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H. Mok

Bio: H. Mok is an academic researcher. The author has contributed to research in topics: Oak Ridge National Laboratory & Data assimilation. The author has an hindex of 4, co-authored 6 publications receiving 2840 citations.

Papers
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Journal ArticleDOI
TL;DR: The Twentieth Century Reanalysis (20CR) dataset as discussed by the authors provides the first estimates of global tropospheric variability, and of the dataset's time-varying quality, from 1871 to the present at 6-hourly temporal and 2° spatial resolutions.
Abstract: The Twentieth Century Reanalysis (20CR) project is an international effort to produce a comprehensive global atmospheric circulation dataset spanning the twentieth century, assimilating only surface pressure reports and using observed monthly sea-surface temperature and sea-ice distributions as boundary conditions. It is chiefly motivated by a need to provide an observational dataset with quantified uncertainties for validations of climate model simulations of the twentieth century on all time-scales, with emphasis on the statistics of daily weather. It uses an Ensemble Kalman Filter data assimilation method with background ‘first guess’ fields supplied by an ensemble of forecasts from a global numerical weather prediction model. This directly yields a global analysis every 6 hours as the most likely state of the atmosphere, and also an uncertainty estimate of that analysis. The 20CR dataset provides the first estimates of global tropospheric variability, and of the dataset's time-varying quality, from 1871 to the present at 6-hourly temporal and 2° spatial resolutions. Intercomparisons with independent radiosonde data indicate that the reanalyses are generally of high quality. The quality in the extratropical Northern Hemisphere throughout the century is similar to that of current three-day operational NWP forecasts. Intercomparisons over the second half-century of these surface-based reanalyses with other reanalyses that also make use of upper-air and satellite data are equally encouraging. It is anticipated that the 20CR dataset will be a valuable resource to the climate research community for both model validations and diagnostic studies. Some surprising results are already evident. For instance, the long-term trends of indices representing the North Atlantic Oscillation, the tropical Pacific Walker Circulation, and the Pacific–North American pattern are weak or non-existent over the full period of record. The long-term trends of zonally averaged precipitation minus evaporation also differ in character from those in climate model simulations of the twentieth century. Copyright © 2011 Royal Meteorological Society and Crown Copyright.

3,043 citations

01 Jan 2011
TL;DR: The Twentieth Century Reanalysis Project helps clarify the role of language and culture in the development of international relations and provides a framework for future policy-makers to address these issues.
Abstract: Compo, G. P.; Whitaker, J. S.; Sardeshmukh, P. D.; Matsui, N.; Allan, R. J.; Yin, X.; Gleason, B. E. Jr.; Vose, R. S.; Rutledge, G.; Bessemoulin, P.; Brönnimann, S.; Brunet, M.; Crouthamel, R. I.; Grant, A. N.; Groisman, P. Y.; Jones, P. D.; Kruk, M. C.; Kruger, A. C.; Marshall, G. J.; Maugeri, M.; Mok, H. Y.; Nordli, Ø.; Ross, T. F.; Trigo, R. M.; Wang, X. L.; Woodruff, S. D.; and Worley, S. J., "Review Article The Twentieth Century Reanalysis Project" (2011). Publications, Agencies and Staff of the U.S. Department of Commerce. 254. https://digitalcommons.unl.edu/usdeptcommercepub/254

28 citations

DatasetDOI
14 May 2009
TL;DR: The Twentieth Century Reanalysis Project (Twentieth century reanalysis project) as mentioned in this paper is an effort to produce a global reanalysis dataset spanning a portion of the nineteenth century and the entire twentieth century (1871 - near present), assimilating only surface observations of synoptic pressure, monthly sea surface temperature and sea ice distribution.
Abstract: The Twentieth Century Reanalysis Project, supported by the Earth System Research Laboratory Physical Sciences Division from NOAA and the University of Colorado CIRES Climate Diagnostics Center, is an effort to produce a global reanalysis dataset spanning a portion of the nineteenth century and the entire twentieth century (1871 - near present), assimilating only surface observations of synoptic pressure, monthly sea surface temperature and sea ice distribution Products include 6-hourly ensemble mean and spread analysis fields on a 2 by 2 degree global latitude-longitude grid, and 3 and 6-hourly ensemble mean and spread forecast (first guess) fields on a global Gaussian T62 grid Fields are accessible in yearly time series (1 file per parameter) and monthly synoptic time (all parameters per synoptic hour) files Ensemble grids, spectral coefficients, and other information will available by offline request in the future The Twentieth Century Reanalysis Project used resources of the National Energy Research Scientific Computing Center managed by Lawrence Berkeley National Laboratory and of the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory, which are supported by the Office of Science of the US Department of Energy under Contract No DE-AC02-05CH11231 and Contract No DE-AC05-00OR22725, respectively Note: Version 2c of this reanalysis (running from 1851 - 2011) is the recommended research version Please see ds1312 to access Version 2c

16 citations

DatasetDOI
10 Sep 2015
TL;DR: The International Surface Pressure Databank version 3.9 (ISPDv3) as mentioned in this paper is available in RDA dataset ds132.2.2 [https://rda.ucar.edu/datasets/ds132.1.2/].
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.

