15

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 slows the near-surface wind more. Aerodynamic resistance emphasises the effect of the boundary layer on surface-atmosphere exchange, i.e., greater mixing ...


14

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 cell centers, u-velocities are at east-west cell edges, v-velocities are at north-south cell edges. See Mesinger and Arakawa 1976, Chapter 4 for a good ...


12

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, but not quite useful enough to trust them when they tell us massively spraying stuff into the stratosphere or the oceans is mostly harmless. Our models can't ...


11

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 UPPV2.2/src/unipost/CALVIS.f. The calculation is based on hydrometeor mixing ratios, and air temperature and pressure, all from the lowest model layer. If your GFS output has hydrometeor mixing ...


11

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 the computation a lot, and to lose only a little accuracy and precision. So if I want to model the UK, which roughly spans 8°W - 2°E, 50°N - 60&...


11

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 they found that there was a 1.8 degree celsius increase across the US during this time frame compared to the three days before and after that time frame. ...


10

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 physics involved. Some topics you'll want an understanding of to understand the process: Physics At the heart of any weather model are our primitive ...


10

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 aerodynamic resistance is basically how much the roughness of the surface slows air movement down. This statement is not correct, and it seems to stem from the ...


9

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): gridtype = lonlat xsize = 30 ysize = 30 xfirst = -10 xinc = 1 yfirst = 40 yinc = 1 This text is written into a text file. See section 1.3.2 CDO Manual for details and ...


9

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, improving the spin-up time of effects you are trying to model I believe the ECMWF resolution has been statistically downscaled from a 0.75 degree dataset, I ...


9

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 itself (i.e., the Sun angle), most aspects of the atmosphere are not symmetric about noon. The low on a clear day typically occurs right around sunrise (not ...


8

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 mainly made up of low-frequency internal Kelvin waves mostly of semi-diurnal tidal period at the continental shelf on the great barrier reef (Wolanski, 1983). ...


8

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 are multiplying the number of cells (or elements) in the model by $2^3 = 8$. Typically the maximum length of the time step that a model may be run at and ...


7

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 very earliest signs that get chaser's attention are a reasonable trough moving into regions with adequate moisture and warmth (sometimes a cut-off upper-level ...


7

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 emphasize the following: a) The implied precision of most climatic modelling output is absurd, so take a long, hard and skeptical look at the data in relation to ...


7

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. Both of these mean that at the start of the day there is less dust and water in the atmosphere at a given location. As the day progresses winds pick up (caused ...


6

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 measures, we'll have put ourselves in a situation where these measures will need to be continued almost indefinitely, regardless of the risks of negative side ...


6

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 day. During the day, the ground is heated by the sun and the air near the ground rises. However, during clear and calm nights, the ground will cool faster ...


6

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 past one month. There has been plenty of media coverage of this event and if you google the term "stationary front" under news one will receive a lot of links to ...


5

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 resolutions (1°x1°, 1/4°x1/4°) mean exactly what they say: the values are reported on a 2-dimensional grid every degree, or quarter degree, across the area of ...


5

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 read between the lines a bit. The archive consists of re-analyses of the system state at 00, 06, 12, and 18 UTC and re-forecasts out to 10 days initialised ...


5

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 point x,y (individual points on X,Y respectively). Why is it important to make this distinction? Because knowing the resolution, span, regularity and structure ...


5

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 data valid at 12:00 based on a re-analysis for 12:00. But asking for data with time = 12:00 and step = 6 means asking for data valid at 18:00, i.e. for data ...


5

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): $$ precip [kg/(m^2 s)] \cdot dt [s] \cdot \frac{1}{ \rho_w [kg/(m^3)]} \cdot 1000 [mm/m] = total\_precip [mm]$$ where $\rho_w$ is the density of water. Practically the last two factors cancel.


5

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 of CO2 at 1atm is $\dfrac{1.977 \text{ kg}}{\text{ m}^3}$ So, first, with assumption (3 and 4) we can compute the volume of CO2 in the atmosphere to be $\approx ...


5

Temperature inversions are important to meteorology and pollution because they are the boundary for atmospheric mixing. If there is a strong inversion, the air above and below an inversion do not easily mix together. In the case of pollution, where the emissions come from the surface, a shallow temperature inversion in the boundary layer traps the ...


5

I finally solved this problem with the following steps: Download the ECMWF data separately for model level variables (Q,T,U,V and geopotential) and surface variables. In this way, you will get 'pure' GRIB1 and 'pure' GRIB2 files rather than the hybrid type. Run ungrib twice: for the model levels files, use this Vtable. For the surface file, use the 'old' ...


5

I imagine you have a horizontal grid (x,y) and wind components u(x,y) and v(x,y). Normally we do 1-degree of latitude constant (y-dimension) and equal to 110000 m. So your dy depends on how many degrees per grid point you have (yresolution). However, dx will vary according to the latitude. dy=110000*yesolution; Now, we may use centered finite differences ...


5

Convergent cross mapping (CCM) is a recently developed tool to answer the question you've asked. It's based on tools developed in nonlinear time series analysis and dynamical systems theory. It allows you to: 1) determine if a causal relationship between two variables is present 2) establish the direction of causality 3) do so even in the presence of noise. ...


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