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1. Propane Dehydrogenation to Propylene on Ni and Ni-Sn Catalysts

   Jason P. Robbins, Lotanna Ezeonu (June 2022, North American Catalysis Society Meeting (NAM-27) Conference in New York, NY in 2022)

   Jason P. Robbins, Lotanna Ezeonu, Ziyu Tang, Xiaofang Yang, Bruce E. Koel, Simon G. Podkolzin, "Propane Dehydrogenation to Propylene on Ni and Ni-Sn Catalysts", North American Catalysis Society Meeting (NAM-27) Conference in New York, NY in 2022, Presentation number Wed-GRAM-1650, https://nam.confex.com/nam/2022/meetingapp.cgi/Paper/28324 

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2. Selective Oxidation of Ethanol over Zeolite-Supported Gold Catalysts

   Yiteng Zheng, Yue Qi (June 2022, North American Catalysis Society Meeting (NAM-27) Conference, New York, NY, 2022)

   Yiteng Zheng, Yue Qi, Junzhi Tan, Simon G. Podkolzin, Bruce E. Koel, "Selective Oxidation of Ethanol over Zeolite-Supported Gold Catalysts", North American Catalysis Society Meeting (NAM-27) Conference, New York, NY, 2022, Presentation number Wed-P-94. https://nam.confex.com/nam/2022/meetingapp.cgi/Paper/29726 

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3. California margin temperatures modulate regional circulation and extreme summer precipitation in the desert Southwest

   https://doi.org/10.1088/1748-9326/acfd43  

   Bhattacharya, Tripti; Feng, Ran; Maupin, Christopher R.; Coats, Sloan; Brennan, Peter R.; Carter, Elizabeth (October 2023, Environmental Research Letters)

   Abstract In August 2022, Death Valley, the driest place in North America, experienced record flooding from summertime rainfall associated with the North American monsoon (NAM). Given the socioeconomic cost of these type of events, there is a dire need to understand their drivers and future statistics. Existing theory predicts that increases in the intensity of precipitation is a robust response to anthropogenic warming. Paleoclimatic evidence suggests that northeast Pacific (NEP) sea surface temperature (SST) variability could further intensify summertime NAM rainfall over the desert southwest. Drawing on this paleoclimatic evidence, we use historical observations and reanalyzes to test the hypothesis that warm SSTs on the southern California margin are linked to more frequent extreme precipitation events in the NAM domain. We find that summers with above-average coastal SSTs are more favorable to moist convection in the northern edge of the NAM domain (southern California, Arizona, New Mexico, and the southern Great Basin). This is because warmer SSTs drive circulation changes that increase moisture flux into the desert southwest, driving more frequent precipitation extremes and increases in seasonal rainfall totals. These results, which are robust across observational products, establish a linkage between marine and terrestrial extremes, since summers with anomalously warm SSTs on the California margin have been linked to seasonal or multi-year NEP marine heatwaves. However, current generation earth system models (ESMs) struggle to reproduce the observed relationship between coastal SSTs and NAM precipitation. Across models, there is a strong negative relationship between the magnitude of an ESM’s warm SST bias on the California margin and its skill at reproducing the correlation with desert southwest rainfall. Given persistent NEP SST biases in ESMs, our results suggest that efforts to improve representation of climatological SSTs are crucial for accurately predicting future changes in hydroclimate extremes in the desert southwest. 

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4. High Latitude Modulation of the Holocene North American Monsoon

   https://doi.org/10.1029/2022GL099772  

   Routson, Cody C.; Erb, Michael P.; McKay, Nicholas P. (August 2022, Geophysical Research Letters)

   Abstract The North American monsoon (NAM) is an important source of rainfall to much of Mexico and southwestern United States. Westerly winds (westerlies) can suppress monsoon circulation and impact monsoon timing, intensity, and extent. Recent Arctic warming is reducing the temperature gradient between the equator and the pole, which could weaken the westerlies; however, the implications of these changes on the NAM are uncertain. Here we present a new composite index of the Holocene NAM. We find monsoon strength reached a maximum circa 7,000 years ago and has weakened since then. Proxy observations of temperature, hydroclimate and upwelling, along with model simulations, show that the NAM was modulated by the westerlies over the Holocene. If the observed Holocene pattern holds for current warming, a weaker meridional temperature gradient and weaker westerlies could lead to a stronger future NAM. 

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5. Impact of the Polar Vortex on Sub‐Seasonal O/N ₂ Variability in the Lower Thermosphere Using GOLD and WACCM‐X

   https://doi.org/10.1029/2024JA032724  

   Martinez, Benjamin_C; Lu, Xian; Pedatella, Nicholas_M; Wu, Haonan; Oberheide, Jens (June 2024, Journal of Geophysical Research: Space Physics)

   Abstract We provide observational evidence that the stability of the stratospheric Polar vortex (PV) is a significant driver of sub‐seasonal variability in the thermosphere during geomagnetically quiet times when the PV is anomalously strong or weak. We find strong positive correlations between the Northern Annular Mode (NAM) index and subseasonal (10–90 days) Global Observations of the Limb and Disk (GOLD) O/N₂perturbations at low to mid‐northern latitudes, with a largest value of +0.55 at ∼30.0°N when anomalously strong or weak (NAM >2.5 or < −2.1) vortex times are considered. Strong agreement for O/N₂variability and O/N₂‐NAM correlations is found between GOLD observations and the Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension (WACCM‐X) simulations, which is then used to delineate the global distribution of O/N₂‐NAM correlations. We find negative correlations between subseasonal variability in WACCM‐X O/N₂and NAM at high northern and southern latitudes (as large as −0.54 at ∼60.0°S during anomalous vortex times). These correlations suggest that PV driven upwelling at low latitudes is accompanied by corresponding downwelling at high latitudes in the lower thermosphere (∼80–120 km), which is confirmed using calculations of residual mean meridional circulation from WACCM‐X. 

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