On the scaling effect in global surface air temperature anomalies

摘要

The annual and the monthly mean values of the land-surfaceair temperature anomalies from 1880–2011, over both hemispheres, are usedto investigate the existence of long-range correlations in their temporalevolution. The analytical tool employed is the detrended fluctuationanalysis, which eliminates the noise of the non-stationarities thatcharacterize the land-surface air temperature anomalies in both hemispheres.The reliability of the results obtained from this tool (e.g., power-lawscaling) is investigated, especially for large scales, by using error boundsstatistics, the autocorrelation function (e.g., rejection of its exponentialdecay) and the method of local slopes (e.g., their constancy in a sufficientrange). The main finding is that deviations of one sign of the land-surfaceair temperature anomalies in both hemispheres are generally followed bydeviations with the same sign at different time intervals. In other words,the land-surface air temperature anomalies exhibit persistent behaviour,i.e., deviations tend to keep the same sign. Taking into account our earlierstudy, according to which the land and sea surface temperature anomaliesexhibit scaling behaviour in the Northern and Southern Hemisphere, weconclude that the difference between the scaling exponents mainly stems fromthe sea surface temperature, which exhibits a stronger memory in theSouthern than in the Northern Hemisphere. Moreover, the variability of thescaling exponents of the annual mean values of the land-surface airtemperature anomalies versus latitude shows an increasing trend from the lowlatitudes to polar regions, starting from the classical random walk (whitenoise) over the tropics. There is a gradual increase of the scaling exponentfrom low to high latitudes (which is stronger over the Southern Hemisphere).