Precipitation

Under precipitation is understood in meteorology water including its impurities, consisting of clouds, fog or mist (both cloud in contact with the ground ) or air containing water vapor ( humidity) is derived and the

Falls to the ground due to gravity in the liquid or solid form
Or is whirled up by the wind
Or deposited on the ground or drains
Or attaches in solid form from ( supercooled ) water as icing on surfaces
Or settles as fitting directly by condensation or Resublimation to objects

In the condensation of humid air is condensing heat, when resublimation goes Resublimationswärme from the water vapor, the freezing is freezing heat from the water into the environment (air, water, vegetation, other surfaces) above. Freeze supercooled fog or supercooled rain so the heat transfer is low. Upon evaporation and sublimation of precipitation heat the area is withdrawn, this affects cooling prevents overheating of the earth's surface and regulates the (small ) climate.

Clouds are formed by condensation nuclei starting by condensation of the moisture in the air. In order to fall as precipitation on the surface again, the size ( or mass ) of the condensed particles must exceed a certain value. Due to the precipitation of the water cycle is closed.

The frequency and the average amount of the precipitate are characteristic for the respective geographical areas. The precipitate is a factor which determines the local climate. Particularly for agriculture, this is relevant because only from a specific rainfall successful rainfed agriculture is possible. Various amounts of precipitation can also be assigned to specific ecozones.

3.1 Precipitation Amounts
3.2 rainfall
3.3 Precipitation duration
3.4 Precipitation Intensity
3.5 Long-term rainfall (average rainfall, cumulative rainfall)

Specifications

Artificial precipitation

Precipitate can be produced artificially under certain meteorological situations by a large amount of artificial ice nuclei, ie condensation nuclei is applied (eg, silver iodide ) in supercooled clouds; see hail flyer. From large-scale water vapor emissions originating industry is just as artificial snow precipitation, which can arise due to civilization.

Demarcation

Artificial snow from snow-making equipment, artificial ice and Schwarzeis ( frozen lake and sea water ) are not counted as rainfall, because the water does not directly and primarily comes from clouds, fog or humidity. Local Displaced precipitation ( for example, offset by snowplow snow, Sprühfahnen, roof avalanches, rain water in rivers ) still remains precipitation.

Regularities of spatial distribution of rainfall

Precipitation Measurement

Is measured with two different types of instruments:

Not Registrant rain gauge ( Rain Gauge )
Registrant rain gauge ( Precipitation Recorder, Pluviographen )

Most rain gauges collect the precipitate as selective precipitation measurement in a measuring vessel. A millimeter ( measuring unit ) corresponds to the height of water (precipitation amount ) of 1 mm, which would result if no water abflösse or evaporated. Alternatively, the amount of water ( rainfall ) is often specified in ( flat surface ). A millimeter is equal to one liter per square meter. Those portions which do not occur in the form of liquid water, can be either the same in the corresponding amount of converted (if the density is known), or in snow and hail, by gentle heating, to reduce the evaporation and the measurement error is converted into water.

In addition to the direct calculation on site rainfall intensities can be determined by radar measurements. To do this, draws on the dependent of the intensity of the rain radar reflectivity. About precipitation radars, the amounts fallen can now be comprehensively estimated. Especially in the field of flood management, this is ( verify selective readings or calibrate ) is important. Besides the pure precipitation amount or quantity especially the precipitation intensity and rainfall duration are important.

Long-term ( climatological ) precipitation measurements allow statistical calculations to indicate the average frequency of different rainfall events ( esp. heavy rain events ), set the intensity and duration of each other with respect.

Amount of precipitation

The amount of precipitation, as used in meteorology, expressed in millimeters and are in turn shed light on the rainfall.

If the amount of precipitation, and the resulting rainfall is not measurable, it is given as " less than 0.1 mm ." In case of snow, hail or sleet, the precipitation amount is given in ( inches ). A conversion into the rainfall in liters, or in the water-equivalent precipitation amount per square meter can be made only after determining the density, as if frozen precipitation can differ widely.

