# Evaluation of the LOTOS-EUROS NO 2 simulations using ground-based measurements and S5P/TROPOMI observations over Greece

The evaluation of chemical transport models, CTMs, is essential for the assessment of their performance regarding the physical and chemical parameterizations used. While regional CTMs have been widely used and evaluated over Europe, their validation over Greece is limited. In this study, we investigate the performance of the Long Term Ozone Simulation European Operational Smog (LOTOS-EUROS) v2.2.001 regional chemical transport model in simulating nitrogen dioxide, NOinline-formula2, over Greece from June to December 2018. In situ NOinline-formula2 measurements obtained from 14 stations of the National Air Pollution Monitoring Network are compared with surface simulations over the two major cities of Greece, Athens and Thessaloniki. Overall the LOTOS-EUROS NOinline-formula2 surface simulations compare very well to the in situ measurements showing a mild underestimation of the measurements with a mean relative bias of inline-formula $M6inlinescrollmathml\sim -normal 10$ 32pt10ptsvg-formulamathimg13608f3dc1bc69445c2e36410c40a5f7 acp-21-5269-2021-ie00001.svg32pt10ptacp-21-5269-2021-ie00001.png  %, a high spatial correlation coefficient of 0.86 and an average temporal correlation of 0.52. The CTM underestimates the NOinline-formula2 surface concentrations during daytime by inline-formula $M8inlinescrollmathml\sim -normal 50$ 32pt10ptsvg-formulamathimg14b9b639daf2a06845c53389ea229fd7 acp-21-5269-2021-ie00002.svg32pt10ptacp-21-5269-2021-ie00002.png inline-formula± 15 %, while it slightly overestimates during night-time inline-formula∼ 10 inline-formula± 35 %. Furthermore, the LOTOS-EUROS tropospheric NOinline-formula2 columns are evaluated against ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) NOinline-formula2 measurements in Athens and Thessaloniki. We report that the CTM tropospheric NOinline-formula2 column simulations over both urban and rural locations represent the diurnal patterns and hourly levels for both summer and winter seasons satisfactorily. The relative biases range between inline-formula∼inline-formula−2 % and inline-formula−35 %, depending on season and relative NOinline-formula2 load observed. Finally, the CTM was assessed also against space-borne Sentinel-5 Precursor (S5P) carrying the Tropospheric Monitoring Instrument (TROPOMI) tropospheric NOinline-formula2 observations. We conclude that LOTOS-EUROS simulates extremely well the tropospheric NOinline-formula2 patterns over the region with very high spatial correlation of 0.82 on average, ranging between 0.66 and 0.95, with negative biases in the summer and positive in the winter. Updated emissions for the simulations and model improvements when extreme values of boundary layer height are encountered are further suggested.

### Zitieren

Zitierform:

Skoulidou, Ioanna / Koukouli, Maria-Elissavet / Manders, Astrid / et al: Evaluation of the LOTOS-EUROS NO2 simulations using ground-based measurements and S5P/TROPOMI observations over Greece. 2021. Copernicus Publications.

### Zugriffsstatistik

Gesamt:
Volltextzugriffe:
12 Monate:
Volltextzugriffe:

### Rechte

Rechteinhaber: Ioanna Skoulidou et al.

Nutzung und Vervielfältigung: