The amount of precipitation is of constant interest to those who monitor the weather. It would seem that the forecast is 10-15 mm, and there is knee-deep snow or huge puddles on the streets. To make it easier for you to navigate the forecasts, we have prepared information on measuring precipitation.
Meteorologists distinguish between two concepts: the depth of snow cover and the amount of precipitation. What we see on the street after a snowfall is the height of the snow cover, which sometimes reaches 50 cm, although the amount of precipitation may be no more than 20 mm. One millimeter of fallen snow is equivalent to 1-1.5 cm of snow depth, depending on the structure of the snow.
According to meteorological instructions, a millimeter of precipitation is one liter of water per square meter. At all weather stations there are precipitation measuring buckets, from which, at 9 and 21 o'clock GMT, precipitation is poured into a special vessel, by which its quantity is measured. Solid precipitation - snow, hail - is melted, and then specialists measure the resulting water.
Everything in St. Petersburg is anomalous warm winter(oh, I wish I could jinx it!), and I, quite tired from the two previous winter reconstructions of the events of the film “The Day After Tomorrow,” am incredibly happy about this. Moreover, a year ago, around this time, there was already a frost outside the window of -20°. Snowboarders and skiers will have artificial snow on the slopes, so they won’t be offended, but I can live well without it.
But while the weather is shaking around zero, every morning turns into a dilemma for me: what to wear so as not to freeze and not get sweaty. And this is where two excellent sites with very accurate weather forecasts come to my aid. At one time, my friend helped me find them, but he doesn’t write on LiveJournal, so I’ll bring the light to the people. Those who know about them, do not rush to throw eggs at the button accordion, because many still go to the stupid and lying Gismeteo and Yandex to find out the weather.
Below is a short overview of two excellent sites: RP5 And YR.no, as well as answers to several questions that may arise after getting to know them. If it seems like there are too many letters, just take into account my recommendations and believe that these two resources have never failed or deceived.
This site, a guest from Norway, unlike RP5, in addition to being very accurate forecasts has a very beautiful design. There is no Russian language, however. But there is English (switches in the upper right corner).
Feature of the site - a bunch different ways providing information, ranging from simple forecast tables familiar from Yandex for 9 days in advance (it is worth noting that the decoding is still very detailed), and ending with graphs and weather maps that change over time.
Personally, for me, the optimal and most understandable graph seems to be a moderately “loaded” graph, which can also acquire a line for pressure and a cloud diagram if you click on the Detailed button on the left, but this information seems unnecessary to me. The blue bars on the time axis are again the precipitation level in millimeters.
Now I will answer a couple of questions that may arise after reading these sites:
Q: Where do the British and Norwegians get their information about our weather? Our hydrometeorological center certainly knows better!
A: Not at all. Both the Hydrometeorological Center and everyone else know exactly the same thing about the actual weather. All information is collected by ground-based weather stations and made publicly available in the system of free international exchange of weather data. Now anyone who has a supercomputer with a thousand or two processors can take this data, process it and try to predict what the weather will be like in a particular place in the near future. It's just a matter of who can do it more accurately.
Q: It is not clear to me when precipitation is designated as 2 mm/6 hours. What to really expect?
A: Very easy to understand. Here's how RP5 explains it:
"The ratio is direct: 1 mm corresponds to 1 liter per 1 square meter. That is, 12 mm is a large 12-liter bucket; 10 mm is a 10-liter bucket; 0.5 mm is a half-liter bottle; 0.2 mm is a glass of water per 1 square meter meter. Perhaps this explanation is not very solid, but it is understandable."
This opens up new horizons compared to those weather forecasts where rain, regardless of the predicted intensity, is indicated by a droplet or an umbrella. You can understand whether this umbrella is needed at all by these millimeters: 0.2-1 mm is very little, and most likely means heavy rain in places (that is, all 10 millimeters will fall on 10% of the city, and the sun will shine over the remaining 90%) . And 4-10 mm is already an impressive amount, spread over a huge area, and most likely the rain will continue to fall for a long time and everywhere.
Q: What rain, it’s winter here, frost -30! How to measure snow in millimeters?
A: Simply multiply by 10. 1 millimeter of precipitation equals 1 centimeter snowdrift.
Q: It would be great if forecasts from 10 different sources could be averaged.
Yeah, someone has already done this
Author Yoelina Diona asked a question in the section Climate, Weather, Time Zones
What does precipitation in millimeters mean? and got the best answer
Answer from Helga[guru]
Precipitation is measured by the thickness of the layer of fallen water in millimeters.
Precipitation is measured by rain gauges, precipitation gauges, pluviographs at meteorological stations, and for large areas - using radar.
In meteorological observations, precipitation is characterized by the duration of its fall and intensity, as well as the amount expressed in the thickness of the layer of fallen water.
