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 Development Antalya, Turkey, February 2010 Source: NOAA CDC Source: 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 anomaly January 2010 Mean T anomaly January 2010 Sunshine anomaly January 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, Studies by Madden and colleagues in the 1990s (IJC 1997, 1999) suggest:

Seasonal influences - ENSO state

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

Information: Current ENSO state NIWA SOI January 2010: SOI (3-month -0.8) CDC SST anomalies (27 Dec Jan 2010) images/sst/sst.anom.month.gif

Loosely Adapted from Dynamical Statistical Information: Predicted ENSO State

Information: SST around New Zealand November 2009 December 2009 January 2010

Regional climate projections from modelling centres Precip Feb-April 2010Temperature 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: average Climate terciles: 25%;50%;25%

Example: hydro-electricity warning La Ni ñ a projections starting May 2007 May % chance of move to LN JuneLN likely to develop JulyLN on its way AugustLN falters but still possible September LN indicators strengthen October LN conditions have developed November LN to stay for summer December LN strengthens January 2008 LN dominates February LN likely to remain until autumn March AprilLN 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