The weather in Guilin in 2008
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The cloud droplets condensed by water vapor in the atmosphere are very small, the radius is about 10 micron, and the concentration is from 1 10,000 to1100,000 per liter. The descending speed is about 1 cm/s, which is usually much slower than the ascending airflow in the cloud, so it is impossible for cloud droplets to fall out from the bottom of the cloud. Even if it leaves the bottom of the cloud and falls, it will quickly evaporate and disappear into unsaturated air. Only when cloud droplets are polymerized and converted into precipitation particles through various microphysical processes can they land on the ground. GguFo+YeZ
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Cloudization causes rainfall through a series of complex microphysical processes: wet air rises, expands and cools, in which water vapor reaches saturation and condenses on some cloud condensation nuclei with strong hygroscopicity, forming the condensation nucleation process of initial cloud droplets; The ice phase formation process in which supercooled water droplets or water vapor in the cloud freeze or condense on the ice core and naturally freeze into initial ice crystal embryos below -40℃; When the water vapor is slightly higher than saturation, it further condenses (condenses) on cloud droplets (ice crystals), making cloud droplets (ice crystals) grow (condensation growth process); The gravity collision process in which a larger cloud droplet collides with a smaller cloud droplet in the falling process and grows up; When ice crystals and supercooled water droplets coexist, the saturated water vapor pressure of supercooled water droplets is higher than that of ice surface, which leads to the gradual evaporation of supercooled water droplets and the gradual growth of ice crystals due to the condensation of water vapor. The scale of precipitation particles is about 100 times that of cloud droplets, but its concentration is only one millionth of that of cloud droplets. +f[ED4E & gt； (
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Due to surface tension, cloud droplets are usually spherical. The saturated vapor pressure on the surface of spherical pure water droplets is higher than that on the plane. Take a water drop with a radius of 0.0 1 micron as an example, and its saturated vapor pressure exceeds 12.5% of the flat water surface. In the pure air without any impurities, the initial cloud droplets can only be produced by the random collision of water vapor molecules. The possibility of random collision of molecules to produce cloud drops decreases with the increase of scale. & gtMPr=W%E
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The tiny initial cloud droplets will only evaporate when the relative humidity reaches several hundred percent. However, the actual water vapor content in the atmosphere rarely exceeds 1% of the saturation value. Therefore, it is difficult to directly form cloud droplets in pure air without impurities. In fact, there are various condensation nuclei in the atmosphere, which provide conditions for condensation into cloud droplets. Xt# 1Qs
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Cloud condensation nuclei are divided into two types: large hydrophilic substances, which are insoluble in water, but can adsorb water vapor and form water films on their surfaces, which are equivalent to larger pure water droplets; Aerosol particles containing soluble salts. It can absorb water vapor and become droplets of salt solution, which belongs to the absorbent core. For example, as long as the relative humidity of the environment is higher than 78%, the saturated aqueous solution of sea salt can condense and grow. f nI|
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With the increase of condensed water, the concentration of solution droplets becomes smaller and smaller, and the required saturated water vapor pressure is also higher. However, with the increase of condensed water, the size of solution droplets also increases, and the required saturated vapor pressure decreases with the increase of scale. Therefore, the saturated vapor pressure required by solution drops with different concentrations and sizes is different. When the ambient vapor pressure is greater than the corresponding critical value, the solution droplets will continue to grow. With the increase of scaling, the saturated vapor pressure of the solution gradually decreases. A particle containing 100 billion grams of salt, as long as the relative humidity of the environment is slightly greater than 100%, can become condensation nuclei and generate cloud droplets. e${)w-R/e
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In supercooled water (ice core) without impurities, the formation of ice phase (water changes from gas or liquid to solid) is a process in which water molecules spontaneously gather and transform into ice-like structure. Due to the fluctuation (pulsation) of molecular thermal motion, the clustered water molecules continue to form and disappear. The probability of molecular clusters increases with the decrease of temperature. When the size of the molecular cluster exceeds a certain critical value, it can continue to increase and form the initial ice crystal embryo. ? -Vjha@BO
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Pure water droplets with a diameter of several microns will spontaneously freeze only when the temperature is below -40℃; However, when there are impurities (ice nuclei) in supercooled water, molecular clusters are more likely to form ice crystal embryos under the action of impurity surface force field. The formation of ice crystals in natural clouds mainly depends on the existence of impurities (ice cores). At -20℃, there is about one ice core in every liter of air, which is only 100,000 times the concentration of condensed nuclei in the same volume of clouds. Therefore, the concentration of ice crystals in clouds is generally far less than that of water droplets. = w$}m_AM
