Atmospheric ReanalysesAtmospheric Reanalyses

Background and History: Background and History: ““Analysis” for weather prediction Analysis” for weather prediction

(automated for NWP)(automated for NWP) The results (“analyses”) used for The results (“analyses”) used for

climate research, monitoring and climate research, monitoring and prediction – never the intended useprediction – never the intended use

Changes in analysis/model system Changes in analysis/model system impacted those applicationsimpacted those applications

““Reanalysis” the obvious solutionReanalysis” the obvious solution

Atmospheric ReanalysesAtmospheric Reanalyses

Implementation:Implementation: Several publications during mid-1980sSeveral publications during mid-1980s Early examples at NASA/DAO and Early examples at NASA/DAO and

ECMWF (ERA-15)ECMWF (ERA-15) First mature reanalysis – NCAR/NCEP First mature reanalysis – NCAR/NCEP

We need more comprehensive climate observations and we must make more efficient use

of those that are and will be available.

THE NEED FOR A SYSTEMS

APPROACH TO CLIMATE

OBSERVATIONSBY KEVIN E. TRENBERTH, THOMAS R. KARL, AND THOMAS W. SPENCE

Because climate is changing, we need to determine how and why. How do we best track and provide useful information of sufficient quality on climate?

Bulletin of the American Meteorological Society:

November 2002, 83, 1593-1602

Observing Observing systemsystem means a comprehensive means a comprehensive approach, includingapproach, including

• Climate observationsClimate observations from both space-based and in situ from both space-based and in situ platforms taken in ways that address climate needs and adhere platforms taken in ways that address climate needs and adhere to the ten principles outlined by the NRC (1999).to the ten principles outlined by the NRC (1999).

• A global telecommunications network and satellite data A global telecommunications network and satellite data telemetry capacity to enable data and products to be telemetry capacity to enable data and products to be disseminated. disseminated.

• A climate observations analysis capability that produces global A climate observations analysis capability that produces global and regional analyses of products for the atmosphere, oceans, and regional analyses of products for the atmosphere, oceans, land surface and hydrology, and the cryosphere, based on four land surface and hydrology, and the cryosphere, based on four dimensional data assimilation capabilities that process the dimensional data assimilation capabilities that process the multivariate data in a physically consistent framework to multivariate data in a physically consistent framework to enable production of the analyses: for the atmosphere and enable production of the analyses: for the atmosphere and oceans, land surface and so on.oceans, land surface and so on.

• Global climate models that encompass all parts of the climate Global climate models that encompass all parts of the climate system and which are utilized in data assimilation and in system and which are utilized in data assimilation and in making ensemble predictions.making ensemble predictions.

Societal Benefits

Climate Variability and

Change

Ocean Resources

Disasters

EnergyHealth

Agriculture

Ecosystem

Water Resources

GEOSS--- Creating a “System of Systems”GEOSS--- Creating a “System of Systems”

Global Observing Systems

GCOSGOOSGTOS

WHYCOSWorld Weather Watch

IGBPIOOSCEOSIGOS

Global Observing Systems

GCOSGOOSGTOS

WHYCOSWorld Weather Watch

IGBPIOOSCEOSIGOS

National/Multinational Observing Systems

Satellites

Surface Observations

Radar

Aircraft

Ocean Observations

Paleo-data

National/Multinational Observing Systems

Satellites

Surface Observations

Radar

Aircraft

Ocean Observations

Paleo-data

Private Sector Observing Systems

Satellites

Mesonets

Lightning

Commercial Aircraft

Private Sector Observing Systems

Satellites

Mesonets

Lightning

Commercial Aircraft

5

Integration / Synthesis / Analysis

Reprocessing and Reanalysis are essential

Given the continuing improvement in climate observations Given the continuing improvement in climate observations and the need for long time series, reprocessing is an and the need for long time series, reprocessing is an

essential element of every climate observing system. essential element of every climate observing system.

•Workshop report distributed•See workshop web site (http://www.joss.ucar.edu/joss_psg/meetings/climatesystem/) for pdf version of report and background information from the workshop.

Workshop on Ongoing Analysis of the Workshop on Ongoing Analysis of the Climate SystemClimate System

18-20 August 2003, Boulder, Colorado18-20 August 2003, Boulder, Colorado

The Workshop concluded that the U.S. must The Workshop concluded that the U.S. must establish a National Program for Ongoing Analysis establish a National Program for Ongoing Analysis

of the Climate System to provide a retrospective and of the Climate System to provide a retrospective and ongoing physically consistent synthesis of earth ongoing physically consistent synthesis of earth

observations in order to:observations in order to:

Guide the design and operation of observing Guide the design and operation of observing systemssystems

Produce and sustain the growing climate recordProduce and sustain the growing climate record Reconcile disparate climate observations and Reconcile disparate climate observations and

characterize analysis uncertaintycharacterize analysis uncertainty Establish initial conditions for climate predictionEstablish initial conditions for climate prediction Validate prediction and projection models on all Validate prediction and projection models on all

time scalestime scales Provide long time series of global and regional Provide long time series of global and regional

climatic analyses for all types of prediction and climatic analyses for all types of prediction and projection verificationprojection verification

Elements of a Comprehensive Ongoing AnalysisElements of a Comprehensive Ongoing Analysis

Enhancing and managing the observational databaseEnhancing and managing the observational database Archeology, new sensors, continuity and feedbackArcheology, new sensors, continuity and feedback

Ongoing analysis:Ongoing analysis: Continually update most recent reanalyses (CDAS)Continually update most recent reanalyses (CDAS) Use OSEs and OSSEs to document impact of continuing Use OSEs and OSSEs to document impact of continuing

observing system changesobserving system changes Provide feedback to observing system developers/operatorsProvide feedback to observing system developers/operators

Periodic reanalysesPeriodic reanalyses Post 1979 reanalysis with goal of continuous climate recordPost 1979 reanalysis with goal of continuous climate record Post 1950 reanalysis with same goalPost 1950 reanalysis with same goal Post 1850 surface NH orientedPost 1850 surface NH oriented Continental-scale regional reanalysis at very high spatial Continental-scale regional reanalysis at very high spatial

resolutionresolution Stewardship and dissemination Stewardship and dissemination

Ensure that the products are useableEnsure that the products are useable Applied researchApplied research

Develop improved methods and products Develop improved methods and products Intended to solve problems identified within programIntended to solve problems identified within program

Atmospheric Reanalyses: status Atmospheric Reanalyses: status and issuesand issues Current status: Current status:

ERA-40 completedERA-40 completed JRA-25 completedJRA-25 completed MERRA underwayMERRA underway

Issues:Issues: No National program as yet – recognition of the problem, No National program as yet – recognition of the problem,

but little actionbut little action Lots of observing system investment, but without the Lots of observing system investment, but without the

integrating (analysis) segment, likely to be inefficient at integrating (analysis) segment, likely to be inefficient at bestbest

Models (climate and weather) cannot be validated (and Models (climate and weather) cannot be validated (and therefore used effectively) without better climate analysestherefore used effectively) without better climate analyses

Users (climate monitoring and prediction, climate Users (climate monitoring and prediction, climate research, decision support, water resources, applications research, decision support, water resources, applications of all sorts) are disconnected from the integration processof all sorts) are disconnected from the integration process

All analysis work to date is based upon NWP – no All analysis work to date is based upon NWP – no evidence that climate applications are best served by evidence that climate applications are best served by methods so developedmethods so developed