Lecture 44. Constituent Lidar (4) Multi-wavelength Raman DIAL & DOAS and MAX-DOAS

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Lecture 44. Constituent Lidar (4) Multi-wavelength Raman DIAL & DOAS and MAX-DOAS q Review conventional DIAL q Raman DIAL for Ozone Measurement q Rotational Vibrational-Rotational (RVR) Raman DIAL q Multiwavelength (Raman) DIAL q Differential Optical Absorption Spectroscopy (DOAS) 1

q DIAL lidar equation LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Lidar Equation for DIAL [ ] P S (λ,r) = P L (λ) β scatter (λ,r)δr % ' & A R 2 (. R 1 * exp 2 α (λ,r)dr ) / 23. R 1 exp 2 σ abs (λ,r)n c (r)dr / 23 η(λ)g(r) [ ] + P B Extinction caused by interested constituent extinction (absorption) Extinction caused by other molecules and aerosols q Compared to resonance fluorescence, the main difference in DIAL is that the backscatter coefficient is from the elastic-scattering from air molecules and aerosols, not from the fluorescence of interested molecules. β Scatter (λ,r) = β aer (λ,r) + β mol (λ,r) q The parameter in the DIAL equation α (λ,r) = α aer (λ,r) +α mol (λ,r) +σ IG (λ,r)n IG (r) Aerosol Extinction Air Molecule Extinction Interference gas absorption 2

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Conventional DIAL Ozone Measurement λ ON = 288.9nm λ OFF = 299.1nm 3

n c (R) = LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Conventional DIAL Solutions 1 2Δσ abs 1 Δσ abs. & ln P S(λ OFF,R) P B ) 2 ( + ' P S (λ ON,R) P B * d & ln P L(λ OFF )η(λ OFF )) / ( + 3 dr ' P L (λ ON )η(λ ON ) * & ln β aer(λ OFF,R) + β mol (λ OFF,R)) ( + 1 ' β aer (λ ON,R) + β mol (λ ON,R) * 4. [ α aer (λ ON,R) α aer (λ OFF,R)] 2 / + [ α mol (λ ON,R) α mol (λ OFF,R)] 3 1 + [ σ IG (λ ON,R) σ IG (λ OFF,R)]n IG 4 All terms non-range dependent vanish after the derivative d/dr Introducing large error when large aerosol gradient or IG exists4

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Ozone Raman DIAL [Ulla Wandinger, Raman Lidar chapter, 25] 5

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Conventional Raman DIAL for O 3 Measurements in Clouds On- Resonance Off- Resonance Conventional Raman DIAL uses two primary wavelengths transmitted (e.g., 38 and 351 nm) into the atmosphere and ozone is calculated from the differential absorption of the corresponding Raman return signals of molecular N 2 (e.g., 332 and 382 nm).

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Raman DIAL Equations q Raman channels (e.g., from N 2 Raman inelastic scattering, instead of elastic scattering from air molecules or aerosols), [ ] ON P S (λ Ref,R) = ON PL (λ ) ON ON % βraman (λ,λref,r)δr ' & / R ON exp α aer (λ,r) ON +αaer (λ Ref,r) ON +αmol (λ,r) ON +αmol (λ Ref,r) 1 A R 2 ( ) dr ON (,r) ) n 2 IGdr 34 ON (,r) ) n c (r)dr 2 4 η(λ ON [ Ref )G(R) ] + P B / R ON exp σ IG (λ,r) +σ IG (λ 1 Ref / R ON exp σ abs (λ,r) +σ abs (λ 1 Ref [ ] OFF P S (λ Ref,R) = OFF PL (λ ) OFF OFF % βraman (λ,λref,r)δr ' & OFF (,r) ) dr OFF (,r) ) n IG dr 2 34 OFF (,r) ) n 2 c(r)dr 4 η(λ OFF Ref )G(R) / R OFF exp α aer (λ,r) OFF +αaer (λ Ref,r) OFF +αmol (λ,r) +αmol (λ 1 Ref / R OFF exp σ IG (λ,r) +σig (λ 1 Ref / R OFF exp σ abs (λ,r) +σ abs (λ 1 Ref 3 ( * ) A R 2 3 ( * ) [ ] + P B 7 2 34 2 34

