HR: 1340h
AN: A43C-0103    [Abstracts]
TI: The Response of a Global Circuit Model with Stratospheric and Tropospheric Aerosol to Cosmic Ray Flux Changes
AU: * Zhou, L
EM: zhoulim@hotmail.com
AF: Institute of Geochemistry, Chinese Academy of Sciences, 73 Guanshui Road, Guiyang, 550002 China
AU: Tinsley, B A
EM: Tinsley@UTDdallas.edu
AF: University of Texas at Dallas, FO22 Box 830688, Richardson, TX 75083 United States
AB: The global circuit is a key intermediate between solar activity and the Earth's climate by controlling the downward current density Jz which can affect cloud microphysics by electroscavenging and electrofreezing process. Atmospheric ionization due to the cosmic ray flux (CRF) dominates the ion production in the troposphere and stratosphere except close to the surface. We have constructed a new model with improved fidelity, in which the ion production rate due to cosmic ray flux is consistent with the 1954-1965 observations by Neher. These include the ionization decreases and geomagnetic cutoff latitude variations due to solar activity. Production of ionization close to the surface over land is controlled by the distribution of radon (Dentener et al., 1999), with different scale heights of the radon vertical distribution for the different seasons. Tropospheric aerosol concentration is from the GADS data base (Hess et al., 1998) providing detailed global aerosol concentrations that also have seasonal variations. Volcanic eruptions increase the atmosphere resistance by increasing the aerosol concentration in the stratosphere and the upper troposphere. We model additional ultrafine aerosol condensed from the volcanic sulfuric acid vapor in the upper troposphere and the stratosphere, that is transported there by the Brewer-Dobson circulation, as discussed by Tinsley (2005). We calculate the columnar resistance distribution over the world and the total global load resistance. We find that the effects of the seasonal variations on the columnar resistance and total load resistance are small. Solar activity increases the global resistance because the reduced CRF decreases the ion pair production rate. Column resistance shows a strong variability at high geomagnetic latitudes because of the solar/geomagnetic modulation of the lower energy CRF. This is reflected in strong variations of Jz. There is a 7~12 percent enhancement of global load resistance on the solar cycle and during Forbush decreases. Volcanic eruption increases the global resistance by 17~25 percent. Volcanic activity increases the solar activity effect especially at the high latitudes, because of the high concentrations of stratospheric ultrafine aerosol particles controlled by the Brewer-Dobson circulation creates a significant stratospheric column resistance there. This is where there is also a large solar cycle variation in the CRF. This region is also strongly affected by ion-pair production from relativistic electron precipitation and associated Bremsstrarhlung X-radiation. The reduction of these at HCS crossing leads to an increase in column resistance and reduction in Jz as observed, and provides on explanation for the observed mid-high latitude response of clouds, atmospheric transparency and vorticity to the HCS crossings. References: Denterner, F., J. Feichter and A. Jueken, Simulation of the transport of Rn222 using on-line and off-line global models at different horizontal resolutions: a detailed comparison with measurement, Tellus, 51B, 573-602 Hess, M., P. Koepke, and I. Schult, Optical properties of aerosols and clouds: The software package OPAC, Bull. Am. Meteor. Soc., 79(5), 831-844, 1998. Tinsley, B. A., On the variability of the stratospheric column resistance in the global electric circuit, Atmospheric Research, in press, 2005.
DE: 0320 Cloud physics and chemistry
DE: 1650 Solar variability (7537)
DE: 2104 Cosmic rays
DE: 3304 Atmospheric electricity
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005