Observation of ENSO linked changes in the tropical Atlantic cloud vertical distribution using 14 years of MODIS observations

Nils Madenach, Cintia Carbajal Henken, René Preusker, Odran Sourdeval, Jürgen Fischer
2019 Atmospheric Chemistry and Physics Discussions  
<p><strong>Abstract.</strong> 14 years (September 2002 to September 2016) of Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) monthly mean cloud data is analyzed to identify possible changes of the cloud vertical distribution over the Tropical Atlantic Ocean (TAO). For the analysis multiple linear regression techniques are used.</p> <p>Within the investigated period, no significant trend in the domain-averaged cloud vertical distribution was found. In terms of linear changes, two
more » ... phases (before and after November 2011) in the time-series of the TAO domain-average Cloud Top Height (CTH) and High Cloud Fraction (HCF) can be distinguished. While phase 1 is dominated by a significant linear increase, phase 2 is characterized by a strong, significant linear decrease. The observed trends were mainly caused by the El Niño Southern Oscillation (ENSO). The increase in CTH and HCF in phase 1, was attributed to the transition from El Niño (2002) to La Niña (2011) conditions. The strong decrease in phase 2, was caused by the opposite transition from a La Niña (2011) to a major El Niño event (2016).</p> <p>A comparison with the large scale vertical motion <i>ω</i> at 500 hPa obtained from ERA-Interim ECMWF Re-Analyses and the Nino3.4-Index indicates that the changes in HCF are induced by ENSO linked changes in the large scale vertical upward movements over regions with strong large scale ascent. A first comparison with the DARDAR data set, which combines CloudSat radar and CALIPSO lidar measurements, shows qualitatively good agreements for the interannual variability of the high cloud amount and its linear decrease in phase 2.</p>
doi:10.5194/acp-2018-1136 fatcat:ty4234i6kvchjkzu4hwweemvpa