DOES THE MOON MOVE?

<div dir="ltr" style="text-align: left;" trbidi="on"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCaGst14oKdUFFmc7jm68Qr7nxRPpfYzRFrIV1lIJ_iSRYWmAYOatl6bz3o4ievvftQAND6DczlgvwBwFHBaBP0ARLuFBIcfCgRhDDVMn44XfRn7_DXZY5ma88vnkb6INo3sp98MjwP0s/s1600/tmp_6985203187_3783f8888b_z889940671.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCaGst14oKdUFFmc7jm68Qr7nxRPpfYzRFrIV1lIJ_iSRYWmAYOatl6bz3o4ievvftQAND6DczlgvwBwFHBaBP0ARLuFBIcfCgRhDDVMn44XfRn7_DXZY5ma88vnkb6INo3sp98MjwP0s/s1600/tmp_6985203187_3783f8888b_z889940671.jpg" /></a></div> This's a very good question every learned person  would like to know. Have you ever wondered why the moon is in a different place every night?.<br /> <br /> There are two reasons.<br /> <br /> First of all, it depends on  what time of day you are looking at the moon. For example, if you go outside tonight at 7:00 and tomorrow at 11:00, you would see the moon in two very different places in the sky. Not only that, but all the stars would be in different places in the sky as well!    This is because the earth is spinning.  It takes 24 hours for the the earth to spin once  around, which means that from our point of view  (sitting on the earth's surface) it looks like the  sky and everything in it is moving around us once  per 24 hours. (This is the same reason that the  sun rises and sets every day, giving us daytime  and nighttime.)<br /> <br /> But what would happen if you went outside on the second night at the exact same time you went out on the first night (7:00)?<br /> The stars will be in almost the same part of the sky as they were the first night. (Since you waited 24 hours, they had time to "move" around the earth once and get back to where they were before.) But the moon will be in a different place! In fact, you would have to wait a little while (usually an extra 30 minutes or an hour) until it got back to the same place as it was the night before.<br /> <br /> So what happened?  How come the moon "fell behind" everything else?<br /> The answer is that the moon is moving. All the  stars in the sky are pretty much standing still -  they only look like they're moving because the  earth is spinning, as I said above. But the moon  is actually moving in orbit around the earth - it  takes about a month for it to complete one circle  around us.    So the moon's motion has two parts to  it. It looks like it's moving around the earth once  per day along with everything else, but in addition to that it is actually moving around the earth once per month. That is what makes it move to a different place on the sky.  It is even possible to watch the moon move, if  you are patient enough.<br /> <br />  If you carefully keep track of the moon and a nearby star for an hour or so, you should be able to see the distance between them change!<br /> <br />  Moreover the moon is a satellite and all satellites  move.</div>

DOES THE MOON MOVE?

This's a very good question every learned person  would like to know. Have you ever wondered why the moon is in a different place every night?. There are two reasons. First of all, it depends on  wha…

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WHY DO WE SALIVATE ON SIGHTING THE FOOD WE LIKE

<div dir="ltr" style="text-align: left;" trbidi="on"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZUABSI1Yq_OzDB0ny88FRoH42iri4bKRcTXq88E3RlnFr_RDfEYX8jVO-FPunarkht42Xr0Z8P-S1q0A4y68r7I278rxtQ5mTAo1UeZ2M5RJbikBBlnGC0mFakNeONyZM61B2n601_O0/s1600/tmp_ae08e4252ff9aa46cd445c75e7dce2371659761849.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZUABSI1Yq_OzDB0ny88FRoH42iri4bKRcTXq88E3RlnFr_RDfEYX8jVO-FPunarkht42Xr0Z8P-S1q0A4y68r7I278rxtQ5mTAo1UeZ2M5RJbikBBlnGC0mFakNeONyZM61B2n601_O0/s1600/tmp_ae08e4252ff9aa46cd445c75e7dce2371659761849.jpg" width="216" /></a></div> Well there is no theory behind this statement . It's only an assumption.<br /> <br /> Here is my own view;<br /> <br /> When we think of good food we want to eat, we are tickling our appetite. When we do so, our salivary glands produce more saliva (hence our mouth "watering") in lieu of the effects to our appetite.<br /> Saliva contains enzymes and lubricants that help you begin the process of digestion as soon as food gets in your mouth.  When you think of savory food,  your body takes this as a cue to start gearing up for another round of digestion.<br /> Your 3 salivary glands (parotids, sublinguals, and submentals) begin excreting what they have stored and producing more for the upcoming morsel.<br /> <br /> This process of preparing to begin digesting food manifests a "watering" in your mouth.  People with Sjogren's Syndrome lose their salivary glands, therefore their mouths don't undergo the same "watering" reaction that most people experience in response to savory food.</div>

