3rd International Conference on GPS Radio Occultation ICGPSRO 2016, Taipei, Taiwan 9–11 March 2016

Characterization of cyclones and volcanic clouds with GPS

radio occultation

A. K. Steiner1, R. Biondi2,1, G. Kirchengast1, and T. Rieckh3,1

1 Wegener Center for Climate and Global Change (WEGC), University of Graz, Austria 2 Istituto di Scienze dell´Atmosfera e del Clima (ISAC), Lecce, Italy

3 COSMIC Project Office, UCAR, Boulder, Colorado, USA

andi.steiner@uni-graz.at

GPS RO data

Year

# oc

culta

tions

PROS • High vertical resolution • Global coverage • High accuracy • Long term stability • Cheap technology • Independent of weather conditions • Independent of sensor • Independent of processing scheme

CONS • Relatively low horizontal resolution • Moist air ambiguity (low-mid tropo)

background info for T, p, e

FUTURE • COSMIC-2 will increase the

number of daily occultations with better coverage of the tropical area

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Method – RO reference climatology

Interpolation: of RO profiles to a common vertical grid of 100 m

Averaging: profiles collected in the period 2001 to 2012 were binned at 5 x 5 degree resolution and averaged to monthly means

Sampling: the final RO reference climatology was sampled at 1 x 1 degree resolution in latitude and longitude

July RO distribution Full archive RO distribution

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Method – cloud top detection

Anomaly computation: difference profiles with respect to climatology for bending angle BA and temperature T

Convective system structure: inversion below cloud top, cooling (T min) corresponding to cloud top

Cloud top height detection: BA max anomaly (>3% within 2km), T min anomaly

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Method – demonstration

Cloud top detection of convective clouds and tropical cyclones Confirmation with CALIPSO (lidar) data

High correlation btw cloud top heights from RO and CALIPSO

Biondi et al., Thermal structure of intense convective clouds derived from GPS radio occultations, Atmos. Chem. Phys., 12, 2012.

Biondi et al., Tropical cyclone cloud-top height and vertical temperature structure detection using GPS radio occultation measurements, J. Geophys. Res., 118, 2013.

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Cyclones cloud top detection with RO – data set

Co-location of tropical cyclones (TC) best tracks and GPS RO

Period: 2001–2012 within <6 hours and <600 km

Number of selected cases: 20732

~500 ROs co-located within 10 minutes/100 km from the TC track

RO classification by ocean basin and storm intensity

Sub-selection of tropical and extra-tropical cyclones

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Cyclones – thermal structure

West Pacific Ocean South Pacific Ocean

Cloud top height & temperature

Different characteristics over different ocean basins

Warmer troposphere, cold cloud top during TC

NH (W.Pacific) warming above cloud top vs SH

Coldest anomalies & highest cloud tops over South Pacific and Indian ocean

Colder and higher cloud tops of storms in the SH than in NH

Double tropopause, convection uplift 7

Possible overshooting into the stratosphere Cloud top height > MM tropopause height High percentage in SH ocean basins 40-50% Western Pacific for high intensity storms 30-50% WP storms: Apr-Dec at 0-30°, Aug-Oct at 30°-40° Overshootings in green and magenta

Cyclones – overshooting

Hcoldest_std > Hmm_trop + Hmstd_trop Hcoldest_std+1 > Hmm_trop + Hmstd_trop + 1 km *

West Pacific Ocean

0-20°

20°-30°

30°-40°

*

Biondi, R., A. K. Steiner, G. Kirchengast, and T. Rieckh, Characterization of thermal structure and conditions for overshooting of tropical and extratropical cyclones with GPS radio occultation, Atmos. Chem. Phys., 15, 5181–5193, doi:10.5194/acp-15-5181-2015, 2015

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Volcanic cloud top detection – method

OMI SO2 data AIRS/IASI ash index

Volcanic cloud type, discriminate against water clouds

SO2 observations (UV-Vis) from OMI instrument

Ash observations from IR sounders AIRS/IASI

Select RO observations in volcanic cloud area

Cloud top detection in BA and T anomaly profiles

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Volcanic cloud top detection – case study

Case study – Nabro 2011 & Puyehue 2011

Nabro, Eritrea (13.37°N, 41.70°E) 12 Jun 2011 mainly SO2 cloud 214 RO profiles to 20 days after eruption Puyehue Chile (40.35°S, 72.07°W) 5 Jun 2011 mainly ash cloud 1022 RO profiles and

Volcano area – climatological conditions

Climatological normal conditions in volcano areas Monthly mean T and BA anomaly profiles averaged over 2007–2013

Puyehue May/June Nabro May/June

mean May stDev May mean June stDev June

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Dust cloud May to Sep, pre-monsoon activity

Convection

Volcanic cloud – thermal structure

RO profile in volcanic cloud Temperature and bending angle anomalies Puyehue June 2011

Cloud (IASI/AIRS) GPS RO CALIPSO track

-10 -8 -6 -4 -2 0 2 4 6 8 100

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Anomaly [Temp in K & Bending Angle in %]

Altit

ude

abov

e m

sl [k

m]

Bending angleTemperature

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CALIPSO

Case study – Puyehue 2011 (ash eruption)

Thermal structure before and after volcanic eruption Detection of volcanic cloud top height for Puyehue cooling in mid-upper troposphere (~11 km)

before (May 2011) after (5-30 June 2011)

Biondi, R., A. K. Steiner, G. Kirchengast, H. Brenot, and T. Rieckh A novel technique including GPS radio occultation for detecting and monitoring volcanic clouds, Atmos. Chem. Phys. Discuss., 1–26, doi:10.5194/acp-2015-974, in review, 2016

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Case study – Nabro 2011 (SO2 eruption)

Thermal structure before and after volcanic eruptions Detection of volcanic cloud top height for Nabro warming in lower stratosphere (16.3 km) before (1-11 June 2011) after (12-14 June 2011)

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Thermal structure after Nabro eruption stratospheric warming months after the eruption (hydrated sulfate aerosols)

before eruption

after eruption

Case study – Nabro 2011 (SO2 eruption)

Conclusions

GPS RO is well suited for

Cloud top height detection

Tropopause height determination

Detection of possible overshooting conditions

Characterization of thermal vertical structure

Improving the detection and monitoring of cyclones

and volcanic clouds, and supporting warning systems.

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The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement n°328233.

Thank you

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Within these fields there are still many unsolved issues making this school fundamental for creating a new generation of scientists able to use the synergy of several different instruments and techniques for supporting policy makers, early warning systems and aviation safety.

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