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 20171206T15:50:26+01:00 (5 years ago)
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branches/2017/dev_r8657_UKMO_OBSoper/DOC/TexFiles/Chapters/Chap_OBS.tex
r8919 r8921 563 563 For most observation types, the horizontal extent of the observation is small compared to the model grid size 564 564 and so the model equivalent of the observation is calculated by interpolating from the four surrounding grid 565 points to the observation location. Some satellite observations (e.g. microwave satellite SST data, or SSS data)566 have a footprint which is similar size or larger than the model grid size (particularly when the grid size is small).565 points to the observation location. Some satellite observations (e.g. microwave satellite SST data, or satellite SSS data) 566 have a footprint which is similar in size or larger than the model grid size (particularly when the grid size is small). 567 567 In those cases the model counterpart should be calculated by averaging the model grid points over the same size as the footprint. 568 568 NEMO therefore has the capability to specify either an interpolation or an averaging (for surface observation types only). 569 569 570 The main namelist option associated with the interpolation/averaging is nn_2dint. This default option can be set to values from 0 to 6.570 The main namelist option associated with the interpolation/averaging is \np{nn\_2dint}. This default option can be set to values from 0 to 6. 571 571 Values between 0 to 4 are associated with interpolation while values 5 or 6 are associated with averaging. 572 572 \begin{itemize} 573 \item n2dint=0: Distanceweighted interpolation574 \item n2dint=1: Distanceweighted interpolation (small angle)575 \item n2dint=2: Bilinear interpolation (geographical grid)576 \item n2dint=3: Bilinear remapping interpolation (general grid)577 \item n2dint=4: Polynomial interpolation578 \item n2dint=5: Radial footprint averaging with radius specified in the namelist as rn_???_avglamscl in degrees or metres (set using ln_???_fp_indegs)579 \item n2dint=6: Rectangular footprint averaging with E/W and N/S size specified in the namelist as rn_???_avglamscl and rn_???_avgphiscl in degrees or metres (set using ln_???_fp_indegs)573 \item \np{nn\_2dint}=0: Distanceweighted interpolation 574 \item \np{nn\_2dint}=1: Distanceweighted interpolation (small angle) 575 \item \np{nn\_2dint}=2: Bilinear interpolation (geographical grid) 576 \item \np{nn\_2dint}=3: Bilinear remapping interpolation (general grid) 577 \item \np{nn\_2dint}=4: Polynomial interpolation 578 \item \np{nn\_2dint}=5: Radial footprint averaging with diameter specified in the namelist as \np{rn\_???\_avglamscl} in degrees or metres (set using \np{ln\_???\_fp\_indegs}) 579 \item \np{nn\_2dint}=6: Rectangular footprint averaging with E/W and N/S size specified in the namelist as \np{rn\_???\_avglamscl} and \np{rn\_???\_avgphiscl} in degrees or metres (set using \np{ln\_???\_fp\_indegs}) 580 580 \end{itemize} 581 581 The ??? in the last two options indicate these options should be specified for each observation type for which the averaging is to be performed (see namelist example above). 582 The n2dint default option can be overridden for surface observation types using namelist values nn_2dint_???where ??? is one of sla,sst,sss,sic.582 The \np{nn\_2dint} default option can be overridden for surface observation types using namelist values \np{nn\_2dint\_???} where ??? is one of sla,sst,sss,sic. 583 583 584 584 Below is some more detail on the various options for interpolation and averaging available in NEMO. … … 695 695 \end{itemize} 696 696 697 Examples of the weights calculated for an observation with rectangular and radial footprints are shown in Figs.~\ref{fig:obsavgrec} and~\ref{fig:obsavgrad}. 698 697 699 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 698 700 \begin{figure} \begin{center} 699 \includegraphics[width= 10cm,height=12cm]{Fig_OBS_avg_rec}701 \includegraphics[width=0.90\textwidth]{Fig_OBS_avg_rec} 700 702 \caption{ \label{fig:obsavgrec} 701 Weights associated with each model grid box (blue lines and numbers) for an observation at 170.5E, 56.0N with a footprint of $1\deg \time 1\deg$}703 Weights associated with each model grid box (blue lines and numbers) for an observation at 170.5E, 56.0N with a rectangular footprint of 1\deg x 1\deg.} 702 704 \end{center} \end{figure} 703 705 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 704 706 705 706 707 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 707 708 \begin{figure} \begin{center} 708 \includegraphics[width= 10cm,height=12cm]{Fig_OBS_avg_rad}709 \includegraphics[width=0.90\textwidth]{Fig_OBS_avg_rad} 709 710 \caption{ \label{fig:obsavgrad} 710 As for figure \ref{obsavgrec} but for a radial footprint with diameter $1\deg$. 711 Weights associated with each model grid box (blue lines and numbers) for an observation at 170.5E, 56.0N with a radial footprint with diameter 1\deg.} 711 712 \end{center} \end{figure} 712 713 %>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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