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CGD Publications: Archived Abstracts
July 2006 Abstracts
A near-global, 2-hourly data set of atmospheric precipitable water from ground-based GPS measurements
"Open access to an unprecedented, comprehensive coordinated set of global coupled climate model experiments for 20th and 21st century climate, climate change commitment and other experiments, represents a new era in climate science research."
Figure. A 2-hourly data set of atmospheric precipitable water (PW) has been produced from ground-based Global Positioning System (GPS) measurements of zenith path delay (ZPD). The PW data are available every two hours at about 80-268 International GNSS Service (IGS, formally International GPS Service) ground stations from 1997 to 2004. An analysis technique is developed to convert ZPD to PW on a global scale. Special efforts are made on deriving surface pressure (Ps) and water-vapor-weighted atmospheric mean temperature (Tm), which are two key parameters for converting ZPD to PW. Ps is derived from global, 3-hourly surface synoptic observations with temporal and vertical adjustments. Tm is calculated from NCEP/NCAR reanalysis with temporal, vertical and horizontal interpolations. The PW dataset is validated by comparing with radiosonde, microwave radiometer (MWR) and satellite data. The comparisons show no systematic bias in the GPS-derived PW data. The GPS and radiosonde PW comparisons at 102 stations around the globe show mean difference of 1.03 mm (drier for radiosonde data) with a mean standard deviation of differences of 1.93 mm. The bias is primarily due to known dry biases in the radiosonde data. The latitudinal and seasonal variations of PW derived from the GPS data agree well with that from International Satellite Cloud Climatology Project (ISCCP) data if the ISCCP data are sampled only at grid boxes containing GPS stations. The validation study also illustrates the value of GPS-estimated PW on examining the quality of other data sets, such as those from radiosondes and MWR.
Authored by Junhong Wang, Liangying Zhang, Aiguo Dai, National Center for Atmospheric Research, P.O. Box 3000, Boulder CO 80307
Teresa Van Hove, University Corporation for Atmospheric Research, Boulder, Colorado
Joël Van Baelen, Laboratoire de Météorologie Physique, CNRS-Université Blaise Pascal, Clermont-Ferrand, France
Corresponding author: Junhong Wang, NCAR/EOL, Email: junhong@ucar.edu, Phone: 303-497-8837
Submitted to Journal of Geophysical Research - Atmospheres, July 17, 2006
The global coupled climate multi-model dataset: A new era in climate change research
"Open access to an unprecedented, comprehensive coordinated set of global coupled climate model experiments for 20th and 21st century climate, climate change commitment and other experiments, represents a new era in climate science research."
Figure. A coordinated set of global coupled climate model experiments for 20th and 21st century climate, as well as several climate change commitment and other experiments, was run by 16 modeling groups from 11 countries with 23 models for assessment in the IPCC Fourth Assessment Report. This effort, as well as the subsequent analysis phase, was organized by the WCRP/CLIVAR Working Group on Coupled Models (WGCM) Climate Simulation Panel, and represents the largest and most comprehensive international global coupled climate model experiment and multi-model analysis effort ever attempted. The Program for Climate Model Diagnostics and Intercomparison (PCMDI) collected, archived, and served roughly 30 tBytes of model data. With oversight from the Panel, the multi-model data were made openly available from PCMDI for analysis and academic applications initially aimed at the IPCC AR4, though this unique and valuable resource will continue to be maintained for at least the next several years. Never before has such an extensive set of climate model simulations been made available to the international climate science community for study. Thus, the ready access to the multi-model data set opens up these types of model analyses to researchers who previously could not obtain state-of-the-art climate model output, and represents a new era in climate science research. As a direct consequence, these ongoing studies are increasing the body of knowledge regarding our understanding of how the climate system currently works, and how it may change in the future.
Authored by Gerald A. Meehl1, Curt Covey2, Thomas Delworth3, Mojib Latif4, Bryant McAvaney5, John F.B. Mitchell6, Ronald J. Stouffer3, and Karl Taylor2
1 National Center for Atmospheric Research, P.O. Box 3000, Boulder CO 80307
2 Program for Climate Model Diagnosis and Intercomparison, Livermore, CA, USA
3 Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA
4 Leibniz-Institut fuer Meereswissenschaften, Kiel, Germany
5 Bureau of Meteorology Research Centre, Melbourne, Australia
6 Hadley Centre, Exeter, United Kingdom
Corresponding author: meehl@ncar.ucar.edu
Submitted to Bulletin of the American Meteorological Society, July 17, 2006
Current and projected impacts of heat events in the Midwest
Over the period 1979-1999, 8,015 deaths in the US were heat-related, of which 3,829 were due to weather conditions [Donoghue et al. 2003]. Populations in the Midwest are particularly at increased risk for illness and death during heat events, as evidenced during heat events occurring in the 1980s and 1990s. A heat event in July 1980 caused a 57% increase in all-cause mortality in St. Louis and a 64% increase in Kansas City [Jones et al. 1982]. The 1995 heat event in Chicago is perhaps the most widely known heat event; it caused an estimated 696 excess deaths [Whitman et al. 1997; Semenza et al. 1999]. A heat event of similar magnitude in 1999 resulted in 119 deaths in Chicago [Palecki et al. 2001].
In addition to the effects of heat on human health, high outdoor temperatures can increase the concentration of air pollutants, particularly ozone, but it is uncertain whether this increases the effects of heat on mortality. A number of studies have investigated the impacts of air pollution and temperature on mortality, with conflicting results [Basu and Samet 2002].
Heat events affect more than people. High outdoor temperatures also affect livestock and agricultural productivity, put strain on electricity generation and distribution systems, and can affect transportation, among others.
Authored by Kristie Ebi, ESS, LLC and Jerry Meehl
NCAR, P.O. Box 3000, Boulder CO 80307
Submitted to: Pew Center on Climate Change Report
The Transient Atmospheric Circulation Response to North Atlantic SST and Sea Ice Anomalies
Figure. The objective of this study is to investigate the transient evolution of the atmospheric circulation response to imposed patterns of SST and sea ice anomalies in the North Atlantic sector using the NCAR Community Climate Model Version 3 (CCM3). The adjustment of the atmospheric circulation to the imposed boundary forcing consists of two stages: an initial stage characterized by a strong out-of-phase relationship between geopotential height anomalies in the lower and upper troposphere localized to the vicinity of the forcing that sets up within a day and lasts for approximately 2-3 weeks; and an equilibrium stage characterized by an equivalent barotropic response that is hemispheric in scale and resembles the model’s leading mode of intrinsic variability (e.g., the Northern Annular Mode), reaching its maximum amplitude in approximately 2 – 2.5 months. The equilibrium response, which is approximately twice as strong as the initial response, is maintained primarily by transient eddy fluxes of heat and vorticity, while the initial response is maintained primarily by diabatic heating anomalies associated with the imposed thermal forcing.
Clara Deser, Robert A. Tomas; National Center for Atmospheric Research, Boulder CO
Shiling Peng, NOAA Earth System Research Laboratory, Boulder CO
Corresponding Author: Dr. Clara Deser
Climate and Global Dynamics Division, NCAR, P.O. Box 3000, Boulder, CO 80307-3000, Email: cdeser@ucar.edu
Submitted to the Journal of Climate, July 25, 2006