17 votes
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How bad is geo-engineering?

The bad part about geo-engineering are the unknown unknowns, to paraphrase a certain US politician. Our climate models are wrong. All models are wrong, but some are useful.. Our models are useful, ...
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17 votes
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Why is WRF most often configured at 3:1 nesting ratio?

To understand why the nesting ratio of 3 is preferred to the nesting ratio of 2, it is important to understand the following two features of WRF: 1) Grids are Arakawa C-staggered: mass points are at ...
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  • 4,935
16 votes
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Why is aerodynamic resistance defined inversely?

It's partly historical, partly point-of-view, but it's not a mistake. The friction coefficient emphasises the effect of the surface on a property of the boundary layer, i.e., greater surface friction ...
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  • 3,303
12 votes
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What is the formula used for atmospheric visibility?

I calculate surface visibility from WRF output using a calculation that I adapted from DTC's Unified Post Processor, specifically from their Fortran routine found in ...
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  • 4,935
11 votes

What exactly is a model grid?

A model is a simplified representation of a system. Rather than try to model everything down to the microscopic level, or as vectors, we often aggregate phenomena across geographic areas, to simplify ...
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  • 4,090
11 votes
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Numerical weather forecasting - resources for a programmer?

The resources you want will vary on what level of understanding you are seeking. For example, knowing the math means you can solve equations or transform them, but it doesn't mean you understand the ...
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11 votes
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What atmospheric radiative effects, if any, do contrails cause?

We had a surprising opportunity to study this very question during the period of September 11-14, 2001, when all air traffic was grounded across the United States. The research was inconclusive, but ...
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  • 2,708
11 votes
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Temperature change in Earth atmosphere models?

There's some kind of explanation about the units under the picture. The formula is based off the average temperature in degrees Celsius (measured over the entire year, and the entire Earth), which is ...
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10 votes

Why is aerodynamic resistance defined inversely?

This is a good question, and the answer is, aerodynamic resistance is not defined inversely. It is rather, defined in a context that is often misinterpreted. In your question, you state that ...
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  • 4,935
10 votes

On the light difference between morning and afternoon

I am asking why the light of a clear day is not symmetrically changing centered at noon. Trying to attribute this to a single cause misses the point. There are multiple causes. Other than lighting ...
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9 votes
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Interpolate Gaussian grids to regular fixed grids using bilinear interpolation?

climate data operators (CDO) define grid We define a lat-lon target grid with 1°x1° grid cell size 30x30 grid cells starting at 40°N and -10°E (=10°W): ...
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9 votes

Does finer input data lead to a better model accuracy?

My experience with the WRF is in tropical cyclone simulation, but here are some things to consider: Smaller scale information might already be resolved in your higher resolution initial conditions, ...
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  • 315
8 votes

How bad is geo-engineering?

Seconding eveything that @gerrit mentioned. Additionally, another major problem with geo-engineering is that once we've started these processes and essentially borrowed time to offset mitigation ...
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8 votes

How do Kelvin waves determine surface temperature variations?

Coastal trapped Kelvin waves are important processes contributing to variability in the sea surface height and temperature near the coast. Field studies have measured large temperature fluctuations ...
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8 votes
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Why does computation cost increase 24 times when the spatial resolution doubles?

I can't answer why there's a 24x increase, according to the textbook - but it may well be the case for a specific model. In general, If you double the resolution of a 3D model in each dimension, you ...
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8 votes

On the light difference between morning and afternoon

I believe the effects you are talking about are due to scattering by dust and water vapor in the atmosphere. During the night winds are lower and wet areas don't dry out as fast as during the day. ...
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7 votes
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Calculate precipitation from WRF model output

Use (1) Precipitation, as it is the sum of convective and non-convective precipitation, integrate it over one day, voilà. converting [$kg/(m^2 s)$] (precip): $$ precip [kg/(m^2 s)] \cdot dt [s] \cdot ...
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  • 438
7 votes

How does the tornado chaser locate the spot?

It starts by identifying days with good overlay of shear and surface-based instability. In the US we have the Storm Prediction Center that helps indicate such days looking at models. Generally the ...
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7 votes

Does finer input data lead to a better model accuracy?

Yes, of course finer input data can lead to better model accuracy, but only if the model's conceptualization is close to the mark. Of the many problems of climatic model misinterpretation, I would ...
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7 votes
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What is the synoptic/atmospheric setup that is causing the U.S. severe weather outbreak in May 2019?

Summarizing the comments I made above in this question and in this one - Does this weather pattern have a name ? I believe significant parts of the US are experiencing a Stationary Front for the ...
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6 votes
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What is the meaning of step in ERA reanalysis data?

The "step" is the number of hours the ERA re-forecast has been run into the future from the "time" of the re-analysis. For example, asking for ERA data with time = 12:00 and step = 0 means asking for ...
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  • 1,673
6 votes

Take all the CO2 in the atmosphere and put it into a layer on the surface of earth, how thick would the layer be?

Ok, based on the comments above, this is where I am at... earth's radius is $6371 \text{ km}$ earth is a sphere There is approximately $3 \cdot 10^{15}$ kg of CO2 in earth's atmosphere The density ...
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  • 221
6 votes

Why are inversion layers so important in meteorology?

Farrenthope is correct, but I would like to add some detail. An inversion occurs when the air is warmer than the ground. It is called an inversion because it is the opposite of what occurs during the ...
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6 votes

How thin is our atmosphere relative to the size of Earth?

The answer to your question depends on where one defines the edge of the atmosphere. The Earth's atmosphere is layered. The thickness, density of composition of each layer varies. The five layers are: ...
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6 votes
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Python, R or etc.?

In my opinion, python is a more established global language that is used by many more disciplines/users, compared to R. This can be advantageous because examples/tutorials are everywhere and you can ...
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5 votes

What exactly is a model grid?

Specifically the term the values are archived on 2.5° grid means that the values that are being reported are being saved and are available at that resolution for historical values. The higher ...
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  • 508
5 votes

Why is radiation and total precipitation not available in ERA Interim Reanalysis at step 0?

The ERA archive description document, Berrisford et al (2011) "The ERA-Interim archive Version 2.0", provides additional information about what is available. It's less explicit on the why, but we can ...
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  • 3,303
5 votes

What exactly is a model grid?

To add a bit more mathematical conception to the idea of a grid: think about a 2-D grid(X,Y) as a matrix: this matrix represents a solution to the system of equations you are trying to solve at grid ...
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  • 6,376
5 votes
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The climatological variance of albedo, soil moisture in weather models

WRF model development is done in such a way that users can run the model independently before you start adding more complex options to ingest observations. There is even an "ideal" mode that new ...
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