Rainfall Measurement and Interpretation

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Transcript of Rainfall Measurement and Interpretation

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RAINFALLMEASUREMENT AND INTERPRETATION

Recall first the instruments being used in measuring precipitation.

1

Standard Rain Gauge

Standard Rain Gauge - consists of funnel attached to a graduated cylinder (=2 cm) which fits inside a larger container (=20 cm, 50 cm tall). The height of the water in the small graduated cylinder is measured, and the excess overflow in the large container is carefully poured into another graduated cylinder and measured to give the total rainfall.

2

Pluviometer

Pluviometer- is a tool that measures the average intensity of rainfall in a certain interval of time. While the rain falls, the water collected by the funnel falls into the container and raises the buoy that makes the pen arm raising in the vertical axis marking the cardboard accordingly.

3

Tipping Bucket Rain Gauge

Tipping Bucket Rain Gauge- consists of a funnel that collects and channels the precipitation into a small seesaw-like container. After a pre-set amount of precipitation falls, the lever tips, dumping the collected water and sending an electrical signal.

4

Weighing Precipitation Gauge

Weighing Precipitation Gauge- consists of a storage bin, which is weighed to record the mass. It can measure other forms of precipitation, including rain, hail and snow. May also contain a device to measure the quantity of chemicals contained in the location's atmosphere.

5

Accoustic Rain Gauge (Acoustic disdrometer)

Acoustic Rain Gauge- Also referred to as a hydrophone, it is able to sense the sound signatures for each drop size as rain strikes a water surface within the gauge.

6

Optical Rain Gauge

Optical Rain Gauge- In an enclosed space below each is a laser diode and a phototransistor detector. When enough water is collected to make a single drop, it drops from the bottom, falling into the laser beam path and records.

7

WEATHER RADAR

WEATHER RADAR - - is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.) from its radius.

8

WEATHER SATELLITE ESTIMATION

WEATHER SATELLITE ESTIMATION - - is a type of satellite that is primarily used to monitor the weather and climate of the Earth.

TYPES Of SatellitesGeostationary Satellite- orbit the Earth above the equator at altitudes. Because of this orbit, they remain stationary with respect to the rotating Earth and thus can record or transmit images

Polar Orbiting Satellite- circle the Earth at a typical altitude in north-south or south-north path. They are able to observe any place on Earth and will view every location

OBSERVATION

VISIBLE SPECTRUMINFRARED SPECTRUM

9

Standard Rain Gauge

Evaporation might affect the amount of water in the gauge

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Amount of Rainfall in a week

Example:So how much is 1 inch of rain?

How Much Rain Falls On Your Roof?So how much is 1 inch of rain? By which I mean something like: How many gallons of water land on your roof in a storm that drops 1 inch of rain? The math is actually pretty straightforwardalthough there are someunit conversionsthat we need to be careful about along the way.

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How Much Rain Falls On Your Roof?1 inch of rainfall = 1 inch deep layer of water on your roof. So the total volume of water on your roof is the square footage of your roof.7.5 gallons = 1cubic foot. A typical barrel shaped container = 55 gallons.

The main thing to realize is that 1 inch of rainfall is enough to create a 1 inch deep layer of water on your roof. So the total volume of water on your roof is the square footage of your rooflet's say it's 1,000 square feettimes 1 inch = 1/12 of a foot. That's about 83.3 cubic feet of water per inch of rain for a 1,000 square foot roof. How many gallons is that?There are just about 7.5 gallons in a cubic foot. Which means that a 1,000 square foot roof is bombarded by 83.3 x 7.5 or about 625 gallons of water per inch of rain. How much is that? Well, a typical barrel shaped container used to transport liquids holds 55 gallons. So if you could collect all of that water, you could fill almost 11.5 barrels from a single inch of rain. That's a lot of water!

