Precipitation Measurement PDF

PRECIPITATION PRECIPITATION Precipitation is the release of water from the atmosphere to reach the surface of the earth. Conditions that need to be met for precipitation to form: ❑ Cooling of the atmosphere ❑ Condensation onto nuclei ❑ Growth of the water/ice droplets  FORMS OF PRECIPITAT...

PRECIPITATION PRECIPITATION Precipitation is the release of water from the atmosphere to reach the surface of the earth. Conditions that need to be met for precipitation to form: ❑ Cooling of the atmosphere ❑ Condensation onto nuclei ❑ Growth of the water/ice droplets  FORMS OF PRECIPITATION D R G S R S H I L L A N A Z A E I O I Z Z E N W L L E T E  RAINFALL CHARACTERISTICS ❖Amount -is an accumulation of volume or a product of intensity times duration ❖Duration -is the length of time that the rainfall occurs ❖Intensity -is the ratio of the total amount of rain falling during a given period to the duration of the period ❖Return Period -is how often rainfall occurs at a particular amount or intensity and duration HYETOGRAPH Hyetograph is a plot of the (Sample hyetograph from ResearchGate.net) intensity of rainfall against the time interval. PHILIPPINES AVERAGE PRECIPITATION  PRECIPITATION MEASUREMENT Rain Gauge -also called udometers, pluviometer, ombrometer, and hyetometer -a device used for measuring precipitation -a cylindrical-vessel assembly kept in the open to collect rain  PRECIPITATION MEASUREMENT Proper Placement of a Rain Gauge ✓The general rule of thumb is to keep the rain gauge twice the distance away from the height of the nearest obstruction (e.g., placing a gauge 20 feet away from 10-foot tall trees). ✓Place the gauge at least 2-5 feet off the ground on the side of a pole, with the top of the cylinder several inches above the top of the pole to prevent splash back. ✓Make sure the top of the rain gauge is level. ✓Keep the gauge away from sources of artificial precipitation that can affect the readings, such as sprinklers.  PRECIPITATION MEASUREMENT Sources of Error in Raingauges 1. Losses due to evaporation 2. Losses due to wetting of the gauge 3. Over-measurement due to splash from the surrounding area 4. Under-measurement due to turbulence around the gauge  PRECIPITATION MEASUREMENT TYPES OF RAIN GAUGE 1. Nonrecording Gauges a) Standard Rain Gauge (SRG) a.k.a. Graduated Cylinder RG 2. Recording Gauges a) Tipping Bucket Type b) Weighing Bucket Type c) Natural Syphon Type d) Telemetering Raingauges  PRECIPITATION MEASUREMENT TYPES OF RAIN GAUGE 1. Nonrecording Gauges a) Standard Rain Gauge (SRG) a.k.a. Graduated Cylinder RG 2. Recording Gauges a) Tipping Bucket Type b) Weighing Bucket Type c) Natural Syphon Type d) Telemetering Raingauges  PRECIPITATION MEASUREMENT Standard Rain Gauge (SRG) (a.k.a. Graduated Cylinder RG) -is used by all professional weather services in manned stations -is the most accurate way of directly measuring rainfall  PRECIPITATION MEASUREMENT National Weather Service 8 Inch Standard Rain Gauge (United States) Four Main Components: ▪ Overflow Can -it catches all the water that overflows from the measuring tube and can hold a maximum of 20 inches of liquid ▪ Collector Funnel -the component that catches the rain and is 8 inches in diameter ▪ Measuring Tube -a tube housed in the overflow can -made of either plastic or brass -water flows directly into it from the Collector Funnel ▪ Measuring Stick -a stick with distinct white markings used to measure rainfall by dipping it through the funnel opening to the bottom of the measuring tube and record the reading  PRECIPITATION MEASUREMENT Met Office 5 Inch Standard Rain Gauge (United Kingdom) Three Main Components: Collector Funnel -catches the rain and is 5 inches in diameter Glass Container -Water flows directly into this container from the collector funnel Graduated Measuring Tube -measures the amount of rainfall collected  PRECIPITATION MEASUREMENT TYPES OF RAIN GAUGE 1. Nonrecording Gauges a) Standard Rain Gauge (SRG) a.k.a. Graduated Cylinder RG 2. Recording Gauges a) Tipping Bucket Type b) Weighing Bucket Type c) Natural Syphon Type d) Telemetering Raingauges  PRECIPITATION MEASUREMENT Tipping Bucket Rain Gauge -is an automated rain meter that uses a "tipping bucket" mechanism to measure rainfall. It is used by professional weather services' remote weather stations  PRECIPITATION MEASUREMENT TYPES OF RAIN GAUGE 1. Nonrecording Gauges a) Standard Rain Gauge (SRG) a.k.a. Graduated Cylinder RG 2. Recording Gauges a) Tipping Bucket Type b) Weighing Bucket Type c) Natural Syphon Type d) Telemetering Raingauges  PRECIPITATION MEASUREMENT Weighing Bucket Rain Gauge -consists of receiving bucket mounted on a weighing device, usually a mechanical mechanism such as a spring. The rain accumulates in the container, and the increased weight compresses the springs.  PRECIPITATION MEASUREMENT TYPES OF RAIN GAUGE 1. Nonrecording Gauges a) Standard Rain Gauge (SRG) a.k.a. Graduated Cylinder RG 2. Recording Gauges a) Tipping Bucket Type b) Weighing Bucket Type c) Natural Syphon Type d) Telemetering Raingauges  PRECIPITATION MEASUREMENT Natural Syphon Rain Gauge -also called Float Type RG -for this type, a float is provided at the bottom of container, and this float raises as the water level rises in the container. Its movement being recorded by a pen moving on a recording drum actuated by a clock work.  PRECIPITATION MEASUREMENT TYPES OF RAIN GAUGE Telemetering Rain Gauge 1. Nonrecording Gauges -a recording type rain gauge which contains electronic units to transfer a) Standard Rain Gauge (SRG) data to the base station, both at regular a.k.a. Graduated Cylinder RG interval or continuous 2. Recording Gauges a) Tipping Bucket Type b) Weighing Bucket Type c) Natural Syphon Type d) Telemetering Raingauges  PRECIPITATION MEASUREMENT OTHER METHODS 1. Radar (Radio Detection And Ranging) -Looks from the earth up into the atmosphere and tries to estimate the amount of precipitation falling over an area. 2. Satellite Remote Sensing - looks from space down towards the earth surface and attempts to estimate the amount of precipitation falling over an area