... what does the shipping forecast tell us about our planet?

Helen Czerski Helen Czerski | 19:40 PM, Wednesday, 13 July 2011

Distance travelled ~ 499'123'200 km

The absolute magic of the shipping forecast is hard to explain to people outside of the UK. Four times a day, a slow soothing voice reads out 350 words which almost no-one understands and almost everyone loves. But hidden in this swirl of familiar words is the story of giant swirls in the atmosphere, mixing air up and moving energy north. There is always another shipping forecast tomorrow, because there is always more energy from the Sun to take that journey.

Let's imagine the shipping forecast as if we were sailors out at sea. First of all, the General Synopsis gives us the position of a region of low pressure, for example in "Irish Sea". Then area forecasts work clockwise around the British Isles, giving the conditions in every section of the sea, and we can put it together like a jigsaw puzzle. We can get the map out and as we listen, we can draw the wind direction and speed on the map for every section. As we draw on the wind arrows, we see that they point anticlockwise around the pressure low. The words have painted a picture of the weather, and it's a swirl. But what's going round what and why?

The UK is in an interesting place from a meteorological point of view, because we're right in the path of a huge boundary in the atmosphere, the boundary between warm air in the south and cold polar air in the north. The Sun heats Earth most at the equator, and all our weather is just the atmosphere's way of moving this energy towards the poles. The poles lose energy to space faster than the equator does, so it's a bit like a conveyer belt for heat. But it's not a smooth process.

swirl of tea

Next time you add some milk to your tea, mix it just a little bit and then watch. Rather than the milk slowly diffusing into the tea, the mixing all happens in the swirls. And the same is true in the atmosphere, but the swirls can be a thousand miles across. These are the cyclones and anticyclones, always moving towards the east, which make up the bulk of UK weather patterns. Where warm and cold air meet, at around our latitude, they get mixed up in swirls. At the centre of each swirl is either a low pressure or high pressure region, and weather fronts (boundaries between warm and cold air) are moving around that region to mix everything up. Warm air moves north, cold air moves south, and overall, energy travels towards the north pole.

So the soothing tones of the shipping forecast are telling the story of the movement of energy on a planetary scale. Next time you're listening to the shipping forecast at bedtime, imagine the swirls in your cup of tea as you drift off to sleep and listen: "Northerly or northwesterly 5 to 7. Moderate or rough. Mainly fair. Good. "

What makes Great British weather?

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David Brayshaw | 19:30 PM, Wednesday, 13 July 2011

Distance travelled ~ 499'123'200 km

The weather of Great Britain is notoriously fickle. One day brings sunshine, the next is dull, while a third pours with rain. Britain froze under a blanket of snow for weeks in December, sweltered in a burst of heat in April and brought umbrellas out during an inclement early summer. But why is Britain's weather so variable? To understand that, we must first understand Britain's place in the world. Britain lies at the downstream end of the North Atlantic storm track, a feature that dominates the weather and climate of the North Atlantic and Western Europe. The phrase "storm track" is used to describe the typical paths of low-pressure weather systems as they move eastward in the jet-stream across the North Atlantic Ocean. Similar storm tracks can be found in both the North Pacific and the Southern Oceans.

north atlantic storms

Figure: The Northern Hemisphere winter storm tracks as simulated using a version of the UK Met Office's HadSM3 climate model as part of the Water, Life and Civilisation project at University of Reading. The colouring shows the average number of storms per year passing through each point on the map (with oranges and reds indicating more storms). The main storm tracks are marked out by the blue arrows over the Pacific, Atlantic and Mediterranean.

Each individual low-pressure weather systems is referred to as either a "cyclone" or a "storm" - the storm track contains many moderate systems as well as the really intense events that are more commonly called storms. Around each storm, the wind flows anti-clockwise along lines of constant atmospheric pressure. To the west of the storm the winds are from the north, bringing cold polar air southward, while to the east the winds is from the south, bringing warmer subtropical air. The join between the warm and cold air masses is known as a "front", like a battle-line between two opposing armies. As a storm moves eastward overhead, we first feel the effects of the warm front - the warm air moving north, raising the local temperature - followed by the cold front - the cold air moving south, lowering the temperature back down again.

Figure: Circulation around a storm in the Northern Hemisphere: warm air is moved polewards and upwards ahead of the storm while cold air sinks as it moves equatorwards behind the storm. The air moving around the storms does not just move horizontally. As the warm air moves northwards it rises above colder polar air and, similarly, the southward moving cold air slides underneath warmer subtropical air. Either way, the warmer air moves upwards, cooling as it does so. As the rising air cools, the water vapour it contains begins to condense into small liquid water droplets. To the onlooker on the ground, large groups of these droplets appear as clouds, the familiar harbingers of rain.