WHY DO WE SALIVATE ON SIGHTING THE FOOD WE LIKE

Well there is no theory behind this statement . It's only an assumption. Here is my own view; When we think of good food we want to eat, we are tickling our appetite. When we do so, our salivary glan…

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WHY DO WE DREAM?

<div dir="ltr" style="text-align: left;" trbidi="on"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3NgfpAVjoff9inVAEfDu-MWx4stJkPV09t0rrmAI9tn9NGFeKFZGxOfOotYEn9XSpWVZw7LPs-Oy-TeXlGK62XnrYz7wG_BC_0iK0TZHF47sbWWg2zeWETQXPNoeyMhPcRbdxcaYGgY8/s1600/tmp_dream5-353573945.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3NgfpAVjoff9inVAEfDu-MWx4stJkPV09t0rrmAI9tn9NGFeKFZGxOfOotYEn9XSpWVZw7LPs-Oy-TeXlGK62XnrYz7wG_BC_0iK0TZHF47sbWWg2zeWETQXPNoeyMhPcRbdxcaYGgY8/s1600/tmp_dream5-353573945.jpg" /></a></div> First, let’s start by answering a basic question –  What is a dream?<br />  A dream can include any of the images, thoughts and emotions that are experienced during sleep. Dreams can be extraordinarily vivid or very vague; filled with joyful emotions or frightening imagery; focused and understandable or unclear and confusing.<br /> <br /> So why do we dream?<br /> What purpose dreams serve?<br /> <br /> While many theories have been proposed, no single consensus has emerged. Considering the enormous amount of time we spend in a dreaming state, the fact that researchers do not yet understand the purpose of dreams may seem baffling.    However, it is important to consider that science is still unraveling the exact purpose and function of sleep itself.  Some researchers suggest that dreams serve no  real purpose, while others believe that dreaming is essential to mental, emotional and physical well-being.<br /> <br /> Ernest Hoffman, director of the Sleep Disorders Center at Newton Wellesley Hospital in Boston, Mass., suggests that "...a possible (though  certainly not proven) function of a dream is to be  weaving new material into the memory system in a way that both reduces emotional arousal and is adaptive in helping us cope with further trauma or stressful events."    Next, let’s learn more about some of the most  prominent dream theories.<br /> <br /> Psychoanalytic Theory of Dreams:  Consistent with the psychoanalytic perspective,  Sigmund Freud’s theory of dreams suggested that dreams were a representation of unconscious desires, thoughts and motivations. According to Freud’s psychoanalytic view of personality, people are driven by aggressive and sexual instincts that are repressed from conscious awareness.  While these thoughts are not consciously expressed, Freud suggested that they find their way into our awareness via dreams.<br /> <br /> In his famous book The Interpretation of Dreams,  Freud wrote that dreams are "...disguised  fulfillments of repressed wishes." He also described two different components of dreams: manifest content and latent content.  Manifest content is made up of the actual images, thoughts and content contained within the dream, while the latent content represents the hidden psychological meaning of the dream.  Freud’s theory contributed to the popularity of  dream interpretation, which remains popular today.  However, research has failed to demonstrate that  the manifest content disguises the real psychological significance of a dream.<br /> <br /> Activation- Synthesis Model of Dreaming:  The activation-synthesis model of dreaming was  first proposed by J. Allan Hobson and Robert  McClarley in 1977. According to this theory, circuits in the brain become activated during REM sleep which causes areas of the limbic system involved in emotions, sensations and memories, including the amygdala and hippocampus, to become active.<br /> The brain synthesizes and interprets this internal activity and attempts to find meaning in these signals, which results in dreaming.  This model suggests that dreams are a subjective interpretation of signals generated by the brain during sleep.<br /> While this theory suggests that dreams are the  result of internally generated signals, Hobson does not believe that dreams are meaningless. Instead, he suggests that dreaming is "…our most creative conscious state, one in which the chaotic, spontaneous recombination of cognitive elements produces novel configurations of information: new ideas. While many or even most of these ideas may be nonsensical, if even a few of its fanciful products are truly useful, our dream time will not have been wasted."<br /> <br /> Information-Processing Theories:  One of the major theories to explain why we sleep is that sleep allows us to consolidate and process all of the information that we have collected during the previous day.  Some dream experts suggest that dreaming is simply a by product or even an active part of this information-processing.<br /> As we deal with the multitude of information and memories from the daytime, our sleeping minds create images, impressions, and narratives to manage all of the activity going on inside our heads as we slumber.</div>

WHY DO WE DREAM?

