Questions tagged [precipitation]

Precipitation is any form of moisture that falls from a cloud and reaches the ground. Precipitation can fall to the ground as rain, snow, sleet, hail, graupel... etc.

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24
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3answers
7k views

What do weather forecasters mean when they say “50% chance of rain”?

What do weather forecasters mean when they say "50% chance of rain"? Even more confusing: weather report often says something like "30% chance of rain. >10mm", then the next day "70% chance of rain &...
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5answers
3k views

Is there a database of global rainfall time series?

Is there any institute out there collecting time series data of precipitation, and making them accessible online? I need data for a few different locations, but: Low spatial resolution is fine. For ...
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3answers
17k views

What is the percentage of the global water cycle (evaporation, precipitation) that occurs over the ocean?

Most of the water cycle studies focus on the processes and changes occurring over land with little emphasis on the ocean. Meanwhile, the ocean covers almost 3/4 of the surface of Earth. How much of ...
16
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1answer
373 views

What is the methodology to analyze future climatic extremes using the results of climate models?

What is the accepted methodology to predict future climatic extremes using the results of climate models? I have recently read a report about climatic extremes considering climate change (MICE, 2002)....
16
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1answer
2k views

How do urban areas affect rain?

Urban areas these days can be quite large, and they can have strong effects on the environment: the urban heat island effect being the most obvious, but there may be other, more subtle effects. The ...
15
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2answers
769 views

What factors affect the size of rain shadows?

Rain shadows are dry areas on the lee side of mountains. Due to humid air condensing and precipitating as they are lifted up and over the mountains, they lose moisture by the time they reach the lee ...
15
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1answer
346 views

Can climate models reliably predict meteorological extremes?

This question is related to and extension of my previous question which was about the methodology used to predict future climatic extremes: What is the methodology to analyze future climatic extremes ...
14
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2answers
3k views

Why One Side of Mountain Range is Lush

I'm new to this site and certainly not someone with any real background in atmospheric science, so please forgive me if this question is a little stupid. I recall learning in High School about ...
14
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1answer
237 views

Is there a standard definition of a “dry-down” event in hydrology?

When studying the land surface, dry-down periods - periods after rain where the soil moisture is decreasing due to evapotranspiration and drainage - are of great interested, because soil moisture has ...
14
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1answer
242 views

How do climatologists define the “start” of a rainy season in a unimodal monsoonal climate?

For a number of gridcells, all between the 500mm and 800mm rainfall isohyets in sub-Saharan Africa, I've got dekadal rainfall (from FEWS). They are pretty spread out over the continent and there are ...
13
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2answers
24k views

Transfer precipitation forecast in mm to expected snowfall in cm

What conversion functions exist to transfer precipitation forecast in mm to expected snowfall in cm? Simple rules of thumbs as well as more advanced methods would be of interest.
13
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2answers
610 views

Why do those glaciers form on the lee side of the mountains?

In the Scandinavian mountains, there is a strong effect of orographic precipitation. The west receives far more precipitation than the east. This difference can be a factor 5 or more in some places. ...
13
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2answers
2k views

How to interpret hourly precipitation forecast?

How should I interpret the hourly precipitation forecasts? Most of the time, when there is rain in the forecast, the maximum Probability of Precipitation (PoP) in the hourly forecast is about the ...
12
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1answer
2k views

Is there any correlation between La Niña/El Niño and seismic activity?

I've read in the past that extreme precipitation levels may have an effect on seismic activity, and wondered if anyone has ever analysed the La Niña / El Niño cycles to see if there are any ...
11
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1answer
199 views

Why is heavy precipitation from atmospheric rivers more likely to hit the West Coasts than the East Coasts?

As an example of an atmospheric river, see http://www.wired.com/2014/03/california-atmospheric-river-rain/. These events have been known to hit areas like California and Bergen, Norway.
11
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1answer
2k views

Intuitive explanation of precipitation amount

I'm trying to learn how to make sense of numbers in a forecast. I can interpret temperature and wind speed, but I don't know what to make of rainfall. What does it mean, for a human, that there will ...
11
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0answers
129 views

Will global climate change alter the interannual and/or intraseasonal variance of temperature and/or precipitation?

