Handbook for Irrigation of Wine Grapes in South Africa

Chapter 9

9.3

PREDICTION OF COLD DAMAGE

) for the following morning, i.e.

The expected minimum air temperature (T min

as predicted by the SAWS, as well as the dry ball temperature (T d

), wet ball

temperature (T w

) and wind speed are used to predict possible cold damage. The and the temperature at the level where cold damage is

difference between T min

expected in the vineyard, also needs to be considered. If a low T min

is predicted for

the next morning, T d must be measured between 17h00 and 20h00. The dew point temperature can then be determined by means of Table 9.1. For example, if the altitude is higher than 500 m, and T d minus T w is 4°C, with T w being 1°C, the expected T dp will be -5.6°C as shown in Table 9.1. Following this, Table 9.2 can be used to indicate the type of expected cold damage. and T w

IRRIGATION OF WINE GRAPES 287