Small droplets, however, do not necessarily cause rain. While the droplets remain small the maximum speed at which they fall through the air is low. Such droplets can be held aloft by the overall upward motion of the rising air. The rain comes when the droplets begin to grow larger - whether by colliding and coalescing with each other or simply by gradual growth from further condensation. Larger droplets are able to reach greater fall-speeds and they are then able to leave the cloud and drop to the ground.

The day-to-day variations in British weather that we experience are intimately connected with the passage of these storm systems eastward across our region. In subsequent blogs, we'll ask why these storms should form at all, look at how they affect European climate (i.e., the "average" weather), and examine how the storm tracks can be dramatically altered by changes in the jet-stream over the North Atlantic.

(David Brayshaw is based in the Department of Meteorology at University of Reading (www.met.reading.ac.uk). Further information about last December's cold UK weather in the UK can be found at http://www.walker-institute.ac.uk/news/Dec_2010/.

This week's space weather roundup and Saturn's northern storm

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Stephen Marsh Stephen Marsh | 16:00 PM, Tuesday, 12 July 2011

Distance travelled ~ 496'550'400 km

Day 193 on our circumnavigation of the Sun. Down on planet Earth it's been a rather boring start to July weather-wise, overcast, a bit humid a bit stormy. But in space it's been anything but dull.

July 5th NASA recorded the fiery death of an unnamed icy comet, which plunged into the Sun.



On July 6th NASA published some photos of a massive electrical storm on the planet Saturn that's been raging for months. The so-called Great White Spot is so massive it would cover half of the Earth and so violent those scientists have counted over ten lightening flashes a second. Such giant storms are relatively rare and only six have been witnessed in the last 135 years.


Image © NASA/JPL-Caltech/SSI



Then on July 7th a Coronal Hole opened up in the surface of the Sun. So what's a coronal hole. Well as we orbit the Sun we're bathed in essential warmth and energy, but we are also blasted by a blizzard of radioactive particles called the solar wind. This barrage is 24/7 but sometimes a hole opens up in the suns surface, a coronal hole, triggering the release of a really intense stream of solar wind. Normal solar wind travels at around 1,440,000 kilometres per hour but the wind blasting out of a coronal hole shoots out at up to 4,000,000kmph. These supercharged solar wind particles finally reached us two days later. Most were diverted by our magnetic shield but some hit the atmosphere and triggered auroras far south across the USA.

Today NASA released footage of some increased activity on the eastern region of the Sun. The Sun was hurling up huge amounts of material high above the stellar surface. You can see it yourself at spaceweather.com
As it happens this activity is not directed towards Earth, but NASA has detected a very active sunspot with the "oh so catchy" name 1247.

sunspots

Image NASA/SDO

But don't let the unexciting name fool you, because it's anything but boring. It has a magnetic field with enough stored energy to create a M-Class solar flare, that's a pretty big explosion from the sun surface. Solar flares are classified according to their x-ray brightness. X-class flares are huge and can cause giant radiation storms and nation-wide radio blackouts. M-class flares are as the "M" suggests medium-sized and can trigger/cause small radio blackouts while C-class flares are small and have no effects on Earth.

NASA predicts there's a 10% chance of an eruption from the sunspot in the next 24 hours, and that one is directed towards Earth so watch this space.

Who said space is empty?

23 Degrees team Colorado update: thermals and paragliding

Distance travelled ~ 486'259'200 km: day 189

Back on day 161 Helen and the 23 Degrees team ventured to Colorado to study and film thermals, another complexity of our atmosphere.

 

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When sunlight hits the surface of the Earth it’s absorbed by the ground, and then radiated back up into the atmosphere as heat. This heat warms the air above it, which expands and becomes less dense than the surrounding cooler air.  The warm less dense air rises in what’s called a thermal column. And it’s these thermal columns that support the Paraglider carrying it up into the sky.
 
Thermals are a bit of a free lift, and many birds have evolved to use them to travel huge distances without expending energy by having to flap their wings. Thermals tend to be stronger in the afternoon when the earth has absorbed enough solar energy to heat the air above it.  

Thermals reveal on a small scale what’s happening to our climate across the Earth because they create a heat gradient between hot and cold air. While warm air is rising, cooler, denser, air flows in to replace this rising column of warm air, until it is also warms, becomes less dense and starts to rise. This action causes the atmosphere to be in a continual state of flux, with warm and cool air moving up and down and horizontally. This constant movement of air transfers energy within the atmosphere and it is this process that drives weather. 
 
Heat gradients form the basis of all weather on planet Earth because nature hates gradients. It likes balance so if one part of the planet is getting more solar energy and heating up the atmosphere, creating a heat gradient cooler air will rush in to cancel it out.  And this movement or air getting rid of heat differences in the atmosphere that generates huge weather patterns powering events like thunderstorms, Tornadoes and even snowstorms

Huge dust storm descends onto Phoenix Arizona 05/07/2011 [VIDEO]

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Aira Idris Aira Idris | 12:00 PM, Wednesday, 6 July 2011

Distance travelled ~ 481'113'600 km: day 187

Phoenix Dust Storm (Haboob) Timelapse July 5, 2011 from Blaine Coury on Vimeo.