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Solution for Raman DIAL Equations q From the two Raman reference channel equations, we obtain the number density of the constituent that we are interested in. & ln P S(λ OFF Ref,R) P ) 2 ( B P S (λ ON + ' Ref,R) P B * 1 d & n c (R) = ln P L(λ OFF )η(λ OFF Ref )) / ( Δσ abs dr ' P L (λ ON )η(λ ON + 3 Ref ) * & ln β Raman (λ OFF Ref,R)) ( ' β Raman (λ ON + 1 Ref,R)* 4 1 Δσ abs. / 1 Δα aer (R) 2 + Δα mol (R) 3 + Δσ IG (R)n IG 4 q Here, the Δ expressions consist of four terms each Δξ = ξ(λ ON ) +ξ(λ ON Ref ) ξ(λ OFF ) ξ(λ OFF Ref ) with ξ = σ abs,α aer,α mol,σ IG 8 A B C D E F

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Solution in Ozone Case q Term B can be measured and it is range-independent, so the derivative is zero, q Term C is only concerned about molecule Raman scattering, so can be calculated. q Term D will be determined through using the Raman channel at OFF wavelength and introducing Angstrom exponent. q Term E is concerned about molecule Rayleigh scattering, so can be be calculated from atmosphere temperature and pressure. q Term F can be minimized through choosing proper wavelengths, thus, can be ignored. 9

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Ozone Raman DIAL Instrumentation Return Signals - On-line: 332 nm (N 2 Raman scattering from 38 nm) Off-line: 382 nm (N 2 Raman scattering from 351 nm) 1

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Ozone Raman DIAL Receiver Return signals 11

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 RVR Raman DIAL for O 3 Measurement Rotational Vibrational-Rotational Raman DIAL transmits single primary wavelength (e.g., 38 nm) into the atmosphere and then ozone measurement is based on differential absorption of ozone between the purely rotational Raman (RR) return signals from N 2 (37 nm) and O 2 (37 nm) as the onresonance wavelength, and the vibrational-rotational Raman (VRR) return signals from N 2 (332 nm) or O 2 (323 nm) as the off-resonance wavelength. 12

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Rotational Vibrational-Rotational (RVR) Raman DIAL with Single Laser 13

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 RVR Raman DIAL [Reichardt et al., Applied Optics, 39, 72-79, 2] 14

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Single-Laser RVR Raman DIAL 15

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 RVR Raman DIAL Equation q For the elastic DIAL channel at ON-resonance wavelength 38 nm, [ ] P S (λ L,R) = P L (λ L ) ( β aer (λ L,R) + β mol (λ L,R))ΔR % ' & A R 2 ( ) * exp. 2 R α (λ,r) +α (λ,r) 1 ( )dr / aer L mol L 23. R 1 exp 2 σ IG (λ L,r)n IG dr / 23 exp. 2 R σ abs (λ L,r)n c (r)dr 1 / 23 η(λ L )G(R) [ ] + P B q For the purely rotational Raman channels from N 2 and O 2 at 37 nm, [ ] P S (λ RR,R) = P L (λ L ) β Raman (λ L,λ RR,R)ΔR / R 2 exp ( α aer (λ L,r) +α aer (λ RR,r) +α mol (λ L,r) +α mol (λ RR,r) 1 )dr 34 % ' & A R 2 / R 2 exp ( σ IG (λ L,r) +σ IG (λ RR,r))n IG dr 1 34 / R 2 exp ( σ abs (λ L,r) +σ abs (λ RR,r))n c (r)dr 1 34 η(λ RR )G(R) ( * ) [ ] + P B The beauty of the RVR Raman DIAL is the utilization of pure rotational Raman (RR) scattering so that aerosol backscatter is excluded in the RR channel. 1

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 RVR Raman DIAL Equation Continued q For the vibrational-rotational Raman channel from N 2 at 332 nm, [ ] P S (λ VRR,R) = P L (λ L ) β Raman (λ L,λ VRR,R)ΔR / R 2 exp ( α aer (λ L,r) +α aer (λ VRR,r) +α mol (λ L,r) +α mol (λ VRR,r) 1 )dr 34 / R 2 exp ( σ IG (λ L,r) +σ IG (λ VRR,r))n IG dr 1 34 % ' & A R 2 / R 2 exp ( σ abs (λ L,r) +σ abs (λ VRR,r))n c (r)dr 1 34 η(λ VRR )G(R) ( * ) [ ] + P B Certainly, the vibrational-rotational Raman (VRR) scattering channel also excludes aerosol backscatter. 17

