Custom Query (964 matches)

A new option, OBS_IMPACT, has been coded to compute the observation impact to W4DPSAS_SENSITIVITY, W4DVAR_SENSITIVITY, and IS4DVAR_SENSITIVITY algorithms.

The difference between observation impact and observation sensitivity is a subtle but important one. Actually, in some cases they explain the same thing in two different ways:

• The observation impact allows us to attribute to each observation the change that occurs in I(dx) where dx is the analysis or forecast increment, and I is some scalar functional of the state (e.g. transport). In this case dx is the change in the state-vector x that occurred by assimilating data (i.e. dx=xa-xb, where xa is the analysis and xb is the background).

• The observation sensitivity answers the question: what would the change to I be if we changed the observations y by an amount dy? Now, it turns out that if we let dy=d (the innovation vector), then the change in I is approximately equal to I(dx) above so observation sensitivity gives the same answer as observation impact. However, the observation sensitivity is more general. For example, if we want to know what the impact on the assimilation would be if we remove all of the SSH data, then choose dy=-dSSH. We can estimate what the change in I would be without having to rerun the assimilation. So the observation sensitivity has great utility for obervation system design and monitoring.

Also corrected miscelaneous bugs in unused options of the spatial convolutions.

Many thanks to Andy Moore for his help coding and testing this new option.

Added missing scripts in the seagrid/presto directory and subdirectories. I also added the mex directory containing subdirectories for conformal mapping and orthogonal grid generation.

I also corrected bugs reported by John Wilkin. For details check the following forum ​posting.

Warning: This is an important upgrade to ROMS biology models.

The light attenuation formulation for photosynthesis (PAR) in couple of biology models in ROMS were revisited. We are now using the averaged (finite volume) value of PAR at the center of the grid cell instead of the median value. It turns out that the old fomulation understimates primary productivity. See the following forum ​post for details. I only correted BIO_FENNEL and NPZD_POWELL. I still need to fix this problem in the NEMURO model, which has in addition a photoinhibition (Platt et al., 1980) formulation.

Many thanks to Mark Baird for bringing this problem to our attention and to Bronwying Cahill for testing this upgrade.

I am also releasing a new NPZD model with iron limitation (Fiechter et al., 2009). This model is similar to the Powell et al. (2006) formulation but it includes iron limitation on phytoplankton growth. This new model is activated with the NPZD_IRON option. To activate the iron limitation on phytoplankton growth, use in addition IRON_LIMIT option. In addition, use IRON_RELAX to simulate the sources of dissolved iron in coastal areas where the bathymetry h(i,j) <= FeHmin (See input script npzd_iron.in for details).

This new NPZD model (npzd_iron.h) also has a tangent linear, representer, and adjoint model version which we are still testing. Many thanks to Jerome Fiechter and Andy Moore for their help on developing this nee model.