The video was taken from a hill at Sun Ray park in Ahwatukee (Phoenix), Arizona. Yesterday's storm was part of the Arizona monsoon season which starts mid june and ends in september.

Aphelion: shouldn't earth be at its coldest today?

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Stephen Marsh Stephen Marsh | 15:30 PM, Monday, 4 July 2011

Distance travelled ~ 475'968'000 km: day 185

Today July 4 is a rather special day in our annual journey around the Sun. At 15.00 GMT Earth will be at the furthest point away from the Sun it will reach all year. I know it sounds bizarre considering how warm it is today but it's true, and it's all down to our orbit.

The Earth's orbit around the Sun is not a perfect circle. It's an ellipse and the Sun does not sit at the centre, it's offset to one side. So today we are 5 million kilometres further away from the Sun than when we were closest to the Sun six months ago in January during Perihelion. And if you remember it was pretty cold in January so you might ask why isn't our proximity to the Sun in winter warming us and our increased distance away from the Sun in summer cooling us down?

sun at aphelion and perihelion

Image © 2001-2011, Anthony Ayiomamitis

The truth is our elliptical orbit and our distance from the Sun is not the primary driving force behind our climate. So what is?

Well number one is the that fact that the Earth is tilted at 23.4 degrees from vertical. During Perihelion the northern hemisphere is tilted away from the Sun, so received less solar radiation and we get winter. In our summer we are tilted towards the Sun so despite being farther away on our orbit we get increased solar radiation. Which is why today in July it's lovely and warm.

But what about the southern hemisphere? Well it's a bit more complex down there. Earth is closest to the Sun during their summer when they are tilted towards the Sun and this means they get 7% more solar radiation. Therefore you'd expect the southern hemisphere summer to be a lot warmer than the northern summer. But it's not, in fact it's actually colder.

And now at Aphelion it's winter down south, and the hemisphere is both furthest away and tilted away from the Sun. So you'd think it's winter would be a lot colder, what with the tilt pushing the hemisphere away from the Sun. Well in fact it's warmer than our winters. And that's all because of the ratio of land to oceans in the hemispheres. The northern hemisphere has a lot of land but the southern hemisphere is predominantly water with very little land and it's this that is powering the climate.

While land reacts very fast to solar heating, it warms up and cools down very quickly. The oceans react very slowly to solar energy. They take a long time to warm up and a long time to cool down. This means that at perihelion in their summer the oceans haven't absorbed enough energy to warm up the atmosphere, they are still cool from the previous winter, so they keep the temperatures cool. In the southern hemisphere winter it's the opposite. The oceans have held onto some of the heat they absorbed during the summer and are keeping the air above warm.

So even though our elliptical orbit takes us at this point of the year further away from the Sun than it will for the rest of the year, it's warm in the north because we are tilting towards the Sun and a milder winter in the south because of the actions of the oceans.

The half way point: a look back over 468'000'000 km of our planet's annual journey

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Stephen Marsh Stephen Marsh | 14:45 PM, Friday, 1 July 2011

Distance travelled ~ 468'249'600 km: day 182 in Earth's orbit

We've come a long way since filming the wintery and snowy mountains of Aonach Mor in Scotland on January 3rd 2011.

We are at the halfway point of our 940 million kilometre [584 million mile] annual circumnavigation of the Sun, hurtling through space at 107,200 kilometres [66,700 miles] an hour. On this odyssey we are discovering how gigantic forces like the tilt of the Earth and its spin determine our climate and influence the life cycle of every living thing on the planet. We will discover how our relationship with the sun creates the seasons, powers the most spectacular weather on the planet, and even dictates how we live our lives.

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So far we have been ice road trucking in Yellowknife, the coldest place in North America, where winter temperatures routinely plunge below minus 35 degrees. We've witnessed the Sun lighting up the serpent on the side of the Temple of Kukulkan , at Chichen Itza in the Yucatan Peninsula of Mexico and the dramatic break of the ice on the waterfall on the Hay River. We have driven into the heart of a snowstorm in Upper New York State and witnessed the awesome destructive power of a Tornado on the Great Plains on Nebraska. We travelled on dog sleds to the very edge of the sea ice in Greenland and sailed deep into the southern ocean off Tierra Del Fuego on the vey southern most tip of South America.

But we're only half round our orbit. Now the northern hemisphere is tilting towards the Sun and it's mid summer. And all that warmth is about to trigger some incredible weather phenomena. Asia is about to experience its annual monsoon and Hurricane season has begun in the Atlantic - so the US can expect some of these monster storms to hit it's eastern seaboard. And the 23 Degree team will be there - witnessing the incredible power of nature unleashed and discovering how our cosmic dance with the Sun drives these stunning weather phenomena.

So stick with us for the second half of our journey - it's going to be a bumpy ride.

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