Showing papers by "Rob Allan published in 2015"
••
TL;DR: In this article, the authors found that recent changes in the means and variability of the North Atlantic Oscillation (NAO) index are related to an increasing trend in the Greenland Blocking Index (GBI, high pressure over Greenland) in summer and a more variable GBI in December.
Abstract: Recent changes are found in the means and variability of the North Atlantic Oscillation (NAO) index. There has been a sustained significant recent decrease in the summer NAO since the 1990s and, at the same time, a striking increase in variability of the winter – especially December – NAO that resulted in three of five (two of five) record high (record low) NAO Decembers occurring during 2004–2013 in the 115-year record. These NAO changes are related to an increasing trend in the Greenland Blocking Index (GBI, high pressure over Greenland) in summer and a more variable GBI in December. The enhanced early winter NAO variability originates mainly at the southern node of the NAO but is also related to the more variable GBI in December. Transition seasons (spring and autumn) have remained relatively unchanged over the last 30 years. These results are corroborated using several NAO indices. The Arctic Oscillation (AO) index, although strongly correlated with the NAO, does not show the recent sustained significant summer decrease, but it does show enhanced early winter variability. These recent observed changes are not present in the current generation of global climate models, although the latest process studies do offer insight into their causes. We invoke several plausible climate forcings and feedbacks to explain the recent NAO changes.
141 citations
••
National Center for Atmospheric Research1, Earth System Research Laboratory2, University of Colorado Boulder3, Met Office4, National Oceanic and Atmospheric Administration5, University of Melbourne6, Oeschger Centre for Climate Change Research7, Royal Netherlands Meteorological Institute8, University of East Anglia9, Rovira i Virgili University10, University Corporation for Atmospheric Research11, Shirshov Institute of Oceanology12, European Centre for Medium-Range Weather Forecasts13, King Abdulaziz University14, South African Weather Service15, Japan Agency for Marine-Earth Science and Technology16, University of Milan17, National Institute of Water and Atmospheric Research18, University of Giessen19, Natural Environment Research Council20, University of South Carolina21, Norwegian Meteorological Institute22, University of Lisbon23, Nicolaus Copernicus University in Toruń24, Environment Canada25, University of Illinois at Urbana–Champaign26, M-Systems27
TL;DR: The International Surface Pressure Databank (ISPD) as mentioned in this paper is the largest collection of global surface and sea-level pressure observations and has been used for various general climate and weather studies.
Abstract: The International Surface Pressure Databank (ISPD) is the world's largest collection of global surface and sea-level pressure observations. It was developed by extracting observations from established international archives, through international cooperation with data recovery facilitated by the Atmospheric Circulation Reconstructions over the Earth (ACRE) initiative, and directly by contributing universities, organizations, and countries. The dataset period is currently 1768–2012 and consists of three data components: observations from land stations, marine observing systems, and tropical cyclone best track pressure reports. Version 2 of the ISPD (ISPDv2) was created to be observational input for the Twentieth Century Reanalysis Project (20CR) and contains the quality control and assimilation feedback metadata from the 20CR. Since then, it has been used for various general climate and weather studies, and an updated version 3 (ISPDv3) has been used in the ERA-20C reanalysis in connection with the European Reanalysis of Global Climate Observations project (ERA-CLIM). The focus of this paper is on the ISPDv2 and the inclusion of the 20CR feedback metadata. The Research Data Archive at the National Center for Atmospheric Research provides data collection and access for the ISPDv2, and will provide access to future versions.
117 citations
••
Arlene P. Aaron-Morrison, Steven A. Ackerman1, Nicolaus G. Adams2, Robert F. Adler3 +470 more•Institutions (138)
TL;DR: The State of the Climate for 2014 as mentioned in this paper is a very low-resolution file and it can be downloaded in a few minutes for a high-resolution version of the report to download.
Abstract: Editors note: For easy download the posted pdf of the State of the Climate for 2014 is a very low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
104 citations
••
Oeschger Centre for Climate Change Research1, University of Bern2, Met Office3, Central Institution for Meteorology and Geodynamics4, University of Barcelona5, Uppsala University6, MeteoSwiss7, Academy of Sciences of the Czech Republic8, Masaryk University9, Cooperative Institute for Research in Environmental Sciences10, University of East Anglia11, National Technical University12, University of Extremadura13, Royal Netherlands Meteorological Institute14, University of Gdańsk15, University of Helsinki16, Karlsruhe Institute of Technology17, University of Giessen18, University of Milan19, Stockholm University20, University of South Carolina21, Aix-Marseille University22, McGill University23, Jagiellonian University24, University of Lisbon25
TL;DR: The eruption of Mount Tambora (Indonesia) in April 1815 is the largest documented volcanic eruption in history and is associated with a large global cooling during the following year, felt particul...