The amount of precipitation is expressed in millimeters of the layer of water that would be formed from precipitation if it did not evaporate, seep into the soil, or run off.
Numerically, the amount of precipitation in millimeters is equal to the number of kilograms of water spilled onto an area of 1 sq. meter, i.e. 1 mm = 1 kg/1 m2.
___________________________
But how can we quantitatively imagine what 1 mm of precipitation is?
Not many can correctly explain how much it is.
For example, how to imagine 1000 mm of precipitation on an area of 1 hectare.
Knowing that 1 hectare = 10,000 m2
This means that 1000 mm of precipitation on an area of 1 hectare is 10,000 liters (or 10,000 tons) of water
or 1000 mm of precipitation is 1000 liters of water per square meter!! !
Accordingly, 1 mm of precipitation is 1 liter of water per square meter!!!
Answer from yoery[guru]
there is such a thing - Molchanov’s precipitation gauge, that’s where precipitation is measured in millimeters, an ordinary measuring cup at the bottom
Answer from Plush cat[master]
According to meteorological instructions, a millimeter of precipitation is one liter of water per square meter. At all weather stations there are precipitation measuring buckets, from which the observer, at 09 and 21 hours GMT, pours the precipitation that has fallen over a 12-hour period into a special vessel, from which the true amount is measured. Solid precipitation, that is, snow, is melted and specialists measure the resulting water.
Answer from 3 answers[guru]
Hello! Here is a selection of topics with answers to your question: what does precipitation in millimeters mean?
Atmospheric precipitation is water that falls from the atmosphere onto earth's surface. Atmospheric precipitation has more scientific name- hydrometeors.
They are measured in millimeters. To do this, measure the thickness of water that has fallen to the surface using special instruments - precipitation gauges. If you need to measure the water thickness over large areas, then weather radars are used.
On average, our Earth receives almost 1000 mm of precipitation annually. But it is quite predictable that the amount of moisture that falls depends on many conditions: climate and weather conditions, terrain and proximity to water bodies.
Types of precipitation
Water from the atmosphere falls onto the earth's surface, being in its two states - liquid and solid. According to this principle, all atmospheric precipitation is usually divided into liquid (rain and dew) and solid (hail, frost and snow). Let's look at each of these types in more detail.
Liquid precipitation
Liquid precipitation falls to the ground in the form of water droplets.
Rain
Evaporating from the surface of the earth, water in the atmosphere collects in clouds, which consist of tiny droplets, ranging in size from 0.05 to 0.1 mm. These miniature droplets in the clouds merge with each other over time, becoming larger in size and noticeably heavier. Visually, this process can be observed when the snow-white cloud begins to darken and become heavier. When there are too many such drops in a cloud, they fall to the ground in the form of rain.
In summer It is raining in the form of large drops. They remain large because heated air rises from the ground. These rising jets prevent the drops from breaking into smaller ones.
But in spring and autumn the air is much cooler, so at these times of the year the rain is drizzling. Moreover, if the rain comes from stratus clouds, it is called cover clouds, and if drops begin to fall from nimbus clouds, then the rain turns into downpour.
Every year, almost 1 billion tons of water fall on our planet in the form of rain.
IN separate category worth highlighting drizzle. This type of precipitation also falls from stratus clouds, but the droplets are so small and their speed is so negligible that the water droplets appear suspended in the air.
Dew
Another type of liquid precipitation that falls at night or early in the morning. Dew droplets are formed from water vapor. Overnight, this steam cools, and the water turns from a gaseous state into a liquid.
The most favorable conditions for dew formation: clear weather, warm air and almost complete absence of wind.
Solid precipitation
We can observe solid precipitation in the cold season, when the air cools to such an extent that water droplets in the air freeze.
Snow
Snow, like rain, forms in a cloud. Then, when the cloud enters a stream of air in which the temperature is below 0°C, the water droplets in it freeze, become heavy and fall to the ground as snow. Each droplet solidifies into a kind of crystal. Scientists say that all snowflakes have different shapes and it is simply impossible to find identical ones.
By the way, snowflakes fall very slowly, since they are almost 95% air. For the same reason they are white. And the snow crunches underfoot because the crystals are breaking. And our hearing is able to catch this sound. But for the fish it’s a real torment, since snowflakes falling on the water emit a high-frequency sound that the fish hear.
hail
falls only in the warm season, especially if the day before it was very hot and stuffy. The heated air rushes upward in strong currents, carrying with it the evaporated water. Heavy cumulus clouds form. Then, under the influence of rising currents, the water droplets in them become heavier, begin to freeze and become overgrown with crystals. These lumps of crystals rush to the ground, increasing in size along the way due to merging with drops of supercooled water in the atmosphere.
It must be taken into account that such icy “snowballs” rush to the ground with incredible speed, and therefore hail is capable of breaking through slate or glass. Hail causes great damage agriculture, therefore, the most “dangerous” clouds that are ready to burst into hail are dispersed with the help of special guns.
