GEWEX-GPCP Workshop on Objective Analysis of Precipitation

ECMWF hosted the GEWEX sponsored Workshop on Objective Analysis of Precipitation from 11 to 13 March 2003.


The primary goals of the workshop were to improve our understanding of the issues involved in the objective analysis of precipitation using the many sources of information available (e.g., gauges, satellite-derived estimates, radar observations and model output data) and to make recommendations for GPCP to advance its efforts to provide global analyses of precipitation.

While the current GPCP precipitation analyses, as well as others that have been constructed, have proven useful for many purposes, it has become clear that efforts to improve their accuracy and consistency are required. This is partly because of the desire for higher spatial and temporal resolution, which necessitates extracting more information from the available data, and partly because the methods currently in use were developed 5-10 years ago and the state of the science has advanced. This workshop brought together members of the GPCP community with experts in the theory and practice objective analysis, including in particular, members of the numerical weather prediction (NWP) community, to describe the current state of the science and to make recommendations to GPCP.

Some of the questions that were considered at the workshop include:

  • What is the best (in terms of efficiency, accuracy and physics) analysis procedure for merging and interpolating (spatially and temporally) the various precipitation estimates?
  • Are different analysis procedures needed for different spatial and temporal scales?
  • What analysis procedures should be used in complex terrain?
  • What is the best way to validate results of analyses? How does one validate over the open ocean?
  • Since objective analysis techniques deal best with unbiased input data:
    • How can biases in the various input data be removed?
    • Are these biases function of satellite type, geographical location, season and even observation time or date?
    • Can they be done once for all or need to be done at every analysis time, i.e., are they stationary or time dependent?
    • Is bias removal best done during the retrieval process or during the analysis of by a combination of both?


PDF iconProgramme


Session I-a: Precipitation analysis procedures (GPCP, CMAP)  

(1) The current approach to GPCP monthly and daily precipitation estimates

(2) The Multi-satellite Precipitation Analysis (MPA) in real and post-real time

George Huffman & Bob Adler (GSFC/NASA)



Techniques used to create CMAP and their potential improvements

Pingping Xie, Yelena Yarosh, John Janowiak (NCEP/NOAA) & Phillip A Arkin (ESSIC/UMD)

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Session I-b: Precipitation analysis procedures (NWP data assimilation)  

Precipitation assimilation at ECMWF

Philippe Lopez (ECMWF)

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Precipitation assimilation at NASA Goddard

Arthur Hou (DAO/NASA/GSFC)


Precipitation assimilation at the Met Office (UK) and COST-717 collaboration in Europe

Bruce MacPherson (Met Office)


Rain estimation from passive microwave satellite observations

Peter Bauer (ECMWF)

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Precipitation assimilation to JMA mesoscale model using 4D-Var method

Ko Koizumi (JMA)

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The precipitation in ERA-40

Per Kallberg (ECMWF)

Session I-c: Precipitation analysis procedures (Other methods)  

Gridding of global precipitation from satellite measurements

Murray Salby (University of Colorado)

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High-resolution daily precipitation analysis over U.S. at CPC/NCEP

Evgeny Yarosh, Wayne Higgins & Wei Shi (NCEP/NOAA)


Blending precipitation data sets from multiple sources at short time scales

Joe Turk (NRL)


The Australian operational daily rain gauge analysis

Beth Ebert (BMO)

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Towards an adaptive method for spatial interpolation of global rain gauge data

Jurgen Grieser (DWD)

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Strategy of error analysis and reduction in the PERSIANN System

Xiaogang Gao, Soroosh Sorooshian & Kuolin Hsu

Session II : Observation characteristics (rain gauge and satellite)  

Operational processing, quality control and analysis of rain gauge data at GPCC

Udo Schneider (GPCC/DWD)

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Precipitation characteristics observed from TRMM PR

Yukari Takayabu (CCSR/University of Tokyo)

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Session III: Validation and Collaboration  

Formulating and creating multisensor-multiscale precipitation datasets and model verification

Efi Foufoula (University of Minnesota)

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The relevance of gridded rainfall observations to verify ECMWF precipitation forecasts

Anna Ghelli (ECMWF)


Error characteristics of rain gauge and radar estimates and validation issues

Witold Krajewski (University of Iowa)


Monitoring precipitation over the Arctic drainage: Data requirements, shortcomings and applications of atmospheric reanalysis

Mark Serreze (NSIDC)

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The international Precipitation Working Group: Opportunities and perspectives

V Levizzani (CNR) & Arnie Gruber (NESDIS/NOAA)