Task 4 - Validation: Progress Meeting 2 R. Siddans, B. Kerridge, Jane Hurley STFC Rutherford Appleton Laboratory

WBS

Task Overview

Outline of Talk TCCON/MLO L2 Comparisons –TCCON, GOSAT MLO Case Study –Mauna Loa in-situ – monthly and interannual dependencies Pixel/Scan Dependence Metop-A/-B –Closest pixels –Inter-pixel and inter-scan angle dependence Cloud Contamination –RAL flag, AVHRR, IASI L2 Summary

TCCON/GOSAT L2 Comparisons TCCON sites

TCCON/GOSAT L2 Comparisons IASI vs TCCON & GOSAT – CH4 VMRs f= *(day_since_start_of_2009)/365.25

TCCON/GOSAT L2 Comparisons IASI vs TCCON & GOSAT – CH4 VMRs (day only)

TCCON/GOSAT L2 Comparisons IASI vs TCCON & GOSAT – number of measurements

TCCON/GOSAT L2 Comparisons IASI vs TCCON & GOSAT – errors

TCCON/GOSAT L2 Comparisons IASI vs TCCON & GOSAT – scatterplots IASI vs. TCCON

TCCON/GOSAT L2 Comparisons IASI vs TCCON & GOSAT – scatterplots IASI vs. GOSAT

TCCON/GOSAT L2 Comparisons IASI vs TCCON & GOSAT – summary IASI vs. TCCON vs. GOSAT: good correlation (up to 95.5%) between measurements <200 km of TCCON sites, with current IASI retrieval scaled to reflect increase of 0.23%/year of N 2 O (update in retrieval TBD).

MLO Case Study IASI vs MLO – monthly averages

MLO Case Study IASI vs MLO – yearly consistency

MLO Case Study IASI vs MLO – correlation

MLO Case Study IASI vs MLO – monthly averages N 2 O fixed CH 4 corrected post-hoc N 2 O corrected in retrieval ( still running…)

MLO Case Study IASI vs MLO – summary Mauna Loa: fair correlation (63-81%) between Jan Dec.2012 IASI (<200 km of Mauna Loa) and MLO in-situ measurements taken. MLO in-situ dataset is correlated by % from year-to-year, whereas the IASI dataset correlates between 15%-85% from year-to-year. Inter-annual variability (comparing month-to-month in nearby years) in CH 4 at Mauna Loa is about 0.02 ppmv, which is less than the intra-annual variability (about 0.06 ppm).

Pixel/Scan Dependence Metop-A/-B Metop-A vs. Metop-B - nearest-pixel

Pixel/Scan Dependence Metop-A/-B Metop-A vs. Metop-B – retrieval products

Pixel/Scan Dependence Metop-A/-B Metop-A vs. Metop-B – pixel dependence CH4 concentrationsOther retrieved parameters Day/night ocean/land separated

Pixel/Scan Dependence Metop-A/-B Metop-A vs. Metop-B – scan angle dependence CH4 concentrationsOther retrieved parameters Day/night, ocean/land separated

Pixel/Scan Dependence Metop-A/-B Metop-A vs. Metop-B – summary Retrieval products: Pixel-by-pixel analysis shows that 82% of collocated Metop-A and –B measurements gave retrieved CH 4 within retrieval error of each other, with a 70% correlation overall. The global distribution analysis showed that the mean difference globally between Metop-A and –B distributions was less than ppmv with a standard deviation of less than ppmv. Products consistency: Slight dependence between IASI pixels/scan angles and the retrieval products (0.008 ppmv and ppmv respectively). Error on individual retrievals ~0.03 ppmv, but many individual retrievals averaged in this analysis.

Cloud Contamination Comparison of different flags

Cloud Contamination Stratification with cloud fraction

Cloud Contamination Summary The effect of cloud contamination on the retrieved concentrations of CH 4 assessed using the cloud fraction retrieved within the RAL retrieval the cloud fractions from AVHRR/3 the cloud fraction from IASI L2 products. The three sets of cloud fractions are uncorrelated. The concentration of retrieved CH 4 generally becomes increasingly scattered over the full ppmv range as the cloud fraction increases, with the average retrieved CH 4 column-average VMR unchanged from 1.75 for all cloud fractions.

TCCON & GOSAT L2 comparison (up to 96% correlation) MLO case study: fair correlation IASI/MLO (63-81%). -interannual variability 0.02 ppmv -intra-annual variability 0.06 ppmv Retrieval products: Pixel-by-pixel analysis shows that 82% of collocated Metop-A and –B measurements gave retrieved CH 4 within retrieval error of each other, with a 70% correlation overall Product consistency: Slight dependence between IASI pixels/scan angles and the retrieval products (0.008 ppmv and ppmv respectively). Error on individual retrievals ~0.03 ppmv, but many individual retrievals averaged in this analysis. Cloud contamination: increases scatter on retrieved CH 4, but doesn’t alter mean XVMR retrieved. Summary