Local climate

Mean daily maximum temperature

Mean daily minimum temperature
Total annual rainfall
Annual mean wind speed
Annual minimum temperature and groundfrost days
 
 

Purpose of indicator

Globally, climate is being monitored to understand how it is changing and how these changes impact seasons and natural events such as storms, droughts and floods. Climate also affects types of crops that can grow successfully in an area. Monitoring changes in Rotorua’s climate provides an understanding of whether the local climate is changing and if so, what impacts may be expected as a result of these changes.


Current information and trend

Figure 1 shows ground frost days has been decreasing since the 1960s. The same figure shows annual minimum temperature has remained about the same, however when looking at the period from 1992 to 2010 (shown by a line on the graph), annual minimum temperatures show a weak increase, and ground frost days are less numerous than the period from 1966 to 1992. In figures 2 and 3 the mean daily minimum and maximum temperatures also show a weak upward trend from 1992 to 2010. Over the country as a whole (and elsewhere around the world), minimum temperatures have risen faster than maximum temperatures.

 


Figure 1: Source: National Institute of Weather and Atmosphere, 2011
 

Figure 2: Source: National Institute of Weather and Atmosphere, 2011
 

Figure 3.  Source: National Institute of Weather and Atmosphere, 2011
 

Rainfall

In general, since the 1960s there has been a small downward trend in rainfall (figure 4), and in the number of wet days (figure 5), with a large amount of year-to-year variability. Projections for the future suggest a continued small downward trend with seasonal and inter-annual variations. It is important to keep in mind that rainfall in individual catchments can have big variations. For example, there are Rotorua rain events where the Mamaku plateau receives lots of rain and none falls on the eastern hills of the Rotorua caldera.


Figure 4: Source: National Institute of Weather and Atmosphere, 2011


Figure 5: Source: National Institute of Weather and Atmosphere, 2011

Wind speed

Mean wind speed (figure 6) at Rotorua airport shows a small upward trend over the past 50 years, which is consistent with the general increase in westerly wind strength over New Zealand.



Figure 6: Source: National Institute of Weather and Atmosphere, 2011
 

In Summary

  • Frequency of ground frosts show a significant decrease since 1960s
  •  Annual maximum temperatures show very little change since 1960s
  • Mean minimum and maximum temperatures show a weak upward trend since 1992
  • Rainfall and number of wet days have shown a small downward trend
  • Mean wind speed shows a small upward trend over the past 50 years

 


 


 


 
Page reviewed: 18 Dec 2013 3:54pm