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Questions tagged [meteorology]

The study of how the earth's atmosphere works, including weather forecasting. Use this tag for questions about the earth's weather. When asking questions specifically about the atmosphere, also include the [atmosphere] tag.

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9
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2answers
1k views

How to compute du/dx and dv/dy in moisture flux convergence?

I have $u$-wind, $v$-wind and specific humidity. I would like to compute moisture flux convergence at a grid point. So I need to compute the value of $q(\frac{du}{dx} + \frac{dv}{dy})$ My question is ...
9
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1answer
64 views

Is there a reliable way to identify regions with negatively-correlated winds?

When examining the potential for large-scale electricity grids, and when identifying the lowest-cost ways to generate clean electricity, a recurring theme is of spreading wind generation across a wide-...
9
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1answer
210 views

Monsoonal interactions with mid latitude disturbances

For the past few years in succession India has witnessed extreme flooding events caused by monsoonal troughs colloding with what appears transitory mid latitude disturbances and these appear to ...
9
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1answer
6k views

What are the key differences between warm and cold core cyclones?

What are the key differences between warm and cold core cyclones? What is an example of each?
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1answer
192 views

Where did the daily temperature variation go?

Currently central and northern Europe are experiencing a very cold, false-spring like weather phenomenon. When i look at local weather charts, the daily temperature cycle seems to be completely gone, ...
9
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1answer
145 views

How would weather change on a tidally-locked terrestrial planet?

On Earth, weather is very much affected by the Earth's rotation around its axis and around the Sun. Even locations that are almost on the equator do have strong annual variations in precipitation and ...
9
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1answer
145 views

Where does the symmetry of cloudy bands come from?

Reading Meteorology Fundamentals by Sylvie Malardel, it says: We observe a symmetry of the cloudy bands with respect to the rotation axis of Earth and between Northern Hemisphere and Southern ...
9
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1answer
115 views

Are there any quantities defined analogically to the virtual temperature, but for other gases?

The virtual temperature is a pseudo-temperature taking into account water vapour in the atmosphere in such a way, that the resulting quantity can be used with the ideal gas law and the molar mass for ...
9
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3answers
3k views

What causes clouds to appear blue?

In a thunderstorm cloud about sunset time, I saw these clouds, including some (in the upper right) that were a unique shade of blue. I don't think I've seen clouds quite that color before. I tried ...
9
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1answer
474 views

How can I downscale daily values of relative humidity?

I have a dataset (The ISIMIP interpolation of CMIP5 output) that contains daily values of the following variables: ...
9
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1answer
155 views

Why should dynamical downscaling of meteorological data be made incrementally?

When downscaling meteorological data by using limited area models, many support forums recommended you to downscale incrementally in small steps. For example let's assume that your input data is on a ...
9
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1answer
225 views

How are thermals really released?

Sailplane, paraglider or hang-glider pilots are used to say 'thermal is released by trigger'. The zones with contrasting albedos (land/water, plowed field/forest) or locations where terrain profile ...
9
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1answer
824 views

Evaporation loss formulas

A while ago I created a spreadsheet to calculate evaporation loss. I found several formulas to do that, two from Kevin Rafferty and one from Engineering Toolbox. The one from Engineering Toolbox was ...
9
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1answer
1k views

Is there a seasonal difference in the average cloud floor?

It always looks like clouds are so much higher in the sky (altitude) in the summer than in the winter. Is that true? If not, is there some sort of optical illusion? If so, why is that? I live in Iowa,...
9
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1answer
157 views

Dependence of solar irradiation through the atmosphere on Sun's altitude

I want to show that the higher the Sun's altitude, the higher the solar irradiation through the atmosphere, through simple experiments. However, I don't have the instrument that measures irradiation. ...
9
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0answers
237 views

What is the finest horizontal grid spacing that Eulerian grid-cell air-dispersion models should use?

