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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31
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1answer
3k views

What factors determine the number of Hadley cells for a planet?

We know (think?) that Earth has three Hadley cells per hemisphere, but from observing gas giants such as Jupiter, we see that they have many more cells. According to a link from a comment in this ...
28
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2answers
36k views

Why are there no hurricanes in the southern Atlantic basin?

We see tropical cyclones (going by different names e.g. hurricane, typhoon, cyclone) all over the tropics, but it seems that there are never any storms in the southern Atlantic. See this map of ...
19
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1answer
5k views

Where does wind come from?

Wind is (according to Wikipedia) the flow of gases on a large scale.On the surface of the Earth, wind consists of the bulk movement of air. What forces would cause such a mass movement of air?
9
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2answers
2k 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 ...
20
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2answers
4k views

What are the major differences between weather models and climate models?

Some weather models include GFS (Global Forecast System) and NAM (North American Mesoscale Model). Some climate models include CCSM (Community Climate System Model) and the NASA GISS (Goddard ...
11
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1answer
768 views

Resources for learning the technical parts of atmospheric modeling

I'm a computer/atmospheric science undergrad and I'm trying to get into atmospheric modeling. Any recommendations for resources to get going or to learn about approaches? I can handle fairly technical ...
27
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3answers
4k views

Equinoxes and solstices: start of the season or mid-season?

In the United States, the upcoming autumnal equinox is marked on most calendars as the "first day of autumn." Similarly the solstices are commonly called the "first day of summer" and "first day of ...
86
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3answers
32k views

Impossible or improbable? Hurricane crossing the equator

No known hurricane has ever crossed the equator. Hurricanes require the Coriolis force to develop and generally form at least 5° away from the equator since the Coriolis force is zero there. Are ...
30
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4answers
4k views

How do weather models work?

We use different weather models all the time, such as the ECMWF and the GFS. These models are simply amazing to me. How do these models work? I know they have to take in various data points - what ...
18
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2answers
6k views

Why does the Hadley cell descend at 30 degrees?

George Hadley's initial model of the Hadley cell described air as being heated at the equator, ascending, and then moving aloft pole-wards where it would cool and descend. Meanwhile surface air would ...
23
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3answers
882 views

How good were climate models of the 1990s at predicting the global temperature trends of the 2000s/2010s?

Was there a significant bias between the ensemble of climate models and the long-term temperature trends? What about spatial patterns?
23
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3answers
58k views

How do I convert specific humidity to relative humidity?

How do I convert specific humidity to relative humidity? What variables are needed (e.g. air temperature, pressure, etc.)?
30
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2answers
52k views

At what humidity does it start to rain?

As far as I understand it is perfectly valid for air to have 100% humidity. At that point, all water can still exist in form of vapor, non-condensed. Does it immediately start to rain if humidity is >...
18
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4answers
16k views

What would be the effect of bringing seawater pipes to the Sahara desert?

This is a childhood dream. What would happen if pipes were installed (similar in principle to the Great Man-Made River, but for seawater) to continuously pump seawater into the Sahara desert. Let'...
15
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3answers
2k views

What causes these banded clouds?

A set of banded clouds can be seen in MODIS imagery during several days in January and February over the Gulf of Maine. They tend to occur with very cold winds from the NW following storms. There are ...
9
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1answer
20k 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
11k 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 ...
17
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2answers
6k views

July/August hottest months (northern hemisphere): because of continued warming or other effects?

In the northern hemisphere, July and August are the hottest months statistically1, but the days start shortening after June 21st. Is this just because the Northern Hemisphere keeps heating up after ...
7
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2answers
10k views

Which clouds can produce lighting and thunder?

There are several number of cloud types, but I only know that cumulonimbus clouds discharge electricity, which in turn produces thunder and lightning. Is this type of cloud (cumulonimbus) the only ...
16
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1answer
515 views

How will cloud feedback effects on the climate change as the result of global warming?

So global warming will increase the tropospheric temperatures, which, in turn, would make the clouds higher than they otherwise would be. And higher clouds (especially cirrus clouds) tend to trap in ...
4
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1answer
107 views

What is the second thermometer in the image from the Esperanza Antarctic temperature record?

Today, the Argentinian meteorological service tweeted about a new temperature record for Antarctica of 18.3°C, made on the Espezanza peninsula. This was subsequently reported by many other sources. ...
13
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4answers
6k views

How to get cell indices from latitude and longitude in WRF model grids?

I am using Weather Research and Forecasting model WRF and the WRF Preprocessing System WPS and could not get a satisfying answer from wrfhelp. Can anyone guide me in transforming latitude and ...
12
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1answer
2k views

Why is WRF most often configured at 3:1 nesting ratio?

In WRF application, nested domain has always been used for weather/air quality modeling for the place of interest in a better resolution. The figure below illustrates this: I have noticed that the ...
13
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2answers
406 views

How to tell if fog is made out of water droplets or ice crystals?

I understand that clouds can be made out of water droplets and/or ice crystals. And that fog is nothing else than low-lying clouds. However, I've experienced fog in a wide ranges of temperatures. I ...
7
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2answers
4k views

Extracting Regional Data from ERA5

This is coming from a newcomer, so please be kind. As I delve into the world of meteo data and reanalysis for the first time, I found that acquiring weather data is a lengthy process, so I'm shouting ...
23
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1answer
18k views

Do tornadoes have eyes?

