The Observational System

NAWDEX aims at quantifying errors of the thermodynamic structure near Rossby waves and their relation to diabatic processes. The aim is to obtain a comprehensive and unprecedented data set in a region that, so far, was not accessible with smaller research platforms.

HALO and Falcon with instrumentation for NAWDEX

HALO provides the required flight range to reach the central and eastern North Atlantic and Europe and the altitude to perform remote sensing observations from above cloud systems. With the help of the established instrument combination of the WALES differential absorption lidar, the cloud radar of the Hamburg Microwave Package (HAMP), different radiometers and the dropsonde device the three-dimensional structure of water vapour, wind, temperature and cloud properties will be observed. Additionally to HALO, DLR will deploy its research aircraft Falcon with a wind lidar payload which allows a detailed observation of jet-level winds. The collected data inside and outside clouds allows to investigate the relevance of different diabatic processes and related weather systems for the Rossby wave evolution by validating different numerical models. Beside upper-level observations, the humidity structure in the lower troposphere is of interest for diabatic processes.

Instrument	Aircraft	Institution	Measured parameter
HAMP (HALO Microwave Package)	HALO	MPI-M Hamburg Univ. Hamburg Univ. Cologne DLR-PA	liquid water path, cloud snow and rain water path temperature + humidity profiles profiles of radar reflectivity depol. ratio + vertical velocity
WALES	HALO	DLR-PA	Profiles of: water vapour backscatter coefficient (532/1064 nm) color ratio of backscatter (532/1064 nm) particle linear depol. ratio (532/1064 nm) particle extinction coefficient at 532 nm
HALO-SR	HALO	Univ. Leipzig	spectral nadir radiance, actinic flux densities spectral nadir radiance (300-2200 nm) spectral upward and downward irradiance (300-2200 nm), cloud top albedo cloud thermodynamic phase liquid and water path cloud optical thickness, effective radius
specMACS	HALO	LMU Munich	spectral nadir radiance, actinic flux densities spectral radiance (400-2500 nm), push-broom imaging, nadir and +/- 17° across track cloud thermodynamic phase liquid and ce optical thickness particle size cloud cover
Dropsondes	HALO	DLR-PA	profiles of relative humidity, temperature and horizontal wind
BAHAMAS	HALO	DLR-FX	In-situ obervations of T,q, u, v, w, 100 Hz data, GPS
A2D	FALCON	DLR-PA	20 degree off nadir LOS velocity profiles
2-µm Doppler Wind Lidar	FALCON	DLR-PA	profiles of the horizontal wind vector
in-situ instruments	FALCON	DLR-FX	In-situ obervations of T,q, u, v, w, 100 Hz data, GPS

Overview of the NAWDEX instrumentation. For a detailed information about the instruments, resolution and accuracy please refer to the NAWDEX CIP

HALO and Falcon will operate over the eastern North Atlantic with the operation base in Iceland to guarantee optimal flight range and proximity to the regions of interest. The observation period in September and October is chosen as the above described weather systems characterized by strong diabatic activity and forecast busts are likely to occur. 100 flight hours from Iceland are envisaged with HALO. 50 flight hours are planned with the DLR Falcon. For a three-dimensional characterization of wind, temperature and moisture at jet level elongated high-level cross-sections across the jet stream and in regions where diabatically modified air masses interact with the wave-guide will be designed depending on the flow field.

For the first time it will be possible to follow the evolution of Rossby waves along the wave guide and to observe weather systems ranging from synoptic to cloud scales. Lagrangian tracking of diabatically modified air masses is planned. This will be tried with consecutive HALO/Falcon flights and by coordinating flights with the international partners. French colleagues applied for the use of the French Safire Falcon to perform measurements in downstream developing weather systems. Additionally, ground-based observations will be performed over Europe.