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Solution for RVR Raman DIAL q From the Rotational Raman (RR) and the Vibrational-Rotational Raman (VRR) equations, the ozone number density can be derived as n c (R) = 1 Δσ abs. & ln P S(λ VRR,R) P B ) 2 ( + ' P S (λ RR,R) P B * d & ln η(λ VRR ( ) ) / + 3 dr ' η(λ RR ) * & ln β Raman(λ VRR,R)) ( + 1 ' β Raman (λ RR,R) * 4 1 Δσ abs. Δα aer (R) 2 / + Δα mol (R) 3 1 + Δσ IG (R)n IG 4 q Here, the Δ expressions consist of four terms each, but the outgoing laser wavelength terms are cancelled out A B C D E F Δξ = [ ξ(λ L ) +ξ(λ RR )] [ ξ(λ L ) +ξ(λ VRR )] = ξ(λ RR ) ξ(λ VRR ) with ξ = σ abs,α aer,α mol,σ IG 18

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Challenge in RVR Raman DIAL q Term B is range-independent, so the derivative is zero, q Term C is only concerned about molecule Raman scattering. q Term D will be determined through using the Raman VRR channel and introducing Angstrom exponent. q Term E is concerned about molecule Rayleigh scattering, so can be be calculated from atmosphere temperature and pressure. q Term F can be minimized through choosing proper wavelengths, thus, can be ignored. The main challenge in RVR Raman DIAL is how to sufficiently suppress the elastic scattering at laser wavelength in the pure rotational Raman (RR) channel, as the wavelength difference is only 1 nm. Modern interference filter has FWHM of.3 nm, but its wing (or tail) can certainly extend to more than 1 nm. Since Rayleigh scattering is about 3 orders of magnitude larger than rotational Raman scattering, the influence from Rayleigh scattering is not easy to be excluded. Thus, RVR Raman DIAL is not easy to be realized. 19

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Multiwavelength (Raman) DIAL 1ON 1OFF 2ON 2OFF Multiwavelength DIAL uses three or more wavelengths transmitted into the atmosphere and ozone is calculated from the differential absorption of several pairs of elastic scattering signals from air molecules and aerosols. The influence from differential scattering and extinction of aerosols are dramatically decreased by properly choosing wavelengths. 2

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Multiwavelength DIAL Equation q For the elastic DIAL channel at 1ON-resonance wavelength, [( ) ΔR ] P S (λ 1 ON,R) = P L (λ 1 ON ) β aer (λ 1 ON,R) + β mol (λ 1 ON,R) % ' & A R 2 ( ) dr ( ) * exp. 2 R α (λ ON,r) +α (λ ON /,r) aer 1 mol 1 [ ] + P B. R exp 2 σ IG (λ ON 1 1,r)n IG (r)dr / 23 exp. 2 R σ abs(λ ON 1 1,r)n c (r)dr / 23 η(λ ON 1 )G(R) q For the elastic DIAL channel at 1OFF-resonance wavelength, [( ) ΔR ] P S (λ 1 OFF,R) = P L (λ 1 OFF ) β aer (λ 1 OFF,R) + β mol (λ 1 OFF,R) % ' & A R 2 ( ) dr ( ) * exp. 2 R α (λ OFF,r) +α (λ OFF /,r) aer 1 mol 1 [ ] + P B. R exp 2 σ IG (λ OFF 1 1,r)n IG (r)dr / 23 exp. 2 R σ abs (λ OFF 1 1,r)n c (r)dr / 23 η(λ OFF 1 )G(R) q For the elastic DIAL channel at 2ON-resonance wavelength, [( ) ΔR ] P S (λ 2 ON,R) = P L (λ 2 ON ) β aer (λ 2 ON,R) + β mol (λ 2 ON,R) q For the elastic DIAL channel at 2OFF-resonance wavelength, [( ) ΔR ] P S (λ 2 OFF,R) = P L (λ 2 OFF ) β aer (λ 2 OFF,R) + β mol (λ 2 OFF,R) % ' & A R 2 ( ) dr ( ) * exp. 2 R α (λ OFF,r) +α (λ OFF /,r) aer 2 mol 2 [ ] + P B. R exp 2 σ IG (λ OFF 1 2,r)n IG (r)dr / 23 exp. 2 R σ abs (λ OFF 1 2,r)n c (r)dr / 23 η(λ OFF 2 )G(R) % ' & A R 2 ( ) dr ( ) * exp. 2 R α (λ ON,r) +α (λ ON /,r) aer 2 mol 2 [ ] + P B. R exp 2 σ IG (λ ON 1 2,r)n IG (r)dr / 23 exp. 2 R σ abs (λ ON 1 2,r)n c (r)dr / 23 η(λ ON 2 )G(R) 21 1 23 1 23 1 23 1 23

