Frequently Asked Questions

Conventions Used in MM5 System

Time: All times used in MM5 modeling system are UTCs which stands for Universal Time. It is the same as Greenwich Mean Time (or GMT). To find out
what the local time at any model times, you need to know how far ahead or behand GMT your local time is.

Latititude/Longitude: 0 degree is at Greenwich, England. Positive longitude is eastward from Greenwich till dateline. Negative longitude is westward
from Greenwich till dateline. Positive latitude is in the northern hemisphere, and negative latitude is in the southern hemisphere.

Model winds: All gridded wind components (U and V) in the model are with respect to model coordinate. This means the U component is in x-direction
of the model, and V component in y-direction of the model. When comparing model winds with station observations, winds need to be rotated to earth
coordinate.

Model array indices: MM5 modeling system programs use array indices I, J, and K, where I is in y direction, J in x direction, and K in z direction.