Direct radiative forcing of aerosol 1)Model simulation: A. Rinke, K. Dethloff, M. Fortmann 2)Thermal IR forcing - FTIR: J. Notholt, C. Rathke, (C. Ritter) 3)Challenges for remote sensing retrieval: A. Kirsche, C. Böckmann, (C. Ritter)

A modeling study with the regional climate model HIRHAM 1)Specification of aerosol from Global Aerosol Data Set (GADS) 2) Input from GADS into climate model:  for each grid point in each vertical level: aerosol mass mixing ratio (0.5 º, 19 vertical)  optical aerosol properties for short- and longwave spectral intervals f(RH) aerosol was distributed homogeneously between 300 – 2700m altitude, no transport 3)Climate model run with and without aerosol  aerosol radiative forcing months March (1989 – 1995)

Global Aerosol Data Set (GADS); Koepke et al., 1997  Arctic Haze: WASO, SOOT, SSAM Properties taken from ASTAR 2000 case (local), so overestimation of aerosol effect

New effective aerosol distribution due to 8 humidity classes in the aerosol block Dynamical changes: Δu(x,y,z) Δv (x,y,z) Δp s (x,y) ΔT(x,y,z) Δq(x,y,z) Δq w (x,y,z) Additional diabatic heating source Q add = Q solar + Q IR Effective aerosol distribution as function of (x,y,z) u(x,y,z) v(x,y,z) p s (x,y) T(x,y,z) q(x,y,z) q w (x,y,z) α(x,y) μ(x,y) Direct climatic effect of Arctic aerosols in climate model HIRHAM via specified aerosol from GADS Direct aerosol forcing in the vertical column Aerosol – Radiation - Circulation - Feedback

2m temperature change [°C] x C1 x W1 x W2 x C2 Geographical latitude Height [km] Temperature change [˚C] Height [km] W1 C1 C2 W2 Height-latitude temperature change Temperature profiles at selected points 1990 [°C] Direct effect of Arctic Haze “Aerosol run minus Control run”, March ensemble Fortmann, 2004 ΔF srfc = 5 to –3 W/m 2 1d radiative model studies: ΔF srfc =-0.2 to -6 W/m 2

[hPa] (“Aerosol run minus Control run”) direct+indirect [K] 2m temperature change Sea level pressure change (“Aerosol run minus Control run”) direct Rinke et al., 2004 March 1990 Direct+indirect effect of Arctic Haze

Conclusion modeling: Critical parameters are: Surface albedo, rel. humidity, aerosol height (especially in comparison to clouds) (indirect: liquid water) But aerosol properties were prescribed here – so no direct statement on sensitivity of aerosol properties (single scat. albedo…) according to GADS, however: chemical composition, concentration and size distribution of aerosol did show strong influence on results (surface temperature) aerosol has the potential to modify global-scale circulation via affected teleconnection patterns

12.5μ8.0μ Rathke, Fischer 2000 Note: deviation is “grey” FTIR:

Easier: radiance flux Flux (aerosol) - flux (clear) Height, temperature and opt. depth of aerosol required significant

For TOA: Assumption: purely absorbing (!) Note similar spectral shape AOD from spectrum of radiance residuals

Radiosonde launch: 11UT (RS82) 11. Mar: cold and wet: diamond dust possible For 30. Oct, 17. Nov: ΔT of 1.5 C needed for saturation

Conclusion FTIR observation: Observational facts: grey excess radiance was found for some days where back trajectories suggest pollution diamond dust unlikely for 30 Oct, 17 Nov. So IR forcing by small (0.2μm) Arctic aerosol? Consider: complex index of refraction at 10μm for sulfate, water-soluble, sea- salt and soot (much) higher than for visible light! (“Atmospheric Aerosols”) example λ \ specimen sulfate water-solu. soot oceanic 0.5 μ e-8i e-3i i e-9i 10μ e-1i e-2i i e-2i Mie calculation (spheres 0.2μm, sulfate): vis: no absorption, ω=1 IR: almost no scat. ω=0 so: ω, n, phase function are all (λ)

Scattering properties by remote sensing? Have seen: single scattering very important, depend on index of refraction. Multi wavelengths Raman lidars can principally calculate / estimate size distribution & refractive index (n) => scattering characteristics. One difficulty: estimation of n: d: data; v: coefficients of volume distribution function M: matrix of scattering efficiencies (λ, k ), depend on n forward problem:

algorithm to solve Fredholm Integ. Eq. of first kind: integral operator: so:

vd shall be element of a finite dimen. subspace of L 2 (r_min, r_max) so : so : let d (data) be: d= T T

Laser wavelengths355nm, 532 nm, 1064 nm Laser pulse energy200mJ 300mJ 500 mJ (new! Since Dec. 2006) Laser pulse rep. rate50 Hz Laser beam divergence0.6 mrad Telescope diameter30cm far (2,0km – 20km) 10.5 cm near (500m – 4km) Telescope FoV0.83 mrad / 2.25 mrad Detection channels (elastic) 355 nm, unpol. 532 nm, normal polar. + perpend. polar nm, unpol. Detection channels (inelastic) N 2 – Raman: 387nm, 607nm H 2 O – Raman: 407nm Range + ResolutionMax. 7.5m / 100 sec typical: 60m / 10 min Raman: 100m / 30 min: 8km Detection limitExtinction round 2e-7 KARL specs

2m temperature change (mean) [°C] x C1 x W1 x W2 x C2 Geographical latitude Height [km] Temperature change [˚C] Height [km] W1 C1 C2 W2 Height-latitude temperature change Temperature profiles at selected points 1990 [°C] Direct effect of Arctic Haze “Aerosol run minus Control run”, March ensemble Fortmann, 2004 ΔF srfc = 5 to –3 W/m 2 1d radiative model studies: ΔF srfc =-0.2 to -6 W/m 2