amax()

This function returns an area maximum -- the maximum value in a grid spanning an X-Y region. The syntax is:

amax(expr, xdim1, xdim2, ydim1, ydim2)

where:

expr    any valid GrADS grid expression
xdim1   starting X or LON dimension expression
xdim2   ending X or LON dimension expression
ydim1   starting Y or LAT dimension expression
ydim2   ending Y or LAT dimension expression

For global maximum, a shorthand may be used:

amax(expr, global) or
amax(expr, g)

amax(expr, lon=0, lon=360, lat=-90, lat=90)

Usage Notes

1. This function will only work with GrADS version 2.0.2 or later.
2. This function is more efficient that using nested max functions.
3. Related functions amaxlocx and amaxlocy will return the grid location (X or Y) of the maximum value. If more than one grid box contains the maximum value, the location returned will be the first one encountered as the grid is scanned. The grid is scanned by rows from south to north, and each row is scanned from west to east.
4. A similar set of functions exists for finding the minimum over an area: amin, aminlocx, and aminlocy.

Examples

1. Get the maximum value of the variable ps over a specified grid domain:
   d amax(ps,x=10,x=120,y=15,y=45)
   
   
2. Get the maximum value of the variable sstanom over the nino3.4 domain:
   d amax(sstanom,lon=-170,lon=-120,lat=-5,lat=5)
   
   
3. Get the maximum value of the variable slp over the global domain, and also get the grid location of that minimum. Check results.
   

   ga-> d amax(slp,g)
   Result value = 105732 
   ga-> d amaxlocx(slp,g)
   Result value = 168 
   ga-> d amaxlocy(slp,g) 
   Result value = 13 
   ga-> set x 168
   LON set to 83.5 83.5 
   ga-> set y 13
   LAT set to -84 -84 
   ga-> d slp
   Result value = 105732