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When the air in the cloud rises, expands and cools, the water vapor condenses continuously. In the process of condensation, the growth rate of cloud droplet radius is directly proportional to the supersaturation of water vapor in the cloud and inversely proportional to the size of cloud droplet itself. Therefore, under certain water vapor conditions, the condensation growth of cloud droplets becomes slower and slower. Under the condition of 0.05% supersaturation, an initial cloud droplet generated by a salt with a mass of one billionth of a gram starts from a radius of 0.75 micron, and it takes 0. 1 5 seconds to grow to 10 micron, 30 minutes to grow to10 micron and more than 4 hours to grow to 30 micron. ? Mee 6
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Although water vapor condenses on a few larger hygroscopic nuclei, it can produce larger cloud droplets, but if it continues to grow to Mao Mao rain with a radius of 100 micron, it will take longer, and the life of cumulus itself is only about one hour, so it is impossible to form raindrops under the above circumstances; In layered clouds, the speed of airflow rising is only a few centimeters per second. When the big cloud drops keep falling, they will walk out of the bottom of the cloud and grow into raindrops after evaporation. In a word, in the actual atmosphere, raindrops can't just be condensed by water vapor. ` ~ cuQ & lt3Tn
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When the cloud droplets are close to each other, they collide and fuse to form larger cloud droplets, which is called cloud droplet collision growth. The cloud drops falling in the gravity field have larger radius and faster speed, and can catch up with the small cloud drops, which is called gravity collision merger. However, when the cloud droplets with different radii are close to each other, only a part of the cloud droplets can collide with the big cloud droplets in the descending process, because the cloud droplets will bypass the big cloud droplets with the airflow replaced by the big cloud droplets. Only some colliding clouds can merge, while others will bounce back. 1 1cWy+8D
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The ratio of collision merging is called collision merging coefficient, and its value is determined by the radius of large and small cloud droplets, usually less than 1. The collision coefficient between a large cloud droplet with a radius less than 20 microns and a small cloud droplet is very small. When a large cloud droplet passes through a cloud composed of a small cloud droplet, the growth rate of its radius in the collision process is directly proportional to the collision coefficient, the relative speed between the large and small cloud droplets and the water content of the cloud droplet. The larger the radius of large cloud droplets, the faster the contact and growth speed. \.g\Zib)
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In the actual atmosphere, the collision between cloud droplets is a random process. The probability that some large cloud droplets collide with small cloud droplets in the cloud is greater than the average result, so they grow particularly fast; The collision speed of other cloud droplets is slower than the average result. Because the concentration of raindrops is only about11000 of that of large cloud drops, only the process that a few large cloud drops with the fastest growth become raindrops needs to be considered. Based on the random collision growth theory established by this concept, the raindrop generation time is much shorter than that of continuous growth, which is closer to the actual situation. 5#QXR+ T
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In addition, the turbulent mixing of airflow and the mutual attraction of cloud droplets under the action of electric field can also make cloud droplets approach each other and collide. It is generally believed that these two mechanisms mainly play a role in the growth of Xiaoyun water droplets. If the cloud body composed of liquid water has enough thickness, enough updraft velocity and liquid water content, then the big cloud droplets in it can grow into raindrops during collision. This process is called warm cloud precipitation process. Xj*vh m%i
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Raindrops with a radius greater than 3 mm will be seriously deformed during falling, and sometimes they will be broken into several small raindrops; In the process of collision between big and small raindrops, sometimes some smaller raindrops are separated, which is collectively called the process of raindrop breaking. Small raindrops repeatedly go through the process of rising, growing, falling and breaking again in the cloud, and under certain conditions, a large number of raindrops are quickly formed, which is the so-called Langsur chain reaction. & lt？ D\+khlq
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At the same temperature below zero, the saturated water vapor pressure on the ice surface is less than that on the water surface, so the water vapor pressure on the ice surface is supersaturated relative to the saturated ambient water vapor pressure on the water surface. Therefore, once ice crystals appear in supercooled clouds with temperatures below 0℃, they can grow rapidly. Ya & ampg$!
