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Benchmarking three low-cost, low-maintenance cloud height measurement systems and ECMWF cloud heights against a ceilometer

Kuhn, Pascal Moritz and Wirtz, M. and Killius, Niels and Wilbert, Stefan and Bosch, J.L. and Hanrieder, Natalie and Nouri, Bijan and Kleissl, J. and Ramirez-Santigosa, Lourdes and Schroedter-Homscheidt, Marion and Heinemann, Detlev and Kazantzidis, A. and Blanc, Philippe and Pitz-Paal, Robert (2018) Benchmarking three low-cost, low-maintenance cloud height measurement systems and ECMWF cloud heights against a ceilometer. Solar Energy, 168, pp. 140-152. Elsevier. DOI: 10.1016/j.solener.2018.02.050 ISSN 0038-092X

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Official URL: https://www.sciencedirect.com/science/

Abstract

Cloud height information is crucial for various applications. This includes solar nowcasting systems. Multiple methods to obtain the altitudes of clouds are available. In this paper, cloud base heights derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) and three low-cost and low-maintenance ground based systems are presented and compared against ceilometer measurements on 59 days with variable cloud conditions in southern Spain. All three ground based systems derive cloud speeds in absolute units of [m/s] from which cloud heights are determined using angular cloud speeds derived from an all-sky imager. The cloud speed in [m/s] is obtained from (1) a cloud shadow speed sensor (CSS), (2) a shadow camera (SC) or (3) derived from two all-sky imagers. Compared to 10-min median ceilometer measurements for cloud heights below 5000 m, the CSS-based system shows root-mean squared deviations (RMSD) of 996 m (45%), mean absolute deviations (MAD) of 626 m (29%) and a bias of −142 m (−6%). The SC-based system has an RMSD of 1193 m (54%), a MAD of 593 m (27%) and a bias of 238 m (11%). The two all-sky imagers based system show deviations of RMSD 826 m (38%), MAD of 432 m (20%) and a bias of 202 m (9%). The ECMWF derived cloud heights deviate from the ceilometer measurements with an RMSD 1206 m (55%), MAD of 814 m (37%) and a bias of −533 m (−24%). Due to the multi-layer nature of clouds and systematic differences between the considered approaches, benchmarking cloud heights is an extremely difficult task. The limitations of such comparisons are discussed. This study aims at determining the best approach to derive cloud heights for camera based solar nowcasting systems. The approach based on two all-sky imagers is found to be the most promising, having the overall best accuracy and the most obtained measurements.

Item URL in elib:https://elib.dlr.de/122789/
Document Type:Article
Title:Benchmarking three low-cost, low-maintenance cloud height measurement systems and ECMWF cloud heights against a ceilometer
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Kuhn, Pascal MoritzPascal.Kuhn (at) dlr.dehttps://orcid.org/0000-0001-9978-5706
Wirtz, M.UNSPECIFIEDUNSPECIFIED
Killius, Nielsniels.killius (at) dlr.deUNSPECIFIED
Wilbert, StefanStefan.Wilbert (at) dlr.dehttps://orcid.org/0000-0003-3573-3004
Bosch, J.L.Universidad de HuelvaUNSPECIFIED
Hanrieder, Natalienatalie.hanrieder (at) dlr.dehttps://orcid.org/0000-0002-9671-351X
Nouri, BijanBijan.Nouri (at) dlr.deUNSPECIFIED
Kleissl, J.University of CalifroniaUNSPECIFIED
Ramirez-Santigosa, LourdesCIEMATUNSPECIFIED
Schroedter-Homscheidt, Marionmarion.schroedter-homscheidt (at) dlr.dehttps://orcid.org/0000-0002-1854-903X
Heinemann, DetlevUniversität OldenburgUNSPECIFIED
Kazantzidis, A.Univ. of Patras, Patras, GRUNSPECIFIED
Blanc, PhilippeMines ParisTechUNSPECIFIED
Pitz-Paal, RobertRobert.Pitz-Paal (at) dlr.dehttps://orcid.org/0000-0002-3542-3391
Date:1 July 2018
Journal or Publication Title:Solar Energy
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:168
DOI :10.1016/j.solener.2018.02.050
Page Range:pp. 140-152
Publisher:Elsevier
Series Name:Elsevier
ISSN:0038-092X
Status:Published
Keywords:Cloud height Determination, All-sky imager, Cloud shadow, speed sensor Shadow camera
HGF - Research field:Energy
HGF - Program:Renewable Energies
HGF - Program Themes:Concentrating Solar Thermal Technology
DLR - Research area:Energy
DLR - Program:E SW - Solar and Wind Energy
DLR - Research theme (Project):E - Impact of Desert Environment
Location: Köln-Porz
Institutes and Institutions:Institute of Solar Research > Qualification
Institute of Networked Energy Systems > Energy Systems Analysis
Deposited By: Kruschinski, Anja
Deposited On:12 Nov 2018 10:08
Last Modified:21 Nov 2019 15:52

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