Frost
Frost, like dew, is formed from water vapor. But in winter and autumn months When it's cold enough, the water droplets freeze and therefore fall out as a thin layer of ice crystals. But they don’t melt because the earth is cooling even more.
Rainy seasons
In the tropics and very rarely in temperate latitudes, there comes a time of year when there is an excessive amount of rainfall. a large number of precipitation. This period is called the rainy season.
In countries located in these latitudes, there are no severe winters. But spring, summer and autumn are incredibly hot. During this hot period, a huge amount of moisture accumulates in the atmosphere, which then pours out in the form of prolonged rains.
In the equator region, the rainy season occurs twice a year. And in tropical zone, south and north of the equator, such a season occurs only once a year. This is due to the fact that the rain belt gradually runs from south to north and back.
Precipitation measurement. Determination of precipitation quality.
Precipitation measurement.
Quantity atmospheric precipitation, fallen on the surface of the Earth in a given place for certain time, is estimated by the thickness of the water layer (in mm). The amount of solid precipitation is measured by the thickness of the layer of water that melted solid sediment would form. One millimeter of precipitation corresponds to a layer of fallen water in the amount of 1 liter per 1 m2. The amount of precipitation is measured by special instruments - precipitation gauges, which are usually located at a distance of several kilometers from one another and record the amount of precipitation over a certain period of time, usually 24 hours. A simple precipitation gauge is a cylindrical bucket of a strictly defined cross-section with a round funnel, installed at a weather site. Rainwater falls into it and flows into a special measuring glass. The area of the measuring cup is also known, so a layer of water 25 mm thick in the measuring cup corresponds to 2.5 mm of precipitation. The design of the rain gauge provides protection from rapid evaporation of precipitation and from blowing out snow that gets into the rain gauge bucket. More complex measuring instruments continuously record the amount, intensity and timing of precipitation (pluviographs). The average annual precipitation over the entire surface of the Earth is about mm. In tropical latitudes, the average annual precipitation is at least 2500 mm, in temperate latitudes - about 900 mm, and in the polar regions - about 300 mm. The main reasons for differences in precipitation distribution are geographical position of a given region, its altitude above sea level, distance from the ocean and the direction of prevailing winds. On mountain slopes facing the winds blowing from the ocean, the amount of precipitation is usually greater than in areas protected from the sea by high mountains.
Analysis of precipitation.
The duration of the study was from 11/25/11 to 11/29/11
Location of the study: Saransk, South-Western district.
Weather conditions: there were short-term snowfalls, which became the object of study.
The water sample was taken within a week, or more precisely during the study period indicated above.
Determination of the quality of precipitation.
Organoleptic method for odor determination:
We determine the nature of the smell by the sensation of the perceived smell (earthy, chlorine, petroleum products, etc.).
Determination method:
We take snow from the rain gauge and wait for it to melt. According to this table
Intensity | The nature of the odor | Rating of odor intensity in points |
There is no smell | ||
Very weak | The smell is not perceived by the consumer, but is detected during laboratory testing. | |
The smell is noticed by the consumer if you pay attention to it | ||
Noticeable | The smell is easily noticed and causes disapproval of the water | |
Distinct | The smell attracts attention and makes you refrain from drinking | |
Very strong | The smell is so strong that makes water unfit for consumption |
Odor intensity 0 points.
Organoleptic method for determining taste:
With this method we determine the character and intensity of taste and aftertaste.
Four basic types of taste: salty, sour, sweet, bitter
Determination method:
The nature of taste or taste is determined by the sensation of perceived taste or taste (salty, alkaline, metallic, etc.)
We took the test water into our mouths in small portions, without swallowing, and held it for 3-5 seconds.
We determine the intensity and character of taste and aftertaste at 20°C and evaluate it using a five-point system (in the table).
Intensity taste, aftertaste | The nature of the manifestation of taste and aftertaste | Rating of taste intensity in points |
Taste and aftertaste are not felt | ||
Very weak | Taste and aftertaste are not perceived by the consumer, but are detected during laboratory testing | |
Taste and aftertaste are noticed by the consumer if they pay attention to it | ||
Noticeable | Taste and aftertaste are easily noticed and cause disapproval of the water | |
Distinct | Taste and aftertaste attract attention and make you refrain from drinking | |
Very strong | The taste and aftertaste are so strong that they make the water unfit for consumption. |
According to the table, the intensity of taste is 2 points.
Photometric method for determining turbidity:
We determined turbidity immediately after sampling. The water is not very cloudy at first glance. It can be assumed that it is suitable for drinking.
Conclusion: the precipitation that fell in this area does not contain impurities or other chemical elements. But if we conduct a more thorough study in the laboratory, I think that impurities or other chemical elements will be found.