A quick skim of the regional chapters in AR5 shows predicted changes to average temperature and precipitation. If I understand (in rough terms) the modelling methodologies used, a variety of models (...
10
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1answer
1k views

Why are there no CO2 snowfalls on Earth?

The CO2 phase diagram shows that at atmospheric pressure and about -78 °C temperature CO2 becomes solid: Wikipedia confirms this: At 1 atmosphere (near mean sea level pressure), the gas deposits ...
10
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2answers
3k views

Why is Egypt so dry?

If you look at this wind map (for July, but following the link you can also view other months): you will see that Egypt gets its air from the Mediterranean sea. During other months it could get less ...
10
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1answer
122 views

Cell Size of Salt Pan Tessellations

Salt Pans (such as in Badwater Basin of Death Valley, California) often show a tessellation pattern which forms presumably due to contraction of the deposited salt crust forming irregular cracks ...
9
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1answer
21k views

Why does it rain more at night than during the day?

I'm living near a sea, and it rains mostly and heavily at night from 11 PM to 3 AM. The weather is mostly clear during daytime. Air is generally cooler at night, and cool air holds less moisture ...
8
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3answers
410 views

Predicting school closures with historical weather prediction data?

I'm interested in predicting when the local schools will be closed due to snow and other winter weather. I have a list of school closure dates and a rough sense of the criteria used to determine the ...
8
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1answer
541 views

Snow from Fire: Could graupel, or even snow, fall from pyrocumulus clouds?

Pyrocumulus clouds often form in areas that experience prolonged fire conditions, particularly forest fires, but are also associated with volcanic eruptions and even nuclear explosions. This question ...
8
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1answer
331 views

Confusion with precipitation values in CORDEX MPI-ESM rcp data

I want to analyze climate projection data for the different RCPs for a region in north western India, which has an arid climate. I chose MPI-ESM data downscaled with CORDEX. An example filename looks ...
8
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2answers
186 views

How can there be a hot summer with rain and no thunderstorms and lightning?

This summer in the south of France we have had two hot months with 29 days over 30'C, while the average maximum is 26'C in July. Normally there are violent storms with lightening up to 20 times a ...
8
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1answer
226 views

Timeline of Himalayas/Tibetan plateau formation

Note: edited based on helpful comments. In Walking with Cavemen, Robert Winston claims an African rainforest existed 8 mya, but by 4 mya it was gone. He attributes this to newly Himalayas-triggered ...
8
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1answer
1k views

Causes and concentration of red rain of Kerala

The red rain phenomenon in Kerala, India has been reported several times in history (1896, 2001, 2012). The color of the rain seems to be associated with the presence of airborne spores of the algae ...
7
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1answer
129 views

Does over-cropping large areas really change the amount of rainfall?

I heard that at one time the Sahara desert was cropped in wheat for the Roman Empire, and that cropping without adding back to the soil was what caused the desert to form. I also heard that this is ...
6
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1answer
195 views

Am I observing orographic rainfall?

I don't know an awful lot about meteorology, so please bear with me. My wife (who has a Geography degree) told me that rain can be generated when moist air is pushed up the side of a mountain. This ...
6
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1answer
2k views

How much rain falls on the Earth each year?

In this resource, it says that the average amount of precipitation falling on the Earth per year is approximately 100 cm. Integrated across the surface of the Earth, that yields approximately 5.1 × ...
6
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1answer
159 views

How does temperature impact the elevation distribution of orographic precipitation?

Consider the case of two weather systems of different temperatures hitting the Andes Mountains from the west: After traveling a long distance over the Pacific ocean I would expect the air in both ...
6
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1answer
288 views

A simple formulation to calculate the sequence and rate of salt precipitation in a brine?

Is there a simple formulation to estimate the rate of salt precipitation in a brine given its ion concentrations and the evaporation rate? For example: if we know the concentrations of Cl−, Na+, Mg2+...
6
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2answers
1k views

How will climate change affect the latitudinal distribution of precipitation over each latitudinal region?