First, let’s start by answering a basic question –  What is a dream?  A dream can include any of the images, thoughts and emotions that are experienced during sleep. Dreams can be extraordinarily viv…

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NOSE: THE ULTIMATE AIR CLEANER

<div dir="ltr" style="text-align: left;" trbidi="on"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtK7g6yULcbk_AHtnGgAuAGLViiaLqGNLl_qNHkxN63p32VkFOQBqBgYsT7iTS1NNPtiWcIgjRNmUUHPzqYWJ0yB4acFIXjkqgewAOsaflsrWPqmkxKFmfXevdwSxE_h6MyOTymIov_SU/s1600/tmp_keep-your-nose-out-of-my-business1659761849.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtK7g6yULcbk_AHtnGgAuAGLViiaLqGNLl_qNHkxN63p32VkFOQBqBgYsT7iTS1NNPtiWcIgjRNmUUHPzqYWJ0yB4acFIXjkqgewAOsaflsrWPqmkxKFmfXevdwSxE_h6MyOTymIov_SU/s1600/tmp_keep-your-nose-out-of-my-business1659761849.jpg" /></a></div> Your nose does more than just decorate your face. Inside, you’re carrying around a personal air treatment system, cleverly designed to protect the delicate tissues of your lungs that transfer oxygen out of the air you breathe and into your body.Whether classically bold or cutely upturned, your nose:<br /> <br /> *.Filters the air, catching and trapping tiny particles before they can get into your lungs.<br /> <br /> *.Humidifies the air, adding moisture to keep your airways from drying out.<br /> <br /> *.Warmsthe air to body temperature beforeit reaches your lungsThis marvelous system is portable, durable–usually fairly quiet – and never needs batteries! But it does require some maintenance to keep it working at peak efficience.<br /> <br /> <br /> What’s Up Your Nose?<br /> <br /> When you breathe through your nose, the air goes past your nostrils into an open area inside your head called the nasal cavity before heading down your trachea and into your lungs through your windpipe.The whole system of airways is lined with a thin layer of sticky mucus that traps dust particles, bacteria and other pollutants. Tiny hairs called cilia sweep mucus from your nasal cavity into the back of your throat where it can be swallowed and neutralized in your stomach. More mucus is constantly being produced (2-4 cups perday) and the cycle goes on.An intricate network of blood vessels takes care of the heating and humidifying work. Folds of tissue (called turbinates) inside your nasal cavity provide a huge surface area of blood vessels that warm the air to body temperature and add moisture within seconds.<br /> <br /> <br /> Meddling With Mucus:<br /> <br /> Mucus must have just the right balance of stickness and fluidity for the filtering process to work efficiently. Allergic reactions and infections can disrupt this balance, and dry air, irritating chemicals and second hand smoke tip the scales even more.Allergens and infections alert your immune system to send extra blood cells to the lining of your nasal passages, making them swollen and inflamed (congested).<br />  the same time, your nose produces extra mucus.<br /> This can overwhelm the cilia’s ability to clean things out – and leave you with a stuffed-up or runny nose.<br /> <br /> Strong scents and chemicals (such as those in tobacco smoke) can affect how well the cilia in your nasal cavity work, alsocausing mucus to build up.A dry nose also has trouble moving mucus effectively. When the air you breathe is very dry especially cold winter air), it may pull more moisture than usual from your nose. The resulting dried out nasal passages and thickened mucus will be less able to sweep out germs, leaving you more susceptible to disease.<br /> <br /> <br /> Mouth Breathing: <br /> <br /> Breathing through your mouth instead of your nose – because your nose is congested, perhaps, or during vigorous exercise – by-passes much of  your body’s natural air filtering and treatment. This can allow germs, allergens and other pollutants to get inside your lungs, where they can damage delicate tissues.It also allows unconditioned air to affect sensitive small airways. For example, drawing cold air into your lungs without letting your nose warm it up first has a two fold effect:<br /> <br /> *.The cold air makes your airways tighten up and constrict, so breathing becomes more difficult<br /> <br /> *.The dryness thickens mucus and clogs the cilia, so your lungs are less able to process oxygen and move it into your bloodstream.<br /> <br /> <br /> ACold in the Nose:<br /> A “cold” is a viral infection in the lining of your nasal passages. You may pick up the germs by touching contaminated surfaces with your hands then touching your nose or eyes or by being exposed to germs from someone’s cough or sneeze. When your nose is working efficiently, cold viruses are swept out of the nasal passages in your mucus. When it’s not, they can sit in your nose and make their way into your nasal tissue, causing infection.<br /> <br /> <br /> Asthma:<br /> Because the connection between the nose and lungs is so important, keeping your nose healthy can help reduce problems in the lungs such as asthma symptoms. Sensitive airways already compromised by underlying inflammation are primed and ready to react when exposed to allergens, irritants, excess mucus or cold air.<br /> <br /> <br /> How To Maintain a Healthy Nose:<br /> <br /> Although you can’t always control the temperature or contents of the air you breathe, you can take steps to keep your nose as healthy as possible by following these tips:<br /> <br /> *.Drink plenty of water to keep mucus thin and fluid.<br /> <br /> *.Help warm the air you breathe in cold weather by wearing a scarf over your nose and mouth.<br /> <br /> *.Keep nasal passages moist with saltwater nasal washes or sprays, especially if you are exposed to dry air, allergens or infection.<br /> <br /> *.When using nasal sprays, be careful to direct the spray toward the outer surface of your nasal passage, away from the center of your nose, to avoid damaging the septum (the tissue that separates the two sides of your nasal passage).<br /> <br /> *.Limit your use of decongestant sprays, which can damage the cilia that clear the nose and sinuses.<br /> *.Ask your healthcare professional whether any other medications you take could contribute to nasal problems.<br /> <br /> <br />  For instance, diuretic blood pressure medications and some anti-anxiety medications have a drying effect on nose and throat; birth control pills, betablockerblood pressure medicines and erectile dysfunction medication can increase nasal congestion;eye drops can aggravate nasal symptoms when they drain into the nose with tears.</div>

