(formerly EC-TOOC)


Persistent EarthCare underflight studies of the ITCZ and organized convection

Mission status: Scheduled

Persons in Charge


  • Julia Windmiller, Bjorn Stevens (MPI-M)
  • Silke Groß (DLR-IPA)

Mission coordinator​

  • Lutz Hirsch (MPI-M)
  • Florian Ewald (DLR-IPA)

Contact point at DLR-FX for this mission:

Antonio Ciadamidaro (Toni) (HALO Project Management): +49 (0)8153 28-1626 (office), +49 (0)173 3641793 (mobile), antonio [dot] ciadamidaro [at] dlr [dot] de

HALO Deployment Bases

Time Period

June – November 2024

Mission phaseDates
Preparation, Payload Integration, EMI Testing17 June - 8 Aug 2023
Mission Execution Part I Cape Verde9 Aug - 5 Sep 2024
Mission Execution Part II Barbados5 Sep - 30 Sep 2024
Mission Execution Part III Oberpfaffenhofen4 - 19 Nov 2024
Dismounting of payload20 - 26 Nov 2024

Project description

Aerosol particles and clouds significantly contribute to the uncertainties in climate predictions. To improve the representation of aerosol particles and clouds in models, their properties and global distribution as well as their interactions will be investigated within the ESA/JAXA satellite mission EarthCARE, which is expected to be launched in 2023. For the first time EarthCARE will combine a cloud radar, a high spectral resolution lidar, a multispectral imager, and a broadband radiometer on one single platform. To use these measurements to their full extent, they have to be well calibrated, carefully validated, and fully characterized (e.g. with respect to sensitivity, spatial resolution, and sampling). Airborne measurements provide a unique opportunity to perform underpasses beneath the satellite track and to sample the same air masses over an extended area. Similar instrumentation to those used on EarthCARE can be employed on HALO, but with higher resolution and sensitivity.

PERCUSION is planned as a nine-week EarthCARE centered campaign that will focus both on EarthCARE characterization and on studies of deep convection over the tropical Atlantic close to the inter-tropical convergence zone (ITCZ) in mid to late summer (between August to October 2024). The objectives of PERCUSION are:

1. PERCUSION will validate EarthCARE both in terms of observed quantities (e.g. reflectivities and radiances) and derived products (e.g. water contents and cloud structures) to guide the use of its data in synergy with a new generation of geostationary satellites for global observation of tropical cloud structures in service of the second objective (O2).

2. PERCUSION seeks to understand how air-mass properties and meso-scale dynamical processes, influence the structure and dynamics of the ITCZ, and to quantify how the organization of both shallow and deep convection influences local and remote cloud radiative properties. In this respect, processes of special interest are: (a) Convective selfaggregation, (b) interactions of aerosol, cloud, and precipitation, (c) ice formation, and (d)
boundary layer dynamics and thermodynamics.

PERCUSION will consist of three parts: (i) test flights and EarthCARE validation flights out of Oberpfaffenhofen, Germany, (ii) research flights out of Barbados, and (iii) out of Cap Verde. One research flight will be used as ferry between (ii) and (iii). Along with two ferry flights the total flight hours amount 250h. All parts will contribute to the overarching goal to validate the new EarthCARE satellite. Oberpfaffenhofen (Germany) as operational base allows for measurement flights to the North Atlantic, Central Europe as well as into the Mediterranean area assuring an extensive validation and characterization of the satellite data under different conditions.

Measurements with the WALES system are well suited to discriminate different aerosol contributions and will help to investigate the quality of EarthCARE algorithms for aerosol classification and separation. WALES measurements were further used to derive the radiative effect of different aerosol layers, which is an essential step on the aim to achieve radiative closure. The cloud radar has demonstrated its high sensitivity and accuracy during former measurements, it is an ideal tool for water, mixed-phase, and ice cloud validation studies. A synergistic retrieval of combined radar and lidar measurements was adapted and further developed to be applied for HALO measurements. Thus, an independent algorithm as well as the EarthCARE algorithm can be applied on the HALO measurements to validate higher level products (Level 2b). In combination with the radiation measurements on board, HALO offers the full bunch of measurements to perform radiative closure studies, so that an EarthCARE-like payload on HALO enables to validate and characterize the whole chain of EarthCARE products.

During the tropical southern part of PERCUSION HALO will first be stationed at Barbados as to link the measurements to the ground observations from the Barbados Cloud Observatory (BCO) and also to the series of NARVAL campaigns, and to EUREC4A. Scientifically this part is complemented by sampling the Eastern Tropical Atlantic with stronger aerosol impact out of Cap Verde. PERCUSION has a different and broader perspective as its predecessor campaigns as it focuses on deeper convection close to the ITCZ and comprises different aerosol regimes over the entire tropical Atlantic.

