Arctic and Antarctic four-month oscillations detected from Advanced Microwave Sounding Unit-A measurements

• Published in: Antarctic Science
• Main Authors: Qin, Z., Zou, X., Weng, F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2012
• Subjects: Geology; Ecology, Evolution, Behavior and Systematics; Oceanography; Arctic; Antarctic; The Antarctic; Antarc*; Antarctic Science; Sea ice
• Online Access: http://dx.doi.org/10.1017/s0954102012000417; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102012000417

Abstract Satellite microwave measurements can penetrate through clouds and therefore provide unique information of surface and near-surface temperatures and surface emissivity. In this study, the brightness temperatures from NOAA-15 Advanced Microwave Sounding Unit-A (AMSU-A) are used to analyse the surface temperature variation in the Arctic and Antarctic regions during the past 13 years from 1998–2010. The data from four AMSU-A channels sensitive to surface are analysed with wavelet and Fourier spectrum techniques. A very pronounced maximum is noticed in the period range centred around four months. Application of a statistical significance test confirms that it is a dominant mode of variability over polar regions besides the annual and semi-annual oscillations in the data. No evidence of this feature could be found in middle and low latitudes. The four-month oscillation is 90° out of phase at the Arctic and Antarctic, with the Arctic four-month oscillation reaching its maximum in the beginning of March, July and November and the Antarctic four-month oscillation in the middle of April, August and December. The intensity of the four-month oscillation varies interannually. The years with pronounced four-month oscillation were 2002–03, 2005–06 and 2008–09. The strongest year for the Arctic and Antarctic four-month oscillations occurred in 2005–06 and 2008–09, respectively. The sign of four-month oscillation is also found in the surface skin temperatures and two-metre air temperatures from ERA-Interim reanalysis, with strongest signal in 2005–06 when this oscillation is strongest in the data. It is hypothesized that the Arctic and Antarctic four-month oscillations are a combined result of unique features of solar radiative forcing and snow/sea ice formation and metamorphosis.