For snow these are, for example, between ( dry, loose snow ) and (strongly bound snow ): fresh snow so has about 1/10 (up to 1/15 to 1/30 ) of the density of water, but sitting pretty quickly (within hours, in particular by the weight of the layers above snowed ) together on roughly 1/3, so that 1 meter of fresh snow and 30 inches of snow set correspond to about 100 mm of rain.
In hail, the disclosure of the amount of precipitation refers only to the duration of an event and usually only on the amount of hail layer at the bottom ( Precipitation in the form of rain is hereby specified separately ). They will be converted according to the conversion random beds in water quantity.

Rainfall

The amount of precipitation is that amount of liquid water ( rain water ), which would have (see also precipitation intensity) collected in a closed basin in precipitation (rain, snow, hail, fog, etc.) in a defined period of time.

The information is given in liters (1 liter is 1 cubic decimeter ). Unless otherwise indicated, the amount of rainfall relates to a square () and is then numerically equal to the amount of precipitation in millimeters ()

Factors such as evaporation, soil percolation or runoff are not considered in the measurement.

Precipitation duration

The term precipitation duration represents the time duration of a single precipitation event. Based on the rainfall duration, a distinction between rainfall duration and showers. In addition, it is necessary for the determination of recurrence intervals of heavy rainfall and flooding scenarios.

Precipitation intensity

When rainfall intensity is defined as the quotient of precipitation amount or quantity and time. It is in principle independent of the assessment area, and therefore a standardized measure of the precipitate. It has the dimension of length (measured in meters) per time (in seconds), ie, LT-1 in m / s, and is usually for rain in millimeters per hour or liters per square meter ( and hour, which often remains unmentioned ) indicated in snow in centimeters per hour.

Rain: 1 liter per square meter per hour equals 1 mm of rain amount / quantity in one hour (mm / h)
Snow: average snow depth in centimeters per hour ( cm / h)

They, together with the rainfall characteristic of a precipitate. Other information for statistical purposes can still millimeters (or centimeters) per day, week, month or year, or the precipitation duration of an event.

A moderate rain showers in Central Europe has an intensity of 5 mm / h, a heavy rain to 30 mm / h or a downpour 5 mm / 5 min. When a violent storm the rainfall can grow to 50 mm / h and more. Rainfall of 100 mm in a few days ( about 300 mm / 4 d) result even if they are extensive, severe floods in the major rivers. Tropical storms reach values of 130 mm / h and far beyond.

Long-term rainfall (average rainfall, cumulative rainfall)

For the average amount of precipitation over a certain period at a defined location or in a particular region following meteorological - climatological expressions exist.

Monthly precipitation, or even monthly mean precipitation, the total amount of precipitation for a given month, averaged over a certain number of years (usually 30 years), which is always averaged over this specific month. The information is given in millimeters per month and is used in various climate diagrams. Referring only to a particular month, then the specification including the year.
Annual precipitation, or an annual average of rainfall is the total amount of precipitation a year, averaged over a certain number of years (usually 30 years). The information is given in millimeters per year and is used in various climate diagrams. Referring only to a very specific year, this will be specified separately.

For the characteristics of a particular year, the measured rainfall are summed (cumulative), and then compared with the mean rainfall of the same assessment period: So, a statement can be made whether a month or year " too dry " to " wet" or, a winter " snowy ", or that in a heavy rain event " like the normal rainfall of the month in three days " is. Likewise, climates and seasons characteristics can be compared, eg " winter dry", " maximum rainfall in late summer ."

Precipitation Records

Rain, positive records

Germany: In the Elbe flood in August 2002 fell within 24 hours in the Ore Mountains in Cínovec George (Saxony ) 312 millimeters. The return period for such 24 -hour rainfall is around 500 years; the Elbe flood was a " flood of the century ".
Until then 260 millimeters within 24 hours were considered German record: from 6 to July 7, 1906 ( every 7 clock CEST) in time grove, circle Riesa (Saxony) and from 7 to July 8, 1954 ( every 7 clock CEST) in stone, circle Rosenheim ( upper Bavaria).

Regional Limited extreme precipitation can also be significantly higher. Such a precipitation of about 240 mm was determined in an hour for the rain event on 2 June 2008 in Baden-Württemberg killer and Starzeltal.

Rain, negative records

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