Climate Information for Hydrological Outlooks

David Wratt, Roddy Henderson, Charles Pearson & James Renwick

NIWA, New Zealand

Technical Conference on Changing Climate and Demands for Climate Services for Sustainable DevelopmentAntalya, Turkey, 16-18 February 2010

Source: NOAA CDCSource: NOAA CPC

Outline

• Methodology overview

• Seasonal climate Updates & Outlooks• Present conditions

• Predictability

• Information used for outlooks

• The probabilistic projections

• Producing hydrological outlooks

• Skill

• Further guidance products

• Summary

Producing Outlooks - Overview

Seasonal Climate Updates and Outlooks

Climate stations

National information base

• 208 open climate stations (118 automatic)

• ~70 soil moisture sites (some NIWA, some local government) - combine with modelled soil moisture from climate data

• Hydrometric network >600 open stations (NIWA + local government)

Climate “update”

Rainfall anomalyJanuary 2010

Mean T anomalyJanuary 2010

Sunshine anomalyJanuary 2010

Soil moisture “update”

Historical average deficit At 9am on 1 Feb (mm)

Actual deficit at 9am on 1 Feb 2010 (mm)

Anomaly at 9am on 1 Feb 2010(mm)

Catchment river flows “update”

At end January 2010

Potential Seasonal Predictability - NZ

• About 50% of the variance of seasonally-averaged temperature is potentially predictable (less in winter). Madden & Kidson, IJC, 1997

• Only 30% or less of the interannual variance of seasonal precipitation is potentially predictable. Madden et al, IJC, 1999.

Studies by Madden and colleagues in the 1990s (IJC 1997, 1999) suggest:

Seasonal influences - ENSO state

Seasonal influences - ENSO state

“Average” El Niño Summer “Average” La Niña Summer

Rain anomaly Rain anomaly

Information: Current ENSO state

NIWA SOI

January 2010: SOI -0.6 (3-month -0.8)

CDC SST anomalies (27 Dec 2009 - 23 Jan 2010)

http://www.cdc.noaa.gov/map/images/sst/sst.anom.month.gif

Loosely Adapted from http://www.bom.gov.au/climate/ahead/ENSO-summary.shtml

Dyn

amic

al

Sta

tistic

al

Information: Predicted ENSO State

Information: SST around New Zealand

November 2009

December 2009

January 2010

Regional climate projections from modelling centres

Precip Feb-April 2010 Temperature Feb-April 2010

IRI

APEC Climate Centre

Six climate forecasting regions

Northland, Auckland, Bay of Plenty

Nelson, Marlborough

Gisborne, Hawkes Bay, Wairarapa

Central North Is, Taranaki, Whanganui, Manawatu, Wellington

West Coast, Alps and Foothills, Inland Otago, Southland

Coastal Canterbury, East Otago

Statistical model predictions based on present conditions

For Feb - Mar - Apr 2010

Summary of Projections

For Feb - Mar - Apr 2010

Consensus probabilistic outlook tables

For Feb - Mar - Apr 2010

Moving to Hydrological Outlooks

• 1-2 hydrologists participate in climate outlook teleconference

• Material on present state and projections passed to ~8 hydrologists

• They do individual forecasts, and merge into a consensus

Assessment by one hydrologist

For FMA 2010

Merging into a “consensus” assessment

For FMA 2010

Include in the “Update” guidance table

Presentation on TCU webpage

Skill of outlooks - Whole Country

Further hydrological product for water supply utility

Now Demand: averageClimate terciles: 25%;50%;25%

Example: hydro-electricity warning La Niña projections starting May 2007

May 2007 50% chance of move to LN

June LN likely to develop

July LN on its way

August LN falters but still possible

SeptemberSeptember LN indicators strengthenLN indicators strengthen

October October LN conditions have developedLN conditions have developed

NovemberNovember LN to stay for summerLN to stay for summer

DecemberDecember LN strengthensLN strengthens

January 2008January 2008 LN dominatesLN dominates

FebruaryFebruary LN likely to remain until autumnLN likely to remain until autumn

MarchMarch LN likely to remain until autumnLN likely to remain until autumn

April LN weakens

These were significant and

serious warnings for

both generators and users!

The outcome

Summary• Common seasonal climate outlook

products + information on present state together provide sufficient input for producing hydrological seasonal outlooks (for soil moisture, catchment flows)

• Skill of climate forecasts for NZ is real but modest. Potential level of predictability sets limits

• NIWA flow outlooks have higher skill levels overall than rainfall outlooks (influence of initial conditions?)

• Media want climate outlooks, but often don’t (or won’t) understand limits

• Using probabilistic outlooks requires sophisticated approach by end-users.

• There is potential for collaborating with users to develop further products targeted to their needs