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According to this truth, bergeron proposed the formation mechanism of precipitated particles in 1933. He believes that there are a lot of supercooled water droplets in the cloud below 0℃, and the appearance of ice crystals destroys the stable state of phase structure in the cloud; The water vapor pressure in the cloud is between the saturation values of the ice surface and the water surface. While water vapor condenses on the ice, water droplets evaporate. Ice crystals can rapidly grow into snow crystals through the condensation of water vapor. In this way, water is continuously transferred from a large number of supercooled water droplets to a small number of ice crystals, and finally precipitated particles are formed. This is the ice crystal process, also known as the Bergeron process. nQ GQWg '
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On the one hand, supercooled water droplets evaporate, and water vapor is transferred to ice crystals to make them grow; On the one hand, it collides with snow crystals and freezes, which makes them grow further. If a large number of supercooled water droplets freeze due to collision, snow crystals will be transformed into spherical graupel particles. Snow crystals may also adhere to each other during movement to form snowballs and drop these solid precipitation particles. What falls to the ground and does not melt is solid precipitation such as snow graupel. Falling in a warm zone with a temperature higher than 0℃ will melt into raindrops. 4hw@yTUo
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In many cases, the concentration of ice crystals is higher than that of ice nuclei in the environment, which indicates that the ice crystals involved in the ice crystal process are not only produced in the process of ice nucleation, but also some broken ice particles produced when solid precipitation particles such as snow crystals collide with supercooled water droplets with a diameter greater than 24 microns at about -5℃, or when brittle dendritic ice crystals are broken. This process of producing secondary ice crystals is called ice crystal propagation. [Section 8
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In mid-latitude areas, stratiform clouds that form large-scale continuous precipitation are often deep, and the top of clouds is often above 0℃. So the temperature in the upper layer of the cloud is low, and a large number of ice cores are activated, which is the source of ice crystals. After the ice crystals grow up, they fall into the middle of the cloud, where there are a lot of supercooled water droplets, which can supply water to the ice crystals through the ice crystal process and make them continue to grow. Therefore, it is generally said that the upper part of this cloud is a seeding cloud and the middle part is a replenishment cloud. In this process, the grown snow crystals and snow masses fall into warm clouds below 0℃ and melt into raindrops. Bright bands showing this melting process can often be observed on radar screens. ; @ [ 0x
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The understanding of the formation, growth and transformation of cloud and precipitation particles is mainly obtained from theoretical research and experiments under controllable conditions. In fact, the environment of natural clouds and the corresponding microphysical processes are very complicated, and the understanding of them is still very shallow. Therefore, the development direction of cloud and precipitation microphysics is mainly to detect and study the evolution law of particle swarm based on natural clouds.
Routine 2008-0 1-26 0 1:33
"Mi Xue" is a kind of solid precipitation, which is white opaque, flat and long particles, solid, with the maximum diameter not exceeding 1 mm, and does not rebound when touching the ground. It is easy to appear in weather with zero degree, fog and high humidity. Rice snow comes from stratus clouds with low height, and sometimes it can form rice snow in dense fog and fall to the ground. Michelle is sometimes called "Mi Nan" by the masses.
Routine 2008-0 1-26 0 1:38
Ice needles usually appear in sunny days, cold mountains (such as Huangshan Mountain in our province) or plateaus, and the water vapor in the air condenses into needles suspended in the air due to radiation cooling. It is similar to dew, so it is not included in the precipitation in the specification. The code is listed as weather phenomenon and code report 76, which represents the specific weather conditions at that time, so it needs to be recorded and compiled. 4 QZ？ }iz
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Author: Sun Jinyuan
Drunk wind 2008-01-2611:28
I wonder what special experience forecasters have in forecasting precipitation patterns.
Routine 2008-01-2613:12
Quote:
Quote 2008-01-261:28: v, EF'-F published on the 4th floor.
I wonder what special experience forecasters have in forecasting precipitation patterns.
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At noon, Bengbu became warm at 700 hectopascals, and the snow turned into ice particles. Hangzhou becomes cold below 850HPA, and freezing rain turns into ice particles. Shall we analyze it? tZ2e！ & ltC
Siemens Wolf 2008-065438
Quote:
Quote JP * B 2008-01-2613:12 published by General on the 5th floor;
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At noon, Bengbu became warm at 700 hectopascals, and the snow turned into ice particles. Hangzhou becomes cold below 850HPA, and freezing rain turns into ice particles. Shall we analyze it? *Zd84wRSj
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It's true in Hangzhou. The snow in the morning has now turned into rain and ice particles. . . ? Not applicable to<v'
The road surface is a mixture of ice, rain and mud.
