NicholasEDKINS,Werner SCHMUTZ,Luca EGLI,Roger DAVIES,Teruo AOKI,and GregM cFARQUHAR

1The University ofAuckland,Victoria StreetWest,Auckland 1142,New Zealand

2Physikalisch-MeteorologischesObservatorium Davos,World Radiation Center,Dorfstrasse 337260 DavosDorf,Switzerland

3Okayama University,1Chome-1-1 Tsushimanaka,KitaWard,Okayama,Okayama Prefecture 700-0082,Japan

4University of IllinoisatUrbana-Champaign,Champaign,Illinois61820,USA

The InternationalRadiation Sym posium 2016

NicholasEDKINS∗1,Werner SCHMUTZ2,Luca EGLI2,Roger DAVIES1,Teruo AOKI3,and GregM cFARQUHAR4

1The University ofAuckland,Victoria StreetWest,Auckland 1142,New Zealand

2Physikalisch-MeteorologischesObservatorium Davos,World Radiation Center,Dorfstrasse 337260 DavosDorf,Switzerland

3Okayama University,1Chome-1-1 Tsushimanaka,KitaWard,Okayama,Okayama Prefecture 700-0082,Japan

4University of IllinoisatUrbana-Champaign,Champaign,Illinois61820,USA

1.Overview

The 2016 International Radiation Symposium,a joint venture between the IRC(International Radiation Commission)and IAMAS(International Association of M eteorology and A tm ospheric Sciences),took place at the University of Auck land from April16th to 22nd.Thew ide scope of atmospheric radiation research was apparent,w ith focuses ranging from theplanetary to theparticulate,and from thehourly to themillennial.The symposium,which was attended by 268scientists from 28 countries,providedan excellent forum for the exchangeof know ledgebetweenmodelersand experimentalists.(Fig.1)

Two awardswere presented by the IRC:the Young ScientistAward,to Zhibo ZHANG(Fig.2),and theGold Medal Award,to Teruyuki NAKAJIMA(Fig.3).Both gavewellreceived keynote talksafteraccepting theirawardsattheconferencedinnerat the Auckland Museum.

2.Plenary sessions

The four keynote talks,in addition to the award w inners’presentations,were the highlight of the conference.Each speaker summarized an importantarea of radiation research, generating several questions and a great deal of discussion afterwards.

Fig.1.IRS 2016 group photo.

David DINER talked about the unique advantages of multi-angle imaging,such as the ability to detect thin hazes by looking through a largerairmass,and reported thatM ISR w inds can significantly improve weather forecasting.Healso discussed theMAIA(Multi-Angle Imager for Aerosols) project,which aims to determ ine the impact of aerosols on human health by linking satellite and epidem iologicaldata.

Martin WILD reported several advances in the understanding of theglobalenergy balance.Henoted that themultimodelmeanof theclear-skyenergybudgetinCM IP5 agrees wellw ith observations,but the variationsbetween individual m odels are large.Separate energy balanceswere calculated for the land and ocean,and these brought the value for latent heat to w ithin the error bars of the observations of the precipitation community,going someway toward solving a long-standing discrepancy.

Richard McKENZIE gavea comprehensive review of all the relevant aspects of current research in the field of solar UV radiation.He highlighted thework done at Lauder on ozonemeasurementand noted that New Zealand has the highest ratesof skin cancer in theworld.

Lesley GRAY also gave a talk covering solar UV,in w hich she described how the surface response to changes in solar radiation is a com plicated m ix of“top-down”and“bottom-up”effects.The effectsof the 11-year cycle are reasonably clear in them iddle atmosphere,but their potential influence on the circulation of the lower atmosphere,affecting surface climate,ismuch harder to understand.

Fig.2.Young Scientistwinner Dr.Zhibo ZHANG.

Fig.3.IRSGold Medal winner Prof.Teruyuki NAKAJIMA and IRC presidentProf.Werner SCHMUTZ.

