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Stefan Metzger, Edward Ayres, David Durden, Christopher Florian, Robert Lee, Claire Lunch, Hongyan Luo, Natchaya Pingintha-Durden, Joshua A. Roberti, Michael SanClements, Cove Sturtevant, Ke Xu, and Rommel C. Zulueta

4 . In short, gaseous-phase stable carbon and water isotopes are measured along the tower vertical profile. Wet deposition sampling occurs at the tower top across 37 TIS sites, which were selected to represent a range of concentrations of nitrate, ammonium, and sulfate. Analysis occurs at the Illinois State Water Survey laboratory at the University of Illinois, which handles the analysis of other atmospheric deposition sampling programs. Stable isotopes in wet deposition are also sampled and

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A. Henderson-Sellers, H. Zhang, G. Berz, K. Emanuel, W. Gray, C. Landsea, G. Holland, J. Lighthill, S-L. Shieh, P. Webster, and K. McGuffie

The very limited instrumental record makes extensive analyses of the natural variability of global tropical cyclone activities difficult in most of the tropical cyclone basins. However, in the two regions where reasonably reliable records exist (the North Atlantic and the western North Pacific), substantial multidecadal variability (particularly for intense Atlantic hurricanes) is found, but there is no clear evidence of long-term trends. Efforts have been initiated to use geological and geomorphological records and analysis of oxygen isotope ratios in rainfall recorded in cave stalactites to establish a paleoclimate of tropical cyclones, but these have not yet produced definitive results. Recent thermodynamical estimation of the maximum potential intensities (MPI) of tropical cyclones shows good agreement with observations.

Although there are some uncertainties in these MPI approaches, such as their sensitivity to variations in parameters and failure to include some potentially important interactions such as ocean spray feedbacks, the response of upper-oceanic thermal structure, and eye and eyewall dynamics, they do appear to be an objective tool with which to predict present and future maxima of tropical cyclone intensity. Recent studies indicate the MPI of cyclones will remain the same or undergo a modest increase of up to 10%–20%. These predicted changes are small compared with the observed natural variations and fall within the uncertainty range in current studies. Furthermore, the known omissions (ocean spray, momentum restriction, and possibly also surface to 300-hPa lapse rate changes) could all operate to mitigate the predicted intensification.

A strong caveat must be placed on analysis of results from current GCM simulations of the “tropical-cyclone-like” vortices. Their realism, and hence prediction skill (and also that of “embedded” mesoscale models), is greatly limited by the coarse resolution of current GCMs and the failure to capture environmental factors that govern cyclone intensity. Little, therefore, can be said about the potential changes of the distribution of intensities as opposed to maximum achievable intensity. Current knowledge and available techniques are too rudimentary for quantitative indications of potential changes in tropical cyclone frequency.

The broad geographic regions of cyclogenesis and therefore also the regions affected by tropical cyclones are not expected to change significantly. It is emphasized that the popular belief that the region of cyclogenesis will expand with the 26°C SST isotherm is a fallacy. The very modest available evidence points to an expectation of little or no change in global frequency. Regional and local frequencies could change substantially in either direction, because of the dependence of cyclone genesis and track on other phenomena (e.g., ENSO) that are not yet predictable. Greatly improved skills from coupled global ocean–atmosphere models are required before improved predictions are possible.

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C. Venkataraman, M. Bhushan, S. Dey, D. Ganguly, T. Gupta, G. Habib, A. Kesarkar, H. Phuleria, and R. Sunder Raman

, for example, levoglucosan, hopanes, and diacholastane; carbon isotope analysis; and key constituents of secondary organic aerosol and brown carbon. F ig . 4. Schematic of ambient measurements, chemical speciation, and receptor modeling for source apportionment. These measurements will permit the application of standard PMF analysis as well as the multilinear engine-2 (ME-2) algorithm and rolling PMF analysis to thermally fractionated carbonaceous aerosol together with molecular markers, carbon

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Anita Drumond, Milica Stojanovic, Raquel Nieto, Sergio Martin Vicente-Serrano, and Luis Gimeno

analyzed the contribution of moisture sources and moisture transport processes to trigger drought episodes in depth at the global scale. The variations in moisture transport are usually related to a precipitation deficit over an area and, in some cases, to the drought occurrence ( Liu et al. 2017 ). Gimeno et al. (2012) provided a detailed review and comparison of the different techniques applied in the investigation of sources of moisture, including isotopes analysis, box models, and numerical water

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Xuhui Lee, Shoudong Liu, Wei Xiao, Wei Wang, Zhiqiu Gao, Chang Cao, Cheng Hu, Zhenghua Hu, Shuanghe Shen, Yongwei Wang, Xuefa Wen, Qitao Xiao, Jiaping Xu, Jinbiao Yang, and Mi Zhang

are configured in gradient mode, switching every 30–60 s between air samples drawn from the heights of 1.1 and 3.5 m above the water surface. The fluxes of H 2 O, CO 2 , and CH 4 and the isotopic compositions of lake evaporation are determined with the gradient-diffusion method. Water samples are collected daily at midday from the 20-cm depth for analysis of pH, D, and 18 O isotopic compositions and dissolved CO 2 , CH 4 , and N 2 O concentrations. Water chemical parameters (pH, turbidity

