Research
My interests lie in understanding the impact of climate natural variability and change on the hydroclimate, with a particular emphasis on high-impact weather events (e.g., droughts, extreme precipitation) in monsoonal, mediterranean and semi-arid climates. In my research, I try to connect the large scale atmospheric circulation, for which we have a better theoretical comprehension and modeling abilities, to the continental/regional scale, which is the one relevant to take concrete actions to adapt to and mitigate the effects of global warming. I combine observations, statistical techniques, and comprehensive and idealized climate models. In the following are the main themes of my current research:
1. Dynamics and hydroclimate of North American Monsoon (NAM)
The North American monsoon (NAM) is one of the smallest-scale and least understood monsoons in the Earth’s atmosphere. While less impressive than its Asian counterpart, this circulation system brings abundant summer rains to vast areas of the North American Southwest, western Mexico and Central America, where it is also often associated with heavy rainfall and flooding. Thus, future changes in the NAM could have significant consequences for regional water resources, natural hazards (e.g., wildfires) and geopolitical crisis (e.g., climate refugees). My current research aims to understand (1) the fundamental dynamics of the monsoon (Pascale et al., 2017, Nat. Clim. Change; Fig. 1), (2) the small-large scale and tropical-extratropical interactions favoring NAM organized convection and extremes (Pascale and Bordoni, 2016, Month. Weat. Rev.) and (3) the effects of natural variability and anthropogenic forcing on the NAM (Pascale et al., 2018, J. Climate; Pascale et al., 2019, Curr. Clim. Change Rep.).
Fig. 1 Attribution of projected North American monsoon precipitation changes. North American monsoon area-averaged precipitation change attributed to each experiment: 2CO2 (red), +2K (green), 2CO2_+2K (blue), 2CO2_pattern (brown) and the coupled 2CO2 FLOR-FA simulations (yellow for ensemble member 1, orange for ensemble member 2). Error bars denote the 95% confidence interval.
References
- Pascale S., Carvalho L. M. V., Adams D. K., Castro C. L., Cavalcanti I. F. A. (2019), “Current and future variations of the monsoons of the Americas under climate change”, invited review for Curr. Clim. Chang. Rep., 5,124-144, https://doi.org/10.1007/s40641-019-00135-w [pdf].
- Pascale S., S.B. Kapnick, S. Bordoni, T.L. Delworth, (2018), The influence of CO2 forcing on the North American monsoon moisture surges, Journal of Climate, 31, 7949-7968 [pdf | online]
- Pascale S., W. R. Boos, S. Bordoni, T. L. Delworth, S. B. Kapnick, H. Murakami, G. A. Vecchi, W. Zhang, (2017), Weakening of the North American monsoon with global warming, Nature Climate Change ,7, 806-812 [ Official version ]
- Pascale S., S. Bordoni, S.B. Kapnick, G.A. Vecchi, L. Jia, T. L. Delworth, S. Underwood and W. Anderson (2016), The impact of horizontal resolution on North American monsoon Gulf of California moisture surges in a suite of high-resolution coupled models, Journal of Climate, 29, 7911-7936 [pdf | online]
- Pascale S., S. Bordoni (2016), Tropical and extratropical controls of Gulf of California surges and summertime precipitation over the southwestern United States, Monthly Weather Review, 144, 2695-2718 [pdf | online]
My talk at the 32nd Hurricane and Tropical Meteorology AMS conference, San Juan, Puerto Rico:
2. Physical drivers of high-impact weather events in Southern African and Mediterranean climates
Southern African (SA) climate is characterized by large inter-annual variability and recurrent droughts (e.g., the El Niño-related 2015/18 summer drought or the “Day Zero” Cape Town water crisis in 2015/17), which can severely impact rural communities dependent on rain-fed subsistence agriculture or densely populated metropolitan areas. SA droughts are influenced by remote forcings such as, e.g., El Niño-Southern Oscillation and extratropical planetary waves, large scale atmospheric circulation like the Hadley cell, and regional circulation features like, for example, the Angola Low. Yet, a detailed comprehension of the interactions of these different drivers remains elusive. For example, my recent work (Pascale et al., 2019b) on this topic explores the modulation of the El Niño teleconnection, typically leading to severe SA summer droughts, by the Angola Low variability, a summertime low pressure system that affects the convergence of low-level moisture fluxes into southern Africa, and the role of anthropogenic global warming in determining the ”Day Zero” Cape Town drought (Pascale et al., 2019).
Similarly, Mediterranean climatic zones (e.g., Mediterranean basin, California, southwestern SA, etc.) are also characterized by strong seasonality, frequent droughts and high-intensity rainfall events (e.g., the Mediterranean hurricanes, or Medicanes, Gonzalez-Aleman, Pascale S., et al., GRL, 2019). These regions are expected to face adverse impacts under global warming such as increases in precipitation extremes, heat waves and dry spells, and decreases in precipitation and river flows. Key questions I am addressing are related to quantifying and understanding the impact of climate change and natural variability on high-impact climate events such as droughts, heavy rainfall and Medicanes in the next decades.
References
- Pascale, S., Kapnick S.B., Delworth T.,Cooke. W. "Increasing risk of another Cape Town “Day Zero” drought in the twenty-first century", under review.
- Pascale S., Pohl B., Kapnick S.B., Zhang H., "On the Angola Low interannual variability and its role in modulating ENSO effects in southern African", J. Climate, 32, 4783-4803 [pdf].
- González-Alemán J. J., Pascale, S., Gutierrez-Fernandez J., Murakami H., Gaertner M. A. and Vecchi G.A., "Potential increase in hazard from Mediterranean hurricane activity with global warming", Geophys. Res. Lett., 46, 1754-1764, doi: 10.1029/2018GL081253 [pdf | online]
Past research
(a) Monsoons
Global circulation models in suggest that in a warming climate, monsoons will tend to intensify and delay their onset. As easy to imagine, the impact of such changes in rainfall seasonality on agriculture and ecosystems may be huge. I am interested in developing new diagnostics to quantify changes in monsoonal hydroclimatic regimes and understanding the fundamental dynamical and thermodynamical mechanisms responsible the monsoon response to climate change.
more on my research on monsoons
(b) Climatic entropy production and planetary atmospheres
Earth's and planetary atmospheres are a non-equilibrium forced dissipative system and may be interpreted as an irreversible thermal engine exchanging energy and entropy fluxes with the external environment. My work in this context has focused mainly on the Maximum Entropy Production conjecture and the conditions for habitability of earth-like planets experiencing extreme seasonal cycles.
more on climatic entropy production and planetary atmospheres