레이저레이더 ( 라이다 ) 를이용한구름주변의기상정보획득 한국원자력연구소양자광학부김덕현
HISTORY 1994-1995 : Study on Stratospheric (15-40 km) Ozone Measurement 1996-1998 : Development of Mobile Pollution LIDAR System - Trophospheric Range (1-3 km) -Ozone, SO 2, NO 2 - Mobile and Scanning Function 1998-1999 : Development of Micropulse LIDAR System - Trophospheric to near Stratospheic Range (1-20 km) - Aerosol Measurement 1999-2000 : Study on Meteorological LIDAR - Water Vapor Density - Temperature 2000-2003: - Aerosol Sizing Measurement Using Multiwavelength Lasers - Wind Velocity (Doppler LIDAR) - Military Applications (Chemical & Biological Detection) 2004 2006 : - 기상라이다 ( 온도, 습도, 에어로졸측정용라이다 ) - 도플러라이다기초연구
발표내용 라이다의원리및장치구성 - 라이다와레이더 - 산란이론 - 라이다의종류 물방울의크기변화측정 - 파장에후방산란계수측정법 - 파장에따른물방울의산란계수 수증기와물방울의상변화측정 - 수증기, 물방울,.. 등의라란산란신호측정 - 물의상변화가일어나는위치및온도측정
라이다? 라이다 (LIDAR : Light Detection And Ranging) (Laser Identification And Ranging) 250 nm 부터 10 um 영역의파장을사용 - 작은입자 (1/λ 4 ~1 ), 분자에의한 Rayleigh(1/λ 4 ) 산란극대화 - 비탄성산란극대화 (1/λ 4 ) - 비교적근거리 ( 고도 : 80 km) 원격 / 직접 ( 실시간 ) 측정, 3 차원 scanning, 구름, 바람장, 온도, 에어로솔습도, 에오솔모양, 레이더 : 망원경라이다 : 현미경
고도에따른기상인자측정한계 Solium : wind, temperature Rayleigh Temperature Incoherent Doppler Coherent CO 2 Doppler Raman water vapor DIAL Water Vapor PRR temperature
Electro-Magnetic Wave Scattering by molecule or particle 원리 : electric dipole interaction 입자의산란특성 분자의회전란만특성 Size parameter (n=1.33, size parameter = π3d/λ)
레이저에의한대기의산란파장특성 1000 cm -1 100 cm -1
Various LIDAR Techniques Mie Scattering LIDAR Raman Scattering LIDAR Doppler Lidar LIDAR Differential Absorption LIDAR (DIAL) hν virtual level λ off λ on Excited level λ Raman hν λ laser Ground level vibrationally excited level λ off Ground level Elastic scattering from particles Large cross sections Non-selectivity Particle sizes can be estimated by using multiwavelength laser sources Inelastic scattering Small cross sections Selectivity by frequency shifts Useful for the atmospheric gases existing with large amount (N 2, O 2, CO 2, H 2 O, etc) Small wavelength Change Seeded Nd:YAG Laser : 0.0045 cm-1 Rayleigh Shift by Thermal Broadening : 0.063 cm-1 Differential attenuation of two laser beams is evaluated from their backscattered signals. ( l on : resonance wavelength, l off : detuned wavelength ) Very sensitive, useful for pollution gas measurement 0.05 cm-1 equal to 400 m/sec or 1.5 GHz Complicated experimental setup (expensive)
실험장치의구성 1 355nm 의회전라만산란신호 ( 질소 ) 와공기분자와에어로졸에의한탄성산란신호 (355nm) 를받아서 355 nm 에서의에어로솔의후방산란신호를얻을수있는채널 532 nm 의의한회전라만산란신호중에서온도에비례하는신호채널 (J=12) 와온도에반비례하는채널 (J=6), 그리고공기분자와에어로졸에의하여산란되는탄성산란신로채널 3 개로나눈다. 최종적으로는온도와에어로졸의후방산란신호를얻는다. 수증기, 물방울, 그리고기타상태의물의진동라만산란신호를얻는채널은 32 개의채널로구성되며, 각채널은수증기, 물방울 ( 수소결합 ), 수소결합이없는물방울, 물방울의표면에존재하는물의라만산란신호그리고이러한물의라만산란신호를규격화 (Normalization) 시키는질소의진동라만산란신호를얻는채널로구성된다.
