GHP and Extremes

GHP SCIENCE ISSUES1995

GHP SCIENCE ISSUES1995

How do water and energy processes operate over different land areas?

Sub-Issues include:

• What is the relative influence of local and non-local controls on precipitation?

• What feedback mechanisms affect the water cycle and how do these influence wet and dry periods?

How

GEWEX SCIENCE ISSUESGEWEX SCIENCE ISSUES

Phase II Science Issues• Are the Earth’s energy budget and water cycle changing?• Can these changes be predicted up to seasonal and interannual

timeframes?• How do global energy and water cycle processes contribute to

climate feedbacks and natural climate variability?• What is the impact of the variability in the global energy budget and

water cycle on water resources?

Most (all) of these can be linked with extremes

EXTREMES AND GHP: A HISTORY

1995 An issue within GHP (GHP #1)

2002 Very short presentation (GHP #8)

2003 Small workshop to discuss whether to proceed (GHP #9)

2004 Short update (GHP #10)

DEFINITIONS AND SCOPE…

Extended wet period: prolonged, substantial precipitation for 24 h to several days that affects basins on scales of at least 10**5 km**2.

Drought: … utilize standard definition(s)

As well as:

Drought-Precipitation Combination: Long periods of dry conditions interspersed with heavy rain

Flood Focus: Those initiated by extensive precipitation rather than very localized flash floods

RECENT EXTREMES

A Few Illustrations

CANADIAN PRAIRIES2002

EUROPEAN DROUGHT2003

AFRICAN FLOODS2003

Worst floodingin 70 years in someregions

BRAZILJanuary 2004

Some regionsexperienced theheaviest rainssince 1910

AUSTRALIAN DROUGHTFebruary 2004

One of the mostIntense heat wavesIn a century

ASIAN FLOODSJuly 2004

US DROUGHT August 2004

SOUTH AMERICAN STORMSJune-July 2004

GLOBAL SYSTEM AND EXTREMES

RECENT DROUGHTS (Hoerling and Kumar, 2003)

• Drought caused widespread destruction in from 1998-2002– Impacting areas in

Canada, United States, Australia, Africa, China, and Scandinavia

• 20% of Earth’s land mass was under drought conditions in 2002

Anomaly (mm)

1998-2002 Precipitation Anomalies

SEA SURFACE TEMPERATURE ANOMALIES1998-2002

Tem

per

atu

re (C

)

2003/04 ACTIVITIES

A start was made on this effort on an ‘ad hoc’ basis (not a formal

working group)

1. Web site(linked through GHP home page)

2. Discussions about activities3. AGU/CGU presentation

IDEAS FOR MOVING AHEAD

1. Synthesis of present state of knowledge

processes and feedbacks

2. Trends in extreme events

3. Focus in a collective manner on extremes during a particular period …

ONE COMPONENT …

Feedback mechanisms affecting wet and dry periods in different regions

What is our current state of knowledge?

Focus:• different regions• common and distinct features• outstanding common as well as specific issues• Identification of appropriate datasets for addressing issues

Steps:• contacts in different regions• outline of final ‘product’ such as a synthesis article• focused activity with iterations until completion

Outcome: Final synthesis article

A SECOND COMPONENTIs the occurrence of extremes changing?

Focus:• Different regions

Approach:• Contacts in different regions• Observed and modelled fields for analysis• Statistical analyses and physical interpretations• Compilation of trend results with physical interpretations

Outcome: • Synthesis article

A THIRD COMPONENT …Focus in a collective manner on extremes during a particular period

Possible periods:• WEBS, CEOP …

Approach:• Focus on a particular period• Examine extremes individually• Relate to each other as well as the overall climate system

Benefits:• Efficient progress • Hands-on experience with such studies

Actions:• (Continue to) carry out individual research projects and update others• Eventually carry out joint research projects

Outcome:• Individual and synthesis articles on individual extremes and their connections

CEOP

1. Objectives:

Water and Energy Theme: Use enhanced observations to better document and simulate water and energy fluxes and reservoirs over land on diurnal to annual temporal scales and to better predict these on temporal scales up to seasonal for water resource applications.

2. Time Period: 2001-04

3. Datasets: unprecedented satellite, surface, model

SPECIFIC ISSUESCEOP period as an example

The following represent issues that could be addressed:

• What extremes occurred during CEOP over the world?

• What are the characteristics of these extremes?

• What factors led to, sustained, and ended these extremes?

• To what degree were the extremes inter-connected?ocean, land surface, and other patterns

• How typical and/or unusual is the CEOP period and why?

• What are the implications for extremes and the climate system?

A CANADIAN EXTREMES EFFORT

To better understand the physical characteristics of and processes influencing Canadian Prairie droughts, and to contribute to their better prediction, through a focus on the 1999-2004 drought

• Quantify the physical features of this recent drought • Improve the understanding of the processes and feedbacks

governing the formation, evolution, cessation and structure of the drought

• Assess and reduce uncertainties in the prediction of drought and its structure

• Compare the similarities and differences of current drought to previous droughts over this region and those in other regions

• Apply our progress to address critical issues of importance to society

SUMMARYGHP #1: What feedback mechanisms affect the water cycle and how do

these influence wet and dry periods?

1. Extremes are important and small steps have started on this issueweb site for ‘extremes’ information presentations and initial ideas …

2. Some components of a project may include:

• Better appreciation of current knowledge in different regions • Better appreciation of trends in extreme events• Special multi-year time period focus (WEBS, CEOP …) • Other suggestions …

3. Not yet clear whether to formally organize as a working group

4. Meeting this Thursday morning (0830 … 1000)Main objective: begin to focus on small number of do-able activities