Posts about weather

Lighting in Slow Motion

Video deleted

The videos provides a super slow motion lighting strike. A separate lighting related item, from NASA: Gigantic Jets:

They are extremely rare but tremendously powerful. Gigantic jets are a newly discovered type of lightning discharge between some thunderstorms and the Earth’s ionosphere high above them. Pictured above is one such jet caught by accident by a meteor camera in Oklahoma, USA. The gigantic jet, at the lower left, traversed perhaps 70 kilometers in just under one second.

Related: posts on weatherClouds Alive With Bacteria

500 Year Floods

Why you can get ’500 year floods’ two years in a row by Anne Jefferson:

Flood probabilities are based on historical records of stream discharge. Let’s use the Iowa River at Marengo, Iowa as an example. It reached a record discharge of 46,600 cubic feet per second* (1320 m3/s) on 12 June. That flow was estimated to have a 500 year recurrence interval, based on 51 years of peak flow records

When you are extrapolating beyond your data by an order of magnitude, the highest points in the dataset start to have a lot of leverage. Let’s imagine that there’s another big flood on the Iowa River next year and we do the same analysis. Now our dataset has 52 points, with the highest being the flood of 2008. When that point is included in the analysis, a discharge of 46,600 cubic feet per second* (1320 m3/s) has a recurrence interval of <150 years (>0.6%). It’s still a darn big flow, but it doesn’t sound quite so biblical anymore.

Urbanization and the adding of impervious surface is one cause of increasing flood peaks, but in Iowa, a more likely culprit is agricultural.

This post is a good explanation that the 500 year flood idea is just way of saying .2% probability (that some people confuse as meaning it can only happen every 500 years). But I actually am more interested in the other factor which is how much estimation is in “500 year prediction.” We don’t have 500 years of data. And the conditions today (I believe) are much more likely to create extreme conditions. So taking comfort in 500 year (.2%), or even 100 year (1% probability) flood “predictions” is dangerous.

It would seem to me, in fact, actually having a 500 year flood actually increases the odds for it happening again (because the data now includes that case which had not been included before). It doesn’t actually increase the likelihood of it happening but the predictions we make are based on the data we have (so given that it happens our previous 500 year prediction is questionable). With a coin toss we know the odds are 50%, getting 3 heads in a row doesn’t convince us that our prediction was bad. And therefore the previous record of heads or tails in the coin toss have no predictive value.

I can’t see why we would think that for floods. With the new data showing a flood, (it seems to me) most any model is likely to show an increased risk (and pretty substantial I would think) of it happening again in the next 100 years (especially in any area with substantial human construction – where conditions could well be very different than it was for our data that is 20, 40… years old). And if we are entering a period of more extreme weather then that will likely be a factor too…

The comments on the original blog post make some interesting points too – don’t miss those.

Related: Two 500-Year Floods Within 15 Years: What are the Odds? USGS – All Models Are Wrong But Some Are Useful by George BoxCancer Deaths – Declining Trend?Megaflood Created the English ChannelSeeing Patterns Where None ExistsDangers of Forgetting the Proxy Nature of DataUnderstanding Data

Clouds Alive With Bacteria

Clouds above the Mesa Trail by John Hunter

Earth’s Clouds Alive With Bacteria

Clouds are alive with tiny bacteria that grab up water vapor in the atmosphere to make cloud droplets, especially at warmer temperatures, a new study shows.

The water droplets and ice crystals that make up clouds don’t usually form spontaneously in the atmosphere – they need a solid or liquid surface to collect on. Tiny particles of dust, soot and airplane exhaust – and even bacteria – are known to provide these surfaces, becoming what atmospheric scientists call cloud condensation nuclei (CCN).

These microbes could be carried into the atmosphere from an infected plant by winds, strong updrafts or the dust clouds that follow tractors harvesting a field. Christner and others suspect that becoming cloud nuclei is a strategy for the pathogen to get from plant to plant, since it can be carried for long distances in the atmosphere and come down with a cloud’s rain.

The next step in determining how big a role biological particles play in cloud droplet formation is to directly sample the clouds themselves, Christner says.

Related: What’s Up With the Weather?20 Things You Didn’t Know About SnowRare “Rainbow” Over IdahoBacteria Living in Glacier – photo by John Hunter, on the Mesa Trail, Colorado

Deforestation and Global Warming

Deforestation: The hidden cause of global warming:

In the next 24 hours, deforestation will release as much CO2 into the atmosphere as 8 million people flying from London to New York. Stopping the loggers is the fastest and cheapest solution to climate change.

Tropical Deforestation, Climate Impacts (NASA by Rebecca Lindsey):

Undisturbed tropical forests may be nearly neutral with respect to carbon, but deforestation and degradation are currently a source of carbon to the atmosphere and have the potential to turn the tropics into an even greater source in coming decades.

Related: Deforestation (from the National Geographic)Deforestation (Greenpeace)Deforestation and the Greenhouse EffectWhat’s Up With the Weather?The Choice: Doomsday or Arbor Day

Rare “Rainbow” Over Idaho

Rainbow like clouds

Rare “Rainbow” Spotted Over Idaho by Victoria Gilman:

The arc isn’t a rainbow in the traditional sense—it is caused by light passing through wispy, high-altitude cirrus clouds. The sight occurs only when the sun is very high in the sky (more than 58° above the horizon). What’s more, the hexagonal ice crystals that make up cirrus clouds must be shaped like thick plates with their faces parallel to the ground.

When light enters through a vertical side face of such an ice crystal and leaves from the bottom face, it refracts, or bends, in the same way that light passes through a prism. If a cirrus’s crystals are aligned just right, the whole cloud lights up in a spectrum of colors.

What’s Up With the Weather?

image of Time cover

No one can say exactly what it looks like when a planet takes ill, but it probably looks a lot like Earth. Never mind what you’ve heard about global warming as a slow-motion emergency that would take decades to play out. Suddenly and unexpectedly, the crisis is upon us.

Time’s cover story – Be worried, be very worried – starts out with this provocative paragraph. Other recent stories on the effects of climate change, rising ocean levels etc.:

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