실험장치의구성 2 PMT N 2 Dichroic Mirror Holographic Notch filter 401-410nm 355nm CHS1 (32) 532nm CHS2(3) CHS3(2) Mirror Rot-Raman1 Rot-Raman2 λ 6 λ 5 λ 4 PMT PMT PMT PMT H 2 O(R) H 2 O(v) H 2 O(l) Surface PMT PMT PMT Temp J=2~6,-6~-2 J=7~12,-12~-7 AEROSOL 1 Aerosol PMT PMT J=-12~+12 Temp AEROSOL2 λ 3
물의변화측정방법두가지소개 Korea Atomic Energy Research Institute 1. 물방울의크기변화측정을통한수증기의상변화관측 - 광학적굴절율이일정한동일물질에대하여적용가능함 - 정확한후방산란신호획득 ( 회전라만신호 + 탄성산란신호 ) - 서로다른파장에서얻은후방산란신호비를구함 2. 수증기와물방울의라만산란측정 - 물방울 (a), 물방울 (b), 물방울 (c), 그리고수증기의서로라만신호를측정한다. - 각각의신호크기비를얻음으로써상대적인양을얻는다. - 두물질간의산호변화 (phase 변화 ) 를구한다. - 보조적으로주위의온도를측정함 후방산란계수에후방산란계수에따른따른입자입자크기 Liquid water Water vapor Filter 1 Filter 2 396 400 404 408 412 Wavelength, nm
물방울크기변화측정방법
상세물방울크기변화측정원리 공기 먼지 P 1 = C Z 2 β air e 2α z P 2 = C Z 2 β air + aerosol e 2α z 신호분리 (P1 & P2)
같은파장그러나선택적 산란신호실례 500 400 공기 Height(x37.5m) 300 200 공기 + 에어로졸 100 Rotation Raman Elastic Ratio ( Elastic/Rotation) 1E-3 0.01 0.1 1 10 100 Y Axis Title
구름주변에서 Backscattering Ratio (BR) Lidar Signal 1E7 1000000 100000 10000 1000 100 10 라이다신호 355 Raman 355 Elastic 532 Raman 532 elastic 두파장에서얻은라이다신호로부터각각의파장에서후방산란신호를얻고이로부터파장에따른후방산란계수를얻으면작은물방울입자의크기가구름주변에서어떻게분포하는지알수있다. 1 Backscattering Coeff. & BR Value 0.1 10 1 0.1 0.01 1E-3 1E-4 0 200 400 600 800 1000 Height(x37.5m) 후방산란신호의비 355nm 532nm BRx5.04 Boundary layer 에서는 BR 값이 0.6 정도되나, 구름에서는그값이증가함을알수있다. 즉입자의크기가구름에서크다는것을말해준다. 궁극적으로이러한측정을실시간으로빠른속도로측정할수있다면, 굵은입자의구름이생기기전에미리그크기변화를알수있다. 40 60 80 100 120 140 160 180 200 220 240 260 280 300 Height(x37.5m)
구름주변에서 Backscattering Ratio (BR) 고도에따라서 BR 값이점점커지는것으로미루어구름알갱이의크기가커지는것을알수있다.
