Tuesday, December 26, 2006

Why summer is bad below 40south

Wondering why summer is bad this year, blame the sun. It is a paradox that not only does the sun warm the climate it cools it. Due to regulation of the ionization of particles in the atmosphere producing cloud cover and increased precipitation it modulates the ozone layers.

Ozone is one of the key constituents of the atmosphere. Despite its relatively small abundance, it effectively absorbs a great part of the UV radiation. Therefore,ozone plays an important role in the energy budget and dynamics of the atmosphere, ie Ozone retains temperature in the atmosphere reduction allows longwave (infrared) radiation to escape the lower atmosphere.

Solar variability is observed on three main time scales: solar rotation (27-day), solar cycle (11year) and the Grand Minima time scale. The magnitude of the variability progressively increases from the short to long scales. Earth's climate responses are now found on all these scales. The most recognized are the responses to solar irradiance variations. These variations strongly depend on wavelength rising from 0.1% per solar cycle in total irradiance (mostly infrared-optical range) to 10% in UV and 100% per solar cycle in X-ray range. The variations in the total irradiance produce a small global effect. More substantial is the effect of solar UV variability on large-scale climate patterns. These patterns are naturally excited in the Earth's atmosphere as deviations (anomalies) from its mean state.

Atmospheric ozone is also affected by natural causes, e.g. due to volcanic eruptions or changes in the solar forcing. For example, the solar ultraviolet flux varies with the 11 year solar cycle much more strongly than the total solar irradiance.Also, ultraviolet radiation received by the atmosphere changes by about 7% with the variation of the distance between the Sun and the Earth. These kind of variations may modulate the middle atmospheric ozone [e.g. Callis et al., 1991]. Therefore, when estimating the changes caused by anthropological sources, it is essential to contrast them with variations and changes due to natural processes.

Among the most striking natural phenomena affecting ozone are solar proton events (SPE), during which energetic solar protons precipitate into the middle atmosphere in the polar regions. Ionisation caused by the protons results in production of odd nitrogen and odd hydrogen species, which then destroy ozone in catalytic chemical reactions.

Solar proton events (SPE), also known as polar cap absorption (PCA) events in the history of radio physics, begin as emission of electrons and ions from the surface of the Sun. The ions are mostly protons (≈ 90%) but heavier particles are also emitted, the relative abundances being similar to those in the solar corona. For the most energetic coronal mass ejections (CME), particle energies can be up to MeV or even GeV level, thus far exceeding the normal solar wind values,

These have the ability to allow penetrating radiation to ground level at the poles,indeed one of the Antarctic phenomena’s is the ambient temperature is 40% from small wave radiation(left side of the spectra) Uv, Gamma, and X ray. Indeed as we see here the radiation levels are 2-3 times sea level radiation backgrounds in the tropics.

In early December we had a large solar proton event indeed the x-class flare was 15Th largest recorded .The flare arrived in 15 minutes in the Antarctic sending graphs up30% and forcing ionization towards the equator.This shut down several satellites and the FAA issued a warning to lower altitudes and several satellites were forced to increase height due to thermosphere temperatures in the radiation belts increasing by 500k.The international space station inhabitants were forced into protective areas and altitude corrections for the space station were required .

An incredible good reconstruction and animation of the 2003 SPE and CME from the SVS Animators at NASA is here (also known as the Halloween storms )

There it is blame the sun for a bad start to summer.


Post a Comment

Links to this post:

Create a Link

<< Home

Web Counters