Jahresbericht 08 - PMOD/WRC
Jahresbericht 08 - PMOD/WRC
Jahresbericht 08 - PMOD/WRC
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Scientific Research Activities<br />
Influence of Galactic Cosmic Rays on Atmospheric Composition and Temperature<br />
Eugene Rozanov and Tatiana Egorova in collaboration with Marco Calisto and Thomas Peter IAC ETH, Zurich<br />
We investigated the influence of Galactic Cosmic Rays<br />
on atmospheric chemistry and temperature using a<br />
Chemistry-Climate model and the most recent parameterization<br />
of ionization rates. The implementation of<br />
Galactic Cosmic Rays in the model causes a ~40% increase<br />
of reactive nitrogen in the entire troposphere<br />
and a ~9 % tropospheric ozone increase over high latitudes,<br />
however, the temperature response is not statistically<br />
significant.<br />
Galactic Cosmic Rays provide an additional source of reactive<br />
nitrogen and hydrogen in the atmosphere due to ionisation<br />
of neutral species. The effects of Galactic Cosmic<br />
Rays on the atmosphere have only been estimated with<br />
simple models and their implications for past trends in atmospheric<br />
ozone and temperature have not been properly<br />
established. Galactic Cosmic Rays forcing was not taken<br />
into account in simulations of the past atmosphere in the<br />
framework of the Chemistry-Climate Model validation<br />
(CCMval) campaign. Therefore, it is important to estimate<br />
the influence of Galactic Cosmic Rays on atmospheric<br />
composition and climate and formulate a recommendation<br />
about their significance in the future.<br />
To answer this question we performed two 13-year (1976-<br />
1988) long transient simulations with the CCM SOCOL<br />
v2.0 model with and without a Galactic Cosmic Rays<br />
source. The ionization rate due to Galactic Cosmic Rays<br />
was adopted from the recent paper by Usoskin and Kovaltsov<br />
(2006). The source of reactive nitrogen and hydrogen<br />
was parameterized according to Porter et al. (1976)<br />
and Solomon et al. (1981). The atmospheric response to<br />
Galactic Cosmic Rays was calculated as the difference between<br />
the results of the run with Galactic Cosmic Rays and<br />
the reference run without Galactic Cosmic Rays, which<br />
gives the upper limit of their effects and also allows the statistical<br />
significance of the obtained atmospheric response<br />
to be estimated.<br />
The results show, that Galactic Cosmic Rays produce a<br />
substantial amount of NOx. The simulated NOx increase<br />
shown in Figure 1 exceeds 30% in the southern polar troposphere,<br />
whereas over low and middle latitudes the NOx<br />
increase only reaches 10-20% and is confined to the upper<br />
troposphere/lower stratosphere. The significant increase of<br />
ozone (see Figure 2) up to 10 % is mostly confined to the<br />
troposphere over the southern hemisphere, where ozone<br />
production via smog reactions is most sensitive to additional<br />
NOx due to low background NOx mixing ratios. The<br />
annual mean temperature response (not shown) is not statistically<br />
significant. From these results we can conclude<br />
that Galactic Cosmic Rays may generally be important in<br />
the troposphere over southern high latitudes.<br />
Altitude (km)<br />
90 o S 60 o S 30 o S EQ 30 o N 60 o N 90 o 0<br />
N<br />
Latitude<br />
Figure 1. Annual mean percentage changes of zonal mean NOx due to<br />
GCR implementation. The areas where changes are significant to better<br />
than the 95 % confidence level are shaded.<br />
Altitude (km)<br />
40<br />
30<br />
20<br />
10<br />
40<br />
30<br />
20<br />
10<br />
5<br />
0<br />
2<br />
5<br />
10<br />
20<br />
30<br />
2<br />
3<br />
0<br />
1<br />
0<br />
5<br />
10<br />
0<br />
2<br />
2<br />
1<br />
0<br />
0<br />
Figure 2. Annual mean percentage changes of zonal mean ozone due to<br />
GCR implementation. The areas where changes are significant to better<br />
than the 95 % confidence level are shaded.<br />
References: Porter H.S., Jackman C.H., Green A.E.S., Efficiencies for<br />
production of atomic nitrogen and oxygen by relativistic<br />
proton impact in air, J. Chem. Phys., 65, No.1, 1976.<br />
Solomon S., et al., The effect of particle precipitation<br />
events on the neutral and ion chemistry of the middle<br />
atmosphere: II. Odd Hydrogen, Planet. Space Sci., 29,<br />
No. 8, 885 – 892, 1981.<br />
Usoskin I.G., Kovaltsov A., Cosmic ray induced ionization<br />
in the atmosphere: Full modeling and practical<br />
applications, J. Geophys. Res., 111, D21206, doi:<br />
10.1029/2006JD007150, 2006.<br />
0<br />
1<br />
2<br />
5<br />
0<br />
2<br />
0<br />
2<br />
10<br />
10<br />
5<br />
0<br />
2<br />
20<br />
90 o S 60 o S 30 o S EQ 30 o N 60 o N 90 o 0<br />
N<br />
Latitude<br />
2<br />
0<br />
0<br />
0<br />
0<br />
19