LENZ - Annual water deficit

7547
565
Added
30 May 2010

This dataset was first added to LRIS Portal on 30 May 2010.

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.

Layer ID 48097
Data type Grid
Resolution 25.000m
Services Raster Query API, Catalog Service (CS-W), data.govt.nz Atom Feed

LENZ - Monthly water balance ratio

4889
300
Added
27 May 2010

This dataset was first added to LRIS Portal on 27 May 2010.

Monthly water balance ratio 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).

This layer differentiates between regions that have minimal water deficit, but vary markedly in the total amount of rainfall they receive. Based on a water balance model using monthly estimates of mean daily temperature, mean daily solar radiation, and mean rainfall. This layer is the annual average of the monthly ratios of rainfall to 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. To calculate the monthly water balance ratio, the ratio of rainfall to evaporation was computed for each month, and then the average of these twelve ratios was calculated.

Additional details such as the climate station locations used in the creation of the layer are defined in the attached LENZ Technical Guide.

Layer ID 48093
Data type Grid
Resolution 25.000m
Services Raster Query API, Catalog Service (CS-W), data.govt.nz Atom Feed

LENZ - October vapour pressure deficit

3603
163
Added
30 May 2010

This dataset was first added to LRIS Portal on 30 May 2010.

October vapour pressure 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).

October vapour pressure deficit, recorded in kPa, is used to estimate the effects of variation in the dryness of the air. 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. Estimates of the vapour pressure deficit for each month were derived by coupling a 100 m DEM with a thin-plate spline surface fitted to an irregular network of 287 meteorological stations, using humidity and temperature data. The resulting 100 metre layer was then interpolated to 25 metres using bilinear interpolation.

Calculation of the vapour pressure deficit first required estimation of the temperature at 0900 hours, the time at which humidity measurements are made. This was calculated from the measured mean daily minimum and maximum temperatures for each month using a function that simulates the temperature course through the day. The estimated temperature at 0900 hours was then used to calculate the saturation water vapour pressure , which indicates the maximum amount of water vapour able to be held in the air given its temperature. Vapour pressure deficits in October were used in LENZ as this is the month when westerly winds are generally most persistent, resulting in strong geographic variation in vapour pressure deficits across New Zealand.

This layer has been multiplied by a factor of 100 (i.e. converted into an integer grid) to save space and make the grids more responsive. A value of 33 is actually 0.33 kPa.

Additional details such as the climate station locations used in the creation of the layer and error maps are defined in the attached LENZ Technical Guide.

Layer ID 48091
Data type Grid
Resolution 25.000m
Services Raster Query API, Catalog Service (CS-W), data.govt.nz Atom Feed