### Precipitation

#### Indicators:

- Annual mean precipitation
- Change of annual precipitation (relative to 1990)

- Precipitation change since 1990 (monthly)
- Precipitation surplus

In situations where precipitation decreases, important negative effects on plant growth can be expected. In the view 'Initial State- observed climate' the observed monthly precipitation is shown for the period 1960-1990. In the years after 1990 the pattern of precipitation is calculated in Geographical Pattern-Scaling (GPS) on the basis of the global temperature change as computed by UDCM.

| #### Annual mean precipitation
| unit: mm/day (mm per day) dimension: None

The default precipitation grid of a GCM is multiplied with the global surface temperature change of UDCM. This change is added to the observed precipitation from the climatology database.

The precipitation change patterns differ considerably between the various GCMs. On the main disc the default pattern is from HADCM2.

| #### Change of annual precipitation (relative to 1990)
| unit: mm/day (mm per day) dimension: None

The change of annual temperature is the result of multiplication of the global-mean temperature change from UDCM with the precipitation change pattern. This pattern is used as input for the terrestrial vegetation model (TVM) and land-cover model (LCM).

The precipitation change patterns differ considerably between the various GCMs. On the main disc the default pattern is from HADCM2.

| #### Precipitation change since 1990 (monthly)
| unit: mm/day (mm per day) dimension: month, landcover type, latitudinal belt

This view presents the changes in monthly precipitation since 1990 for the different IMAGE landcover types on the different latitudinal belts (90oN-60oN, 60oN-30oN, 30oN-0o, 0o-30oS, 30oS-60oS and 60oS-90oS). With use of the 'Time Manager' the differences on a timescale from 1990 to 2100 can be analyzed.

The precipitation change patterns differ considerably between the various GCMs. On the main disc the default pattern is from HADCM2.

| #### Precipitation surplus
| unit: mm/yr (mm per year) dimension: None

Precipitation surplus is computed for each 0.5 by 0.5 degree grid as the difference between total annual precipitation and the annual actual evapotranspiration. This surplus is an indicator for water surpluses and shortages in ecosystems, and runoff and water resources.

The precipitation change patterns differ considerably between the various GCMs. On the main disc the default pattern is from HADCM2.