In other words... How will it affect precipitation in the tropics? The mid-latitudes? And the polar latitudes? I'm interested in both the mean and variance of the precipitation.
6
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1answer
132 views

Does a hurricane classification exists where estimated rainfall is taken into account?

Hurricanes are classified with the Saffir–Simpson hurricane wind scale. However an extreme amount of rainfall can cause a disaster although the windspeeds are not extreme. Is there some sort of ...
5
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2answers
65 views

Can I interpolate rainfall data from stations outside of watershed for the watershed?

I have only few station inside the watershed so I want to use the stations outside if I can to get better results
5
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2answers
5k views

Why doesn't it snow even when it is below freezing?

I know the temperature of a place is determined by various factors, a few of which I can think of are: Altitude, distance from sea, latitude, wind etc. My question is basically regarding latitude. ...
5
votes
1answer
804 views

Where can I get historic hourly precipitation data for Italy?

I am looking for a time-series of hourly precipitation for Naples, Italy. I'd like to learn how to find this sort of data for Italy in general, as well. Ideally this data would cover a recent year ...
5
votes
1answer
76 views

Digitalizing precipitation data from the image of weather map

I have a set of very old precipitation anomaly maps, from 1995-2006 for Brazil. The data of these maps, is to the best of my knowlegde, lost. I would like to have them digitalized, ie, to NetCDF or ...
5
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1answer
1k views

Deciphering NCDC data

I need US monthly climate data for the years 1992-2012. It would be great to get down to a county level, but by state would be just fine. Every site that I go to inevitably kicks me to the NCDC, but I ...
5
votes
1answer
171 views

Need help understanding rain rate formulas from drop sizes

I have come across different formulas by which the rain rate [mm/s] or [mm/h] can be computed from the drop size distribution. I'm somehow unable to convert the different formulas into each other. It ...
5
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1answer
127 views

How is heavy rainfall determined in National Climate Assessment

I'm trying to understand/reproduce/revise this chart in the Southeast section of the United States National Climate Assessment. The truncated scale for the bars is what caught by eye as a classic ...
5
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0answers
53 views

Near Future Precipitation and Temperature estimations?

I was wondering if anyone here is familiar with temperature and precipitation estimation? I need to estimate P and T from April to July 2016. I am planning to use excel to do the calculation because ...
4
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2answers
126 views

Need help understanding variables that relate to meterology terminology

I am working on a project in predicting the weather and I had a few brief questions. I understand that radar works by bouncing waves off of precipitation and measuring reflectivity. I have a variable ...
3
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2answers
100 views

Is there a risk with putting out smouldering underground coal reserves? [closed]

According to this Discovery News video about Centralia Pennsylvania and other underground coal fires, there are many smouldering underground coal reserves making the land above it uninhabitable to ...
3
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3answers
1k views

Dissolved minerals

I have a question that I am confused about. If a mineral (say limestone) was added to a groundwater system, say like an aquifer and is completely dissolved in solution, can it ever be a solid again ...
3
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1answer
3k views

ERA Interim, how to handle total precipitation

I am trying to compute accumulated annual precipitation for year 2000-2001 based on the ERA Interim, but I am stuck with some unresolved questions: If I download the synoptic monthly means of "total ...
3
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1answer
1k views

What is the difference between Precipitable Water (PW or PWAT) and Quantitive Precipitation Forecast (QPF) in terms of computer weather model data?

When I take a look at weather models, there is an option to take a look at PWAT or QPF. What's the difference?
3
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1answer
131 views

Circular rain cloud observed in rain radar

This circular rain pattern was observed in Sydney’s rain radar today. It remained for the entire loop, wiggling around a bit but mostly staying in the same place. The fact that it’s centred around ...
3
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1answer
155 views

Is there a maximum size for a single snowflake?

Just based on my previous experiences a wetter snow, in general, has larger flakes. Some online sources say that raindrops do have a maximum size before they start to break apart when surface tension ...
3
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1answer
52 views

Is there a data source for annual global precipitation?

Is there a data source for cumultative global precipitation by year? Units would presumably be mass, volume, or height of water equivalent. Also, what about cumulative global precipitation over land ...