PERCUSION plans to fly large circular flight patterns, encircling convective regions, with additional bisectional flights to sample the convective environment and measure the microphysical structure of the deep convective regions. It is intended to use the maximum ceiling of HALO to stay above possible cirrus outflow – typically at 13–14 km altitude. EarthCARE underpasses will build the core of these measurement flights. The large scale patterns are designed to measure and close the atmospheric energy budget about the ITCZ; which is closely related to the overall aim of EarthCARE, and relate this to the specific state of condensate (also temperature and water vapor) within the atmosphere, as deduced from combined active and passive observations. The lack of measurements in these environments, linking circulation to convection on different space and time scales, leaves a great number of questions that haven’t been answered by past studies. Measurements during PERCUSION will support associated modeling activities using storm resolving models and large-eddy simulations. Synergies with the ground based stations (BCO and measurements at Mindelo by the Leipzig Institute for Tropospheric Research (TROPOS) as well as the envisioned ship-based campaign BOWTIE further enhance research opportunities and activities.


    • Max Planck Institute for Meteorology (MPI-M), Hamburg
    • University Hamburg
    • German Aerospace Center, Institute of Atmospheric Physics (DLR-IPA)
    • Leipzig University
    • University of Cologne
    • Ludwig-Maximilians-Universität München (LMU)

Scientific instruments and payload configuration

  • List of scientific instruments for the mission:

The radar is a nadir staring instrument that measures in the water-vapor window at a frequency of 35.5 GHz (Ka-band). This system, similar to cloud radars operated on the Barbados Cloud Observatory, is operated with a 200 ns pulse length and a pulse repetition frequency of 5kHz. Two receivers provide co- and cross-polarization reflectivity measurements.
Three downward looking radiometer modules passively measure the microwave emissions of Earth’s atmosphere in twenty-six channels probing two water vapor and two oxygen absorption features, as well as window channels. Beam widths of 2.7º to 5.0º and a sampling rate of about 1 s.
WALES operates at four wave-lengths near 935 nm to measure water-vapor mixing ratio profiles covering the whole atmospherebelow the aircraft. At typical flight speeds it has a resolution of 200 m in the vertical and 6 km in the horizontal. The system also contains additional aerosol channels at 532 nm and 1064 nm with depolarization. WALES uses a high-spectral resolution technique, which distinguishes molecular from particle backscatter, to make direct extinction measurements with a resolution of 15 m in the vertical and 200 m in the horizontal.
The Spectral Modular Airborne Radiation measurement sysTem (SMART) measures spectral irradiances from zenith and nadir oriented sensors. An additional nadir looking sensor measures radiances. Measurements span the visible and near infrared (300 nm to 2200 nm) with a 2 nm to 3 nm spectral resolution for wavelengths shorter than 1000 nm and a 10 nm to 15 nm spectral resolution for longer wavelengths.
(Leipzig Univ.)
The spectrometer of the Munich Aerosol Cloud Scanner (specMACS) consists of two camera systems, both looking nadir, one in the visible/near-infrared (400 nm to 1000 nm), and another in the short-wave infrared (1000 nm to 2500 nm). The systems produce a spectrally resolved line image with 1312 pixels covering a 32.7º field of view in the visible/near infrared, and with 320 pixels covering a 35.5º field of view in the short-wave infrared.
(LMU München)
A broadband camera system with a filter to take broadband (7.7 μm to 12 μm) and narrow band images near 8.6μm, 10.8 μm; 11.6 μm; and 12 μm. The camera has 640x512 spatial pixesl for a 21.7° x 17.5° field of view. This gives roughly 6m by 6m spatial resolution for a target at 10 km distance. The camera operates betwen -60ºC and 100ºC with a sensitivity better than 0.05 K.
(Leipzig Univ.)
AVAPS dropsonde system using Vaisala RD-94 sondes to measure temperature with an accuracy of 0.2 ºC, humidity with an accuracy of 2 %RH, pressure with an accuracy of 0.4 hPa. Winds are derived from GPS position measurements with an estimated accuracy of 0.1 m/s. The receiver can track four sondes simultaneously. For the measured descent time of about 750 s from a drop altitude of 9.5 km, the capability of the receiver allows a sonde to be launched roughly every three and a half minutes.
(Leipzig Univ.)
Aircraft state variables, position, three-dimensional turbulent winds (from five hole probe on boom), humidity (diode laser), temperature and pressure.
Broadband radiometers for downwelling and upwelling irradiances in both the SW (< 4 μm) and LW parts of the spectrum.
(Leipzig Univ.)

Cabin and exterior configuration of HALO for the mission


HALO flights for this mission

Aircraft registrationDateTake off - Landing / UTTotal flight time / hFrom - ToMission #
D-ADLRyyyy-mm-ddhh:mm:ss - hh:mm:sshCODE - CODE1
D-ADLRDatehh:mm:ss - hh:mm:sshCODE - CODE2
D-ADLRDatehh:mm:ss - hh:mm:sshCODE - CODE3
D-ADLRDatehh:mm:ss - hh:mm:sshCODE - CODE4
D-ADLRDatehh:mm:ss - hh:mm:ssh
D-ADLRDatehh:mm:ss - hh:mm:sshCODE - CODE6
D-ADLRDatehh:mm:ss - hh:mm:sshCODE - CODE7
D-ADLRDatehh:mm:ss - hh:mm:sshCODE - CODE8
D-ADLRDatehh:mm:ss - hh:mm:sshCODE - CODE9
D-ADLRDatehh:mm:ss - hh:mm:sshCODE - CODE10
D-ADLRDatehh:mm:ss - hh:mm:sshCODE - CODE11

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