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IntensityRate of PrecipitationLight rain < 2.5mm (0.098in) per hourModerate rain between 2.5mm (0.098in) - 7.6mm (0.30in) or 10mm (0.39in) per hourHeavy rain > 7.6mm (0.30in) per hour,or between 10mm (0.39in) and 50mm (2.0in) per hourViolent rain > 50mm (2.0in) per hour Euphemisms for a heavy or violent rain include gully washer, trash-mover and toad-strangler. The intensity can also be expressed by rainfall erosivity. R-factor

Rainfall intensity is classified according to the rate of precipitation:Light rain when the precipitation rate is < 2.5mm (0.098in) per hourModerate rain when the precipitation rate is between 2.5mm (0.098in) - 7.6mm (0.30in) or 10mm (0.39in) per hour[105][106]Heavy rain when the precipitation rate is > 7.6mm (0.30in) per hour,[105]or between 10mm (0.39in) and 50mm (2.0in) per hour[106]Violent rain when the precipitation rate is > 50mm (2.0in) per hour[106]Euphemisms for a heavy or violent rain include gully washer, trash-mover and toad-strangler.[107]the intensity can also be expressed by rainfall erosivity.R-factor

13

Pluviometer

pluviograph

Pluviometer- is a tool that measures the average intensity of rainfall in a certain interval of time. While the rain falls, the water collected by the funnel falls into the container and raises the buoy that makes the pen arm raising in the vertical axis marking the cardboard accordingly.

14

Tipping Bucket Rain gauge

Tipping bucket rain gauge (classic recorder)

The tipping bucket rain gauge is not as accurate as the standard rain gauge because the rainfall may stop before the lever has tipped.16

Close up of a tipping bucket rain gauge recorder chart17

Digital / Modern tipping Bucket Rain Gauge

Simplier to read and to interpret18

Weighing precipitation gauge

The motor under the cylinder around which the chart is wrapped must be manually reset every 7 days by hand cranking a small handle. Most weighing rain gauges use spring-loaded motors. There are some that run on battery-powered motors as well.~ Steve Woodruff and Devin Lussier

20

Weighing precipitation gaugeAny increase (in the ascent of the ink line) indicates precipitation occurrence. If this ascent ends and the ink line remains level, this indicates a dry period during the storm system; a time period when rainfall has stopped.

The pluviograph, the manual graph of standard rain gauge, the classic record of a tipping bucket rain gauge, graph for weighing precipitation gauge, is somehow the same manner in how to read them.Mm vs. time.

21

Accoustic Rain Gauge (Acoustic disdrometer)

Rain that falls on the disdrometer sensor moves a plunger on a vertical axis. The disdrometer transforms the plunger motion into electrical impulses whose strength is proportional to drop diameter. Data are collected once a minute.22

So how many drops hit?Rainfall IntensityRainfall Rate (mm/hr)Average Diameter (mm)Detector Area (mm2)Hits (#/s)Light< 2.5 mm/hr1.012571.33Moderate2.5 - 10 mm/hr1.512570.99Heavy10-50 mm/hr2.012572.08

Optical Rain Gauge

PrecipitationParticle size:0,16> 8 mmParticle velocity:0,2 20 m/s

The Distrometer calculates the intensity, volume (water equivalent) and the precipitation spectrum ( diameter and velocity) as well as the meteorological visibility (MOR) in the rain and the radar reflectivity (Z).

With the PC-software LNM-View, available as accessory, all measuring values, delivered by the LNM, can be acquired, filed and analyzed. The client/server architecture allow a multi-user operation. The software supports several instruments in parallel, while the maximum number is limited only by the PC-hardware. In order to achieve a high efficiency with the analysis, the user can select the data and their representation individually, thus adapting the software accordingly to the respective measuring task25

Weather radar

Belgium

Green color represents Moderate snowBlue color is Light snow.

26

Weather Satellite

Visible spectrum observationAug. 56-16,17,2015

Infrared spectrum observation (like a night vision)Aug. 16,17,2015

27

Weather satellite

We will not be discussing on how to read the visible spectrum observation in a satellite, since it is easy to interpret even by the average person.

INFRARED SPECTRUM

What typhoon do you think that is?

The animation shows the PERSIANN-CCS 3-hourly accumulations focusing on Super Typhoon Soudelor precipitation output from August 1, 2015 00:00Z through August 7, 2015 14:59Z

Soudelor has caused major damage to the island of Saipan and is almost to Taiwan as of 15:00Z August 7 (currently category 3) with expected rain totals over 10 inches if not much more in some mountain areas.

28

Infrared Spectrum reading from satellite Rainfall as of August 14, 2015Just base on the legend to interpret reading from a radar or even on a infrared satellite observation29