itimproved wording - cosmo - front and backend for Markov-Chain Monte Carlo inversion of cosmogenic nuclide concentrations Err mx1.adamsgaard.dk 70 hgit clone git://src.adamsgaard.dk/cosmo URL:git://src.adamsgaard.dk/cosmo mx1.adamsgaard.dk 70 1Log /src/log.gph mx1.adamsgaard.dk 70 1Files /src/files.gph mx1.adamsgaard.dk 70 1Refs /src/refs.gph mx1.adamsgaard.dk 70 1README /src/file/README.md.gph mx1.adamsgaard.dk 70 1LICENSE /src/file/LICENSE.gph mx1.adamsgaard.dk 70 i--- Err mx1.adamsgaard.dk 70 1commit a53b33ee8911d15bcfd27b48dad8944d0fd86baa /src/commit/a53b33ee8911d15bcfd27b48dad8944d0fd86baa.gph mx1.adamsgaard.dk 70 1parent 1d8bf4c603bb8c5c9084c8c7e3c82d0f6fe5a87d /src/commit/1d8bf4c603bb8c5c9084c8c7e3c82d0f6fe5a87d.gph mx1.adamsgaard.dk 70 hAuthor: Anders Damsgaard URL:mailto:anders.damsgaard@geo.au.dk mx1.adamsgaard.dk 70 iDate: Fri, 27 Nov 2015 16:46:59 +0100 Err mx1.adamsgaard.dk 70 i Err mx1.adamsgaard.dk 70 iimproved wording Err mx1.adamsgaard.dk 70 i Err mx1.adamsgaard.dk 70 iDiffstat: Err mx1.adamsgaard.dk 70 i M pages/methods.html | 51 ++++++++++++++++--------------- Err mx1.adamsgaard.dk 70 i Err mx1.adamsgaard.dk 70 i1 file changed, 26 insertions(+), 25 deletions(-) Err mx1.adamsgaard.dk 70 i--- Err mx1.adamsgaard.dk 70 1diff --git a/pages/methods.html b/pages/methods.html /src/file/pages/methods.html.gph mx1.adamsgaard.dk 70 it@@ -62,19 +62,18 @@ Err mx1.adamsgaard.dk 70 i with uniform probability across the logarithmic parameter Err mx1.adamsgaard.dk 70 i interval. The temporal parameter (tdegla) Err mx1.adamsgaard.dk 70 i and climate record threshold value Err mx1.adamsgaard.dk 70 i- (δ18Othreshold) is tested with Err mx1.adamsgaard.dk 70 i+ (δ18Othreshold) are tested with Err mx1.adamsgaard.dk 70 i uniform probability across the linear parameter interval. Err mx1.adamsgaard.dk 70 i- The user specifies the bounds of the model parameters. Err mx1.adamsgaard.dk 70 i

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When model parameters Err mx1.adamsgaard.dk 70 i (εint, εgla, Err mx1.adamsgaard.dk 70 i tdegla, Err mx1.adamsgaard.dk 70 i δ18Othreshold) are varied within Err mx1.adamsgaard.dk 70 i- specified limits, they can be thought of as orthogonal axes Err mx1.adamsgaard.dk 70 i- creating a coordinate system in higher-order space. Every Err mx1.adamsgaard.dk 70 i- position in this model space is associated with a certain Err mx1.adamsgaard.dk 70 i- set of model parameter values. Err mx1.adamsgaard.dk 70 i+ specified limits, they can be thought of as being orthogonal Err mx1.adamsgaard.dk 70 i+ axes spanning a coordinate system in four-dimensional space. Err mx1.adamsgaard.dk 70 i+ Each position in this model space is associated with a Err mx1.adamsgaard.dk 70 i+ unique set of model parameter values. Err mx1.adamsgaard.dk 70 i

Err mx1.adamsgaard.dk 70 i Err mx1.adamsgaard.dk 70 i

Given a single value of model parameters Err mx1.adamsgaard.dk 70 it@@ -86,7 +85,7 @@ Err mx1.adamsgaard.dk 70 i computed. This forward model describes a possible Err mx1.adamsgaard.dk 70 i history of exhumation and TCN production in a sample volume Err mx1.adamsgaard.dk 70 i as it experiences the variable physical environment of the Err mx1.adamsgaard.dk 70 i- Pleistocene.

Err mx1.adamsgaard.dk 70 i+ Quaternary.

Err mx1.adamsgaard.dk 70 i Err mx1.adamsgaard.dk 70 i Err mx1.adamsgaard.dk 70 i Err mx1.adamsgaard.dk 70 it@@ -105,7 +104,9 @@ Err mx1.adamsgaard.dk 70 i require more than 10 m of ice thickness for production due Err mx1.adamsgaard.dk 70 i to spallation (>50 m for muons). Interglacial periods are Err mx1.adamsgaard.dk 70 i assumed to have been characterized by 100% exposure and zero Err mx1.adamsgaard.dk 70 i- shielding.