9 citations

DatasetDOI
19 Aug 2010
TL;DR: The International Surface Pressure Databank (ISPD) as discussed by the authors is the world's largest collection of pressure observations, which 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 Climate Diagnostics Center (CDC) of the University of Colorado's Cooperative Institute
Abstract: The International Surface Pressure Databank (ISPD; Cram et al. 2015) [http://reanalyses.org/observations/international-surface-pressure-databank] is 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 Climate Diagnostics Center (CDC) of the University of Colorado's Cooperative Institute for Research in Environmental Sciences (CIRES). The ISPDv2 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. NOTE: A newer version of this dataset, the International Surface Pressure Databank version 3, is available in RDA dataset ds132.1 [http://rda.ucar.edu/datasets/ds132.1/]. Users are recommended to access this updated dataset. The Twentieth Century Reanalysis Project used resources of the National Energy Research Scientific Computing Center [http://www.nersc.gov/] and of the Oak Ridge Leadership Computing Facility [http://www.olcf.ornl.gov/] at Oak Ridge National Laboratory, which are supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and Contract No. DE-AC05-00OR22725, respectively.

4 citations


Cited by
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Journal ArticleDOI
TL;DR: ERA-Interim as discussed by the authors is the latest global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), which will extend back to the early part of the twentieth century.
Abstract: ERA-Interim is the latest global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). The ERA-Interim project was conducted in part to prepare for a new atmospheric reanalysis to replace ERA-40, which will extend back to the early part of the twentieth century. This article describes the forecast model, data assimilation method, and input datasets used to produce ERA-Interim, and discusses the performance of the system. Special emphasis is placed on various difficulties encountered in the production of ERA-40, including the representation of the hydrological cycle, the quality of the stratospheric circulation, and the consistency in time of the reanalysed fields. We provide evidence for substantial improvements in each of these aspects. We also identify areas where further work is needed and describe opportunities and objectives for future reanalysis projects at ECMWF. Copyright © 2011 Royal Meteorological Society

22,055 citations

Journal ArticleDOI
TL;DR: The Modern-Era Retrospective Analysis for Research and Applications (MERRA) was undertaken by NASA's Global Modeling and Assimilation Office with two primary objectives: to place observations from NASA's Earth Observing System satellites into a climate context and to improve upon the hydrologic cycle represented in earlier generations of reanalyses as mentioned in this paper.
Abstract: The Modern-Era Retrospective Analysis for Research and Applications (MERRA) was undertaken by NASA’s Global Modeling and Assimilation Office with two primary objectives: to place observations from NASA’s Earth Observing System satellites into a climate context and to improve upon the hydrologic cycle represented in earlier generations of reanalyses. Focusing on the satellite era, from 1979 to the present, MERRA has achieved its goals with significant improvements in precipitation and water vapor climatology. Here, a brief overview of the system and some aspects of its performance, including quality assessment diagnostics from innovation and residual statistics, is given.By comparing MERRA with other updated reanalyses [the interim version of the next ECMWF Re-Analysis (ERA-Interim) and the Climate Forecast System Reanalysis (CFSR)], advances made in this new generation of reanalyses, as well as remaining deficiencies, are identified. Although there is little difference between the new reanalyses i...

4,572 citations

Journal ArticleDOI
TL;DR: An overview of the MERRA-2 system and various performance metrics is provided, including the assimilation of aerosol observations, several improvements to the representation of the stratosphere including ozone, and improved representations of cryospheric processes.
Abstract: The Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), is the latest atmospheric reanalysis of the modern satellite era produced by NASA’s Global Modeling and Assimilation Office (GMAO). MERRA-2 assimilates observation types not available to its predecessor, MERRA, and includes updates to the Goddard Earth Observing System (GEOS) model and analysis scheme so as to provide a viable ongoing climate analysis beyond MERRA’s terminus. While addressing known limitations of MERRA, MERRA-2 is also intended to be a development milestone for a future integrated Earth system analysis (IESA) currently under development at GMAO. This paper provides an overview of the MERRA-2 system and various performance metrics. Among the advances in MERRA-2 relevant to IESA are the assimilation of aerosol observations, several improvements to the representation of the stratosphere including ozone, and improved representations of cryospheric processes. Other improvements in the quality of M...

4,524 citations