NOSE: THE ULTIMATE AIR CLEANER

Your nose does more than just decorate your face. Inside, you’re carrying around a personal air treatment system, cleverly designed to protect the delicate tissues of your lungs that transfer oxygen …

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SUN PILLAR

<div dir="ltr" style="text-align: left;" trbidi="on"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinhmtARPnd3izG4IlZ-OtbIcKiy5Sai3vN-WNntRUWYsYgcACV2Ke5hBXGHTB_hyphenhyphendUSA2Jei2U7nPhMnwomGipjvp92tpEai93_F1zXIf8UDtxDuI9E1BLaByCD43kzIeJznzM_dCsGE8/s1600/tmp_1538820_241779699341760_9015297717516198505_n889940671.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinhmtARPnd3izG4IlZ-OtbIcKiy5Sai3vN-WNntRUWYsYgcACV2Ke5hBXGHTB_hyphenhyphendUSA2Jei2U7nPhMnwomGipjvp92tpEai93_F1zXIf8UDtxDuI9E1BLaByCD43kzIeJznzM_dCsGE8/s1600/tmp_1538820_241779699341760_9015297717516198505_n889940671.jpg" /></a></div> Sun pillar is a halo phenomenon of a vertical shaft of light extending upward or downward from the sun. Typically seen during sunrise or sunset, sun pillars form when sunlight reflects off the surfaces of ice crystals associated with thin, high-level clouds (e.g.cirrostrat us clouds). The hexagonal plate-like ice crystals fall with a horizontal orientation, gently rocking from side to side as they fall.<br /> <br /> When the sun is low on the horizon, an area of brightness appears in the sky above (or below) the sun as sunlight is reflected off the surfaces of these tipped ice crystals. However, often only the upper pillar appears. Sun pillars are seen best within a few minutes of sunrise or sunset. Initially the have about the same colour and width as the sun, but sunpillars will gradually change their colour from orange-white to red-orange. Sun pillars generally fade 20 to 60 minutes after sunset.<br /> <br /> Under favourable conditions, e.g. icy fog, sun pillars might stretch out up to 30° above the sun, while light streaks of 5° to 10° are most common. On rare occasions, regarded with awe in more superstitious times, it may occur with part of the parhelic cycle to give the appearance of a cross centred on the Sun. The sun pillar is comparable with the light course, the setting sun produces on a water surface.</div>

