Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmgc11a0687c&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #GC11A-0687
Astronomy and Astrophysics
Astrophysics
[1616] Global Change / Climate Variability, [1650] Global Change / Solar Variability, [3305] Atmospheric Processes / Climate Change And Variability, [7536] Solar Physics, Astrophysics, And Astronomy / Solar Activity Cycle
Scientific paper
In a recent series of papers (refs), we have analyzed daily land-based temperature series (maximum, minimum, mean, differences between maximum and minimum) from tens of meteorological stations in several regions (Europe, USA, Australia). We select stations with long (100 to 300 years), homogeneous series with almost no gap. The long-term (decadal to centennial) evolution of temperature disturbances (which display characteristic times from several days to 1-2 weeks) reveals a clear solar signature: the trend consists of a small number of quasi-linear segments separated by rather sharp changes in slope. The secular trend of disturbances rises from 1900 to 1950, decreases from 1950 to 1975 and then increases again, decreasing in the most recent decade. This trend is the same as that found for a number of solar indices. Our investigations reveal high heterogeneity and seasonality of the climate system and underlines regional and seasonal variations in the observed solar signature. We compare short-term autocorrelation properties of temperature disturbances for different seasons at decadal timescales. The solar signature appears to be significantly stronger in Winter and in the late Fall seasons. Intensities of disturbances may vary by a factor in excess of 2. We have performed a special analysis of tens of station data from two 2.5°x2.5° areas of the US North Pacific: again we find that the long term evolution of temperature disturbances from 1945 to 2008 closely follows that of solar activity, with a large (30%) modulation compared to corresponding changes in solar irradiance. In another study, we have analyzed the longest (up to 300 years) series from 3 European stations. We have partitioned daily temperatures and their differences in two subsets as a function of high vs low solar activity. We follow a pattern recognition approach and demonstrate, using the two-sample Kolmogorov-Smirnov statistics, that the separation is statistically significant and robust. Differences between the annual changes for the two classes are large (1°C). In all of these studies, significant solar forcing is present and may be a rather general feature. We speculate over possible mechanisms and the role of teleconnections (and for instance tropical influence) on the temperature disturbances of the regions we have studied. These may involve cloudiness, cosmic rays, solar activity, the EUV part of the solar flux, the downward ionosphere-earth current density,…). Further investigations that could improve our understanding of these sun-climate connections will be suggested. Refs: J.L. Le Mouël, V. Courtillot, E. Blanter and M. Shnirman, C.R.Geoscience, 340, 421-430, 2008, doi:10.1016/j.crte.2008.06.001 J.L. Le Mouël, E. Blanter, M. Shnirman and V. Courtillot, J. Atmos. Solar-Terr. Physics, 71, 1309-1321, 2009, doi:10.1016/j.jastp.2009.05.006 V. Courtillot, J.L. Le Mouël, E. Blanter, and M. Shnirman, J. Atmos. Solar-Terr. Physics, 71, 2009, in revision. J.L. Le Mouël, V. Kossobokov, and V. Courtillot, C.R.Geoscience, J. Atmos. Solar-Terr. Physics, 71, 2009, in revision.
Blanter Elena
Courtillot Vincent E.
Kossobokov Vladimir G.
Le Mouel J.
Shnirman Mikhail
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