A comparison of the Hadley circulation in modern reanalyses

Abstract

Previous studies using reanalysis data suggest an intensification and poleward expansion of the tropical Hadley circulation (HC) throughout the twentieth century, yet the HC climatology and trends remain undocumented for many of the newest reanalyses. An intercomparison of eight reanalyses is presented to better elucidate the mean state variability and trends concerning HC intensity and width. Significant variability between reanalyses was found in the mean HC intensity with less variability in HC width. Certain reanalyses (e.g., ERA40 and the Climate Forecast System Reanalysis) tend to produce stronger meridional overturning, while others (National Centers for Environmental Prediction–National Center for Atmospheric Research and Modern‐Era Retrospective‐Analysis for Research and Applications) are constantly weaker. The NOAA–Cooperative Institute for Research in Environmental Sciences Twentieth Century Reanalysis best matched the ensemble averages with the exception of a poleward shift in the subtropical terminus. Ensemble trends regarding HC intensity and width are broadly consistent with previous work, indicating a 0.40 (0.07) × 1010 kg s−1 decade−1 intensification in the northern (southern) cell and a 1.1° decade−1 widening in the past 30 years, although some uncertainty remains regarding the intensity of the southern cell. Longer‐term ensemble trends (i.e., 1958–2008) containing fewer ensemble members suggest a weaker northern cell intensification but stronger southern cell intensification and a more modest widening of the HC (i.e., 0.53° decade−1) compared to the last 30 years. Separation of the seasonally averaged stream function magnitudes by the El Niño–Southern Oscillation (ENSO) phase revealed a weak clustering and statistically significant strengthening of the mean circulation for El Niño compared to ENSO neutral and La Niña events for the winter cell with little difference in the summer cell intensity.

Atmospheric circulation features in the ACCESS model simulations for CMIP5: historical simulation and future projections

“…3(b)). This is consistent with the findings of Stachnik and Schumacher (2011), who discussed the differences in the Hadley cell strength, expansion and trend in a number of reanalyses, including ERA-Interim and CFSR. The model simulations show mixed results: in coupled simulations (Fig.…”

Changes in the width of the tropical belt due to simple radiative forcing changes in the GeoMIP simulations

“…Tropical expansion estimates based on reanalyses, however, may suffer from spurious trends and discontinuities in basic meteorological fields (Trenberth et al, 2001;Bengtsson et al, 2004). The rate of Hadley cell expansion and even the mean strength of the Hadley cells vary among the reanalyses (Stachnik and Schumacher, 2011), which could indicate that the meridional winds are not well constrained. There is also significant uncertainty in the observed rate of tropical expansion because it is highly variable for different metrics and data products (Birner, 2010;Davis and Rosenlof, 2012;Davis and Birner, 2013;Lucas et al, 2014).…”

“…An expansion of the Hadley cells has been detected in reanalyses (Hu and Fu, 2007;Johanson and Fu, 2009;Stachnik and Schumacher, 2011;Davis and Rosenlof, 2012;Davis and Birner, 2013;Nguyen et al, 2013;Chen et al, 2014). Tropical expansion estimates based on reanalyses, however, may suffer from spurious trends and discontinuities in basic meteorological fields (Trenberth et al, 2001;Bengtsson et al, 2004).…”

Tropical atmospheric circulation response to the G1 sunshade geoengineering radiative forcing experiment

“…151 We used the following variables from 8 climate models and reanalysis data (Table 152 1): sea level pressure (SLP), sea surface temperature (SST), zonal wind (U), 153 meridional wind (V) Sea level pressure and sea surface temperature interpolated onto 154 a regular 1°× 1°grid. The zonal and meridional wind are regridded onto a common 155 horizontal fixed grid of 2.5°× 2.5°as in many preceding studies (Bayr et al, 2014;Ma 156 and Zhou, 2016; Stachnik and Schumacher, 2011). All the data we used are 157 monthly-mean model output.…”