3.General rem otesensing

At present,the radiative transfer model is usually the bottleneck in a physical retrieval algorithm.Xu LIU presented amodel,PCTRM(PrincipalComponent-based Radiative TransferModel),which allows spectral data to be compressed through eigenvector representation,allow ing for improved speed.

Bing LIN presented a method to determ ine the surface pressure rem otely using thedifferentialabsorption ofoxygen.

Marwan KATURJIshowed resultson the remoteinfrared sensing of eddies.

4.Understanding climateusing satellitedata

The phenomenon of brightening in Europe isw idely observed,but,asArturo Sanchez-LORENZO reported,itisstill notcaptured fully by satellites.Itwassuggested thatthismay be due to tem porally varying aerosols.

B.J.SOHN showed that including a representation of atmospheric stability allow s better modeling of the Pacific Walker Circulation and ElNi˜no-likeevents.

Dominique BOUNIOL documented the contribution of themesoscaleconvectivesystem to theenergyandwaterbudgetsof the tropics.

The negative feedback between cloud-top heightand surface temperaturewas investigated by AbhnilPRASAD using measurements from CALIPSO.

5.Sou thern Ocean and An tarctica:Radiation,clouds, aerosolsand sea-ice

Looking downwards from satellites and upwards from the surface of the ocean,a network of observations ishelping to improveourunderstanding of the Southern Ocean and Antarctica.

On the sea-borne side,Makoto KUJIused observations from shipboard whole-sky cameras and ceilometers to producemapsof cloud fraction for the region between Japan and the Antarctic.

YuekuiYANG found thatsnow blow ing in the Antarctic can have an appreciable radiative effect—about5W m-2.

Luca PALCHETTInoted the lack of observations in the far infrared spectrum of surface longwave radiation over the eastAntarctic plateau.

Roger DAVIES,who isalso a LocalOrganizer(Fig.4), presented observations from M ISR of the cloudmorphology over the South Pacific,and discussed them icrophysics that could be inferred from these.The aim was to determine whether therewereobservabledifferencesbetween thehem ispheres,which was found to be the case.

6.Par ticle rad iative properties

M ichael KAHNERT,the invited speaker,presented a novelparticlemodel for the lightscattering propertiesof heterogeneousaerosolsw ith complex shapes.The performanceof this“core-grey-shell”model in predicting scattering propertieswas investigated.

Another highlightwas the talk given by Konrad KANDLER,who presented 3D images,obtained through scanning electronmicroscopy,ofm ineraldust inwhich severaldifferentmineralswereaggregated.

Fig.4.Localorganizer Prof.Roger DAVIES.

7.Radiation budgetand forcing

The radiation budget and radiative forcing session addressed the princip le of the greenhouse effect and global warm ing.In particular,the specific contributions of energy inputand output in the Earth’satmosphereon a globalscale werepresented.MartinW ILD estimated theamountof longwave radiation w ith high accuracy and w ith comparison to ground-basedmeasurements.

Norman LOEB described the failureof land surfacemodels thatdo notallow for divergence from themean climatology of a region to account for droughts,w ith reference to the m illennium droughtrecently experiencedby Australia.

Two paperswere presented on the brightening and dimm ing effectsof air pollution over China and Japan.

8.Weather,climateand environmentapplications

As Allen HUANG noted,satellites providemost of the forecastskill for currentweather predictions.Heoutlined the useof ahyperspectralenvironmentalsounder fornearcasting severeweatherevents,and described the processof forecasting volcanic ash for aviation applications.An overview of thestateofhyperspectral IRobservationswasgivenby David Tobin.

Yunfei FU investigated aerosol–cirrus interactions,and found that the distance to the nearest cirrus cloud can have a 20W m-2effecton theupward radiative forcing.

Steven PLATNICK presented a suite of common algorithms forMODISand VIIRSobservations,whichwereproduced in order to ensure continuity in the cloud climate data record. HuaZHANG presenteda calculation of the totaleffective radiative forcing of anthropogenic aerosols,while Toshihiko TAKEMURA exam ined the SO2aerosol effect,specifically in Asia.Talkswerealso given on cloud–radiation feedbacks inmonsoon conditionsand a coupled convection–cloud fraction parameterization.

