Model and Satellite data

Question 1

What is a synoptic analysis?

Answer 1

A simple analysis based on the observed synoptic data provides an instantaneous snapshot of the state of the atmosphere

Question 2

what are the problems with synoptic analysis?

Answer 2

Scattered observations…excessive interpolation in data sparse regions
Bias by individual measurements
Instrument error
Sample unrepresentative of general conditions

Question 3

what is the solution to problems with synoptic analysis?

Answer 3

use model data to help generate analysis.

Question 4

What are three advantages of using model data in analysis

Answer 4

Data from past observations affects present analysis (4D variable assimilation)
Regions without observations are handled more realistically because information from past observation upwind propagates into data-sparse region.
Raw observations are smoothed during interpolation onto model grid – helps remove bias from non-representative measurements

Question 5

what are the limitations of using model data in analysis ?

Answer 5

Generally better than just sparse observations, BUT it is not real data – errors are very hard to assess.

Question 6

What is the NWP forecast cycle?

Answer 6

The inclusion of observations in the previous forecast is called data assimilation and takes a large part of the time within a forecast cycle of 6 hours.

Question 7

What is a NWP model?

Answer 7

Global models divide the world into a grid, data is held on the intersections of the grid

Question 8

what do the met office limited area models give

Answer 8

higher resolution

Question 9

how does the uk use the NWP

Answer 9

uses the global model to provide intialisation and boundary conditions

Question 10

how precise is the resolution over the UK

Answer 10

1.5km

Question 11

how many vertical levels in both the global and limited area models

Answer 11

70

Question 12

what is model resolution too low to resolve

Answer 12

Individual clouds, even large thunderstorms.
Full details of topography
Details of changes of surface type

Question 13

what is parameterisation

Answer 13

Parameterisation is the simplification of a complex physical process in terms of parameters that are available to the model, or readily measured.

Question 14

Models must use parameterisations of processes that ….

Answer 14

Take place on scales smaller than the model grid

Involve parameters that are not explicitly defined in the model

Question 15

examples of processes that are parameterised

Answer 15

turbulence, convection and cloud microphysics

Question 16

which companies produce reanalysis

Answer 16

ECMWF and (ECEP in USA)

Question 17

why is reanalysis done

Answer 17

Not all observations are available in time to be included in regular forecast cycle
Allows time for extra quality control and corrections to be applied

Question 18

What does reanalysis provide

Answer 18

the best estimate of past atmospheric data given the available observations

Question 19

Reanalysis data are widely used in research for…..

Answer 19

Climatological studies - reanalysis provides a consistent dataset over decades.
Model initialization fields in data-sparse regions or upper atmosphere.
Providing boundary conditions for regional-scale modelling studies

Question 20

New reanalyses are produced from time to time to use new assimilation techniques or model, e.g. ECMWF have produced the following reanalysis datasets….

Answer 20

ERA-15: 1978 - 1993
ERA-40: 1958 - 1997
ERA-Interim 1979 - present.

Question 21

when was ERA-15 created

Answer 21

1978-1993

Question 22

when was ERA-40 created

Answer 22

1958-1997

Question 23

when was ERA-interim created

Answer 23

1979 - present

Question 24

What does TIROS stand for

Answer 24

Television Infrared Observation Satellite

Question 25

when was the first TIROS launched

Answer 25

April 1960

Question 26

What is a geostationary satellite

Answer 26

remain in the same spot on earths surface - orbital period =rotation of the earth

Question 27

How high are geostationary satellites

Answer 27

36000 km above the surface

Question 28

how many geostationary satellites give the whole coverage of the earth

Answer 28

5/6

Question 29

what is a polar orbiting satellite

Answer 29

orbit is orientated north/south slightly (often sun syncronus)

Question 30

what is the orbital period of a polar orbiting satellite

Answer 30

100 mins

Question 31

do they pass over the same spot at the same time

Answer 31

no, passes over the same spot at irregular intervals and different parts of the surface with every orbit

Question 32

what altitude is polar orbiting satellites at

Answer 32

700-800km so low altitude but this allows much higher resolution

Question 33

what is a passive sensor

Answer 33

Passive sensors monitor some form of radiation (visible, infra-red or microwave data) coming from Earth, e.g. images, temperature and humidity observations.

Question 34

what is an active sensor

Answer 34

Active sensors emit some radiation and monitor the returning signal, e.g. surface winds over water from radar scatterometer.

Question 35

what are satellite data retrievals also used to make estimates of

Answer 35

sea surface temperature
wind speeds by tracking cloud movements
land use (amount of vegetation)
amounts of various chemicals (e.g. O3, NO2).