Annual water deficit data layer used in the creation of Land Environments of New Zealand (LENZ) classification. The classification layers have been made publicly available by the Ministry for the Environment (see data.mfe.govt.nz/layers/?q=LENZ for to access these layers).
Based on a water balance model using monthly estimates of mean daily temperature, mean daily solar radiation, and mean rainfall, this layer is used as an indicator of soil dryness. The layer calculated as the sum of any deficits between rainfall and potential evaporation calculated using the method of Priestley and Taylor (1972). The resulting 100 metre layer (The temperature, solar radiation and rainfall layers were all 100m) was then interpolated to 25 metres using bilinear interpolation.
The climate station data used in the development of this climate surface were derived from summaries of climate observations published by the New Zealand Meteorological Service, using data collected over the period from 1950-1980 The data layer was derived from surfaces fitted to monthly data describing daily average temperature, daily solar radiation and monthly rainfall. The rainfall surface was fitted using NZMG coordinates, elevation, and a model describing relationships between topography and westerly winds.
Having derived the 36 input climate layers, an empirical model was first used to calculate the monthly potential evaporation from the monthly estimates of solar radiation and temperature. These estimates of evaporation were then compared with the monthly rainfall estimates. Where the rainfall exceeded evaporation, the monthly deficit was assumed to be zero, but where monthly evaporation exceeded monthly rainfall, the shortfall was accumulated through the year to derive an estimate of the annual water deficit.
The units for this layer are in mm, higher values are areas that have a larger deficit.
Additional details such as the climate station locations used in the creation of the layer are defined in the attached LENZ Technical Guide.
|1.||LENZ Technical Guide||3.17 MB||
|Category||Climatology / Meteorology / Atmosphere > Climate > Climatic factor|
|Tags||Rainfall, Climate, Water Supply, Water deficit, LENZ, New Zealand, Water Demand|
|Metadata||Dublin Core, ISO 19115/19139|
|Services||Raster Query API, Catalog Service (CS-W), data.govt.nz Atom Feed|