smc(nz) briefing: drought - soil, rivers, climate, outlook
TRANSCRIPT
SPEAKERS:
Dr Andrew Tait: Climate Scientist, NIWA
Roddy Henderson: Hydrologist, NIWA
Dr Brett Mullan: Principal scientist, NIWA
Dr David Wratt: Chief Climate Scientist, NIWA
SMC Briefing: Drought – soil, rivers, climate, outlookBriefing start time: 10.30 am (NZT)
Also on the line for questions:
Stuart Anderson - Resource Policy North Island Regions Manager, Ministry Primary Industry (MPI)
2013 droughtMedia briefing: 22 March 2013
Dr Andrew Tait: soil moistureRoddy Henderson: river flow
Dr Brett Mullan: historical perspective and outlookDr David Wratt: the drought and climate change trends
Widespread drought conditions have developed over the last three months
Beginning of January soil moisture status
“Normal”Same time last year This year
Beginning of February soil moisture status
“Normal”Same time last year This year
Beginning of March soil moisture status
“Normal”Same time last year This year
Mid-March soil moisture status
“Normal”Same time last year This year
Current soil moisture status
“Normal”Same time last year This year
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.
Historical perspective on 2013 drought and seasonal outlook
Dr Brett MullanPrincipal Scientist
How do the 2008 and 2013 droughts compare?
PED = ‘Potential Evapotranspiration Deficit’ = water needed for optimum plant growth over growing season
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
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
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 NormalNear NormalBelow Normal
The drought and climate change trends
Dr David WrattChief Climate Scientist