Siemens Wolf 2008-065438
Update, it is estimated that 850HPA will continue to get cold, and it is snowing in Hangzhou now. . . . +~2rW8
There is serious snow on the roof, carport, trees, grass and roof.
eoj 329 2008-0 1-26 13:49
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Quote: AE | p "kz, released on 5th floor of General 2008-01-2613:12.
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At noon, Bengbu became warm at 700 hectopascals, and the snow turned into ice particles. Hangzhou becomes cold below 850HPA, and freezing rain turns into ice particles. Shall we analyze it? %]Cjhs"v
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This is a reversal process!
eoj 329 2008-0 1-26 13:49
The following is a simplified version of precipitation formation, which is convenient for beginners. Shihy * (v
The appearance of precipitation requires water vapor condensation, which is the opposite process to evaporation when the relative humidity F > = 100% (that is, the actual water vapor pressure E > = the saturated water vapor pressure e in the atmosphere) is supersaturated. In order to make the water vapor in the atmosphere saturated or supersaturated, there must be condensation nuclei (such as suspended particles in the atmosphere). Of course, the increase of water vapor content in the atmosphere and the decrease of atmospheric temperature also contribute to the saturation process of water vapor.
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Generally speaking, there are four cooling modes in the atmosphere: adiabatic cooling, radiation cooling, advection cooling and mixed cooling.
In which adiabatic cooling forms clouds and rain; Radiation cooling, advection cooling and mixed cooling mainly form fog. lb q _ ~
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There are two conditions for precipitation: 1, and the falling speed of rain is greater than the rising speed of airflow; 2. Rainwater did not completely evaporate when it fell from the cloud to the ground. {，v $ *
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Precipitation generally occurs in large-scale systems, so it is related to the formation of cloud droplets. The formation process includes two parts: the condensation growth of cloud droplets and the parallel growth of cloud droplets. F x 1ce
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In the process of cloud droplet condensation and growth, there will be water droplets and ice crystals, which is the ice crystal effect. Simply put, at the same temperature, because the saturated water vapor pressure on the ice surface is lower than the water surface, water droplets will continue to evaporate and become smaller, while ice crystals will continue to condense and become larger. % 1JDIHTAL。
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The parallel growth of cloud droplets is mainly due to the process that cloud droplets of different sizes form different velocities under the action of gravity and increase continuously in the atmosphere. For cloud droplets lacking ice water at low latitudes, parallel growth of cloud droplets is very important.
Zhejiang Cixi vermicelli 2008-0 1-26 14:06
Personally, the formation condition of freezing rain is that there is a warm layer (inversion layer) in the middle and low altitude, which can melt snow or ice crystals in the cloud, but the near-surface temperature (including the surface temperature) must be below 0 degrees, and supercooled water can only freeze into ice after falling to the ground, thus forming freezing rain (also called rain).
Carlson 2008-065438
I'm not familiar with the local terrain, nhTb, G, Z.
