progress meeting #27, 21-23 april 2015, barcelona spain t3.2 retrieval algorithm estrella olmedo bec...

Progress Meeting #27, 21-23 April 2015, Barcelona SPAIN

T3.2 Retrieval algorithm

Estrella Olmedo BEC team

SMOS Barcelona Expert CentrePg. Marítim de la Barceloneta 37-49, Barcelona SPAINE-mail: [email protected]: www.smos-bec.icm.csic.es

21-04-2015, Barcelona SPAIN

1. Work plan progress

2. General overview of our internal processing chain

3. Levenberg-Marquardt

4. Single incidence angle retrieval

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Contents


1. Work plan progress

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Start contract

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Work plan and progress

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT

PM#27

Delivery of PRP

During this period, we have updated, implemented and

tested software to be ready for the different simulations to be

done in this task

TASK 3.2 RETRIEVAL ALGORITHM: Alternatives for the retrieval:T3.2.1 Test of various L2OS configurations for retrieving SSST3.2.2 Two-step retrievalT3.2.3 Monte Carlo approaches


2. General overview of our internal processing chain

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21-04-2015, Barcelona SPAIN 6 / 38

General overview

L0MTS: TB

computation

Compute OTT

Tb geo-localization and OTT correction

Computation of forward model and

download measured TBs at

BOA

SSS and WSN retrieval

L3/L4 map computation

ARGO validation

BEC

inte

rnal p

rocessin

g

ch

ain

ESA input

L1B

Change format

L2

ARGANS input

BEC outputARGO

statisticsL3/L4 maps

SSS semi-orbits and SSS distributions


SSS and WSN retrieval

This task corresponds to

this point

The idea is having an independent software for testing and analyzing

different computation options

General overview


How can we retrieve salinities?

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General overview

Retrieve SSS only

One SSS per measurement

Retrieve SSS and

WSN

Our software, at this moment, has not implemented

TEC retrieval

One SSS per grid point

One SSS and one WSN per

grid point

Levenberg-Marquardt

1-D Newton method First

Stokes

DUAL

FULL

BOA

ARF

Constraints

No Constraints


3. Levenberg-Marquardt

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• We have implemented a Levenberg-Marquardt algorithm that allows different configurations

• Using the same input data and running L2PP and L2BEC with the same configuration, the resulting salinities are the same

• The complete processing chain is different:

• Different grid for snapshots• Different grid for semi-orbits• Etc..

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Levenberg Marquardt


Levenberg-Marquardt

• TEC is fixed

• Very simple pre-filtering conditions are implemented so far

• The post-filtering criteria is not yet analyzed

• The program allows also retrieving in BOA


Levenberg Marquardt: preliminary tests


ARGO comparison

ARGO Global Tropic NPac Tarf Z122 Z124 Z126 Z131 Z132 OTT

L2PP Mean -0.26 -0.26 -0.80 -0.16 -0.10 0.01 -0.29 0.03 -0.38 -0.07

Std 0.54 0.51 0.6 0.28 0.22 0.37 0.38 0.88 0.37 0.34

Nbuoy 2667 1468 124 76 72 273 429 460 81 170

L2BEC Mean -0.21 -0.22 -0.61 -0.18 -0.14 -0.03 -0.29 0.00 -0.41 -0.04

Std 0.62 0.54 0.77 0.59 0.39 0.53 0.51 0.91 0.52 0.47

Nbuoy 2644 1486 125 76 77 279 432 408 81 169

Both processors provide similar results• L2PP provides slightly better standard deviations• L2BEC provides slightly better global means• In some specific regions L2PP works better

We need to improve L2BEC to reproduce L2PP results and then test alternative retrieval methods

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4. Single incidence angle retrieval

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We consider the following set of functions:

only depends on the salinity and on the incidence angle.Since the measurement () is fixed, the incidence angle is also fixed .

So far, just first stokes has been considered.

The measurements have been corrected with the corresponding OTT

If we plot all ) in a range of salinities in 30-40 psu the result is a set of parabolas without any apparent order

Single incidence angle retrieval: Approach

The minimum of each one of these parabolas represents the salinity measured by SMOS at that point for the corresponding incidence angle

We compute this minimum with a Newton method.

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We consider now 7 consecutive 9-days maps in June 2014.

We selected 16 points on the ocean.

At each cell of 0.25x0.25 degrees we plot the distribution of the minima of last equation that have been accumulated in the 9 days.

We only consider those minima between 0 and 50 psu

We differentiate between the measurements provided by ascending orbits only; descending orbits only; and both together.

We look at the shape of the salinity distributions at those points and the temporal evolution of them

Single incidence angle retrieval: Histograms

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Salinity distributions: 9-day map starting from 20140603

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Can we use this information for filtering “bad” measurements?

We compute joint histograms depending on the incidence angle and the distance to the center of the swath

We are working in different ways of using this information for improving the retrieval

Single incidence angle retrieval: Filter definition

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Single incidence angle retrieval: Joint histograms

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Conclusions & future work

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• We have set up an internal chain, in order to control de retrieval process and test different retrieval strategies

• L2BEC is now capable to ingest data from diverse sources and different formats, and provide results similar to those of L2PP

• We have implemented single-angle retrievals, which provides us L3 statistics of the quality of retrieved salinities

• We have used the L3 histograms to study the influence of the across-track distance to the center of the swath and incidence angle, and to propose new filtering schemes accordingly.

progress meeting #27, 21-23 april 2015, barcelona spain t3.2 retrieval algorithm estrella olmedo bec...

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