A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #


see Zulu Time

Z-R Relationship

a mathematical equation that converts radar-measured reflectivity to an estimated rainfall rate. The reflectivity factor (Z) is related to both the drop-size distribution and the 6th power of the drop diameters. However, the radar only measures reflectivity, not the drop-size distribution. Hence, the drop-size distribution must be assumed and can be wrong. Unfortunately, different drop-size distributions can produce the same reflectivity factor but have markedly different rainfall rates. For example, many small drops can produce the same reflectivity as one large drop; however, the rainfall rate from the small drops is very different from the one large drop. 

Zeroth Law of Thermodynamics

if two systems are put in contact with each other, there is a net exchange of energy between them unless their thermal energy per unit volume is equal (at thermal equilibrium). This law states that if two systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. The Zeroth law was added after the First, Second, and Third laws.



Zonal Flow

large-scale atmospheric motion along a mostly east-west path (nearly along a line of latitude).


see Freezing Rain

Zulu Time (Z)

global time scale based on the local time observed on the Prime Meridian; also called Greenwich Mean Time (GMT) or Universal Coordinated Time (UTC)