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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How can friction and Coriolis force balance each other out in the Ekman layer?

In most derivations of the Ekman spiral we begin by assuming a steady state in which only frictional (drag) and Coriolis forces are acting- and then we equate them to get the spiral. I have two issues ...
bog creature's user avatar
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Weather patterns and national borders

I've been observing weather patterns, especially rain, and to me it looks like there is a correlation with national borders. Of course it is nonsense to think rain clouds stop at national borders to ...
Gyro Gearloose's user avatar
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Where does snow falling at the polar ice caps originate?

When snow falls at the polar and Greenland ice caps, where did the water originally evaporate from? I can think of two ideas: The water mostly evaporated from the nearest ice-free ocean because water ...
Peter A's user avatar
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Do tropical cyclones impact climate?

Do tropical cyclones (TCs) have a global impact on climate? Maybe in terms of their impact on air-sea heat or gas fluxes? For example cooling the surface ocean, or enhancing CO2 fluxes? The motivation ...
ouranos's user avatar
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Can frictional force be un-aligned with wind direction?

There is a well known solution to Navier-Stokes equations for atmospheric boundary layer according to Ekman (see for instance PalArya's book "Introduction to Micrometeorology" or Holton's &...
MichaelW's user avatar
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How does coastal fog form on the Chilean coast?

When traveling through the northern parts of Chile (La Serena, Antofagasta) during November and December, I noticed a thin layer of coastal fog very close to the coastline. Since this fog was present ...
mu88's user avatar
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2023-2024 El Nino Season 5th Strongest on Record Meaning

I was reading the Press Release of World Meteorological Organization press release that was dated March 5, 2024 and I was curious on what they meant by the sentence "The 2023-24 El Niño season ...
theic_ocean's user avatar
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What are the current theories on the formation of satellite tornados

I have already searched the web for information on the formation of satellite tornadoes but all the sites say the mechanism is unknown. What are the current leading theories for their formation?
Harrychink's user avatar
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metpy divergence module array indexing error

i am trying to find out moisture divergence using metpy divergence module and i used qu12=q3b*u3b qv12=q3b*v3b HMD12 = mpcalc.divergence(qu12, qv12) here qu12 ,...
Letitbe's user avatar
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2 answers
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How does the wind transport latent heat?

I'm a meteorology student, and this sentence in my lab book confused me: "Both sensible and latent heat are transferred by winds." I understand how sensible heat could be transported by wind—...
Aubrey's user avatar
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Is this the correct way to extract U and V wind components from NEXRAD weather radar?

I am working with NEXRAD radar data, and I am trying to plot the U and V wind velocity for each point on a grid. There is a channel in the data called "Velocity" described as "A measure ...
scp's user avatar
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Units of meteorological data from the NOAA website

I want to check the precipitation, temperature, and rainfall data of South Asian locations. I downloaded the data from: https://www.ncei.noaa.gov/access/search/data-search/global-hourly?stations=...
Mala Pokhrel's user avatar
1 vote
2 answers
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Explanation of geopotential height

I am currently struggling to really understand geopotential height on a conceptual level. Let's say we look at the geopotential height of 500hPa over Europe, where it is usually around 5.5km. Does it ...
AkariYukari's user avatar
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How do I know where clouds form from a skew-T diagram?

I should know where clouds form in the atmosphere from the skew-T diagram below. The anwer should be that there is a big stromcloud from a height of 300hPa to 900hPa, but I don't get why. My reasoning ...
stancallewier's user avatar
3 votes
1 answer
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cfgrib does not take the proper variable name

Era5 data for wind ...
Antonio Serrano's user avatar
2 votes
1 answer
64 views

Where can I obtain the raw atmospheric data that weather forecast images are based on?

There is a lot of weather forecast data available online, such as this one https://www.wetter3.de/animation_dt.html But as a student, where do I get according raw GFS data instead of images to do my ...
MichaelW's user avatar
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What is the correct velocity to calculate propagation speed of a Rossby Wave?

Rossby Waves have different phase- and group velocities. For a pure zonal wave with wave number k they are $$v_p=\overline u - \frac{\beta}{k^2}$$ $$v_g=\overline u + \frac{\beta}{k^2}$$ So group ...
MichaelW's user avatar
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How can gaseous abundance in ppm be converted to density?

Consider a measurement of the concentration of a gas such as ozone in Earth's atmosphere in pseudo-units of parts-per-million (ppm). What is needed to convert such a measurement to density of the gas? ...
user900940's user avatar
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Are clouds aerosol?

