How do we calculate average annual rainfall?
Calculate the averages. Once you’ve recorded data of rainfall for a month using rain-guage, you can analyze your data and see overall rainfall trends. Adding up the rainwater of all 7 days in a week, then dividing it by 7, will give you the average rainfall of that week. Over a longer period of time, you could do this for months (or even years, if you’re particularly dedicated).The formula for finding an average is easy to apply. The average equals the sum of all the items (in this case, rainfall measurements for a day, week, or month) divided by the number of items (however many days, weeks, or months you’ve added up).[7] If you're looking for average weekly rainfall over 4 weeks, with recorded weekly rainfall totals of 20 inches, 12 inches, 6 inches, and 25 inches, we would say 20 + 12 + 6 + 25 = 63 (the sum of the items) / by 4 (the number of weeks) = 15.75 inches average weekly rainfall. Source: http://How to Measure Rain
An extended period of well-below-average rainfall is known as a?
It's a drought (A).
What would happen to the desert if the average rainfall increased significantly?
Most deserts receive significant rainfall. It is the annual average that is very, low, not the fact that rain never falls.So we know what happens.The desert's life makes use of that water as best it can. This is problematic, since the hardpan surfaces of baked earth don't absorb water very well. Flash flooding may be a problem because the water just slides downhill, nearly every drop heading for the ocean.But if you mean that the annual average changes, then the desert, by climate definition, is no longer desert. If this happens gradually, the plants (which are evolved to adapt to a low-rainfall environment) will start to die out and neighboring plants that can adapt to the new environment will encroach. Eventually the desert will become a new biome, appropriate to the new climate.
What really mean of 16 inch rain fall and how do they measured as 16 inch?
Although we usually just say "inches," we really mean "inches in the storm" or "inches in the last 24 hours" or "inches in some time period." Why does that matter? Well, obviously 1 inch of rain in a 15 minute period is a lot more water than 1 inch of rain in the last month. So we really don't know how much it's rained if we don't know the time period we're talking about. So what does 1 inch, 2 inches, or whatever number of inches of rain in some time period mean? Well, if all the rain that falls stays right where it lands—meaning it doesn't run off and accumulate in streams and rivers and eventually in lakes and oceans, and it isn't absorbed into the ground—then 1 inch of rain in an area is enough to evenly cover the ground in that area with a layer of water 1 inch deep. Of course, water typically does run into streams and is absorbed into the ground, so 1 inch of rain rarely means an inch of standing water. But whether or not we actually see 1 inch of water on the ground for each inch of rain, we can use this definition to construct a device that measures how much it has rained—a so-called rain gauge. It's very easy to build a rain gauge. In fact, there's a good chance you did it in school at some point. All you have to do is take a straight-sided can with a flat bottom (like a cylinder), make marks up its side every inch, set it out in the open, and wait for rain. If you see that the can has filled with water up to the 1 inch mark, then you know it has rained 1 inch. Up to the 2 inch mark, it has rained 2 inches. The size of the cylinder, in other words, its diameter doesn't matter (This fact was a surprise to me as well when I first read about it). The height of the water in the can is equal to the volume of water in the can divided by the area of the opening. And the volume of water in the can is proportional to the rate of rainfall (measured in something like drops per square inch) times the area of the can. If we put these together, we find that the area of the can cancels from the top and bottom of the ratio—meaning the area doesn't matter.Quoting a fact, "A 1,000 square foot roof is bombarded by 625 gallons of water per inch of rain."Hope this helps.
What is the average time taken by a raindrop to fall from a cloud to the ground?
