Desert dust remote sensing with the new zenith looking narrow‐band radiometer 

based system (ZEN)A. F. Almansa1,2,5 , E. Cuevas1, B. Torres3, A. Barreto1,2, R. D. García1,4, V. E. Cachorro5, C. Guirado1,5, A. M. de Frutos5, C. 

López6 and R. Ramos11Izaña Atmospheric Reseach Center, AEMET, Spain

2Cimel Electronique, France3Laboratoire d’Optique Atmospherique, Université des Sciences et Technologies de Lille, 

Villeneuve d’Ascq, France 4Air Liquide España, Delegación Canarias, Candelaria, Spain

5Grupo de Óptica Atmosférica, Universidad de Valladolid, Valladolid, Spain6Sieltec Canarias S. L., La Laguna, Spain

Madrid, September 2016 

• INTRODUCTION

• THE ZEN SYSTEM ZEN‐R41 radiometer ZEN‐LUT methodology

• IZAÑA AND TAMANRASSET STATIONS

• RESULTS ZEN‐LUT performance evaluation at Tamanrasset (2014‐2016) ZEN system performance evaluation at Tamanrasset (2015) ZEN system performance evaluation at Izaña (2015‐2016)

• ONGOING ACTIVITIES

• CONCLUSIONS

LIST OF CONTENTS

INTRODUCTIONAEROSOL IMPORTANCE

• Advantages: global and long‐term aerosol monitoring (key importance fornumerical climate models and model assimilation).

• Drawbacks: Low temporal resolution, cloud contamination and correction ofground reflectivity.

http://earthobservatory.nasa.gov/

INTRODUCTIONSATELLITE MONITORING

CIMEL CE-318 photometer

• Optical and mycrophysical properties (key importance in model evaluationand assimilation and satellite‐products validation).

• Accurate aerosol monitoring (ΔAOD<0.02), high temporal resolution but lowspatial coverage.

• AERONET is the most extended network of ground‐based photometers.

INTRODUCTIONGROUND‐BASED MONITORING

• AERONET (and other networks) has a lack of coverage in desert regions.• Reasons:

Manpower: maintenance (trained staff) High cost Power consumption

• Poor description of dust cycles and lack of information of aerosolproperties in dust source regions

INTRODUCTIONGROUND‐BASED MONITORING OVER DESERTS

THE ZEN SYSTEM

ZEN‐R41 RADIOMETER

ZEN‐LUT METHODOLOGY+

=AOD RETRIEVAL FROM ZSR 

(zenith sky radiances)

Published in AMTD: Almansa et al., 2016.

• Robust external case• No moving parts• Four silicon detectors and

four optical 10‐nm filters(440, 500, 675 and 870nm)

• Operational temperaturerange: ‐40C and 85C

• Internal sensors for humidityand temperature monitoring

• Optional external blower fordust removal

• Solar panels• Internal electronics (auto‐

check and product)

THE ZEN SYSTEMZEN‐R41 RADIOMETER

Simple, robust and low‐cost instrument with low maintenance is suitable to be deployed in remote desert areas

THE ZEN SYSTEMZEN‐LUT Methodology

‐Atmosphere vertical profile definition: P, T, gases …‐Surface reflectance definition‐Four spectral ranges: 10 nm FWHM filter function‐Aerosol definition:  N vertical profiles of OPAC components ‐Solar position:  θsun

Earth‐Sun distance corrected measured signal at four 

spectral bands

Calibration

ZSR and AOD simulationZSR measurement

Lmλ(θsun,θv=0)

λ (spectral band index)

, , ,

,

Lcλ,i(θsun,θv=0)AODc

λ,iλ (spectral band index)i (aerosol profile index)

Minimum(εi) AODrλ Almansa et al., 2016.

IZAÑA AND TAMANRASSET STATIONS

‐ Izaña high mountain station (the Canary Islands,Spain, 28.3N, 16.5 W, 2373 m a.s.l).‐Most of the time under atmospheric backgroundconditions.‐ Ocassional influence of mineral dust due to theproximity to Saharan desert (mainly insummertime).

‐ Tamanrasset station (Algeria, 22.8N, 5.5 E, 1377m a.s.l).‐ Key location near the most important dust sourcesof Mali, Algeria, Libya and Chad.‐ Dust is the main aerosol type.‐ Prevailing clear sky conditions in winter and highturbidity events in summer.

RESULTS

RESULTSZEN‐LUT performance evaluation at Tamanrasset (2014‐2016)

YEAR R2 RMSE

2014 0.91 0.06

2015 0.94 0.07

2016 0.83 0.12

Just withCE318 

information

RESULTSZEN system performance evaluation at Tamanrasset (2015)

Device R2 RMSE

ZEN‐R41 0.81 0.02

CE318‐LUT 0.71 0.02

RESULTSZEN system performance evaluation at Izaña (2015‐2016)

R2=0.97; RMSE=0.02

ONGOING ACTIVITIES

• Autonomous cloud screening

• ZEN‐LUT methodology for different aerosol conditions

• Total column water vapour estimation

CONCLUSIONS• We have shown the good performance of the ZEN‐LUT method and ZEN‐R41 radiometer

for AOD estimation, by comparing with the CE318 AERONET in Tamanrasset (R2 ≈ 0.81,RMSE ≈ 0.015) and in Izaña (R2 ≈ 0.97 and RMSEs up to 0.023).

• These results indicate that ZEN system is appropriated to monitor atmospheric dust withlittle maintenance in remote desert locations, allowing us to fill important observationalgaps and improve our knowledge on dust cycles in key regions near dust sources.

• This system could also play an important role in dust model assimilation, satellitevalidation and early warning within the World Meteorological Organization (WMO) Sandand Dust Storm Warning Advisory and Assessment System (SDS WAS).

Thanks for your attention!