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 3-Wavelength Dual-DIAL for O 3 q From above equations, we can derive the following $ ln P S (λ ON 1,R) P B P S (λ ON 2,R) P ' $ & B P S (λ OFF 1,R) P B P S (λ OFF ) = ln P L (λ ON 1 )η(λ ON 1 ) P L (λ ON 2 )η(λ ON 2 ) ' & % 2,R) P B ( % P L (λ OFF 1 )η(λ OFF 1 ) P L (λ OFF 2 )η(λ OFF ) 2 ) ( $ + ln β aer (λ ON 1,R) + β mol (λ ON 1,R) β aer (λ ON 2,R) + β mol (λ ON 2,R) ' & % β aer (λ OFF 1,R) + β mol (λ OFF 1,R) β aer (λ OFF 2,R) + β mol (λ OFF ) 2,R) ( R 2 [( α aer (λ ON 1,r) α aer (λ OFF 1,r)) ( α aer(λ ON 2,r) α aer (λ OFF 2,r))] dr R 2 [( α mol (λ ON 1,r) α mol (λ OFF 1,r)) ( α mol(λ ON 2,r) α mol (λ OFF 2,r))] dr R 2 [( σ IG (λ ON 1,r) σ IG (λ OFF 1,r)) ( σ IG (λ ON 2,r) σ IG (λ OFF 2,r))] n IG (r)dr R 2 [( σ abs (λ ON 1,r) σ abs (λ OFF 1,r)) ( σ abs (λ ON 2,r) σ abs (λ OFF 2,r))] n c (r)dr Three wavelengths form a dual-pair DIAL, with λ 1OFF = λ 2ON. Thus, the influence from aerosol extinction and backscatter can be minimized by choosing appropriate pairs of wavelengths. 22

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Solution for Dual-DIAL O 3 q Ozone number density can be derived from above equations: n c (R) = 1 2Δσ abs 1 Δσ abs 4 & ln P S(λ ON 1,R) P B P S (λ ON 2,R) P ) 8 ( B P S (λ OFF 1,R) P B P S (λ OFF + ' 2,R) P B * d +ln P L (λ & ON 1 )η(λ ON 1 ) P L (λ ON 2 )η(λ ON 2 ) ) 5 ( dr ' P L (λ OFF 1 )η(λ OFF 1 ) P L (λ OFF 2 )η(λ OFF + 9 2 )*. & + ln β aer (λ ON 1,R) + β mol (λ ON 1,R) ) & ( ' β aer (λ OFF 1,R) + β mol (λ OFF + ln β aer (λ ON 2,R) + β mol (λ ON 2,R) ) 1 ( 1,R)* ' β aer (λ OFF 2,R) + β mol (λ OFF + 3 7 / 2,R)* 23 : 4 ( α aer (λ ON 1,R) α aer (λ OFF 1,R)) α aer (λ ON 2,R) α aer (λ OFF 8 [ ( 2,R))] + [( α mol (λ ON 1,R) α mol (λ OFF 1,R)) ( α mol (λ ON 2,R) α mol (λ OFF 5 2,R))] 9 + [( σ IG (λ ON 1,R) σ IG (λ OFF 1,R)) ( σ IG (λ ON 2,R) σ IG (λ OFF 2,R) 7 )] n IG (R) : A B C D E F Where the differential absorption cross-section is defined as Δσ abs = ( σ abs (λ ON 1,r) σ abs (λ OFF 1,r)) ( σ abs(λ ON 2,r) σ abs (λ OFF 2,r)) 23

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Choice of Wavelength for Dual-DIAL % Δβ = ln β aer (λ ON 1,R) + β mol (λ ON 1,R) ( % ' & β aer (λ OFF 1,R) + β mol (λ OFF * ln β aer (λ ON 2,R) + β mol (λ ON 2,R) ( ' 1,R) ) & β aer (λ OFF 2,R) + β mol (λ OFF * 2,R) ) Δα aer = ( α aer (λ ON 1,R) α aer (λ OFF 1,R)) ( α aer (λ ON 2,R) α aer (λ OFF 2,R)) Δα mol = ( α mol (λ ON 1,R) α mol (λ OFF 1,R)) ( α mol (λ ON 2,R) α mol (λ OFF 2,R)) Δσ IG = ( σ IG (λ ON 1,R) σ IG (λ OFF 1,R)) ( σ IG (λ ON 2,R) σ IG (λ OFF 2,R)) Δσ abs = ( σ abs (λ ON 1,r) σ abs (λ OFF 1,r)) ( σ abs (λ ON 2,r) σ abs (λ OFF 2,r)) q Different channels interact on the same aerosols and interference gases (IG) but with different wavelengths. The main error in conventional DIAL is caused by the uncertainty of the wavelength dependence and information (like density) of the backscatter, extinction, and interference owing to aerosols and IG. β aer (λ) 1 λ a, α aer(λ) 1 λ a q If the wavelength dependence (Angstrom factor) is stable within the detection wavelength range, it is possible to cancel the influence by carefully choosing the wavelengths of two pairs - the difference between two pairs can be minimized. 24

