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The Storm “Hazel”

Synoptic Resumé of Its Development as It Approached Southern Ontario

J. L. Knox
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M. A. Jenkins, W. C. Wong, K. Higuchi, and J. L. Knox

Abstract

This paper examines the 27-yr record of precipitation measurements at Ocean Weather Station “P” (50°N, 145°W). The credibility of the rainfall observations is assessed, and the testing of certain extraordinary features of the fall and winter seasonal precipitation time series is outlined. Using the portion of the record established to be close to “ground truth” (1954–1967), the authors have statistically related present weather observations to seasonal precipitation amounts at Ocean Weather Station “P.” With this approach, the authors have reproduced the first half (1954–1967) and predicted the second half (1969–1980) of the precipitation time series to compare to observations. Precipitation is physically estimated by determining the vertical moisture convergence at Ocean Weather Station “P” and comparing the relative consistency of the moisture convergence time series to the contemporaneous seasonal rate of measured precipitation. The analysis suggests that the Ocean Weather Station “P” record of measured precipitation is a substantial improvement over previous estimates of precipitation in the northeast Pacific for the period between 1954 and 1967, but that the second half of the record, particularly during the early 1970s, remains questionable. Reliable rainfall estimates along with measurements for the 27-yr record are given to aid studies dealing with energy balance calculations and the verification of oceanic precipitation generated by global climate models.

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Emily L. Pauline, John A. Knox, Lynne Seymour, and Andrew J. Grundstein

Abstract

The occurrence of extreme weather and climate events has increased in recent decades. This increasing frequency has adversely impacted economic and health outcomes, leading to an increasingly urgent need to study climate extremes. The National Centers for Environmental Information (NCEI) created the Climate Extremes Index (CEI) in 1996 to quantify climate extremes. In this article, we explore the potential for enhancing the CEI via the use of the Z-score statistic to calculate the CEI on a numerical scale, to increase usability at smaller spatial scales, and to allow the creation of a new climate Extremes Vulnerability Index (EVI). The EVI combines the results from the revised CEI with values from the Social Vulnerability Index from the Centers for Disease Control and Prevention (CDC). The EVI can be used by policy-makers, planners, and the public to understand a subregion’s vulnerability to climate extremes. This information from the EVI could then be used to implement policies and changes in infrastructure that mitigate risk in vulnerable climate divisions. In a trial application, it is found that the southeastern and portions of the central United States had the highest levels of vulnerability for the abnormal month of December 2015.

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J. L. Spiesberger, T. G. Birdsall, K. Metzger, R. A. Knox, C. W. Spofford, and R. C. Spindel

Abstract

Phase-coded signals with 60 rms resolution were transmitted twice weekly for several months from acoustic sources at ∼2000 m depth in the Sargasso Sea to three bottom-mounted receives designed as West, East, and North stations at ranges approximately between 1000 and 2000 km. The transmission paths to West and East stations were entirely in the Sargasso Sea. The path to North station crossed the Gulf Stream and so traversed one of the most time- and range-dependent environments found anywhere in the ocean. Arrivals at all three stations were stable and could be identified from range-dependent ray traces. Travel times at West station clearly change is response to the warming of the seasonal thermocline from spring to summer. The travel-time change with predictions. Travel-time changes at North station primarily respond to the north-south meandering of the Gulf Stream.

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Kenneth E. Kunkel, Karen Andsager, Glen Conner, Wayne L. Decker, Harry J. Hillaker Jr., Pam Naber Knox, Fred V. Nurnberger, Jeffrey C. Rogers, Kenneth Scheeringa, Wayne M. Wendland, James Zandlo, and James R. Angel

Daily observations of precipitation and maximum and minimum temperature from the National Weather Service's cooperative observer network collected prior to 1948 were keyed into a digital database. This database includes stations in the nine midwestern states of Illinois, Indiana, Iowa, Kentucky, Michigan, Minnesota, Missouri, Ohio, and Wisconsin. The primary source used in this project was the publication Climatological Data, which began in 1896. This database provides a substantial enhancement to the National Climatic Data Center's TD-3200 Summary of the Day database, which includes little data prior to 1948. Approximately 2 × 107 data values were keyed, increasing the amount of pre- 1948 digital data by about a factor of 3 and substantially improving its spatial uniformity. The data were subjected to an extensive set of quality control procedures. It is expected that these data will find their greatest value in applications requiring very long historical records, such as assessments of the risks of extreme events.

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Sara H. Knox, Robert B. Jackson, Benjamin Poulter, Gavin McNicol, Etienne Fluet-Chouinard, Zhen Zhang, Gustaf Hugelius, Philippe Bousquet, Josep G. Canadell, Marielle Saunois, Dario Papale, Housen Chu, Trevor F. Keenan, Dennis Baldocchi, Margaret S. Torn, Ivan Mammarella, Carlo Trotta, Mika Aurela, Gil Bohrer, David I. Campbell, Alessandro Cescatti, Samuel Chamberlain, Jiquan Chen, Weinan Chen, Sigrid Dengel, Ankur R. Desai, Eugenie Euskirchen, Thomas Friborg, Daniele Gasbarra, Ignacio Goded, Mathias Goeckede, Martin Heimann, Manuel Helbig, Takashi Hirano, David Y. Hollinger, Hiroki Iwata, Minseok Kang, Janina Klatt, Ken W. Krauss, Lars Kutzbach, Annalea Lohila, Bhaskar Mitra, Timothy H. Morin, Mats B. Nilsson, Shuli Niu, Asko Noormets, Walter C. Oechel, Matthias Peichl, Olli Peltola, Michele L. Reba, Andrew D. Richardson, Benjamin R. K. Runkle, Youngryel Ryu, Torsten Sachs, Karina V. R. Schäfer, Hans Peter Schmid, Narasinha Shurpali, Oliver Sonnentag, Angela C. I. Tang, Masahito Ueyama, Rodrigo Vargas, Timo Vesala, Eric J. Ward, Lisamarie Windham-Myers, Georg Wohlfahrt, and Donatella Zona

Abstract

This paper describes the formation of, and initial results for, a new FLUXNET coordination network for ecosystem-scale methane (CH4) measurements at 60 sites globally, organized by the Global Carbon Project in partnership with other initiatives and regional flux tower networks. The objectives of the effort are presented along with an overview of the coverage of eddy covariance (EC) CH4 flux measurements globally, initial results comparing CH4 fluxes across the sites, and future research directions and needs. Annual estimates of net CH4 fluxes across sites ranged from −0.2 ± 0.02 g C m–2 yr–1 for an upland forest site to 114.9 ± 13.4 g C m–2 yr–1 for an estuarine freshwater marsh, with fluxes exceeding 40 g C m–2 yr–1 at multiple sites. Average annual soil and air temperatures were found to be the strongest predictor of annual CH4 flux across wetland sites globally. Water table position was positively correlated with annual CH4 emissions, although only for wetland sites that were not consistently inundated throughout the year. The ratio of annual CH4 fluxes to ecosystem respiration increased significantly with mean site temperature. Uncertainties in annual CH4 estimates due to gap-filling and random errors were on average ±1.6 g C m–2 yr–1 at 95% confidence, with the relative error decreasing exponentially with increasing flux magnitude across sites. Through the analysis and synthesis of a growing EC CH4 flux database, the controls on ecosystem CH4 fluxes can be better understood, used to inform and validate Earth system models, and reconcile differences between land surface model- and atmospheric-based estimates of CH4 emissions.

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