I recently came across a science writer's page according to which clouds are liquid water. I pointed out to this author that in reality clouds are made up of a dispersion of water micro-droplets in a ...
gryphys's user avatar
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1 answer
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How Low pressure moves across land

I understand that low pressure systems (like hurricanes), can move across oceans since they are constantly fed by warm air from below. But what is it that enables it to move across land? Especially in ...
Guy's user avatar
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2 answers
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At 100% relative humidity, why does the air still feels dry?

At 100% relative humidity, the dew point temperature is the same as the current temperature. One would probably conclude that water would start condensing on surfaces. But seems that is not always the ...
Koala Yeung's user avatar
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(topic: dynamic meteorology) Problem understanding a picture from Holton version 2004

I'm studying for an exam and I'm having a problem understanding a picture from book "An Introduction to Dynamic Meteorology" by James R. Holton (fig 6.6 in version 2004). I'm not sure if I ...
zetpokaz's user avatar
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How do we detect thunderbolts in real time?

When I look at radar data (in Windy for example), and I'm looking into a thunderstorm, I often see thunderbolts appearing in 'real time' on the map. How does that work ? I assume some satellites have ...
Fefe_needs_help's user avatar
3 votes
1 answer
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Why does relative vorticity in spherical coordinates have an extra term as compared to the usual cartesian derivation?

With $u, v$ denoting the components of wind velocity along zonal (x) and meridional (y) direction, atmospheric (relative) vorticity is usually defined by $$\zeta_z = \frac{\partial v}{\partial x} -\...
MichaelW's user avatar
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2 votes
1 answer
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Drawing the cloud cover bar of Skew-T plot

I'm trying to display cloud cover info by altitude from sounding data in a compact widget of an app for free-flight pilots. It's basically the vertical bar showing different shades of gray according ...
nandilugio's user avatar
1 vote
0 answers
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Water on our planet, where did it come from? [closed]

Water on our planet, where did it come from? A water molecule is created when two atoms of hydrogen combine with one atom of oxygen. W The volume of all water (on our planet) is about 332.5 million ...
farsideofourmoon's user avatar
2 votes
0 answers
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Three cell model of prevailing winds

I understand the Coriolis Effect, but how does that make the rising air cool 1/3 of the way to the poles, as opposed to non rotating Earth?
Guy's user avatar
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4 votes
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Better method to identify seasons in temperature time series?

I'm trying to find a way to automatically detect the start/end of the 4 seasons based on a time series of daily mean temperature. According to this paper summer and winter can be defined as (smoothed) ...
Droid's user avatar
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1 vote
2 answers
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Why is U used for relative humidity in atmospheric measurement equipments?

RH is the symbol of relative humidity in many textbooks. But, in my experience, U is often used in atmospheric measurements. For example, Vaisala PTU300 means pressure, temperature and humidity. I ...
Oone's user avatar
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Can firecrackers be used to subside thunderstorms due to cumulonimbus clouds

Cumulonimbus clouds are associated with thunderstorms. Firecrackers which go up high in the sky and then burst into glittering show, can such crackers be injected in a cumulonimbus cloud and then ...
lousycoder's user avatar
1 vote
1 answer
287 views

Why are eastern Oregon and southeastern Washington so dry?

Why are eastern Oregon, southeastern Washington and southern Idaho so arid, as compared to the humid and lush western Oregon and Washington? In Oregon and Washington there is quite an abrupt boundary ...
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4 votes
1 answer
344 views

Why was the flooding in Derna, Libya so catastrophic?

I have watched storm Daniel on the internet while it was in Greece and what I saw was much heavier rain than what came down in Libya. But in Libya, property damage and death toll were much heavier, ...
Gyro Gearloose's user avatar
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0 answers
112 views

Mass weighted vertical average of stream function in python

I have a netCDF file of stream function (psi) having dimension (latitude, level), level is pressure level. There are 5 pressure levels (700,600,500,400,300 hPa). I need to compute the mass weighted ...
Aman's user avatar
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1 vote
1 answer
384 views

Dew-point temperature and absolute humidity

I am looking for a reference (e.g. book, peer-reviewed paper) that asserts that absolute humidity is "equivalent" to the dew-point temperature. Such statement should be true, AFAIU. Online, ...
Yair Daon's user avatar
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2 votes
1 answer
147 views

Why do tropical areas have low air pressure?

From the question Why are pressure levels raised on warm days?, my understanding is that the air pressure at surface level is not affected by temperature, as the mass of the imagined air column stays ...
bigfoot's user avatar
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3 votes
0 answers
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How to explain "Vacuum Cleaner Effect" for upper level PV anomaly?

