Showing papers by "Andrew Lorrey published in 2019"

Towards a more reliable historical reanalysis: improvements for version 3 of the Twentieth Century Reanalysis system

Abstract: Historical reanalyses that span more than a century are needed for a wide range of studies, from understanding large‐scale climate trends to diagnosing the impacts of individual historical extreme weather events. The Twentieth Century Reanalysis (20CR) Project is an effort to fill this need. It is supported by the National Oceanic and Atmospheric Administration (NOAA), the Cooperative Institute for Research in Environmental Sciences (CIRES), and the U.S. Department of Energy (DOE), and is facilitated by collaboration with the international Atmospheric Circulation Reconstructions over the Earth initiative. 20CR is the first ensemble of sub‐daily global atmospheric conditions spanning over 100 years. This provides a best estimate of the weather at any given place and time as well as an estimate of its confidence and uncertainty. While extremely useful, version 2c of this dataset (20CRv2c) has several significant issues, including inaccurate estimates of confidence and a global sea level pressure bias in the mid‐19th century. These and other issues can reduce its effectiveness for studies at many spatial and temporal scales. Therefore, the 20CR system underwent a series of developments to generate a significant new version of the reanalysis. The version 3 system (NOAA‐CIRES‐DOE 20CRv3) uses upgraded data assimilation methods including an adaptive inflation algorithm; has a newer, higher‐resolution forecast model that specifies dry air mass; and assimilates a larger set of pressure observations. These changes have improved the ensemble‐based estimates of confidence, removed spin‐up effects in the precipitation fields, and diminished the sea‐level pressure bias. Other improvements include more accurate representations of storm intensity, smaller errors, and large‐scale reductions in model bias. The 20CRv3 system is comprehensively reviewed, focusing on the aspects that have ameliorated issues in 20CRv2c. Despite the many improvements, some challenges remain, including a systematic bias in tropical precipitation and time‐varying biases in southern high‐latitude pressure fields.

State of the Climate in 2018

Abstract: El documento contiene la seccion c. Central America and the Caribbean del capitulo 7. Regional Climates

Unlocking pre-1850 instrumental meteorological records: A global inventory

Abstract: Instrumental meteorological measurements from periods prior to the start of national weather services are designated “early instrumental data.” They have played an important role in climate...

Wiggle-match radiocarbon dating of the Taupo eruption

Abstract: The Taupo eruption 1 deposit is an isochronous marker bed that spans much of New Zealand’s North Island and predates human arrival2. Holdaway et al.3 (HDK18 hereafter) propose that the current Taupo eruption date is inaccurate, and that the eruption occurred decades to two centuries after the published wiggle-match estimate of 232 ± 10 CE (2 SD)4 derived from a tanekaha (Phyllocladus trichomanoides) tree at the Pureora buried forest site5,6. HDK18 propose that trees growing at Pureora (and other near-source areas) that were killed and buried by the climactic ignimbrite event were affected by 14C-depleted (magmatic) CO2. HDK18’s proposal utilises a wide range of published 14C data, but their work results in assertions that are implausible. Four parts to their hypothesis are considered here. The 14C-date compilation used by HDK18 to claim that the Pureora and other near-source dates are anomalously old is flawed. The dataset used to construct HDK18’s Fig. 1 is incomplete: at least 18 additional ages (including short-lived leaf and seed material)7 on Taupo eruptives from various sites (e.g., ref. 8) were not included. Most of the dates used in the figure have large errors and calibrated mean values extend between 650 CE and −100 CE, making them statistically indistinguishable and undermining the significance of any purported best fit correlation. This wide range of ages was a principal reason why wiggle-match dating of the Pureora buried forest logs was undertaken4. Ages in HDK18 (Supplementary Table S1), used to infer an age-vs.-distance relationship, represent a collation of data obtained over more than half-a-century from different laboratories, using differing dating methods (i.e., solid-carbon, gas proportional counting, liquid scintillation spectroscopy, accelerator mass spectrometry), differing pretreatment regimes (i.e., no pretreatment, acid–base–acid pretreatment, cellulose extraction), and differing age calculation procedures (i.e., non-Conventional Radiocarbon Age (CRA) vs. CRA). Indeed, many of the apparently anomalous oldest reported ages are from analyses dating to the 1950s–60s9. Even with modern techniques and consistent protocols, there remain inter-laboratory differences that preclude simple collation of 14C data sets. For example, Hogg et al.4 (Fig. 4) show that the Rafter and Waikato laboratory analyses, undertaken on wood derived from the same tanekaha tree-ring chronology6, have a systematic offset, with Rafter analyses, which dominate HDK18 (Supplementary Table S1), on average 40 years younger. Of critical importance, the Waikato study circumvented such laboratory bias by analysing a 250-year series of contiguous decadal 14C dates from the Pureora tanekaha tree and wiggle-matched them against known calendar-age kauri (Agathis australis) to derive a date for the eruption of 232 ± 10 CE4. Relationships between the dates in HDK18’s Supplementary Table S1 (36 values), Supplementary Fig. S2 (45 values) and the Taupo eruption deposits are also unclear, with the stratigraphic context often lacking, impairing the value of the age estimates. An example of best practice is from a section10 at Kaipo bog, far removed from any possible magmatic 14C contamination3, which incorporates the Taupo eruption deposits. Here, stratigraphically ordered, independent age points (37 local 14C ages and 16 tephrochronological ages) were used10 to derive dates (not cited by HDK18) for the Taupo layer of 231 ± 12 CE (OxCal) and 251 ± 51 CE with a weighted-mean date of 240 CE (Bacon-software-derived), statistically identical to the Pureora wiggle-match estimate4. The potential impact of injected 14C-depleted magmatic CO2 on reservoir ages in Lake Taupo (and the Waikato River draining the lake) is documented11. HDK18 present 14C dates of organic materials from this area, i.e., within 60 km of the Taupo eruption source (HDK18, Fig. 3), and propose that these dates are biased towards older ages by CO2 degassed from groundwater. We discount this proposition at the Pureora forest site for several https://doi.org/10.1038/s41467-019-12532-8 OPEN