In the movie Into the Storm (2014) near the end, storm chaser Pete sees the eye of a massive tornado. In 1928 (real life), Will Keller was in his barn when a huge tornado passed through. He reported ...
21
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5answers
4k 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 ...
20
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6answers
19k views

Why doesn't the sun reach its highest point overhead at exactly 12:00 noon?

Many sources state that 12:00 noon is the high-point or mid-point of the sun's path across the sky. However, for where I am, this is obviously wrong. In my own town the high point of the sun occurs ...
18
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2answers
6k views

Where is the calmest place on Earth?

I have done some research online, and I've found out that Antarctica has the calmest winds (lowest maximum wind speed) recorded on Earth. However, it is uninhabitable for human life. Other very calm ...
17
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1answer
1k views

Why do tropical cyclones not tear themselves apart?

A tropical cyclone is the generic term for a hurricane, typhoon, or tropical storm. Tropical cyclones derive their energy from evaporation of water at the ocean surface which ultimately recondenses ...
13
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2answers
4k views

Why are the clouds white and Australia black in weather satellite infrared images?

The question Is the sunlight on the GOES-16 Imagery reaching from the east? shows a visible light image and so in the night areas the Earth appears dark and in the day areas the Earth is a bit ...
6
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2answers
15k views

What are the differences between Climatology, Meteorology and Atmospheric Science?

Please explain the main differences between Climatology, Meteorology and Atmospheric Science. Thank you
15
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2answers
5k views

Why are weather service atmospheric pressures systematically different from those I measure in Johannesburg?

I live in the northern suburbs of Johannesburg in South Africa. I have noticed while working with synoptic weather charts in geography class that the isobars indicate that Johannesburg should have ...
13
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1answer
2k views

What is the formula used for atmospheric visibility?

I am working on NCEP GFS data to plot various maps. One such plot I would like to have is visibility. I have seen some of the sites showing visibility charts and the source of the data was shown as ...
11
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1answer
6k views

Plotting wind barbs in python

I'm trying to plot wind barbs in basemap and I have two separate netCDF files. Here is what I am trying to produce, or something like it: How do I read a uwnd variable in a netCDF file in python? <...
7
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2answers
2k views

What causes a rainbow, its colours and its shape?

What is the cause of rainbows? Do they appear due to rainfall or any other natural phenomenon. What makes it form a semi-circle in the atmosphere and its colours?
6
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3answers
1k views

Why are inversion layers so important in meteorology?

I keep hearing the term "inversion layer" when reading about pollution and meteorology. I know it vaguely amounts to "some place where the gradient of temperature is inverted". But why are inversion ...
14
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2answers
4k views

Why is the Atlantic Hurricane Season defined as being between June 1 and November 30?

Historically, the Atlantic Hurricane Season has shifted, as close as June 15 to October 31, but since 1965, it has been between June 1 and November 30(1). Why is the Atlantic Hurricane Season defined ...
11
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1answer
797 views

How much energy is needed to alter the path of a hurricane?

Suppose we spot an Atlantic hurricane very early. How much energy should we expend to alter its track: with nuclear detonations (let's forget about the side effects for the moment)? with a large ...
11
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3answers
271 views

Water on Mars and Earth

If water on Earth came from meteorites, why doesn't Mars have substantial water? What made it more highly probable on Earth than on Mars?
10
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4answers
945 views

How could humans alter storm intensity or direction other than cloud seeding?

I am familiar with the concept of cloud seeding, where precipitation can be induced with aerosols, thereby altering storm intensity further downwind. Are there methods that could be used to ...
8
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1answer
1k views

Why is it colder in the mountains than at sea level?

I have heard numerous reasons why that is. I just want to know which one is right.
8
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2answers
458 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 ...
7
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1answer
920 views

Statistical weather prediction

Assuming I have time evolution of air temperature, air pressure, wind speed, wind direction, relative humidity and cloudiness, how can I predict weather based on this information? I know that high ...
3
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1answer
815 views

How can temperature be calculated given relative humidity and dew point?

While looking into the better indicator of how miserable it feels outside, either dew point or relative humidity, I came across this statement: The optimum combination for human comfort is a ...
3
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0answers
48 views

In the future, is the World Meteorological Organization going to allow Hurricanes Zeta, Eta, and Theta to exist simultaneously?

In the 2005 Atlantic Hurricane Season, we got all the way to Tropical Storm Zeta, which is the current record. This year we may very well surpass that. However, right after Zeta come Eta and then ...
2
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1answer
182 views

What are these Gizmos at Mauna Loa Observatory?

Artist Rosten Wu's Vimeo channel has a video title Bridging Time and there is discussion about the Keeling Curve and the site where it all began in Hawaii. In the video there is a shot of a weather ...
2
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1answer
2k views

WRF vertical integrated moisture flux using NCL

Does anyone know how to calculate the vertical integrated moisture flux using NCL in WRF. It would be best if you can share a NCL script. Here is my code, I used this code to calculate the averaged ...
2
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1answer
58 views

How does a whirling hygrometer work, how does it differ from static dry/wet bulb thermometer, and how to obtain humidity from its readings?

Answers to my previous question How is relative humidity determined from a wet and dry bulb readings? provide equations for converting the two temperature measurements to a relative humidity. In ...
1
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0answers
51 views

wrf_chemi file with 30 time steps

I creat wrfchemi file for my wrf-chem, my wrfchemi file has 30 time step, frames_per_auxinput5 = 30, 30, auxinput5_inname = "wrfchemi_d", auxinput5_interval_m = 60, 60, ...