RTTOV - the fast

radiative transfer Radiative transfer is the physical phenomenon of energy transfer in the form of electromagnetic radiation. The propagation of radiation through a medium is affected by absorption, emission, and scattering processes. The equation of radiative trans ...

model for calculations of radiances for satellite infrared or microwave nadir scanning radiometers (see

push broom scanner A push broom scanner, also known as an along-track scanner, is a device for obtaining images with spectroscopic sensors. The scanners are regularly used for passive remote sensing from space, and in spectral analysis on production lines, for exampl ...

). Given an atmospheric profile of temperature, variable gas concentrations, cloud and surface properties RTTOV calculates

radiance In radiometry, radiance is the radiant flux emitted, reflected, transmitted or received by a given surface, per unit solid angle per unit projected area. Radiance is used to characterize diffuse emission and reflection of electromagnetic radiatio ...

s and

brightness temperature Brightness temperature or radiance temperature is the temperature at which a black body in thermal equilibrium with its surroundings would have to be in order to duplicate the observed intensity of a grey body object at a frequency \nu. This conc ...

s. The only mandatory input is water vapour. Optionally

ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

nitrous oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has ...

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ear ...

and

carbon monoxide Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

can be variable with all other constituents assumed to be constant. The range of temperatures and water vapour concentrations over which the optical depth computations are valid depends on the training datasets which were used. The spectral range of the RTTOV9.1 model is 3-20

micrometres The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer ( American spelling), also commonly known as a micron, is a unit of length in the International System of Un ...

(500 – 3000 cm-1) in the infrared. RTTOV contains

forward Forward is a relative direction, the opposite of backward. Forward may also refer to: People * Forward (surname) Sports * Forward (association football) * Forward (basketball), including: ** Point forward ** Power forward (basketball) ** Sm ...

, tangent linear,

adjoint In mathematics, the term ''adjoint'' applies in several situations. Several of these share a similar formalism: if ''A'' is adjoint to ''B'', then there is typically some formula of the type :(''Ax'', ''y'') = (''x'', ''By''). Specifically, adjoin ...

and K (full Jacobian matrices) versions of the model; the latter three modules for variational assimilation or retrieval applications. One of several applications of RTTOV are retrievals of brightness temperature and

sea surface temperature Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of ''surface'' varies according to the measurement method used, but it is between and below the sea surface. Air ma ...

from

Advanced Very High Resolution Radiometer The Advanced Very-High-Resolution Radiometer (AVHRR) instrument is a space-borne sensor that measures the reflectance of the Earth in five spectral bands that are relatively wide by today's standards. AVHRR instruments are or have been carried b ...

sensor.

FASTEM

Surface emissivity model which parameterizes surface emissivity. FASTEM2 computes the surface emissivity averaged over all facets representing the surface of the ocean and an effective path correction factor for the down-welling brightness temperature. FASTEM2 is applicable for frequencies between 10 and 220 GHz, for earth incidence angles less than 60 degrees.

References

* Eyre J. R. 1991 A fast radiative transfer model for satellite sounding systems. ECMWF Research Dept. Tech. Memo. 176 (available from the librarian at ECMWF). * Matricardi, M., F. Chevallier and S. Tjemkes 2001 An improved general fast radiative transfer model for the assimilation of radiance observations. ECMWF Research Dept. Tech. Memo. 345. http://www.ecmwf.int/publications * Saunders R.W., M. Matricardi and P. Brunel 1999 An Improved Fast Radiative Transfer Model for Assimilation of Satellite Radiance Observations. Quart. J.Royal Meteorol. Soc., 125, 1407-1425.

External links

* https://nwp-saf.eumetsat.int/site/software/rttov/ RTTOV homepage * http://research.metoffice.gov.uk/research/interproj/nwpsaf/rtm/rttov_applications/simulated_imagery.html Example use of RTTOV with the

Unified Model The Unified Model is a numerical weather prediction and climate modeling software suite originally developed by the United Kingdom Met Office, and now both used and further developed by many weather-forecasting agencies around the world. The Unifi ...

* http://cimss.ssec.wisc.edu/itwg/groups/rtwg/fastrt.html Exaplanation of tangent linear, adjoint and K radiative transfer models. {{DEFAULTSORT:Rttov (Radiative Transfer Code) Atmospheric radiative transfer codes Satellite meteorology

FASTEM

See also

References

External links