Showing papers by "Gilbert P. Compo published in 2015"

The International Surface Pressure Databank version 2

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.

Need for Caution in Interpreting Extreme Weather Statistics

Abstract: Given the reality of anthropogenic global warming, it is tempting to seek an anthropogenic component in any recent change in the statistics of extreme weather. This paper cautions that such efforts may, however, lead to wrong conclusions if the distinctively skewed and heavy-tailed aspects of the probability distributions of daily weather anomalies are ignored or misrepresented. Departures of several standard deviations from the mean, although rare, are far more common in such a distinctively non-Gaussian world than they are in a Gaussian world. This further complicates the problem of detecting changes in tail probabilities from historical records of limited length and accuracy.A possible solution is to exploit the fact that the salient non-Gaussian features of the observed distributions are captured by so-called stochastically generated skewed (SGS) distributions that include Gaussian distributions as special cases. SGS distributions are associated with damped linear Markov processes perturbed by...

A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816

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 ...

Southward shift of the Northern tropical belt from 1945 to 1980

Abstract: The width of the tropical belt affects the subtropical dry zones and has expanded since 1980. Analyses of observations and climate–chemistry model simulations suggest that the northern tropical edge retracted between 1945 and 1980.

A twentieth-century reanalysis forced ocean model to reconstruct the North Atlantic climate variation during the 1920s

Abstract: The observed North Atlantic multi-decadal variability for the period 1872–2009 is reconstructed with the Max Planck Institute ocean model, which is forced with an ensemble of the atmospheric twentieth century reanalysis. Special emphasis is put on the early part of the experiments, which includes a prominent climate variation during the 1920s. The experiments are in agreement with selected hydrographic records, indicating a transition from cold and fresh North Atlantic water properties, prior to the 1920 climate variation, towards warm and saline waters afterwards. Examining the variation reveals that sea level pressure (SLP) anomalies prior to the 1900s resemble a negative phase of North Atlantic Oscillation and associated weak winds result in a weak North Atlantic Current (NAC) and sub-polar gyre (SPG). This leads to a reduced transport of warm and saline waters into the higher latitudes. Simultaneously, Arctic freshwater release results in the accumulation of cold and fresh water properties, which cover the upper layers in the Labrador Sea and subsequently suppress convection. From the 1910s, the Arctic freshwater export is reduced, and, NAC and SPG are strengthened as a result of an increased SLP gradient over the North Atlantic. Concurrently, Labrador Sea convection and Atlantic meridional overturning circulation (AMOC) increase. The intensified NAC, SPG, and AMOC redistribute sub-tropical water into the North Atlantic and Nordic Seas, thereby increasing observed and modelled temperature and salinity during the 1920s.

Dynamical Downscaling and Loss Modeling for the Reconstruction of Historical Weather Extremes and Their Impacts: A Severe Foehn Storm in 1925

Abstract: AFFILIATIONS: Stucki, brönnimann, anD Welker—Oeschger Centre for Climate Change Research and Institute of Geography, University of Bern, Bern, Switzerland; martiuS—Oeschger Centre for Climate Change Research, Institute of Geography, and Mobiliar Lab for Natural Risks, University of Bern, Bern, Switzerland; rickli—Institute of Geography, University of Bern, and Meteotest, Bern, Switzerland; Dierer—Meteotest, Bern, Switzerland; breSch—Swiss Reinsurance Company, Zurich, Switzerland; cOmPO anD SarDeShmukh—Cooperative Institute for Research in Environmental Sciences, University of Colorado, and Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado CORRESPONDING AUTHOR: Peter Stucki, Oeschger Centre for Climate Change Research and Institute of Geography, University of Bern, Hallerstrasse 12, Bern, Switzerland E-mail: peter.stucki@giub.unibe.ch

Upper-air observations from the German Atlantic Expedition (1925–27) and comparison with the Twentieth Century and ERA-20C reanalyses

Abstract: Between April 1925 and June 1927, the research vessel Meteor cruised the tropical and southern Atlantic Ocean in the framework of the German Atlantic Expedition. One purpose was to systematically explore the vertical structure of the atmosphere. To this end, the ocean was crossed in 14 profiles across parallels of latitude. 801 pilot balloons and 217 kites were launched. The resulting data have been digitised in the framework of the European project ERA-CLIM. Here, they are compared to the Twentieth Century (20CR) and ERA-20C reanalyses, independent datasets based on the assimilation of synoptic pressure and hurricane pressure records, and marine surface winds for the latter, using monthly sea surface temperature and sea ice as boundary conditions. Both reanalyses display similar patterns of systematic differences relative to the observations for temperature, specific humidity, and wind. Furthermore, 20CR and ERA-20C show generally comparable anomaly correlations for all parameters, with the highest values found for pressure and temperature. In the southern extratropics, high (> 0.75) anomaly correlations are found for pressure in both 20CR and ERA-20C, and for temperature in 20CR. Medium (> 0.5) anomaly correlations are found for specific humidity in 20CR. Moderate anomaly correlations (> 0.44) are found for meridional wind in both 20CR and ERA-20C, and for temperature in ERA-20C. In contrast, low anomaly correlations (< 0.44) are found for zonal wind both in 20CR and ERA-20C, and for specific humidity in ERA-20C. In the Tropics, low anomaly correlations are found for all parameters except for pressure, which shows medium anomaly correlations for both 20CR and ERA-20C, and for meridional wind, which shows moderate anomaly correlations for 20CR. In all regions, both reanalyses strongly underestimate the observed range of zonal and particularly meridional wind variability. Even though remaining errors in the observational data cannot be excluded, we estimate that the inherent observational uncertainties do not alter our conclusions. Vice versa, two pieces of evidence support the credibility of the early upper-air data: the robust regressions of both 20CR and ERA-20C against observed pressure and temperature over a large spatial and temporal range, and the similarity between the uncertainties predicted by 20CR and the actual uncertainties determined from the root mean square difference of reanalysis and observation values.

The International Surface Pressure Databank version 3

Abstract: Notice: A newer version of this dataset, the International Surface Pressure Databank version 4, is available in RDA dataset ds132.2 [https://rda.ucar.edu/datasets/ds132.2/]. Users are recommended to access this updated dataset. This dataset contains the International Surface Pressure Databank version 3.2.9 (ISPDv3), 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 ISPDv3 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, ISPDv3 contains feedback from the 20th Century Reanalysis version 2c (20CRV2c), 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 3 and 20th Century Reanalysis version 2c used resources of the National Energy Research Scientific Computing Center which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

The Tosontsengel Mongolia world record sea-level pressure extreme: spatial analysis of elevation bias in adjustment-to-sea-level pressures

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.