In Jonathan Martin's Book "Mid-Latitude Atmospheric Dynamics" there is a chapter dedicated to anomalies of potential vorticity (PV). The scenario shown in the image below depicts a situation,...
MichaelW's user avatar
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1 vote
0 answers
43 views

How to use 1D function metpy.parcel_profile in ERA5 xarray dataset open with dask

I really need help, I'm working on ERA5 hourly data on pressure levels. I've extracted relative humidity and temperature on several atmospheric pressure levels. I use Metpy's '...
nietreil's user avatar
1 vote
1 answer
55 views

Why air laterally diverges before entering a cyclone/anticyclone?

I'm a newbie in meteorology so sorry if this is a dumb question. I get the general idea of how cyclones form, but one thing I can't wrap my head around is why must the air diverge laterally when ...
user29373's user avatar
1 vote
0 answers
107 views

What is the highest evaporation rate in the world? I know evaporation rates for Australia

I have been searching for the above answer for more than 25 years. I am providing a map of Australia for comparison http://www.bom.gov.au/climate/maps/averages/evaporation/ Is evaporation rate 4000 ...
Tad Soroczynski's user avatar
0 votes
0 answers
33 views

How to use CMIP6 to predict windspeed in the future?

I'm very new to climate modelling and forecasting, I have chosen a project to forecast wind energy output in the future using wind speed prediction, I wish to use CMIP6 to predict. But I have very ...
Phil's user avatar
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5 votes
1 answer
454 views

How is this global temperature chart compiled?

In this BBC News article, there is a chart labelled "Hottest day on record globally - Daily average air temperature, 1940-2023". It shows temperatures that are higher in summer and lower in ...
user29329's user avatar
3 votes
2 answers
79 views

Radially symmetric rainfall radar pattern?

I notice this radially symmetric weather radar pattern over London, UK today. Is this a real weather pattern, or a measurement or model artefact? If it is a real weather pattern, what causes it? The ...
Croad Langshan's user avatar
5 votes
1 answer
355 views

Will the hot Atlantic shape global/local weather and if so, how?

So the Atlantic Ocean exhibits record-breaking temperatures currently with about 1 degree Celsius above-average mean surface temperatures. This article, for example, mentions that a more severe ...
hschoell's user avatar
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1 vote
0 answers
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Visualization of formation of cirrus vertebratus?

I am trying to understand how Cirrus Vertebratus are formed. My book and many web pages simply say "waves orthogonally to the initial cloud formation direction, in fitting conditions, forming ...
323242323242's user avatar
1 vote
1 answer
103 views

Weather record last month in the UK

On 22 June 2023 in my village in LE8, south Leicester, UK, there was a large deluge of rain and my house got lightly flooded - the only time ever in 30 years. I'm trying to make a claim now; the ...
Oliver Walters's user avatar
4 votes
0 answers
48 views

Why positive PV Anomaly moves westwards?

In Jonathan Martin's Book "Mid-Latitude Atmospheric Dynamics" there is a chapter about PV anomalies. As an example, a positive PV anomaly is discussed. What is the reason, that high PV is ...
MichaelW's user avatar
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0 votes
1 answer
21 views

Accurate Rainfall with TBRG

For an accurate flood forecast, up to what height maximum from the ground level one can put the TBRG without any obstacles and still receive accurate rainfall?
pravat kumar senapaty's user avatar
3 votes
0 answers
57 views

What is the deeper difference between QG Omega equation and QG Height tendency equation?

The quasi-geostrophic $\omega$-Equation is a diagnostic equation for $\omega$ (=dp/dt = vertical motion) in terms of geopotential. It is derived in a few steps by manipulating vorticity and ...
MichaelW's user avatar
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1 vote
0 answers
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Comparing expressions for Ertel Potential Vorticity and Quasi Geostrophic Potential Vorticity

In Meteorology there is a quantity called "Ertel Potential Vorticity" $q_e$ which is conserved considering isentropic flow ($\theta=const)$: $$\frac{d}{dt}\left(\frac{1}{\rho} \vec \eta \...
MichaelW's user avatar
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6 votes
2 answers
4k views

Why isn't Summer Solstice plus and minus 90 days the hottest in Northern Hemisphere?

If Summer Solstice around June 21 every year is the longest day of the year and closest to the sun for the Northern Hemisphere (maybe I should say receive the most direct facing sunlight), then why ...
Stefanie Gauss's user avatar

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