NWP basics

Question 1

weather prediction forecast range from

Answer 1

24 hours to 7 days

Question 2

Numerical Weather Prediction (NWP) definition

Answer 2

o) is the part of Meteorology Science which is dealing with modeling of the atmospheric conditions and trying to predict these conditions in the near future.

Question 3

models of NWP

Answer 3

• WRF (Weather Research & Forecasting) model for weather parameters prediction
• WAM (Wave Model) for sea state forecast
• WRF-CHEM for pollutants and dust transport

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Question 4

NWP consists in:

Answer 4

1. Subdividing a chosen geographic 3D area in thousands (or millions) of little cubes (boxes)
2. Gathering all current (and past) actual information about atmosphere and ocean : all types of observational data.
3. Affecting one value for the main meteorological parameters (Pressure, Temperature, Wind, Humidity) in each cube.
4. Calculating through complex equations (momentum, thermodynamics, physics) the modifications affecting these meteorological parameters in time.
5. Presenting the predicted parameters values in a comprehensible standard format (charts, meteograms, soundings, …etc).

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Question 5

which type of resolution can show you the small scale phenomenas

Answer 5

When resolution is fine enough (< 10km), small scale phenomena (thunder storms, convective cells, sea breeze, local sand storms… etc) could be well depicted.

Question 6

—Increasing………………………. by a factor of two (2) increases the number of “cubes”, and implies computation machines ………..times faster.

Answer 6

horizontal resolution

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Question 7

The horizontal resolution of an NWP model is directly related to

Answer 7

—to the size of the weather feature it can simulate.

Question 8

The resolution is related to

Answer 8

—either the spacing between grid points for grid-point models

or the number of waves used to represent weather data for spectral models.

Question 9

conditions for vertical resolution grids

Answer 9

1. Vertical resolution must be quite fine (on the order of a few millibars) near the earth’s surface.
2. An increase in resolution is necessary near and below the tropo-pause to predict the jet stream accurately.
3. Different numerical models use a variety of vertical coordinates types to represent atmospheric layers.

Question 10

Atmospheric state at t

Answer 10

t = to + Δt

Question 11

Atmospheric state

Answer 11

to + N*Δt

Question 12

Hydrostatic approach

Answer 12

assume hydrostatic equilibrium, in which the downward weight of the atmosphere balances the upward-directed pressure gradient.

Question 13

Non-hydrostatic

Answer 13

—processes and their effect become important when the length of a feature is approximately equal to its height.

Question 14

—Some atmospheric phenomena need to be parameterized in order to take into account their impact, because:

Answer 14

• Computers are not yet powerful enough to directly treat them.
• They are often not understood well enough to be represented by an equation.
• Their effects profoundly impact model fields and are crucial to creating realistic forecasts

Question 15

Global models

Answer 15

resolve atmospheric equations on the whole globe

Question 16

global models can not use …………… because of…………………

Answer 16

very fine resolution

computer limitations

Question 17

global models cannot detect

Answer 17

small scale phenomena

Question 18

Global models are used to

Answer 18

—forecast general synoptic circulation and to provide Initial and Lateral Boundary Data for Limited Area models.

Question 19

—The most popular global models are :

Answer 19

ECMWF/IFS

NCEP/GFS

German DWD global model.

Question 20

A represents

Answer 20

Schematics for Global Atmospheric Model

Question 21

B represents

Answer 21

Horizontal grid (latitude-Longitude)

Question 22

C represents

Answer 22

Vertical Grid (Height or Pressure)

Question 23

LAM stands for

Answer 23

Limited Area Models

Question 24

Define LAM

Answer 24

They resolve the atmospheric equations on regional or local limited area domains.

Question 25

LAM:

They can use…………………………….. and ……………………………… They can …………………………………….

Answer 25

very high resolution (100m to 50km)

more vertical levels

catch very small phenomena

Question 26

LAM:

They are adequate to incorporate

Answer 26

complex physics parameterizations (especially microphysics, deep/shallow convection and boundary layer turbulence).

Question 27

LAM:

can run on

Answer 27

small to medium computers (normal PCs, workstations, Servers, Clusters)

Question 28

LAM:

They are obliged to

Answer 28

get LBC and Initial data from global models (NCEP/WAFS, NCEP/GFS, ECMWF, UKMO, JMA …etc).

Question 29

LAM:

widely used by

Answer 29

Weather Centers over the world.

Question 30

The most popular LAMs are:

Answer 30

• ALADIN
• COSMO / LM
• MM5
• ETA
• WRF / NMM (Weather Research & Forecasting)

Question 31

Initial Data

Answer 31

The actual situation used by the model to start integrate equations.

Question 32

Initial data is created by techniques called

Answer 32

data assimilation

Question 33

The information used to create initial data are:

Answer 33

• GTS data (Conventional observations) : SYNOP, SHIP, BUOY, SYNOR, TEMP,
• NonConventional Data (Data not transmitted through GTS, and private in PILOT, AIREP, AMDAR, ACAR, SATEM, SATOB). general) : RADAR, TOVS, SSMI, …etc
• Old forecast valid at the time of this initial situation (used to compensate data in regions devoid of observations).

Question 34

The process of initial data creation (…………………………………….) is more ……………………………………………………………………………

Answer 34

analysis and data assimilation

complicate than the forecast model itself, and more consumer in term of CPU time.

Question 35

Lateral Boundary Data are used in

Answer 35

the LAM models

Question 36

Lateral Boundary Data are used in the LAM models for the following reasons:

Answer 36

• To be able to compute derivatives at the model borders.
• To know what is likely to penetrate the domain of interest from outside.
• To avoid noisy fields at the borders.

Question 37

LBC stands for

Answer 37

Lateral Boundary Conditions

Question 38

LBC data come

Answer 38

from global or regional models including the LAM domain.

Question 39

LBC data are downloaded from the Internet; they are generally………………………………….

Answer 39

very heavy (large size)

Question 40

LBC data are downloaded from the Internet; they are generally very heavy (large size)

Answer 40

• GFS ~ 3.5 GB per day (0.5 degree horizontal resolution, 25 vertical levels)
• WAFS ~ 120 MB per day (1.25 degrees resolution, 11 vertical levels).

Question 41

The operational suite of a model is

Answer 41

a set of programs developed to automate all its execution steps from the gathering of data until the production of outputs.

Question 42

Models Operational Suites:

It is based on

Answer 42

Unix/Linux/Perl Command Languages

Question 43

Models Operational Suites:

it requires

Answer 43

an HA (High Availability) and HPC (High Performance Computing) computing machine.

Question 44

Models Operational Suites:

it must be

Answer 44

permanently monitored by specialized operators.

Question 45

Models Operational Suites

Answer 45

• Gathering and processing observations.
• —Getting LBC data
• —Getting / Creating INIT data.
• —Integrating the forecast model in time.
• —Post-processing fields.
• —Creating graphics and portable files.
• —Dispatching data to different users
• —Checking the quality of the forecasts.