This is an interesting question realistic we never thought this, very nice and thank you.The fall of rain drop from the cloud to the earth can not be treated as free fall because the rain drop mass is very small. The Air present will have more effect on the rain drop. Hence I am treating rain drop as an object of fixed size and the air as fluid through which it move. This reminds me one experiment you might come across with your graduation studies, namely the “Stokes viscosity experiment”. In this experiment a spherical ball (rain drop here) travel in a viscous liquid such as caster oil (here it is air). The situation is identical. Hence I apply stokes method here to find the velocity of the rain drop.Density of air (1.2Kg/m2), density of rain drop (1000kg/m2) viscosity of wet air (8.91x10–4 Pas), acceleration due to gravity (9.8m/s2) are known things. Using these data let assume that the rain clouds are at the height of 2km from earth surface and a rain drop size is 5mm falling down.The velocity of the rain drop comes out be V = 15.26m/sTime taken travel 2km = 131s = 2.2minutes.A rain drop of 5mm dia requires about 2.2 minutes reach earth from the cloud at 2km. If the drop is bigger it takes more time.For calculation please refer Lab Experiment Vol-12, No-2, Page-130, June 2012.
Which device is to measure rainfall?
Since rain is basically water that falls from the sky, something that measures rainfall would need to be nothing more than a container. But a container alone isn’t enough because you want will more than likely want to know how much rain fell over a certain period of time. You also need to consider how LONG of a period you will be measuring. (One hour of rainfall would take a smaller container than one day, or one week, for example.)So, you decide how long you want to measure, and that dictates the size of the container. Then you go out and capture water from the sky for that period of time.Now what?Well… you COULD weigh the water by placing the container and water on a scale, then subtracting the weight of the container. (You DID measure its weight before you put it outside, RIGHT??) “A pint’s a pound the world around.” (Sorta… close enough for estimates, anyway.) Then do some math to convert the weight into the measurement you want.Or you could stick a ruler in the container and see how deep the water is. But to really calculate how MUCH water there was you’d need to know the volume of water, so you’d better measure the size of the container as well, then jump into some mathematics to convert your measurements into the measurement you want.Or you could go buy a cheap rain gauge. There are tons available, from simple plastic, to crazy ornamental ones. Most of them have a ruler of sorts on the side that will give you a standardized measurement, whether in millimeters, centimeters, or inches.Long story short, a rain gauge is used to measure rainfall, and it is little more than a container that catches water and gives you a standardized way to measure how much is inside. All you need to do is look at a clock when you place it in the rain, then look at a clock when you read the scale, and you know how much fell over that time period.Although there’s still math involved. You need to be able to calculate how much time has elapsed. But you didn’t ask for information on how you measure time, so I’ll leave that for another day.
Does it really rain every day in london?
I am one of those people who are fascinated with the idea of visiting London some day and possibly living there should the opportunity present itself. What can you tell me about London? if you've been there or live there?
In medieval times, why didn't the archers just rain down arrows on the enemy?
They did. At least the armies that had really good archers with really good bows and arrows, and tactics good enough to make it count: the English and their longbowmen.They couldn't make it rain arrows for hours, though. As others pointed out, for logistical reasons that would have been impractical. In just one minute 5000 archers could shoot something like 40,000 arrows. At that rate, they would go through a million arrows in less than half an hour. That's a ridiculous amount of arrows to be lugging around, as it would seriously impede your army's mobility.That's aside from whether they could physically maintain that rate of fire for over 10 minutes, since pulling a longbow is some seriously strenuous stuff.But they did make it rain arrows for long enough to ensure some stunning victories at the battles of Crécy , Poitiers , and Agincourt during the Hundred Years War.In short, making it rain arrows was, for a long time, a highly effective tactic. Only the English (in Europe) could do it effectively, though. And even then, not for hours.Mounted Steppe horsemen such as the Mongols also made it rain arrows, but unlike the English they did so from a mobile platform in a fluid field of battle.
How far in advance can the weather be realistically predicted? How accurate is it?
Most weather forecast websites rely on a few forecast models such as GFS, ECMWF, WRF, UKMO, CMC and many other weather forecast models. Normaly the weather forecast is based on the initial conditions of forecast run. When we reach day 2 forecast there could be different out come from use of different forecast models. This difference gets amplified as we go to day 3 and then day 4 and day 5. Hence for all practical purpose weather forecasts are reliable up to 80% till 4 days ahead and may be 60 % till 7 days ahead. All forecast after day 7 should not be taken seriously but an indication of what is in store ahead. There are some websites which use multiple weather forecast model and give the forecast as an ensemble or mean of the forecast. One such website is Forecast .I will be glad to answer any further query/clarification on this subject.