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Evaluation of ECMWF water vapour analyses by airborne differential absorption lidar measurements: a case study between Brasil and Europe

Flentje, H. and Dörnbrack, A. and Fix, A. and Ehret, G. and Hólm, E. (2007) Evaluation of ECMWF water vapour analyses by airborne differential absorption lidar measurements: a case study between Brasil and Europe. Atmospheric Chemistry and Physics, 7, pp. 5033-5042.

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Official URL: http://www.atmos-chem-phys.net/7/5033/2007/

Abstract

Airborne Differential Absorption Lidar (DIAL) observations of tropospheric water vapour over Brazil and between Brazil and south Europe in March 2004 are compared to 1-hourly short-range forecasts of the European Centre for Medium Range Weather Forecasts (ECMWF). On three along-flight sections across the tropical and sub-tropical Atlantic between 28° S and 37° N humidity fields are observed which represent typical low latitude conditions. H<sub>2</sub>O mixing ratios vary between q≈0.01–0.1 g/kg in the upper troposphere (UT), in subsiding air layers and a stratospheric intrusion. They reach up to 0.5 g/kg at UT levels inside the Intertropical Convergence Zone (ITCZ) and exceed 10 g/kg at lower levels. Back-trajectories reveal that the humidity fields are largely determined by transport. The observed water vapour distributions are properly reproduced by 1-hourly ECMWF Integrated Forecasting System (IFS) short-range forecasts at T799/L91 spectral resolution. As transport largely determines the water vapour fields, the IFS skill is to a large extend based on a good representation of the dynamics. The mean relative bias accounts to few percent (0%, 3% and 6% for the three sections) being about or even below the accuracy of the DIAL measurements of 5%. The larger deviations between analyses and observations on small scales are due to relative spatial shifts of features with large gradients. The correlation is quite high, ranging between 0.71 and 0.88. Over sea the analyses tend to underestimate the PBL height. At mid-levels near deep convection the mid-troposphere tends to be analyzed too humid indicating shortcomings in the convection parameterization. Humid tendencies are also found in the upper troposphere, particularly in tropical regions.

Document Type:Article
Title:Evaluation of ECMWF water vapour analyses by airborne differential absorption lidar measurements: a case study between Brasil and Europe
Authors:
AuthorsInstitution or Email of Authors
Flentje, H.DWD, Hohenpeißenberg
Dörnbrack, A.UNSPECIFIED
Fix, A.UNSPECIFIED
Ehret, G.UNSPECIFIED
Hólm, E.ECMWF, Reading, UK
Date:2007
Journal or Publication Title:Atmospheric Chemistry and Physics
Refereed publication:Yes
In Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:7
Page Range:pp. 5033-5042
Status:Published
Keywords:Airborne Differential Absorption Lidar (DIAL), tropospheric water vapour, ECMWF analyses
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben LIDAR-Forschung und -Entwicklung (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Lidar
Deposited By: Jana Freund
Deposited On:04 Oct 2007
Last Modified:20 Oct 2014 14:32

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