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Gretchen L. Mullendore, Mary C. Barth, Petra M. Klein, and James H. Crawford

ratios can provide a sort of chemical clock for understanding the balance between chemistry and mixing as air is transported from source regions. The isotopic constituents, Be-7 and Pb-210, have specific source regions with Be-7 originating from cosmic ray activity in the stratosphere and Pb-210 from the rapid decay of terrestrial emission of Rn-222. While they have long half-lives, they are also subject to wet removal, thus their distributions provide valuable constraints on transport between the

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B. Wolf, C. Chwala, B. Fersch, J. Garvelmann, W. Junkermann, M. J. Zeeman, A. Angerer, B. Adler, C. Beck, C. Brosy, P. Brugger, S. Emeis, M. Dannenmann, F. De Roo, E. Diaz-Pines, E. Haas, M. Hagen, I. Hajnsek, J. Jacobeit, T. Jagdhuber, N. Kalthoff, R. Kiese, H. Kunstmann, O. Kosak, R. Krieg, C. Malchow, M. Mauder, R. Merz, C. Notarnicola, A. Philipp, W. Reif, S. Reineke, T. Rödiger, N. Ruehr, K. Schäfer, M. Schrön, A. Senatore, H. Shupe, I. Völksch, C. Wanninger, S. Zacharias, and H. P. Schmid

important mechanism in the study area. So, not surprisingly, hydrochemical analysis and groundwater-level measurements indicate the existence of exchanges between groundwater and surface water (not shown here). However, the detailed mechanisms of runoff generation and storage system interactions are not satisfyingly understood in this region. To explore the runoff-generation dynamics and the connections of stream water to the local aquifer system, the water isotopic composition was analyzed during the

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Paquita Zuidema, Claudia Alvarez, Samantha J. Kramer, Lillian Custals, Miguel Izaguirre, Peter Sealy, Joseph M. Prospero, and Edmund Blades

concentrations shown within Figs. 1 – 3 . The rare long-term surface time series of dust data open up other research opportunities as well. Examples include isotopic analysis that allow for the geochemical fingerprinting of dust emission sources ( Pourmand et al. 2014 ). Soluble ions, extracted from the filters, can provide indications of the mixing of anthropogenic pollution with the African dust (e.g., Savoie et al. 1989 ) that is also useful for understanding cloud-dust interactions after long

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I. A. Renfrew, R. S. Pickart, K. Våge, G. W. K. Moore, T. J. Bracegirdle, A. D. Elvidge, E. Jeansson, T. Lachlan-Cope, L. T. McRaven, L. Papritz, J. Reuder, H. Sodemann, A. Terpstra, S. Waterman, H. Valdimarsson, A. Weiss, M. Almansi, F. Bahr, A. Brakstad, C. Barrell, J. K. Brooke, B. J. Brooks, I. M. Brooks, M. E. Brooks, E. M. Bruvik, C. Duscha, I. Fer, H. M. Golid, M. Hallerstig, I. Hessevik, J. Huang, L. Houghton, S. Jónsson, M. Jonassen, K. Jackson, K. Kvalsund, E. W. Kolstad, K. Konstali, J. Kristiansen, R. Ladkin, P. Lin, A. Macrander, A. Mitchell, H. Olafsson, A. Pacini, C. Payne, B. Palmason, M. D. Pérez-Hernández, A. K. Peterson, G. N. Petersen, M. N. Pisareva, J. O. Pope, A. Seidl, S. Semper, D. Sergeev, S. Skjelsvik, H. Søiland, D. Smith, M. A. Spall, T. Spengler, A. Touzeau, G. Tupper, Y. Weng, K. D. Williams, X. Yang, and S. Zhou

air parcels. We sampled the isotope composition of water vapor continuously during leg II of the cruise using a Picarro L2140i with a heated inlet system. In addition, we performed isotope analysis of precipitation samples, of water column samples from the CTD rosette, and on 10 of the research flights. A precipitation sampling program along transects near Akureyri, in northern Iceland, further supplemented the IGP water isotope sampling and will provide unique insight into the water turnover, in

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Hann-Ming Henry Juang, Shyh-Chin Chen, Songyou Hong, Hideki Kanamaru, Thomas Reichler, Takeshi Enomoto, Dian Putrasahan, Bruce T. Anderson, Sasha Gershunov, Haiqin Li, Kei Yoshimura, Nikolaus Buenning, and Diane Boomer

both direct flux anomalies and indirectly through changes in the stability of the overlying atmosphere, which in turn affects the wind speeds and thus latent heat flux. SEASONAL PREDICTION. Haiqin Li (The Florida State University) presented an analysis of the two-tiered Florida Climate Institute–Florida State University Seasonal Hindcast at 50 km (FISH50). Six ensemble members for each of the seasonal hindcasts were run for a 6-month period. FISH50 was initialized at two different times of the year

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