However, these trends can be roughly seen .. WO/=# O
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There is a wind tangent w7ZG oh near 850 hectopascals (
925-850 hectopascals are the coldest, and 750-700 hectopascals are the top temperature inversion. Among them, Guiyang 0 126_00Z dew point inversion temperature exceeds 12 degrees. _jDS "
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10 12 HPA 125m 1.0C 0.6C 97% 295 deg n ` qo(pZ6+
1000 HPA 232m-0. 1C- 1.4C 9 1% 325 deg q ' 2 ` 0 MRA
925 HPA 852m-3.7c-5.1c 90% 20 degrees- NQ \W
* 850 HPA 1532m 6.2C 3.5C 83% 250 deg km } MqBQl
700 HPA 3 132m 4.2C 1.6C 83% 240 deg 4y 1 & gt；
500 hectopascals 5800 meters-10.3c-23.3c34% 230degu' = (&; & gt& lt
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1009 HPA 185m- 1.5C-3. 1C 89% 0 deg y]& lt； #%F h
1000 HPA 252m-2.3C-3.8C 89% 355 deg O % prD } x
955 HPA 6 10m-4.6C-6. 1C 89% 45 deg a 1 = _ nt)5
925 hectopascals 866m -6.3c-7.8c 89% 25 degrees h * {
884 HPA 12 19m-3.3C-4.8C 90% 2 15 deg D { Oq \ *
850 HPA 1528m-0.7C-2. 1C 90% 150 deg IO * l vy
760hpa 2438m1.6c0.1c 89% 260deg q g $ (USD
* 700 HPA 3 122m 3.4C 1.7C 89% 250 deg nW ~ $(Qnd
654 HPA 3658m 0.6C- 1. 1C 88% 250 deg @ W # fui & lt； & lt}Y
56 1 HPA 4877m-5.7c-7.6c 86% 255 deg l 43`^； u
500 hectopascals 5790 m-10.5 degree-12.5 degree 85% 245 degree
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1008 HPA 166m-0.3C-2.2C 87% 0 deg SW[oQ！ f
1000 HPA 229m-0.9C-2.7C 88% 10 deg 1B6C & lt； CL: sue
925 hectopascals 846m -4.9C-6.2C 9 1% 35 degrees -MDO Zz\
* 850 HPA 15 17m 3.4C 1.9C 90% 130 deg 5/TJ
700 HPA 3 1 14m 2.8C 0.7C 86% 235 deg v # iFQVBq
500 hectopascals 5770 meters-10.3c-34.3c12% 240 degrees. S & lt？ 07Z
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850 HPA 1533m-7.3C-8.6C 90% 40 deg JOJh，8C) 6
794 HPA 2066m-5.3C-6.6C 9 1% 342 deg(' T4Db
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* 756 HPA 2458m 5.8C 4.2C 89% 300 deg O |？ Z~
700 HPA 3084m 1.6C 0. 1C 90% 235 deg 5 woigo 3 x
683 HPA 3282m 0.0C- 1.3C 9 1% 236 deg MhHr *！ N"}
650 HPA 3677m-3.9C-2 1.9C 23% 237 deg \ nC5，Rz
640 hectopascals 3799 m -4.7 cm -35.7 cm 7% 238 degrees g4zT(ZY
604 HPA 4258m-2.3C- 13.3 c 43% 239 deg = t @:F
574 HPA 466 1m-4.5C- 14.5 c 46% 24 1 deg = zch 1j 5 "
500 hectopascals 5730m-13.3g-20.3g 56% 245 degrees
Zhuifeng 2008-0 1-26 20:30
Quote:
Quote e 7Yb=/F published by fans in Cixi, Zhejiang Province on 10/6/2614, 2008.
Personally, the formation condition of freezing rain is that there is a warm layer (inversion layer) in the middle and low altitude, which can melt snow or ice crystals in the cloud, but the near-surface temperature (including the surface temperature) must be below 0 degrees, and supercooled water can only freeze into ice after falling to the ground, thus forming freezing rain (also called rain).
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Hehe ~ correct it ...
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Crystals formed by supercooled rain dripping on cold objects on the ground are called raindrops ~ ~
eoj 329 2008-0 1-26 2 1:38
Another point is that snowballs are easy to form on the windward side, that is, the areas affected by the north wind are more likely to appear.
General 2008-065438
Looking at the critical forms of freezing rain and snowfall in some areas, it seems that the conditions of freezing rain, the thickness, temperature, temperature difference and duration of inversion layer and cold layer are a comprehensive and interactive whole, and it is difficult to predict without accurate calculation by computer. pHI % jHHJ
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Which soldier analyzed the following sounding and weather conditions: Y-}hNZn"{
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At 20 o'clock on the 26th in Quxian County, Zhejiang Province, it began to rain (58633 Quxian County) (&; N $ W & amp
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At 8 o'clock on the 26th in Hangzhou, freezing rain turned to ice particles (58457 ZSHC Hangzhou) {V =:O
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At 20 o'clock in Hangzhou on the 26th, ice particles turned to snow (58457 zshchhangzhou)1w6n [XG
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At 20 o'clock in Changsha on the 26th, it was sleet (57679 ZGCS Changsha) * OWD; ]4_
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At 20 o'clock on 26th, it was freezing rain in Guilin (57957 ZGKL Guilin) jy)9EU=
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General motors 2008-065438
At 08: 00 on 26th in Nanchang, freezing rain (58606 zscn Nanchang)-%qezu &;
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Nanchang at 20 o'clock on the 26th (58606 ZSCN Nanchang)? 2bE=|
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Guiyang is high above sea level, so don't look.