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An update on cloud dynamic and microphysics products derived from RASTA measurements during HYMEX-SOP1

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HAL Id: insu-01140560

https://hal-insu.archives-ouvertes.fr/insu-01140560

Submitted on 10 Apr 2015

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An update on cloud dynamic and microphysics products derived from RASTA measurements during

HYMEX-SOP1

Julien Delanoë, Jean-Paul Vinson, Christophe Caudoux, Marie Ceccaldi, Emmanuel Fontaine, Alfons Schwarzenboeck, Cyrille Flamant

To cite this version:

Julien Delanoë, Jean-Paul Vinson, Christophe Caudoux, Marie Ceccaldi, Emmanuel Fontaine, et al.. An update on cloud dynamic and microphysics products derived from RASTA measurements during HYMEX-SOP1. 8th HyMeX Workshop, Sep 2014, La Valletta, Malta. pp.P2.14, 2014. �insu-01140560�

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An update on cloud dynamic and microphysics products

derived from RASTA measurements during HYMEX-SOP1

Julien Delanoë1, Jean-Paul Vinson1, Christophe Caudoux1, Marie Ceccaldi1, Emmanuel Fontaine2, Alfons Schwarzenboeck2 and Cyrille Flamant1 1Laboratoire ATmosphère, Milieux, et Observations Spatiales (LATMOS), France

2Laboratoire de Météorologie Physique (LaMP), Université Blaise Pascal/CNRS/OPGC, Aubiére, France

HYMEX context

The airborne 95GHz cloud radar RASTA was operated on-board the Falcon 20 during HyMeX SOP1.1 (September/October 2012). In addition to the radar, state of the art in-situ microphysical probes, such as CDP, 2DS, CPI, PIP, and

Robust probe were deployed to characterize bulk and individual hydrometeor microphysics. The underlying idea was to combine radar and in-situ

measurements to infer cloud processes that originate precipitation. The

spatially limited detailed cloud description using in-situ measurements can be extended to the area covered by the radar.

RASTA instrument

Airborne cloud radar at 94 GHz (sensitivity ~-30dBz)

Doppler: it measures targets velocity of a sampled volume

Why several antennas?

Measure Doppler velocity along 6 different directions => cloud wind retrieval (WIND): U, V, W+Vt

Microphysical information (retrieve ice cloud properties) is retrieved combining the terminal fall velocity and the reflectivity (RadOnvar)

Products

One file per antenna (Instrument oriented)

•  L0 data (netcdf): file containing Z and Doppler velocity uncorrected. 1.2 s horizontal / 60 m vertical

•  L1 data (netcdf): file containing Z (calibrated) and Doppler velocity uncorrected. 1.2 s horizontal / 60 m vertical

•  L2 data (netcdf): file containing Z (calibrated) and Doppler velocity (unfolded) radar gates are geo-localised. Interpolation between upper/lower domain and correction of reflectivity near

the aircraft

Multi antenna products (variational technique)

•  3D cloud WIND: re-gridded data 1.2 s horizontal /120 m vertical •  Ice cloud microphysics (IWC etc) 1.2 s horizontal /120 m vertical

Related presentations and posters:

•  M4.3 - Intercomparison and evaluation of 3-D wind fields derived from airborne and ground-based radars during HyMeX, O. Bousquet, J. Delanoë

•  Th1.6 - Convection and extreme rainfall during the development of two intense Mediterranean cyclones in the HyMeX campaign, E. Flaounas, V. Kotroni, K. Lagouvardos, C. Claud, J. Delanoë, C. Flamant, E. Madonna, H. Wernli •  P1.7: A data assimilation experiment of RASTA airborne cloud radar data during HyMeX IOP16, G. Saussereau, O. Caumont, J. Delanoë

•  P2.11: Verification of Meso-NH forecasts of cloud structure and water content against remote sensing Observations, J.-P. Chaboureau, J. Delanoë

•  Th1.2: Deep convective clouds and convective overshootings characterization during HyMeX SOP1: a multi-instrument approach, J.-F. Rysman, C. Claud, B. Funatsu, JP Chaboureau, J. Delanoë, O. Bousquet

1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12 A A B B C C D D E E F F G G H H

banc RASTA2 angles

caillou 10/12/2013

Conçu par Vérifié par Approuvé par Date

1 / 1

Modification Feuille Date

vue latérale sens du vol >>>> vue de l'arrière

référence avion

oblique 23°2 arrière zénith 3°37 avant

oblique lat. 3°25 avant oblique lat. haut 25°4 droite

oblique lat. bas 24°6 droite

zénith 0°49 gauche

oblique lat. 4°22 arrière

nadir 3°61 arrière

oblique 26°8 arrière oblique 0°86 gauche

nadir 0°67 droite oblique 0°05 droite

0°37 droite par rapport au nadir

réf. avion 0°06 vers l'avant par rapport au nadir view from the

back

up transverse up backward

zenith

down transverse nadir

down backward a) b) c) 6 antennas, 3 downwards, 3 upwards

Calibration

RASTA nadir reflectivity is calibrated using the ocean surface return technique (Li et al. 2005). We use

data collected during the MT-Maldives campaign on the 22nd of December 2011 above Indian Ocean.

This flight was especially dedicated to the calibration of the radar as the aircraft was flown in clear sky

area. Microphysics: Variational technique (Radonvar): Vz+Z+Temperature => Dm (mean volume

diameter), IWC and W Knowing a priori

information derived from the microphysical

probes.

Once we know Dm, IWC and W other parameters are calculated using

parameterizations derived from in-situ measurements.

Two radiosondes were available before and after the 1:30 hour flight, Figures a, b, c represent the relative humidity, temperature and pressure profiles respectively. These profiles are used to calculate the two way attenuation at 94 GHz presented in panel d. Note that HYMEX and MT-Maldives system configurations were similar and therefore we use the same calibration

constants.

Figure e illustrates the normalized ocean surface echo (σ0) as a function of the incidence

angle once the nadir reflectivity has been calibrated and compared to simulated ocean returns for different wind speeds.

Example of L2 data for nadir and zenith

•  Top panel represents the calibrated/corrected

reflectivity

•  Middle panel represents the Doppler velocity (unfolded and corrected from aircraft velocity)

•  Bottom panel shows the classification of the data (cloud, ground, interpolated reflectivity at aircraft altitude…)

Wind field retrieval:

Dots at aircraft altitude correspond to in-situ measurements

Vz is the sum of the terminal fall velocity (Vt) and the vertical air

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