시간 / 고도에따른황사입자의크기 (BR) 변화 4 월 17일전국적으로황사가출현한날초저녁엔 BR 값이낮은지역에선 1 에서높은고도에선 0.2 까지낮아짐. 즉낮은고도엔큰입자들이많이존재하고높은고도에서는작은입자들이존쟈함그리나 10 시이후늦은시간부터는고도에따른입자의크기분포에뚜렷한구별없음그리고에어로졸의절대밀도 ( 후방산란계수 ) 는비슷한것으로미루어황사밀도는변화가없음 β ΑΕ /β Μο and BR 1000 100 10 1 3555nm 532 nm BR 4 월 7 일초저녁 and BR β ΑΕ /β Μο 1000 100 10 1 늦은저녁 355nm 532 nm BR 0.1 0.1 0.01 18 27 36 X Axis Title 20 40 60 Height(x37.5m)
다채널라이다를이용한물의상변화연구
다채널물라만라이다의목적 최종목적 : 물의상변화실시간관측을통한실시간대기온도측정을통한구름형성메커니즘이해및구름의이동경로추적모델링에서중한입력파라메타의다차원제공 본연구의범위 Designing & manufacturing Multi-channel Raman lidar Measuring multi channel water vapor (liquid water ) Raman signal Identify the difference of Liquid water/water vapor channels
Why Multi channel? Complexity of Raman scattering spectrum depend on the number of OH bond, structure and temperature Raman spectrum of surface water (prl, vol. 70, 2313p) Raman spectrum for different phase (J. chem. Phys. Vol.77, 47p)
Key point in designing Raman system
시스템디자인아이디어및개략적인구성 구름측정에서는다른라만신호측정보다구름에의한탄성산란신호의제거가매우중요하다. 일반대기상태에서두신호의비 ( Elastic : Water 라만 = 1: 10-5 ) Double grating Monochrometer(10-8 ) + Holographic notch Filter ( 10-6 ) -> 10-14 Blocking ratio 탄성산란신호차단효과를얻을수있다. Optical Fiber Holographic Notch Filter Optical Fiber Lens(d=100mm,f=1000mm Lens(d=50mm,f=500mm Grating (100x100mm,1800g/mm) BA=21.1 degree 32 channel Photon counter Grating (50x50mm,1800g/mm)
전체시스템구성 355nm 532nm Holographic Notch filter 32 channel Rot-Raman1 Water vapor/liquid water Nitrogen Raman filter PMT J=2~6,-6~-2 Temp Temperature Aerosol backscattering Coeff.@532nm PMT J=7~12,-12~-7 PMT concentration of water per dry air( g /kg ) AEROSOL 1 Aerosol
파장검정 (CALIBRATION) 방법및전형적인 32 채널라만신호 Calibration with Mercury Lamp Channel 17 : 404.6 nm(3453 cm -1 ) Channel 22 : 407.8 nm(3647 cm -1 ) Raman signal 2 0 5 10 15 Channel(wavelength) Ch12 Ch19Ch25 Ch29 20 25 30 20 60 40 Height(x37.5m) Channel 12 : Liquid 1 Channel 19 : Liquid 2 Channel 25 : Vapor 1 Channel 29 : Vapor 2
본연구발표에서정의한물방울 / 수정기의용어정의 Liquid Bulk Water - Open : water Hydrogen bonded molecule : overtone of bending vibration of molecular water : 3250 cm -1 ( liquid1 ) - Closed : symmetric and anti-symmetric stretching vibration : 3450 cm -1 ( liquid2 ) Low temperature ice water ( completely coupled water) 3150 cm -1 Water molecule 3652 cm -1 ( Vapor1 ) Surface water Include Broken H bond > 3700 cm -1 ( free OH bond) ( vapor2 )
물의라만스펨그럼 개발된 32 채널수신장치로얻은라만스펙트럼 ( 온도 : 25 도 ) 기존의장치를이용하여얻은라만스펙트럼 0.020 0.018 Liquid water Signal& fitting 0.016 0.014 0.012 0.010 0.008 0.006 0.004 0 5 10 15 20 25 30 35 Channel 2832 cm -1 4035 cm -1
맑은날얻어지는전향적인라이다신호및그비 (ratio) (Oct. 2, 2006) All of the lidar signal have the same profile : constant Lidar signal gives the concentration of each phase liquid water(liquid1) and Vapor2 signals are quite low and similar shape Lidar Signal 100 10 1 Liquid1 Liquid2 Vapor1 Vapor2 Ratio of Lidar signal 1 0-1 Liquid1/Vapor1 Liquid2/Vapor1 Vapor2/Vapor1 1000 2000 Height(m) 1000 2000 Height(m)
