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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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1answer
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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 ...
25
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2answers
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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 ...
25
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3answers
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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 ...
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?
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3answers
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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.)?
9
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2answers
898 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 ...
18
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2answers
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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 ...
10
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1answer
639 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 ...
8
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1answer
13k 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)....
23
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3answers
670 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?
16
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1answer
455 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 ...
79
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2answers
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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 ...
29
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4answers
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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 ...
20
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2answers
3k 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 ...
13
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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 ...
12
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4answers
5k 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 ...
13
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2answers
289 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 ...
29
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2answers
41k 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 >...
21
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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 ...
20
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6answers
14k 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
5k 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
799 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 ...
14
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1answer
1k 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 ...
15
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1answer
5k views

What is the range of possible atmospheric pressures on the surface of the Earth?

I'm developing an Android app which uses a pressure sensor. Due to storage limitations I have to normalize and scale the atmospheric pressure values. For this I need to know the extreme values of ...
7
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2answers
755 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?
14
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2answers
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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 ...
14
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2answers
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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 ...
11
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2answers
154 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?
11
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1answer
656 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 ...
10
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1answer
626 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 ...
7
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2answers
423 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 ...
2
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1answer
144 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 ...
0
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1answer
122 views

Does being in the air provide any protection from an asteroid?

How does radiation and shock waves from a radioactive asteroid or atomic explosion disperse throughout Earth's atmosphere? Are there specific areas on Earth that are less likely to receive the shock ...
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5answers
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Why do snowflakes form into hexagonal structures?

Snowflakes are known to form into pretty hexagonal structures. The image below shows a variety of such structures that are possible (although by all means not an exhaustive list): What is the ...
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3answers
4k views

Why does Coriolis determine the rotation direction of a cyclone but not my drain?

It is a common misconception that Coriolis is responsible for the direction the water swirls down a toilet, tub or sink drain. E.g. does a toilet flush the other way in the southern hemisphere? (If ...
20
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1answer
702 views

What data does a skilled meteorologist look at to predict thunderstorms?

An uneducated layman like me would just look at CAPE numbers and make rough guesses on possible thunderstorms. In a related but non-duplicate question, vertical wind shear is discussed. If we are ...
16
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1answer
368 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)....
12
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1answer
1k views

Numerical weather forecasting - resources for a programmer?

There is a community wiki question over at A good book or source for climate science and meteorology basics? that talks about meteorology basics. Building on that, but with a slightly different focus,...
23
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2answers
1k views

What is the cause of the jet streams?

Jet streams are fast-flowing currents of air in our earth's atmosphere. An enormous amount of energy is necessary to keep a jet stream going. Where does this come from and why?
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3answers
6k views

How would an icicle “grow” upwards?

The other day a friend of my dad's showed him a picture of an icicle that appeared to be "growing" upwards out of a crack in a sidewalk. There were no roofs, overhangs or vehicles parked near by... It ...
18
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1answer
354 views

How is global weather model skill measured?

The models I have in mind are the major global models such as the Global Forecast System (GFS) and the European Center for Medium range Weather Forecasting (ECMWF). These models produce numerous ...
17
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1answer
457 views

Why are weather kites no longer used (much) operationally?

Figure 1.12 from the IPCC AR5 WG1 report (reproduced below) illustrates the different instruments that have been used for weather forecasting. Most of the methods have been in continuous use since ...
16
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1answer
5k views

What do quasi-geostrophic and ageostrophic mean?

I know that geostrophic flow means straight wind flow that is balanced by the pressure gradient and Coriolis forces. But what do quasi-geostrophic and ageostrophic mean specifically?
15
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1answer
334 views

What is the predictability of El Niño/La Niña?

What is the maximum period of time into the future that an El Niño event can be forecasted with reasonable accuracy and what are the limitations in predicting the time limit?
15
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1answer
336 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 ...
10
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1answer
99 views

Rainbow dynamics?

How would steam refract light compared to fog and how would the rainbow appear? Does the temperature of the water drop or ice crystal effect the rainbow in any way? I know the size of the water drop ...
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2answers
3k views

Interpolate Gaussian grids to regular fixed grids using bilinear interpolation?

I want to regrid GCM data available on Gaussian grids to regular grids, say at 1 deg X 1 deg. How to do this using CDO or Python ...
21
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2answers
3k views

How do tropopause folds form and do they have any impact on synoptic scale weather?

What is the process that creates a tropopause fold? Do these features have any significant impact(s) on weather patterns or the atmosphere?
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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 ...
12
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1answer
394 views

How is the Rossby Radius used to determine that synoptic weather systems are 1000-2000km across?

In one of his presentations, Sandy MacDonald (of NOAA and ESRL) talks about the Rossby Radius of Deformation in connection with the size of synoptic weather systems: he describes how it sets the ...