Abstract ........................................................ i
Kurzfassung ................................................... iii
1 Introduction ................................................. 1
1.1 The scientific problem .................................. 1
1.2 State of the art of global aerosol-climate modeling ..... 5
1.3 Aim of the thesis ....................................... 7
1.4 Structure of the thesis ................................. 7
2 Atmospheric aerosol .......................................... 9
2.1 Characterization of atmospheric aerosol ................. 9
2.1.1 Particle size and concentration .................. 9
2.1.2 Chemical composition ............................ 10
2.1.3 What is it meant by black carbon and dust? ...... 11
2.1.4 Morphology ...................................... 11
2.2 Sources of aerosol: emissions, coagulation and
nucleation ............................................. 12
2.3 Sinks of aerosols: dry and wet deposition,
coagulation and ageing ................................. 13
2.4 The role of aerosols in cloud formation ................ 14
2.5 The climate effects of aerosol ......................... 14
3 The aerosol model: MADEsoot ................................. 17
3.1 Description of the aerosol population .................. 17
3.2 Representation of aerosol microphysics ................. 22
3.2.1 Gas/aerosol partitioning ........................ 23
3.2.2 Condensation of sulfuric acid and organic
material ........................................ 25
3.2.3 Nucleation of new particles ..................... 26
3.2.4 Particle coagulation ............................ 26
3.2.5 Particle growth ................................. 31
3.2.6 Ageing of black carbon and dust particles ....... 32
4 The three-dimensional model: ECHAM5/MESSy-MADEsoot .......... 35
4.1 The starting point: ECHAM5/MESSy-MADE .................. 35
4.2 Modifications for modeling the upper troposphere ....... 30
4.3 Implementation of MADEsoot in ECHAM5/MESSy ............. 40
4.3.1 Sources of aerosols ............................. 40
4.3.2 Activation of aerosol particles ................. 43
4.3.3 Effect of aerosol on radiation .................. 44
4.3.4 Scavenging by ice and rain and evaporation of
droplets ........................................ 44
4.3.5 Dry deposition .................................. 45
5 Reference simulation and model evaluation ................... 47
5.1 Model set-up ........................................... 47
5.2 Evaluation ............................................. 48
5.2.1 Vertical profiles of aerosol mass
concentrations .................................. 49
5.2.2 Vertical profiles of aerosol number
concentrations .................................. 51
5.2.3 Surface measurements ............................ 53
5.2.4 Comparison of the mixing state of black carbon
particles ....................................... 57
5.3 Conclusions ............................................ 58
6 Characterization of sub-micrometer aerosol and potential
ice nuclei .................................................. 61
6.l Characterization of the sub-micrometer aerosol ......... 6l
6.1.1 Number concentration ............................ 61
6.1.2 The size distribution of the global aerosol ..... 65
6.1.3 Chemical composition ............................ 66
6.1.4 Burden and life time of atmospheric aerosol ..... 69
6.1.5 Comparison with ECHAM5/MESSy-MADE ............... 72
6.2 Characterization of the potential ice nuclei ......... 73
6.2.1 Number concentration ............................ 73
6.2.2 Size distribution ............................... 78
6.2.3 Chemical composition of the coating ............. 79
6.2.4 Thickness of the coating ........................ 79
6.3 Ageing of black carbon and dust particles .............. 82
6.3.1 Effectiveness of the single ageing processes .... 83
6.3.2 Transformation time of externally mixed black
carbon and dust ................................. 90
7 Summary and outlook ......................................... 97
A Prognostic equations ....................................... 103
A.l Prognostic equations in MADE .......................... 103
A.2 Prognostic equations in MADEsoot ...................... 105
B Technical details .......................................... 109
B.l Calculation of the condensation coefficients .......... 109
B.2 Calculation of the coagulation rate ................... 110
С Chemical reactions ......................................... 113
C.l The chemical mechanism of MECCA ....................... 113
C.2 The chemical mechanism of SCAV ........................ 114
D Acronyms ................................................... 117
Bibliography .................................................. 121
Acknowledgments ............................................... 131
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