Harmonic analysis of climatological temperature over Antarctica: present day and greenhouse warming perspectives

Abstract

ABSTRACT:On the basis of ERA40 and NCEP/NCAR Reanalysis (NNR) and simulations from CCCma, CCSM, CSIRO, HadCM3, MIROC-MEDRES and GFDL, which support the Intergovernmental Panel on Climate Change (IPCC) 4th Assessment Report (AR4), we demonstrated that the amplitude of the annual and the semi-annual harmonics delivered by the ERA40 and NNR is dominated by distinct seasonal variability. The maximum first harmonic amplitude of near surface temperature 2-metre air temperature (t2m) according the NNR is located over the Plateau of East Antarctica, whereas analyses for ERA40 show maximum amplitude over the west Antarctic ice sheet. The spatial pattern of the first harmonic of t2m in NNR more closely corresponds to station observations, suggesting that the seasonal cycle of t2m over Antarctica may be biased in ERA-40. A comparison between the global climate models (GCMs) and NNR demonstrates that the models satisfactorily simulate the amplitude of the first and second harmonics; however, the modelling results differ among themselves in terms of the amplitude values. Larger seasonal variability is identified for CCCma, HadCM3 and MIROC-MEDRES with values as high as 20°C over the Antarctic plateau. We have further identified that the CSIRO GCM does not reproduce the seasonal amplitude of t2m as compared to other models, which is primarily due to its overestimation of the cloud cover and weak seasonal changes of precipitation. Calculations of the harmonic analysis based upon greenhouse warming (GW) conditions reveal that there is no substantial seasonal difference between the amplitude of the first harmonic as projected by GW and present day (PD) simulations over the Antarctic continent. Over the polar ocean, however, the amplitude of the first harmonic is reduced in all climate models under future conditions. In order to narrow down the uncertainties on future climate projections, analyses of the cloud forcing which include the short-and long-wave radiation and the surface mass balance (SMB) may provide substantial information on the cause of the discrepancies as simulated by climate models over the Antarctic region.

Climate change impacts on sugarcane attainable yield in southern Brazil

“…The results presented have been interpolated to a 0.5×0.5 degree grid by applying OACRES (Objective Analysis using the Cressman scheme (Cressman 1959) following the approach used by Justino et al (2011).…”

Influence of the Antarctic Oscillation, the Pacific–South American modes and the El Niño–Southern Oscillation on the Antarctic surface temperature and pressure variations

“…Although Bromwich & Fogt (2004) found a low level of skill in ERA-40 data before 1978, ERA-40 re-analysis data are also compared and validated (Uppala et al 2005). Justino et al (2010) found the seasonal cycle of the temperature 2 m above ground level over Antarctica may be biased in ERA-40. Yu et al (2010) also compared two re-analysis from 1979-2001 with observational data and found at the interannual timescale, atmospheric pressures at different height levels in ERA-40 are in better agreement with the observed pressure than that in the NCEP-NCAR re-analysis.…”

A modified seasonal cycle during MIS31 super-interglacial favors stronger interannual ENSO and monsoon variability

“…The first harmonic shows the dominance of the annual cycle when most of the variance is represented by this harmonic. It has to be stressed that investigations based upon area-averaged time series are embedded with small-and large-scale processes dictated by distinct periodicity; this in turn hampers the identification of periodic climatic signals in the spacetime domain (Justino et al, 2010(Justino et al, , 2016.…”