My colleagues run the Advanced Research Weather Research & Forecasting (WRF) model in predictive mode, and then test the skill of the model anywhere from 12 - 84 hours out from the initialization ...
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0answers
132 views

Is there a distinction between gap winds and channelled flow?

I have seen gap flows mentioned in the literature, for example [Gohm et al. 2004, Zängl 2002, Mayr et al. 2007]. Whiteman 2000 defines a gap as a "major erosional opening through mountain ranges" and ...
9
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1answer
4k views

What is the loudest thunder ever recorded (dB) at ground level and where did it occur?

Sound travels fastest through warm air and conditions such as temperature inversions can help to amplify the sound of thunder (source). Conversely, during a thundersnow event the falling, and ...
8
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2answers
1k views

How far up do you have to go before most of the atmosphere is below you?

If I wanted to make an air shield around the earth to contain exactly half the planet's atmosphere (by mass), how far above sea level would I have to build it? It's slightly complicated to me because ...
8
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4answers
138 views

How do I find the horizontal pressure level that divides the atmosphere into 2 layers of equal mass?

Surface pressure given is p = 1000 hPa. (the temperature along the atmosphere is constant (T = −10 °C; hydrostatic equilibrium assumed). I tried using the hypsometric equation to find the height of ...
8
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2answers
175 views

What determines the differences in results between various weather models?

It's often said that the ECMWF model is more accurate than the GFS. But what are the reasons why? Also, how does the NAM compare with these two and other forecasting models?
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2answers
448 views

What are these Gizmos at Izaña Atmospheric Research Center in Spain?

This tweet from the account of the Centro de Investigación Atmosférica de Izaña (AEMET) http://izana.aemet.es Izaña Atmospheric Research Center (AEMET) shows images of meteorological instruments ...
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1answer
185 views

Regarding compression, shuffle filter of netcdf4

I read the doc but still have no idea about what are the advantages to enable or disable the shuffle, what level [0-9] of compression is optimal, what's the best choice of chunk size?
8
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3answers
414 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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2answers
1k views

How accurate is a tipping-bucket rain gauge?

My question is simple - how accurate is a tipping-bucket rain gauge? I have read about what causes the errors (wind, bucket mechanics for extreme events, ...) and I know the accuracy is strictly ...
8
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1answer
329 views

Has a hurricane or cyclone ever reformed after passing over a large land mass?

Hurricane Michael recently hit Florida as a Category 4 storm, and after the remnants passed across a great deal of the east coast of the United States it appears to have re-emerged into the Atlantic ...
8
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2answers
304 views

Are there websites where I can get “lightning frequency maps” in near-real time (worldwide)?

I have an NASA Inspire VLF-3 radio receiver kit that I'm going to put together. It amplifies VLF electromagnetic signals that are already in the audio frequency range and makes them audible. One of ...
8
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3answers
1k views

Effect of urbanization on weather events

At what stage is the studies on effect of urbanization on weather events (eg: Rainfall, Temperature, UHI) are now? There has been a number of observational and modelling studies around the world and ...
8
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1answer
550 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
369 views

What is this cloud formation?

What is the cloud formation in this video? I don't know where this footage was taken. Here's the link to the video again.
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1answer
290 views

Why does the road appear wet on a sunny day?

Whenever I'm travelling by road on a hot sunny day and I look towards the horizon, it appears as though there is puddle ahead but as I approach it, it disappears. Why does this happen?
8
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2answers
848 views

How are 'Morning Glory' clouds maintained?

Reading the Physics.SE question What is the current physical theory of what causes the 'Morning Glory' roll cloud over Northern Australia? (pictured below): Image source: NASA Astronomy picture of ...
8
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1answer
134 views

Why does air seem to affect local surface temperatures so much?

Last winter, several areas in the US and Canada were hit by a "polar vortex." I happen to live in one of those areas and was amazed how much the temperature seemed to change so suddenly just because a ...
8
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1answer
226 views

How does El Niño affect thunderstorm/tornado/CAPE activity in the central United States?

