intensity, duration and distribution. 3) Thiessen Polygon - This is another graphical technique which calculates station weights based on the relative areas of each measurement station in the Thiessen polygon network. Annual rainfall is the total accumulated rainfall in a year, using daily rainfall estimates of the Virtual Climate Station Network (NIWA, nd). Rainfall is measured in either millimeters or inches. The magnitude and extent of the resultant rainfall areas of coverage are then considered versus the area in question in order to estimate the areal precipitation value. While rainfall is measured in inches in the United States, most countries in the world adopt the metric system and use millimeters or centimeters instead of inches. NIWA produces virtual climate station estimates every day, for every 25km 2 in the country. Precipitation is a major component of the water cycle, and is responsible for depositing most of the fresh water on the planet.Approximately 505,000 km 3 (121,000 mi 3) of water falls as precipitation each year, 398,000 km 3 (95,000 cu mi) of it over the oceans. Annual rainfall percentage of normal, 1972–2013 – interactive map. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres (39 in). Average annual precipitation is a vital piece of climatic data - one that is recorded through a variety of methods.

The specific unit of measurement used depends on the county.

As defined in Chapter 1, water harvesting is the collection of runoff for productive use. A tropical savanna is a grassland biome located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes, with rainfall between 750 and 1,270 mm (30 and 50 in) a year. … Rain forests are characterized by high rainfall, with definitions setting minimum normal annual rainfall between 1,750 and 2,000 mm (69 and 79 in). The rate of rainfall can be heavy, moderate or light. (O.K., so the question should have said "the least annual rainfall per unit area," but it didn't.)

3.1 Introduction.

Precipitation (which is most commonly rainfall but also includes snow, hail, sleet, and other forms of liquid and frozen water falling to the ground) is measured in units over a given time period. Runoff is generated by rainstorms and its occurrence and quantity are dependent on the characteristics of the rainfall event, i.e. Definition and methodology.

Average annual precipitation is a vital piece of climatic data - one that is recorded through a variety of methods.