climate information for hydrological outlooks david wratt, roddy henderson, charles pearson &...
TRANSCRIPT
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