# Tagged Questions

Meteorology is the interdisciplinary scientific study of the atmosphere.

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### What does “downshear” mean?

I occasionally read descriptions such as "downshear of the vortex" in meteorological publications. What does this mean?
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Adiabatic lapse rate is defined as $$\Gamma_a \equiv -\left(\frac{dT}{dz}\right)_{\rm parcel}=-\frac{R_{\rm a} T}{c_p \,p}\left(\frac{dp}{dz}\right)_{\rm parcel} = \frac{g}{c_p}$$ $R_a$ is gas ...
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### Weather Meridians

Are there meridians that effect cloud movement? While observing radar images of moisture bearing cloud movements (at my location in Florida), I've noticed a splitting of the cloud formations a ...
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### How could I calculate the Heat Index with low humidity?

The formula shown in the Heat Index(HI) requires that the relative humidity should be equal to or greater than 40%, so how to calculate the heat index when the humidity is less than 40%? Or is there ...
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### How are homogeneity or heterogeneity of materials decided?

How is the homogeneity or heterogeneity of materials decided? What kind of measurement or assessment exists for inferring when e.g. the density of the material of an object is uniform across the ...
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### Why is it always foggy on new years eve?

I live in Hamburg in northern Germany and a few years ago I started to notice this: It is always foggy on new years eve. Yesterday there even was a sight distance of about 10 meters at some point. ...
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### Dispersion parameters for Pasquillâ€“Gifford stability class G (extremely stable)

Gaussian plume models are often used to model atmospheric dispersion because they are simple and computationally efficient. When not constrained by the ground or by inversion layers, the Gaussian ...
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### How can I interpret negative values of potential evapotranspiration?

If I extract Potential Evaporation (PET, W/m$^2$) from the National Centers for Environmental Prediction (NCEP), climate reanalysis data (downloadable as netCDF files here), there are some negative ...
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### What is the explanation of the glory (optical phenomenon)?

Yesterday, I took the following picture. I was looking downwards from within an aircraft and I saw the 'glory' around the shadow of the plane on the clouds below. Wikipedia has an entry on the ...
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### Is there a theoretical maximum speed for wind?

What we call wind is actually molecules moving into an area of lower particle density due to their thermal motion. A lower particle density offers less collisions (resistance), so more molecules move ...
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### Hildring - Influence of vertical temperature gradient on light beam curvature

In special atmospheric condition it is possible to see coastline that normally is behind the horizon. It is apparently lifted to become visible. In Scandinavian the phenomenon is called 'hildring', a ...
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### What is the domain of validity of the Omega equation?

The Omega eqation is used in meteorology for estimate the value of the vertical velocity. Considering that the horizontal velocity field and density is given by observation. Under which condition ...
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### calculating air humidity from air temperature and specific humidity

Is it possible to calculate air humidity in mb from measurements of specific humidity (kg/kg) and air temperature (degC)? I'm trying to run a model (http://www.flake.igb-berlin.de/sourcecodes.shtml#...