9.Radiative transfer theory and m odeling

A focusof this session was the new techniquesand algorithms developed for the retrieval of optical properties from cloudy scenes,a taskwhich presentsmany uniqueproblems.

EliMLAWER introduced an updated version of RRTM, which makes use of advances in computing architecture to improve the speed of radiation calculations in GCMs.Improved radiative transfermodelswere also presented by Anthony DAVISand Jerome VIDOT.

Sheng-Hsiang WANG highlighted shortcomings in the assumption of uniform aerosol optical properties.A transportw ith two layers was observed and a two-layer aerosol modelwas developed to explain this.

10.Ice clouds:Light scattering,radiometric polarimetric rem otesensing,and radiation

The invited speaker,Dr. Brian KAHN,spoke about retrieving ice-cloud properties from hyperspectral infrared observations.Observations from AIRS were found to be very usefulin characterizing ice clouds,andmulti-sensorapproaches show a lotof prom ise.

W hile observations have been successful,there is p lenty of work to be done on the theory of light scattering by ice crystals,particularly in the resonance region(where the size of the scattering particle is similar to the incident wavelength),and effects such as photon tunneling need to be further explored.Thismay require a novel physical–geometric opticsapproach.

11.Surfacemeasurementsand f eld experiments

Von WALDEN presented the results of the ICECAPS (Integrated Characterization of Energy,Clouds,A tmospheric state,and Precipitation at Summ it)experim ent,which aim ed to determine the effectof cloudson Greenland’s surface energy budget.

A lively discussionwassparked by invited speaker Julian GR¨oBNER’s talk,inwhich hedescribed an efforttomeasure cloud fractions24 hoursa day,using an infrared cameraand agold-coated sphericalmirrorobserving 180°of thesky during day and night.

M ikhail KRINITSKIY described another method for determ ining cloud fraction,which distinguishes between cloudy and clear sky using only color saturation.

Improved measurements of aerosol–cloud interaction, aerosol optical depths,and the solar spectrum were also reported,and updatesweregivenonseveralongoingcalibration and intercomparisonprojects for radiometers.

12.Ocean op tics

KnutSTAMNES,Jacek CHOWDHARY and J¨urgen FISCHER allspoke on the topic of the retrievalof optical propertiesusing satellitemeasurementsof ocean color.

Neural networkswere used to train the algorithms presented in several talksat the conference.In thissession,success was reported in their use form erging data collected sim ultaneously by different instruments,and for retrieving parameters from SeaW iFS(Sea-View ing W ide Field-of-View Sensor),greatly improving thespeed of the retrieval.

13.Solar UV radiation

Several authors presented the results of UV measurements over a period of about20 years,in both oral presentationsand posters,including overviewsby invited speakers GermarBERNHARD and Ben LILEY.Themeasurementsof broadband radiometers in general show no significant trend in recent decades.However,a strong daily and annualvariability of UV exposure caused by clouds and aerosols has become apparent,and the research focus has shifted to this area.

Finally,the consequences of UV exposure for both humans and m aterialswere discussed.For humans,a balance between the positive(vitam in D production)and the negative (skin cancer)needs to be struck,and the research from this sessionw illaid in this.

Acknow ledgements.We thank Ping YANG and Mario BLUMTHALER for their contributions,and K ipp&Zonen,EKO Instruments,and the Department of Physics of the University of Auckland for their sponsorship.

:Edkins,N.,W.Schumutz,L.Egli,R.Davies,T.Aoki,and G.McFarquhar.Adv.Atmos.Sci.,33(12),1325–1328,

10.1007/s00376-016-6180-1.

∗Corresponding author:Nicholas EDKINS

Email:nedk437@aucklanduni.ac.nz

©Institute of A tm ospheric Physics/Chinese Academ y of Sciences,and Science Press and Springer-Verlag Berlin Heidelberg 2016