SUN PILLAR

Sun pillar is a halo phenomenon of a vertical shaft of light extending upward or downward from the sun. Typically seen during sunrise or sunset, sun pillars form when sunlight reflects off the surfac…

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THE MIRAGE

<div dir="ltr" style="text-align: left;" trbidi="on"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0ro-cyQbENoKqS7mF66mzz07BtrtQpzjeaEZrlJSl4z1JGMwbqp2GIUxV0jbicKucfSwd2NsLo94p2eiKwcyo8GWK0aHPSuF9JUHm3UVG-l01BtDA7ma-bWpgYTWgz-Q20s-roKL5uM0/s1600/tmp_Dsc_3561d70sm21659761849.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0ro-cyQbENoKqS7mF66mzz07BtrtQpzjeaEZrlJSl4z1JGMwbqp2GIUxV0jbicKucfSwd2NsLo94p2eiKwcyo8GWK0aHPSuF9JUHm3UVG-l01BtDA7ma-bWpgYTWgz-Q20s-roKL5uM0/s1600/tmp_Dsc_3561d70sm21659761849.jpg" /></a></div> It's 2:00 p.m. on a very hot afternoon, and we've just pulled out of the entrance to the express road. Far ahead of us a puddle seems to be continuously evaporating off the sun-baked pavement, its receding edge matching its speed to ours. Even when my old man floor the accelerator we can't catch up to the water, but somehow the cars passing ours easily do. They drive into it without a splash, and they seem to be reflected in it, upside down.<br /> <br /> Of course, real water doesn't behave this way. The retreating puddle is just the most familiar form of that often misunderstood phenomenon of air and light, the mirage.<br /> Is the puddle mirage real or is it an illusion? It's actually a little of both-straightforward physics plus the workings of the human mind. Add a little dehydration, which we almost always experience on hot days like this, and perhaps we're even more inclined to see water where it isn't! Scientists relax and read.<br /> <br /> To understand how a mirage forms, one must first understand how light travels through air. If the air is all the same temperature--cold or hot--light travels through it in a straight line. If a steady temperature gradient exists, however, light will follow a curved path toward the cooler air. The standard freshman physics explanation for this phenomenon is that cold air has a higher index of refraction than warm air does. As a result, photons (particles of light) travel through hot air faster than they can through cold air because the hot air is less dense.<br /> <br /> The quantum electrodynamics explanation is that photons always take the path of minimum time when traveling from one point to another. In order to get from one point to another in a minimum time, photons will take "shortcuts" even though the length of the path is curved and it covers a longer distance than the direct route. Mirages are a direct result of photons taking the path of minimum time in vertical temperature gradients. Ideal conditions for a mirage are still air on a hot, sunny day over a flat surface that will absorb the sun's energy and become quite hot. When these conditions exist, the air closest to the surface is hottest and least dense and the air density gradually increases with height. Incoming photons take a curved path from the sky to the viewer's eye. The illusion comes from the fact that quantum electrodynamics is not intuitive and the human brain assumes that light travels in a straight line. A viewer looking at, say, the road ahead on a hot, still, day will see the sky because photons from the sky are taking the curved path that minimizes the time taken. The brain interprets this as water on the road because water would reflect light from the sky in much the same way that a vertical temperature gradient does.</div>

THE MIRAGE

It's 2:00 p.m. on a very hot afternoon, and we've just pulled out of the entrance to the express road. Far ahead of us a puddle seems to be continuously evaporating off the sun-baked pavement, its re…

