Методы автоматического распознавания наличия и вида осадков

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Методы автоматического распознавания наличия и вида осадков

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МЕТЕОКЛУБ : независимое сообщество любителей метеорологии (Европа и Азия) : ФОРУМ О ПОГОДЕ И ПРИРОДЕ / Метеорология: наука и практика / Методы автоматического распознавания наличия и вида осадков
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CorvusCorax
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Владимир (г. Байконур)
# Дата: 5 Ноя 2019 11:14


Интересная статья попалась (на английском).

https://www.icao.int/safety/meteorology/amofsg/AMO FSG%2016%20Archive%20Material/AMOSSG%204/AMOSSG%20 4%20SoD.pdf

Начиная с 49 страницы.

In France, studies have shown the usefulness of temperature measurement instruments (not
protected by a shelter) placed at two levels above the ground, e.g. at +10 cm and +50 cm, called T+50 and T+10.
When there is no precipitation, these two temperatures are often different, because there is a temperature
gradient above the ground: at night, with a clear sky, the ground is cooler, so T+10 is cooler than T+50; by day,
with a clear sky, the ground is warmer, so T+10 is warmer than T+50. However, in the presence of fog or
precipitation, these two temperatures are subject to the same atmospheric conditions, which minimize the
differences in temperature that can exist between the two measurements. This fact can be used, but the
absence of a temperature gradient does not mean that there is fog or precipitation. For the same reasons, the
comparison with air temperature (Tair) is also useful.


CorvusCorax
Автор сайта
Письмо
Владимир (г. Байконур)
# Дата: 5 Ноя 2019 11:15


6.4.6 Algorithms for detection

6.4.6.1 The following conditions normally lead to an absence of precipitation, so a wrong diagnostic
from the sensor can be corrected.
— difference Tair - T+10 > 3°C over a 20-minute period º no precipitation;
— difference T+50 - T+10 > 1.5 °C over a 20-minute period º no precipitation;
— (T+50 > Tair + 2) and (T+10 > T+50 + 2) day time º no precipitation;
— no clouds detected above 4500 m (15000 ft) º no precipitation;
— visibility > 40 km for 5 minutes º no precipitation.
— relative humidity (RH) < 50 per cent º no precipitation;
— RH diminishes or the difference between Tair and dew point depression increases
and visibility increases º no precipitation;
— sudden diminution of difference between T+50 and T+10 (outside sunrise and
sunset) º start of precipitation or arrival or fog; and
— isothermia (constant temperature) of T+50 or T+10 at 0°C (or temperature very
close to 0°C, considering uncertainty of measurement) º melting snow probable.


CorvusCorax
Автор сайта
Письмо
Владимир (г. Байконур)
# Дата: 5 Ноя 2019 11:16 - Поправил: CorvusCorax


6.4.7 Algorithms for identification
— cases of snow with a Tair > 4°C are very rare;
— when Tair < -5°C, there are no longer any liquid precipitation;
— cases of mixed rain and snow occur nearly always with Tair in the interval [-1°C,
5°C];
— isothermia (constant temperature) of T+50 or T+10 at 0°C (or te;perature very
close to 0°C, considering uncertainty of measurement) º melting snow
probable (and melting snow if a present weather sensor has diagnosed
precipitation). Sometimes, hoar frost or freezing fog;
— wet-bulb temperature, noted as Twb, presents a limit for rain and snow. Snow is
not observed when Twb > 1.5°C; and
— position in a Tair diagram, RH or a Twb diagram, RH. There are zones where
some varieties of hydrometeor are observed alone, and some zones where some
varieties are not observed. Such diagrams alone are not enough to determine the
type of hydrometeor, but they can help identify or correct the sensor's initial
diagnostic. For example, at a negative temperature with an RH less than 80 per
cent (Tair < 0°C and RH < 80 per cent), only snow is encountered. Drizzle is
often accompanied by high RH (> 90 per cent).


CorvusCorax
Автор сайта
Письмо
Владимир (г. Байконур)
# Дата: 5 Ноя 2019 11:17


— visibility < 1000 m and cloud base height > 1500 m (5000 ft) º
snow type;
— drizzle occurs only when there are stratus, clouds whose base is
lower than 500 m (1660 ft);
— precipitation detected and no clouds above 3000 m (10000 ft) º
rain;
— in the presence of drizzle, visibility is less than 10 km;
— with equal intensity (expressed in mm/h), snow causes a loss of
visibility (or MOR) 4 to 10 times greater than rain. There are criteria
that link visibility, intensity of precipitation and the type of
precipitation.


CorvusCorax
Автор сайта
Письмо
Владимир (г. Байконур)
# Дата: 5 Ноя 2019 11:23


Далее в тексте более подробно описаны методы распознавания разных осадков и атм. явлений.

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