Regional Intensification of the Tropical Hydrological Cycle During ENSO

Abstract

This study provides observational evidence for feedbacks that amplify the short-term hydrological response associated with the warm phase of the El Niño-Southern Oscillation. Our analyses make use of a comprehensive set of independent satellite observations collected over decades to show that much larger local changes to cloud (~50%/K) and precipitation (~60%/K) occur than would be expected from the guidance of Clausius-Clapeyron theory (~7%/K). This amplification comes from atmospheric feedbacks involving shifts in the patterns of latent and radiative heating that mutually act on the dynamics enhancing changes to the hydrological cycle. We also confirm the existence of an opposing negative flux feedback at the ocean surface, driven largely by solar radiation changes, that opposes the surface warming. Estimates of the strength of this and other feedback factors associated with warming in the Niño3 region are provided from observations. These observations are also used to examine comparative processes and feedbacks in model experiments from the Coupled Model Intercomparison Project Phase 5 Atmospheric Model Intercomparison Project.Plain Language Summary It is a widely held paradigm of a warming world the "wet gets wetter and dry drier." It is also argued that in this context precipitation in wet areas is expected to increase at a rate of approximately 7%/K, which is in accordance with expected increases in water vapor availability from elementary theory (the so-called Clausius-Clapeyron response). One of the main wet regions of the planet is the region of deep tropical convection organized into broad convective zones referred to as the Inter-Tropical Convergence Zone, and this region undergoes variability that is often used to test ideas thought to be relevant to climate change. Our study pieces together several independent measurements collected over multiple decades to reveal a strong, positive feedback on tropical convection associated with the short-term climate variations of the El Niño/Southern Oscillation. The feedback is a result of coupled dynamical-radiative processes that combine to produce intensification of the tropical hydrological cycle that is more than twice that expected from the CC response alone.

From Point to Area: Worldwide Assessment of the Representativeness of Monthly Surface Solar Radiation Records

“…For the ENSO region, we also find teleconnections, meaning that there are high correlations with positive and negative signs throughout the region as is exemplarily shown in Figure (note that we show correlation coefficients [r] and not squared ones [ R 2 ] as used for the calculation of δ ). The finding of positive and negative correlations of SSR in the ENSO region is in line with previous studies that focused on the impact of ENSO on SSR (e.g., Pavlakis et al, ; Pinker et al, ; Stephens et al, ). As these studies either used modeled SSR, satellite‐derived SSR estimates with coarse resolution, or SSR from reanalysis, our finding can be counted as additional evidence based on high‐resolution satellite data for the strong influence of ENSO on SSR.…”

Ice cloud microphysical trends observed by the Atmospheric Infrared Sounder

“…The well-documented (Wylie et al, 2005;King et al, 2013;Stubenrauch et al, 2013) spatial distributions of ice clouds with maxima in the tropics and extratropical storm tracks and minima in the subtropical gyres are shown in Fig. 1.…”

“…Secular changes in the joint histograms themselves, and, furthermore, changes in the frequency of occurrence within the joint histogram bins, must be quantified to deduce if trends or variability in CWV, rain occurrence, surface wind speed, and other relevant geophysical parameters such as low-level convergence (e.g. Stephens et al, 2018) could explain in part or whole secular trends in r ei .…”

“…Stubenrauch et al, 2013). Climate GCM simulations of the radiative response of high clouds have a large inter-model spread (e.g.…”

Preface to stable isotopes in hydrological studies in the tropics: Ecohydrological perspectives in a changing climate

“…Their study highlights the shifting of the intertropical convergence zone and the South Pacific convergence zone, which establish a major change in the spatial distribution of rainfall anomalies. Across the tropics, the impact of ENSO is largely associated with changes in rainfall anomalies (Stephens et al, 2018) and the consequent development of drought and wetter than normal conditions depending on the region and the phase of ENSO; with an identified opposite effect of ENSO on rainfall over land and ocean (Neelin, Chou, & Su, 2003). In the maritime continent, ENSO has been found to FIGURE 1 Literature search of published studies (ISI Web of Science) combining the keywords "isotopes" and "Europe"/"North America"/"Tropics" from 2000 to 2018 leverage air-sea interactions and generate a remotely driven wind forcing, which can lead to a local feedback mechanism between the winds and the SST anomalies, resulting in the development of a dry season (Hendon, 2003).…”