Climate Spectra and Stochastic Climate Models

Abstract

As the power spectra of extratropical atmospheric variables are essentially white on time scales between about 10 days and a few years, many climatic fluctuations can be understood as the response of the slow climate variables to stochastic forcing by the fast atmospheric fluxes (Hasselmann, 1976). The stochastic climate model explains the statistical properties of mid-latitude sea surface temperature anomalies on time scales of up to a few years, and has been applied to long term climate changes, quasi-geostrophic ocean fluctuations, sea ice variability, soil moisture fluctuations, and ocean circulation variability, providing a simple but powerful framework to investigate climate variability. After briefly describing the spectral characteristics of the atmospheric variables, the concept of the stochastic climate model is introduced in this chapter. Its application to climate variations is then illustrated in the context of the midlatitude sea surface temperature anomalies. The other applications are then briefly discussed.