Nature - Images

Interesting Images: Nacreous Clouds

Clouds in the stratosphere are very rare. Yet for the past week they have been seen every day. Yesterday, Feb 2nd, Sean Crane of Harrogate UK hopped out of his bath to photograph the display:

These fantasticaly-colored clouds are floating more than 80,000 feet above Earth's surface. Normally, the thin air up there is crystal clear. Not this week. Water molecules are crystalizing in the lower stratosphere and the resulting ice crystals are assembling into polar stratospheric clouds (PSCs).

Also known as "nacreous" clouds, PSCs form in the lower stratosphere when temperatures drop to a staggeringly-cold -85ºC. High-altitude sunlight shining through tiny ice particles ~10µm wide produce bright iridescent colors by diffraction and interference.

Because these clouds require extreme cold, they are most often seen around the Arctic Circle. In recent days, however, they have been spotted as far south as the UK.

Environment

Clouds Over Southern Ocean Made by Ocean Creatures

The Southern Ocean is reckoned as the cloudiest region in our planet and it almost nearly blanketed all through the year. But it might be surprising that it is the tiny marine organisms known as Phytoplankton that live in the stormy waters of the ocean that are responsible for creating these clouds.

Measuring how the gases and particles emitted by these tiny creatures entered the atmosphere to become cloud seeds was the subject of a recent study. This study was also the first large scale correlation between cloud formation and biological activity in the Southern ocean. Establishing that link constitutes a significant first move towards understanding the role played by clouds and the tiny particles of air known as aerosols in the context of climate change and climate modelling.

In climate models, aerosols and clouds constitute two important wild cards and comprehending their impact on climate gets further complex when we consider the question of how they interact with each other. Soot is a type of aerosol that comes from human activities, but we also have other natural aerosols like sulphate, sea spray and ammonium salts in the atmosphere. All these particles form the ‘seeds’ and water vapour condenses around these to become tiny droplets and turn into clouds.

Clouds can have a key role when we consider climate – but that role is complicated. The planet tends to get cooled by the low lying clouds that functions as reflectors and bouncing the solar radiation back to space. Higher clouds on the other hand tend to trap the heat and prop up warming. Climate models in the Southern Ocean have been pretty poor in capturing the influence of the clouds by estimating less reflected radiation than what actually exists. Scientists will have to understand more about aerosols that help in formation of the clouds and how they have impacted the climate over the past 2 centuries, to improve these models. But the task gets difficult for tracking in the absence of knowledge on the number of ‘natural’ aerosols present in the atmosphere before industrialisation began.

If concentration of aerosols were higher during the preindustrial times, then the impact from human perturbations to aerosols would be smaller.

This also brings into focus the Southern Ocean. Apart from being the cloudiest place on the planet, it is also one among the cleanest and relatively unharmed by human activity. That makes it the perfect laboratory for examining the interaction between cloud and aerosols.

Nature - Images

Interesting Images:

Interesting thunderstorm cloud formations:

Global Warming

Plants Could Be Moderating Climate Change

Small particles released by plants in warmer weather could help to boost cloud production and reduce the effect of global warming, a new study suggests.

By surveying nearly a dozen forests across Europe, North America and southern Africa, a team of Finnish physicists found that in warmer weather, plants tend to emit higher concentrations of volatile organic compounds (VOCs) into the atmosphere.

When these small, floating chemicals bind with water vapor, they can create the “seeds” of clouds.

With more VOCs in the air, we can expect to see more clouds in the sky.

That could be good news for those concerned about climate change.

As warmer weather leads to higher levels of cloud production, more sunlight will be deflected back into space and prevented from warming the surface of the Earth.

But the authors of the study, writing in the journal Nature Geoscience, caution that the global impact of this cloud-seeding effect is expected to be quite small.

While higher VOC emissions may help to cut rising local temperatures by as much as 30 percent, the study found that it can only be expected to slow the global warming trend by a mere one-percent.

The implications of the study may still be important. As Pauli Paasonen, lead author of the study points out, the role of sun-deflecting “aerosols” in the atmosphere is one of the least well understood factors of climate change.

Environment

Clouds

This unusual, but interesting image shows a Fallstreak hole. Fallstreak holes are a cloud formation that occurs as gaps in mid or high level cloud layers; below them trails of ice crystals dangle.

Climate Change

Researchers from New Zealand’s University of Auckland suggest that according to satellite data from March 2000 to February 2010, the average height of clouds declined by approximately 100 to 130 feet.

A reduction in cloud height would allow the planet to radiate more heat into space thereby slowing the effects of global warming.

More research needs to be done, as the test period is too short to determine a definite trend.