ABSTRACT
This chapter briefly examines atmospheric water vapor and the different measures of humidity, following a discussion of precipitation processes, measurement and analysis. Water vapor in the atmosphere is the source for precipitation. The residence time of atmospheric water vapor is short. Four factors are required to generate measurable precipitation: continuous influx of moisture, mechanism to lift the air mass, condensation and cloud droplet growth. Cloud seeding to generate precipitation is one type of weather modification. Other types of modification include fog dispersal, hail suppression and frost prevention. The final topic of this chapter risk, in hydrology means the probability of an event occurring within a specified period of time. The techniques of measurement and analysis described in this chapter are only the most basic. An important input to the hydrologic system is energy which drives the hydrologic system by transforming precipitation into water vapor. While water vapor was covered in this chapter as a prerequisite to the formation of clouds.
