Why t+0 in while looping the variable with DEFINE

[Mallikarjun]

Hello Grads Users,

 In the Grads manual I could not understand why we should use t+0
while calculating climatology of 10 years. It is written that t+0
uses the start time that is whatever time the define command is
using as it loops. I could not understand this point.

it goes like this;

set lon -180 180
set lat -90 90
set lev 500
set t 1 12
define zave = ave(z,t+0,t=120,1yr)

also, could you please tell me the exact syntax of AVE function since
I came across different types of AVE syntax.


Thanks in advance.

--
Mallikarjuna.K
J.R.F
Centre for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012