Changes in New Zealand pan evaporation since the 1970s

Date

2005

Authors

Roderick, Michael
Farquhar, Graham

Journal Title

Journal ISSN

Volume Title

Publisher

John Wiley & Sons Inc

Abstract

Several previous studies have reported declines in pan evaporation rate throughout the Northern Hemisphere of about 2-4 mm a-2 for various periods since the 1950s. A recent analysis of Australian pan evaporation reported a similar decline and raises the possibility that part of the phenomenon may be related to the greenhouse effect. To assess that possibility, one needs to know whether the decline in evaporative demand is happening in other parts of the Southern Hemisphere. As a first step to addressing the latter question, we examined the trend in pan evaporation at 19 New Zealand sites. We found statistically significant declines in pan evaporation rate at 6 of the 19 sites. There were no sites with statistically significant increases in pan evaporation. When averaged across all 19 sites, the decline in pan evaporation rate was roughly 2 mm a-2 (i.e. mm per annum per annum) since the 1970s. Over a 30-year period, this is equivalent to a decline of about 60 mm a-1 in annual pan evaporation. These results are generally consistent with those reported throughout the Northern Hemisphere and in Australia. We conclude that the trend for decreasing evaporative demand previously reported throughout the Northern Hemisphere terrestrial surface may also be widespread in the Southern Hemisphere. This maybe, in part, a greenhouse-related phenomenon.

Description

Keywords

Keywords: Climate change; Evaporation; Greenhouse effect; Hydrology; Precipitation (meteorology); Statistical methods; Enhanced greenhouse effect; Hydrological cycle; Pan evaporation; Potential evaporation; Water cycle; Climatology; climate change; evaporation; hyd Climate change; Enhanced greenhouse effect; Hydrological cycle; Pan evaporation; Potential evaporation; Water cycle

Citation

Source

International Journal of Climatology

Type

Journal article

Book Title

Entity type

Access Statement

License Rights

DOI

10.1002/joc.1262

Restricted until

2037-12-31