Science Media Centre New Zealand - Online media briefing 22 March 2013. Climate scientists answer questions about the ongoing drought in New Zealand. Audio available at sciencemediacentre.co.nz

1. SMC Briefing: Drought – soil, rivers, climate, outlook
Briefing start time: 10.30 am (NZT)
SPEAKERS:
Dr Andrew Tait: Climate Scientist, NIWA
Roddy Henderson: Hydrologist, NIWA
Dr Brett Mullan: Principal scientist, NIWA
Also on the line for questions:
Stuart Anderson - Resource Policy North Dr David Wratt: Chief Climate Scientist, NIWA
Island Regions Manager, Ministry Primary
Industry (MPI)

2. 2013 drought
Media briefing: 22 March 2013
Dr Andrew Tait: soil moisture
Roddy Henderson: river flow
Dr Brett Mullan: historical perspective and outlook
Dr David Wratt: the drought and climate change trends

3. Widespread drought conditions have
developed over the last three months

4. Beginning of January soil moisture status
Same time
“Normal” last year This year

5. Beginning of February soil moisture status
Same time
“Normal” last year This year

6. Beginning of March soil moisture status
Same time
“Normal” last year This year

7. Mid-March soil moisture status
Same time
“Normal” last year This year

8. Current soil moisture status
Same time
“Normal” last year This year

9. February 2013 river flows
• Map shows river flows across
New Zealand for February,
related to previous Februaries.
• Much of the country has flows
that are in the lowest 10% of
recorded values for that
month (red).
• Nearly all the country has
flows in the lowest third (red
and orange).
• Data from NIWA, Regional
Councils, power companies
and NZX.

10. Historical perspective on 2013 drought
and seasonal outlook
Dr Brett Mullan
Principal Scientist

11. How do the 2008 and 2013 droughts compare?
PED = ‘Potential Evapotranspiration Deficit’ = water needed for optimum plant growth over growing season

12. How does the 2013 drought rank?
• 2013 is ‘worst’ (highest deficit)
in large parts of: Northland,
Auckland, Waikato, Bay of
Plenty, Hawkes Bay, West Coast.
• 17% of grid-points ‘worst’ in
2013.
• 2013 is second only to 1973 in
fraction of NZ ranked ‘worst’ in
41 years of record (affected
Wairarapa, Tasman, Otago,
Southland).
Colour range (purple through olive): purple = worst in 41 years; olive = not in top 5

13. Seasonal outlook: March – May 2013
Lower pressures than usual are likely over northern Australia, with high pressures
south of New Zealand.
Rainfall for the March – May period as a whole is likely to be in the near normal
range for most regions, except for the West Coast of the South Island, where
normal to above normal rainfall is likely. Because of the existing soil moisture
deficits across the North Island and in the eastern South Island, soil moisture
levels and river flows are expected to take some time to recover in these areas.
Autumn temperatures are likely to be above average across the South Island, and
average to above average in the North Island.
Soil moisture levels and river flows are projected to be normal to below normal
for the autumn season as a whole for the North Island, as well as the eastern
South Island, and near normal elsewhere.
Next outlook (April – June 2013) due for release Tuesday 2 April

14. Seasonal outlook: March – May 2013
March-May rainfall likely to be “near normal” in North Island regions.
How should this be interpreted?
Outlook Tercile Probabilities
Above Normal
Near Normal
Below Normal

15. The drought and climate change trends
Dr David Wratt
Chief Climate Scientist