Err mx1.adamsgaard.dk 70 i+ shielding. The production of TCNs takes place during the Err mx1.adamsgaard.dk 70 i+ interglacials, while erosion removes the land surface at Err mx1.adamsgaard.dk 70 i+ different rates during the glacials and interglacials.

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Err mx1.adamsgaard.dk 70 it@@ -121,8 +122,8 @@ Err mx1.adamsgaard.dk 70 i evaluates if the output result matches the observational Err mx1.adamsgaard.dk 70 i record better or worse than the output at its previous Err mx1.adamsgaard.dk 70 i position in model space. If the new results better matches Err mx1.adamsgaard.dk 70 i- the observed dataset, it continues walking along Err mx1.adamsgaard.dk 70 i- approximately in the same direction in model space. Err mx1.adamsgaard.dk 70 i+ the observed dataset, it continues walking in the same Err mx1.adamsgaard.dk 70 i+ direction in model space. Err mx1.adamsgaard.dk 70 i

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Err mx1.adamsgaard.dk 70 it@@ -142,19 +143,19 @@ Err mx1.adamsgaard.dk 70 i

Err mx1.adamsgaard.dk 70 i For a given observational data set more than one set of Err mx1.adamsgaard.dk 70 i model parameters may produce forward models which Err mx1.adamsgaard.dk 70 i- sufficiently satisfy the MCMC walker as solution Err mx1.adamsgaard.dk 70 i- approximations. In this case the solution is Err mx1.adamsgaard.dk 70 i- non-unique. Even worse, a single MCMC walker may find Err mx1.adamsgaard.dk 70 i- an area in model space which seemingly is in good Err mx1.adamsgaard.dk 70 i- correspondence with the observational data set, but is Err mx1.adamsgaard.dk 70 i- missing a much better set of model parameters since they are Err mx1.adamsgaard.dk 70 i- located somewhere entirely different in the model space. In Err mx1.adamsgaard.dk 70 i- order to mitigate these issues, MCMC inversions are often Err mx1.adamsgaard.dk 70 i- performed using several MCMC walkers. The starting point of Err mx1.adamsgaard.dk 70 i- each MCMC walker is chosen at random, resulting in unique Err mx1.adamsgaard.dk 70 i- walks through the model space. If a single walker is caught Err mx1.adamsgaard.dk 70 i- in an area of non-ideal solutions, chances are that the Err mx1.adamsgaard.dk 70 i- other walkers will find the area of better model parameters. Err mx1.adamsgaard.dk 70 i+ sufficiently satisfy the MCMC walker. Err mx1.adamsgaard.dk 70 i+ In this case the solution is non-unique. Even worse, Err mx1.adamsgaard.dk 70 i+ a single MCMC walker may find an area in model space which Err mx1.adamsgaard.dk 70 i+ seemingly is in good correspondence with the observational Err mx1.adamsgaard.dk 70 i+ data set, but the walker is missing a much better set of Err mx1.adamsgaard.dk 70 i+ model parameters since they are located somewhere entirely Err mx1.adamsgaard.dk 70 i+ different in the model space. In order to mitigate these Err mx1.adamsgaard.dk 70 i+ issues, MCMC inversions are often performed using several Err mx1.adamsgaard.dk 70 i+ MCMC walkers. The starting point of each MCMC walker is Err mx1.adamsgaard.dk 70 i+ chosen at random, resulting in unique walks through the Err mx1.adamsgaard.dk 70 i+ model space. If a single walker is caught in an area of Err mx1.adamsgaard.dk 70 i+ non-ideal solutions, chances are that the other walkers will Err mx1.adamsgaard.dk 70 i+ find the area of better model parameters. Err mx1.adamsgaard.dk 70 i

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Err mx1.adamsgaard.dk 70 it@@ -162,8 +163,8 @@ Err mx1.adamsgaard.dk 70 i walkers. When casually trying out the calculator we Err mx1.adamsgaard.dk 70 i recommend using low numbers of MCMC walkers (1 to 2) in Err mx1.adamsgaard.dk 70 i order to obtain fast results and reduce load on the server. Err mx1.adamsgaard.dk 70 i- When attempting to produce high-quality reliable results, Err mx1.adamsgaard.dk 70 i- the number of walkers should be increased (3 to 4). Err mx1.adamsgaard.dk 70 i+ When attempting to produce high-quality and reliable Err mx1.adamsgaard.dk 70 i+ results, the number of walkers should be increased (3 to 4). Err mx1.adamsgaard.dk 70 i

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Err mx1.adamsgaard.dk 70 i Err mx1.adamsgaard.dk 70 .