I assume your data is a matrix of the form
data(lat,lon,time)
with dimension of the latitude, longitude and time. So you can just keep the borders of the lat and lon you want finding the indices. Eg if you need to keep the latitudes from 20 to 60 degress North, assuming that you have global latitude from -90 to 90 each 5 degrees:
lat = -90:5:90';
you just find the indices
id = (lat>=20&lat<=60);
data1 = data(id,:,:); % get the latitude dimensions you want and keep all the other dimension
Same approach cab be applied for longitude too