Traditional Raman spectrum on cloudy day (Sep. 25, 2006) Liquid1 lidar signal is strongly depend on the cloud. Vapor1, liquid2 and Vapor2 are different from each other Vapor2 and liquid 2 have similar shape aerosol backscattering coeff. 4 3 2 1000m Lidar signal and ratios 3 2 1 liquid1/vapor1 liquid2/vapor1 vapor2/vapor1 1000 2000 Height(m) 600m 1000 2000 Height(m)
구름이있는날얻어지는전형적인라만스펙트럼 ( Sep. 19, 2006) Lidar signal (normalized with nitrogen Raman)(g/kg) Ratios 1 10 liquid1/vapor1 liquid2/vapor1 vapor2/vapor1 Lidar Sugnal 0.1 Liquid2 Vapor1 Ratio 1 0.01 Cloud 0.1 500 1000 1500 2000 2500 Height(m) 2250m 0 1000 2000 3000 Height(m) 2000m
그름주변에서의온도변화및구름의밀도 ( Sep. 25, 2006) 100000 6000m 10000 Lidar Signals 1000 100 10 Nitrogen Raman(387nm) Rotational Raman(J=6) 0.6 0.5 1 0.1 Elastic (532nm) Rotationa Raman(J=12) temperature 1000 2000 3000 4000 5000 6000 7000 8000 Height(m) Temperaure 0.4 0.3 0.2 0.1 5500m 4000 5000 Height(m) 5500m
물의밀도와온도상의변화 Sep.9, 2006 1 C1 C2 C3 C4 PC1 PC2 0.4 0.1 Signal and ratio 0.01 Liquid2 Vapor1 Liquid2/vapor1 Liquid2/vapor1 1E-3 0.2 1E-4 1000 2000 3000 Height(m) 1000 2000 3000 Height(m)
Summary 기상파라메타측정용라이다시스템을개발 물의라만신호를나타내는각채널은대기상태에따라다른특성을지님을확인. 물의상변화는구름근처에서일어난다. ( 구름내부보다는, 외곽에서물과수증기의비가크다 ) 구름의성장혹은연무가발달하여구름을형성하는경우공간적으로그크기분포를알수있기때문에밀도를측정하는것보다. 각지점의물의상태 ( 상, 물방울크기 ) 를파악하는데도움이된다. 구름주변에서온도를관측할수있었고, 때론구름내부보다가장자리에서온도가더낮은경우도관측할수있었다. 이러한기상라이다에서얻어지는정보는, 직접적으로는온도, 습도정보제공, 공기의이동경로에대한정보를제공할수있을것으로판단된다.
이상한구름 ( 에어로졸, 갈색구름??) Sep.29, 2006 Concentration of water ( g/kg) 0.05 0.04 0.03 0.02 0.01 liquid2: 21:00 liquid2: 23:00 Difference of Temperature 0.04 0.02 0.00-0.02-0.04-0.06 0.00 1000 2000 Height(m) -0.08 500 1000 1500 2000 2500 3000 Height(m) Ratio(v2/v1) 1 0 21:00) 23:00 Aerosol backscattering Coeff. 25 20 15 10 5 E G 0 1000 2000 3000 500 1000 1500 2000 Height(m)
Time dependence of water concentration and phase distribution(1): peak is not cloud Sep.29, 2006???? Contration of Water(g/kg) 0.09 0.00 Loquid1 : 21:00 Liquid1 : 23:00 600 1200 1800 Height(m)? Ratio 2.4 2.0 1.6 1.2 ch12/ch25 X Aerosol backscattering Coeff. 25 20 15 10 5 21:00 23:00 0.8 0 300 600 900 1200 1500 Height(m) 1000 2000 3000 Height(m)
Time dependence of water concentration and phase distribution(2) peak is not cloud? Sep.29, 2006 Concentration of water ( g/kg) 0.05 0.04 0.03 0.02 0.01 liquid2: 21:00 liquid2: 23:00 0.00 1000 2000 Height(m) 0.16 21:00 23:00 25? Liquid2/vapor1 0.08 0.00 Aerosol backscattering Coeff. 20 15 10 5 21:00 23:00 20 40 X Axis Title 0 1000 2000 3000 Height(m)
Aerosol density change very quickly & Temperature change (Sep.29, 2006) E F G 10 Y Axis Title 1 0.1 0.6 X Axis Title E F G 100 0.5 Y Axis Title 0.4 X A xis T itle 100