Abstract: The eruption of Mount Tambora (Indonesia) in April 1815 is the largest documented volcanic eruption in history. It is associated with a large global cooling during the following year, felt particul ...
51 citations
••
TL;DR: In this article, the authors highlight the inherent value of multi-cross/inter-disciplinary projects in providing better syntheses and understanding of human and environmental/climatic variability and change.
Abstract: The value of historic observational weather data for reconstructing long-term climate patterns and the detailed analysis of extreme weather events has long been recognized (Le Roy Ladurie, 1972; Lamb, 1977). In some regions however, observational data has not been kept regularly over time, or its preservation and archiving has not been considered a priority by governmental agencies. This has been a particular problem in Southeast Asia where there has been no systematic country-by-country method of keeping or preserving such data, the keeping of data only reaches back a few decades, or where instability has threatened the survival of historic records. As a result, past observational data are fragmentary, scattered, or even absent altogether. The further we go back in time, the more obvious the gaps. Observational data can be complimented however by historical documentary or proxy records of extreme events such as floods, droughts and other climatic anomalies. This review article highlights recent initiatives in sourcing, recovering, and preserving historical weather data and the potential for integrating the same with proxy (and other) records. In so doing, it focuses on regional initiatives for data research and recovery – particularly the work of the international Atmospheric Circulation Reconstructions over the Earth’s (ACRE) Southeast Asian regional arm (ACRE SEA) – and the latter’s role in bringing together disparate, but interrelated, projects working within this region. The overarching goal of the ACRE SEA initiative is to connect regional efforts and to build capacity within Southeast Asian institutions, agencies and National Meteorological and Hydrological Services (NMHS) to improve and extend historical instrumental, documentary and proxy databases of Southeast Asian hydroclimate, in order to contribute to the generation of high-quality, high-resolution historical hydroclimatic reconstructions (reanalyses) and, to build linkages with humanities researchers working on issues in environmental and climatic history in the region. Thus, this article also highlights the inherent value of multi/cross/inter-disciplinary projects in providing better syntheses and understanding of human and environmental/climatic variability and change.
17 citations
••
TL;DR: In this article, the authors examined the relationship between SLP extremes and corresponding station elevation and temperature using the Integrated Surface Database (ISD-Lite) of NOAA's National Climate Data Center.
Abstract: A World Meteorological Organization (WMO) committee evaluated the record sea-level pressure (SLP) measurement of 1089.4 hPa on 30 December 2004 in Tosontsengel, Mongolia (1724.6 m). Although instrumentation and data collection procedures were properly followed according to the assessment of the committee, concern was raised regarding the reliability of SLP adjustment from such a high-elevation station. This paper addresses this concern with a number of analyses that look at relationships between SLP extremes and corresponding station elevation and temperature. First, we selected data from stations extracted from the Integrated Surface Database (ISD-Lite) of NOAA's National Climate Data Center. A spatial analysis indicates that elevation shows little to no association (R2 values essentially zero) to extreme SLP. However, a second analysis between extreme SLP and air temperature indicates that high regionalism exists in spatial correlations (local R2) between those two variables. This relationship to temperature is likely the result of differences in SLP adjustment formulae used around the world. Based on this analysis, on the need to differentiate the SLP values adjusted using extremely cold temperatures (and generally high elevation), and following past WMO SLP guidelines, the WMO Rapporteurs for Climate and Weather Extremes therefore have created two distinct SLP records: (a) highest adjusted SLP (below 750 m), currently 1083.3 hPa recorded on 31 December 1968 at Agata, Evenhiyskiy, Russia; and (b) highest adjusted SLP (above 750 m), currently 1089.4 hPa (by Russian method; 1089.1 hPa by WMO formula) on 30 December 2004 in Tosontsengel, Mongolia. Future WMO guidance regarding SLP adjustment may lead to re-evaluation of this and other SLP records.
5 citations