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HOW DO CLOUDS AND RAIN FORM

<div dir="ltr" style="text-align: left;" trbidi="on"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuuhl0sbW27K0WuEzFj85qW3bNVubmte32RdpUW2STUPRyv6fdmnywbfxXzfXKJHJ9iHvrMse-US5xijh6iN9bDbvDHe4DvUrK_rq3Vt8FyiwvwhluU7zP1i4Dbny47a7zfHHq56tKzqw/s1600/tmp_Rain+clouds+015-1882715361.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuuhl0sbW27K0WuEzFj85qW3bNVubmte32RdpUW2STUPRyv6fdmnywbfxXzfXKJHJ9iHvrMse-US5xijh6iN9bDbvDHe4DvUrK_rq3Vt8FyiwvwhluU7zP1i4Dbny47a7zfHHq56tKzqw/s1600/tmp_Rain+clouds+015-1882715361.jpg" /></a></div> Water vapour saturation:<br />  The air in our atmosphere always contains some water vapour, whose density can only climb to a certain saturation value at any given temperature. The maximum possible water vapour content of the air however increases out of proportion to any increase in temperature. Equally, it is always possible to cool an air parcel, reducing the water vapour saturation value, to a temperature at which the water in it starts to condense. The temperature at which this starts to happen is known as the dew point. Further cooling results in the excess water vapour being deposited onto fixed surfaces (dew formation) or onto condensation nuclei, leading to the formation of droplets. Tiny particles of various origin, the so-called aerosols, are usually present in abundance in the atmosphere and serve as these condensation nuclei.<br /> <br /> Clouds:<br />  As an air parcel rises it cools, the water vapour condensing when it reaches the dew point. Sunlight is scattered from the resultant droplets so that the emergent clouds can be seen by human eyes by their white, diffuse light. The best example of this is when air parcels rise from the warm ground in summer; those with only a small buoyancy compared to the surrounding atmosphere produce ‘fine weather’ clouds, those with stronger buoyancy climb higher and form thick clouds and heavy rainfall. In low pressure systems with their cyclonic (anti- clockwise, in the northern hemisphere) air flow, warm, humid, subtropical air is transported to the north-east. Due to its lower density it moves up over the colder northern air, cooling as it rises. This is how clouds form on the warm fronts of such pressure systems in the mid-latitudes. Conversely, on the western side of the low the cold air moves southward, pushing under the warmer subtropical air and raising it up above its condensation level to form clouds on the cold front. Clouds can also be formed from the cooling and condensation that occurs when air flows over physical obstructions like mountain ranges.<br /> <br />  Precipitation:<br /> Cloud droplets are tiny, only 1/100 mm in diameter, and are thus very light and practically float freely in the air. As the droplets collide, with time some grow larger than others and start to slowly fall, falling faster as they accumulate more and more droplets. If the cloud of droplets is dense enough to form droplets greater than 1/10 mm in diameter through this process, the droplets survive the fall through the air below the cloud, despite evaporation, and reach the ground as rain. This process develops what is known as ‘warm rain’, but in our part of the world it is responsible for only the weakest drizzle from near surface clouds. In the warm tropics it is responsible for intense rainfall from clouds lower than 5 km. More important in the formation of heavier rain is a process that involves frozen particles. Although the temperature at cloud level is often below 0 ºC, the droplets themselves remain in liquid form – this is known as ‘super cooling’. In these circumstances, a tiny disturbance (a collision, or the presence of a suitable ice nuclei) is enough to cause the droplets to suddenly freeze solid. Water vapour condenses more easily onto ice particles than onto liquid water droplets, so these ice particles grow faster than the surrounding droplets and begin to fall sooner. They grow further through the accumulation of other droplets and quickly become large enough to reach ground level. Since the ice particles encounter ever warmer layers of the atmosphere as they fall, they often melt as they fall and reach the ground as rain. If they have formed in a very thick cloud however they can become so large that they do not melt before they reach the ground and fall as granulated ice particles. Storm clouds can contain upward winds that are so strong that ice particles that have already melted at the surface are pulled back up into the cloud and freeze anew. At some point they will fall again, growing by the accumulation of other droplets and melting again. Occasionally this process is repeated a number of times, leading to the eventual formation of large, layered hailstones.<br /> <br /> Types of Clouds :<br />  Clouds are basically divided into two classes, based on appearance: there are single layer (stratiform) clouds and accumulated (cumuliform) clouds, which can both occur at different altitudes throughout the troposphere. Stratiform clouds are formed through the large-scale rising of entire layers of air, whilst cumulus clouds are primarily formed through the action of small scale vertical mixing processes. The following table gives a brief overview of the appellations of the main cloud types: Clouds are further named to denote their origin, details of their appearance or their degree of development (e.g. St Fr – Stratus Fractus – Broken Stratus)</div>

HOW DO CLOUDS AND RAIN FORM

Water vapour saturation:  The air in our atmosphere always contains some water vapour, whose density can only climb to a certain saturation value at any given temperature. The maximum possible water …

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