The International Surface Pressure Databank version 4

Abstract: This dataset contains the International Surface Pressure Databank version 4.7 (ISPDv4), the world's largest collection of pressure observations. It has been gathered through international cooperation with data recovery facilitated by the ACRE Initiative and the other contributing organizations and assembled under the auspices of the GCOS Working Group on Surface Pressure and the WCRP/GCOS Working Group on Observational Data Sets for Reanalysis by NOAA Earth System Research Laboratory (ESRL), NOAA's National Climatic Data Center (NCDC), and the University of Colorado's Cooperative Institute for Research in Environmental Sciences (CIRES). The ISPDv4 consists of three components: station, marine, and tropical cyclone best track pressure observations. The station component is a blend of many national and international collections. In addition to the pressure observations and metadata, ISPDv4 contains feedback from the 20th Century Reanalysis version 3, including quality control information and uncertainty information. Support for the International Surface Pressure Databank is provided by the U.S. Department of Energy, Office of Science Biological and Environmental Research (BER), and by the National Oceanic and Atmospheric Administration Climate Program Office. The International Surface Pressure Databank version 4.7 and 20th Century Reanalysis version 3 used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231.

The Representation of the South Pacific Convergence Zone in the Twentieth Century Reanalysis

Abstract: The South Pacific convergence zone (SPCZ) is the largest rainfall feature in the Southern Hemisphere, and is a critical component of the climate for South Pacific island nations and territo...

Identifying and Quantifying Tree-Ring Chronology Variance Artefacts Related to Co-Occurring Changes in Growth Rate

Abstract: Expectations that a warming world will be associated with more hydro-climatological extremes has motivated research exploring if an associated signal is evident in paleoclimate archives. Tree-ring chronologies are central to this work because of their high temporal resolution, but they are also potentially compromised by variance artefacts associated with the evolving composition of the chronology and with data processing. Here we present two empirical methods to identify and quantify potential artefacts related specifically to temporally varying growth rate (local level, LL): LL-based partitioning analysis and LL-based chronology stripping. The two methods were developed and tested using a multi-site New Zealand kauri (Agathis australis) living-tree data set. Our results show that the methods are complementary in terms of artefact identification and quantification, and that they can provide useful insight into causal processes when used conjointly. Our results also indicate that data pre-processing to remove LL-related artefacts may be sub-optimal, that there may be an optimal standardization that minimizes bias, and that the evolving variance of kauri master chronologies over the last 500 years is not significantly affected by LL-related artefacts.

NOAA-CIRES-DOE Twentieth Century Reanalysis Version 3

Abstract: The Twentieth Century Reanalysis Project, produced by the Earth System Research Laboratory Physical Sciences Division from NOAA and the University of Colorado Cooperative Institute for Research in Environmental Sciences using resources from Department of Energy supercomputers, is an effort to produce a global reanalysis dataset spanning a portion of the nineteenth century and the entire twentieth century (1836 - 2015), assimilating only surface observations of synoptic pressure into an 80-member ensemble of estimates of the Earth system. Boundary conditions of pentad sea surface temperature and monthly sea ice concentration and time-varying solar, volcanic, and carbon dioxide radiative forcings are prescribed. Products include 3 and 6-hourly ensemble mean and spread analysis fields and 6-hourly ensemble mean and spread forecast (first guess) fields on a global Gaussian T254 grid. Fields are accessible in yearly time series (1 file per parameter). The NOAA-CIRES-DOE Twentieth Century Reanalysis Version 3 uses the NCEP Global Forecast Model that was operational in autumn 2017, with differences as described in (Slivinski et al. 2019). Sea ice boundary conditions are specified from HadISST 2.3 (Slivinski et al. 2019). Sea surface temperature fields prior to 1981 are prescribed from the 8-member ensemble of pentad Simple Ocean Data Assimilation with sparse input (SODAsi.3, Giese et al. 2016) and from the 8-member ensemble of pentad HadISST 2.2 for 1981 to 2015. Observations from ISPD version 4.7 are assimilated using an ensemble Kalman filter. The Twentieth Century Reanalysis Project version 3 used resources of the National Energy Research Scientific Computing Center managed by Lawrence Berkeley National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used resources of NOAA's Remote Deployed High Performance Computing Systems. Version 3 is a contribution to the international Atmospheric Circulation Reconstructions over the Earth initiative. Support for the Twentieth Century Reanalysis Project is provided by the Physical Sciences Division of the NOAA Earth System Research Laboratory, the U.S. Department of Energy Office of Science (BER), and the NOAA Climate Program Office MAPP program.

Correspondence: The Taupo eruption occurred in 232 ± 10 CE, and not later

Abstract: The Taupo eruption deposit is an isochronous marker bed that spans much of New Zealand’s North Island and pre-dates human arrival. Holdaway et al. (2018, Nature Comms 9, 4110) propose that the current Taupo eruption date is inaccurate and that the eruption occurred “…decades to two centuries…” after the published wiggle-match estimate of 232 ± 10 CE (2 s.d.) derived from a tanekaha (Phyllocladus trichomanoides) tree at the Pureora buried forest site. HDK18 propose that trees growing at Pureora (and other near-source areas) that were killed and buried by the climactic ignimbrite event were affected by 14C-depleted (magmatic) CO2. HDK18’s proposal utilises a wide range of published 14C data, but their work results in assertions that are implausible.