Articles written in Journal of Earth System Science
Volume 119 Issue 2 April 2010 pp 201-209
We apply Fourier and wavelet analyses to the precipitation and sunspot numbers in the time series (1901–2000) over Australia (27°S, 133°E), Canada (60°N, 95°W), Ethiopia (8°N, 38°E), Greenland (72°N, 40°W), United Kingdom (54°N, 2°W), India (20°N, 77°E), Iceland (65°N, 18°W), Japan (36°N, 138°E), United States (38°N, 97°W), South Africa (29°S, 24°E) and Russia (60°N, 100°E). Correlation analyses were also performed to find any relation among precipitation, sunspot numbers, temperature, and cloud-cover at the same spatial and temporal scale. Further correlations were also performed between precipitation with electron and proton fluence at the time interval, 1987–2006. All these parameters were considered in annual and seasonal scales. Though correlation study between precipitation and other parameters do not hint any linear relation, still the Fourier and wavelet analyses give an idea of common periodicities. The 9–11 year periodicity of sunspot numbers calculated by Fourier transform is also confirmed by wavelet transform in annual scale. Similarly, wavelet analysis for precipitation also supports the short periods at 2–5 years which is verified by Fourier transform in discontinuous time over different geographic regions.
Volume 126 Issue 2 March 2017 Article ID 0019
Sudden stratospheric warming (SSW) events are identified to investigate their influence on the equatorial tropospheric climate. Composite analysis of warming events from Era-Interim (1979–2013) record a cooling of the tropical lower stratosphere with corresponding changes in the mean meridional stratosphericcirculation. A cooling of the upper troposphere induces enhanced convective activity near the equatorial region of the Southern Hemisphere and suppressed convective activity in the off-equatorial Northern Hemisphere. After selecting vortex splits, the see-saw pattern of convective activity in the tropospheregrows prominent and robust.
Volume 127 Issue 5 July 2018 Article ID 0068
Residual mean circulation changes during the evolution of sudden stratospheric warming (SSW) are investigated by composite analyses of 76 major warming events identified in a present day simulation performed with a coupled ocean–troposphere–stratosphere model from 299 winters. Their dynamical signatures are compared with the 17 SSW events identified from 35 years of Era-Interim data. The main difference is that, relative frequency of simulated SSW events is smaller than that obtained from reanalysis. SSW events are classified as displacement or split events based on the geopotential field values at 10 hPa. The geopotential field values identify 10 and 3 split events in simulation and observationrespectively. The model quite accurately simulates some of the dynamical features associated with the major SSW. Residual mean circulation induced by EP-flux divergence, sum of advection and residual forcing are stronger in split events than in displacement type SSW has been confirmed by both simulation and observation. Moreover, the contribution of EP-flux divergence or planetary wave forcing is larger than the contribution of other types of forcing.