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Paper: Co-variability of the Atmospheric and Geophysical Parameters in the Mid-latitude Troposphere
Volume: 504, Coimbra Solar Physics Meeting: Ground-based Solar Observations in the Space Instrumentation Era
Page: 263
Authors: Morozova, A.; Blanco, J. J.; Ribeiro, P.
Abstract: The study is based on the analysis of locally measured parameters at the mid-latitude region (Iberian Peninsula). The Principal Component Analysis (PCA) of meteorological parameters (air temperature T and geopotential heights gph) at different pressure levels in troposphere and tropopause regions was used to extract components which strongly resemble variations of the cosmic rays (CR, neutron monitor data) and geomagnetic field (Dst index and locally measure horizontal component of geomagnetic field, COI H). The results of the analysis allowed to make two main conclusions.

Firstly, on the time scale of weeks-to-months, the pressure corrected neutron monitor data show variations that correlate with atmospheric conditions in the upper troposphere-tropopause-lower stratosphere - the region where most of the ground level measured neutrons are generated by interacting CR with atmospheric atoms. This co-variability can be explained assuming that the ground neutron monitor data corrected for pressure and efficiency using a standard procedure are not completely free from the atmospheric effect. The principal component analysis of the seasonal trends of the T and the gph series allows to extract not only variations related to the seasonal annual cycle (1st mode explaining 93-97% of the seasonal trends variations), but also modes which anti-correlate with the seasonal trend of the CR series (2nd and the 3rd modes explaining 3-5% of the seasonal trend variability). The obtained co-varying modes have the following features:
•they are located in the upper troposphere-tropopause and such co-variability is not seen near the ground;
• the data are obtained in mid-latitudes (no effect from the relativistic electron precipitations is expected);
•the sign of the correlation correspond to one that is expected for atmospheric effect on the secondary particle production (Alpin et al. 2005).
Therefore, we might conclude that this co-variability results rather from a part of the atmospheric effect on the CR particles flux that cannot be corrected using the standard procedure, and reflects the dynamics of the upper troposphere-tropopause-lower stratosphere region.
Secondly, the short-term (with characteristic period from days to weeks) variations of the atmospheric parameters (obtained as differences between the original data and their seasonal trends, dsT and dsgph) show similarities with the variations of the geomagnetic field (similarly defined, dsDst and dsCOI H). These variations can be observed at most of the tropospheric pressure levels, but are more intense in the upper troposphere. No significant correlation was found between these short-term atmospheric modes and dsCR flux changes. To our mind, these variations result from ionospheric disturbances and ionosphere-stratosphere interactions. The 1st PCA mode (68-90% of the detrended series variations) co-varies relatively well with the geomagnetic activity parameters. The time intervals of the warmer lower troposphere with increased height of the pressure levels coincide with the epochs of the decreases (geomagnetic disturbances) of the dsDst and dsCOI H series. On contrary, the epochs of the increased dsDst and dsCOI H series coincide with periods of the colder lower troposphere with decreased pressure levels heights. The temperature of the upper tropopause changes in the opposite directions. The amplitude of these dsT and dsgph variations is higher during late autumn-winter and spring seasons. These similarities (as well as localization of these modes in the upper troposphere-tropopause region) allowed us to propose the following hypothesis:
1. The variations of the detrended series of the atmospheric and geomagnetic parameters are related or have a similar origin;
2. These relations are more prominent during the cold season (from autumn to spring);
3. These relations are more intense during the equinox periods and are probably due to higher level of the geomagnetic activity;
4. These variations appear to be not related to the cosmic ray particles effect seen in the upper atmosphere;
5. These co-variations can be a result of the electric field variations or of coupling between the stratospheric air masses at the high and middle latitudes, or even of their conjunction effect (this hypothesis needs to be tested thoroughly);
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