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Solution for Dual-DIAL O 3 q By choosing the pairs of wavelengths, terms C-F (now the difference between two pairs of DIAL wavelengths) can be minimized or cancelled out. Thus, the O 3 measurement errors caused by the uncertainties of terms C- F can be dramatically decreased. q Notice that the choice of the pairs of wavelengths must satisfy one important condition that the differential absorption cross-section given above must be large enough to meet the requirements of measurements sensitivity and spatial resolution. q For the O 3 measurements, the dual-dial can be carried out by three wavelengths chosen at 277.1, 291.8, and 313.2 nm. The middle wavelength 291.8 nm acts as the off-wavelength for the 1st pair, while the onwavelength for the 2nd pair. q To minimize the influence from aerosol backscatter and extinction, a constant C can be introduced into above lidar equation. C is approximately determined by the ratio of the wavelength differences between two pairs of DIAL: C = λ 1 ON λ 1 OFF λ 2 ON λ 2 OFF λ 1 OFF = λ 2 ON Here 25

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Solution with Constant C Introduced n c (R) = 1 2Δσ abs 1 Δσ abs 4 & ln P S (λ ON 1,R) P B P S (λ ON C & 2,R) P ) ) 8 ( B P S (λ OFF ( 1,R) P B ' P S (λ OFF + + ( ' 2,R) P B * + * & d +ln P L (λ ON 1 )η(λ ON 1 ) P L (λ ON 2 )η(λ ON C & 2 ) ) ) ( dr P L (λ OFF 1 )η(λ OFF ( 1 ) ' P L (λ OFF 2 )η(λ OFF + + 5 9 ( 2 ) ' * + *. & + ln β aer (λ ON 1,R) + β mol (λ ON 1,R) ) & ( ' β aer (λ OFF 1,R) + β mol (λ OFF + Cln β aer (λ ON 2,R) + β mol (λ ON 2,R) ) 1 ( 1,R)* ' β aer (λ OFF 2,R) + β mol (λ OFF + 3 / 2,R)* 23 7 : 4 ( α aer (λ ON 1,R) α aer (λ OFF 1,R)) C α aer (λ ON 2,R) α aer (λ OFF 8 [ ( 2,R))] + [( α mol (λ ON 1,R) α mol (λ OFF 1,R)) C( α mol (λ ON 2,R) α mol (λ OFF 5 2,R))] 9 + [( σ IG (λ ON 1,R) σ IG (λ OFF 1,R)) C( σ IG (λ ON 2,R) σ IG (λ OFF 2,R) 7 )] n IG (R) : A B C D E F Where the differential absorption cross-section is defined as Δσ abs = ( σ abs (λ ON 1,r) σ abs (λ OFF 1,r)) C ( σ abs(λ ON 2,r) σ abs (λ OFF 2,r)) 2

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Simulation Results for Dual-DIAL O 3 C =.5 27

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Dual-DIAL for SO 2 Measurements Fukuchi et al., Opt. Eng., 38, 141-145, 1999 Fujii et al., Applied Optics, 4, 949-95, 21 28

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Dual-DIAL for SO 2 Measurements 29

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Differential Optical Absorption Spectroscopy (DOAS) di(λ) = I(λ)α(λ)dz = Iσ ik (λ)(n i N k )dz & I(λ,z) = I exp '( ) σ ik (λ)(n i N k )dz * + è I(λ,z) = I e σ (λ)(n i N k )L = I e z -- Lambert-Beer s Law α (λ)l 3

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 DOAS Configurations 31

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 DOAS 32

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 DOAS Principles [Platt and Stutz, DOAS Book, 28] 33

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 DOAS Principles 34

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 DOAS Principles 35

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 DOAS Principles 3

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 MAX-DOAS Principles [Hönninger et al., ACP, 24] 37

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 MAX-DOAS Principles [Hönninger et al., ACP, 24] 38

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 MAX-DOAS Measurements [Hönninger et al., ACP, 24] 39

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 MAX-DOAS Measurements [Hönninger et al., ACP, 24] 4

LIDAR REMOTE SENSING PROF. XINZHAO CHU CU-BOULDER, SPRING 21 Multi-Angle Pointing TOPAZ Lidar Horse Pool site: Winter 213 9 2 2 Composite vertical O3 and aerosol profiles every 5 min [Courtesy of Dr. Chris Senff]