Or in other words, does it increase the amount of heat+moisture advection from the Gulf of Mexico into the Central United States? And is this increase associated with increased CAPE/tornado/...
8
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1answer
9k views

Why does the wind periodically change direction?

Image Subtitle: Wind going across the page - and changing direction To clarify, imagine you were sat in a boat in the middle of a lake recording the wind direction every minute. You notice that the ...
8
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3answers
1k views

A good book or source for climate science and meteorology basics?

I have a mainly a hydro-geological and geo-statistical background, I would like to have a basic introduction to meteorological, climatic processes and modelling techniques related to these fields. Any ...
8
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1answer
14k views

How to calculate specific humidity with relative humidity, temperature, and pressure

I know there is this question already How do I convert Relative Humidity into specific humidity but I don't have ρws = density of water vapor (kg/m3) and ρ = density of the moist or humid air (kg/m3)....
8
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1answer
241 views

What's with this anomaly in this sounding (the CAPE and CIN readings)?

This sounding is from 2 hours after the 2.6 mile wide El Reno tornado on May 31 2013.
8
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1answer
7k views

What is the difference between a “flood” and a “flash flood”?

Whenever weather warnings come up, I have heard of both a flood watch/warning and a flash flood watch/warning. What is the difference between a "flood" and a "flash flood"? Are there any specific ...
8
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1answer
453 views

Can overshooting tops enter the stratosphere, or will they rather push the tropopause upward?

Convective overshooting tops reach above the normally horizontal flat layer of the convective system, a layer that should coincide with the tropopause. If we have such an overshooting top, does this ...
8
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1answer
188 views

Does the global temperature vary daily (hotter and colder days)?

Earth's current average global temperature (i.e. including hot deserts and cold polar caps) is reported be somewhere between 14°C and 16°C (depending on sources and methods). This temperature varies ...
8
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2answers
3k views

Are lightning storms more common at night?

I have, to my knowledge, seen far more lightning strikes and heard more thunderclaps at night than I have during the day. Are lightning storms more common at night, or are they just more noticeable ...
8
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1answer
187 views

What is the best way to stay safe while photographing lightning storms?

Occasionally, I go out with my camera and tripod and capture cumulonimbus clouds from distance. Sometimes I am worried when I hear thunder that I could be hit by a lightning bolt. I have seen several "...
8
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1answer
126 views

Why does the Northern polar vortex usually have two centers?

From http://glossary.ametsoc.org/wiki/Polar_vortex polar vortex A planetary-scale mid- to high-latitude circumpolar cyclonic circulation, extending from the middle troposphere to the ...
8
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1answer
416 views

How does the amount of mass in an atmosphere affect the seasonal changes and dynamics of the planet's climate?

I was thinking about this question, which may turn out to be simple, about climate dynamics: How does the amount of mass in an atmosphere affect the seasonal changes and dynamics of the planet's ...
8
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1answer
1k views

Continuous lightning for over an hour; is this phenomenon common and does it have a name?

A few months ago, I witnessed something off the coast of Florida that I have never seen in my life. From my apartment, from about 10PM - 12AM, I saw pretty much continuous cloud to cloud lightning. I ...
8
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1answer
105 views

Why don't tropical cyclones hit Hawaii?

Image by Wikipedia user Citynoise using NOAA data. If you look at this map of tropical cyclone tracks, you'll notice that there's a gap in the central northern Pacific where tropical cyclones ...
8
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1answer
625 views

How is the vertical velocity defined in sigma-pressure-coordinates?

I have a problem in deriving/understanding the vertical velocity in sigma-pressure coordinates. The vertical coordinate is defined as: $$\sigma(x,y,p)=\frac{p(x,y)-p_t}{p_s(x,y)-p_t}$$ where $p(x,y)...