130 Atmospheric Physics Lab Institute for Atmospheric and

1/30 Atmospheric Physics Lab Institute for Atmospheric and Climate Sciences IACETH ( 701 -1264 -00 L) Zamin A. Kanji Organizational Meeting and Lecture 1 Mon. 1 st March 2021 Online on Zoom

Objective of this meeting Institute for Atmospheric and Climate Sciences IACETH 2/30 ● Decide on groups - choose your partner(s) ● Overview of course and grading system ● How to write a lab report for an experiment – ● Grading assessment Choose your experiments (3 out of 4) – Sun Photometry – Ice Nucleation – Particle Measurements – Dynamics

Overview of Experiments and TAs 3/30 (1) Sun Photometry (2) Ice (3) Aerosols (4) Dynamics – Nucleation (DMPS) tank Asstnt 1: Colin Tully Guangyu Li Jake Casselma Asstnt 2: Lucas Ferreira Correa Group. Nr. First name Last name Baptiste Testa Kai Jeggle Slot 5 26/04 - 07/05 Slot 6 10/05 - 21/05 End: EGU 30/04 Ascension day 13/05 Slot 7 24/5 - 04/06 Whit Monday 24/05 Finish reports no experiments Institute for Atmospheric and Climate Sciences IACETH 1 2 3 4 5 6 Slot 1 01/03 - 12/03 Slot 2 15/03 - 26/03 Slot 4 29/03 - 09/04 12/04 - 23/04 Easter Fri 02/04 Sechseläuten 19/04 Easter Mon 05/04 Start: EGU: 19/04

Grading 4/30 Institute for Atmospheric and Climate Sciences IACETH ● Graded on 3 experiments worth 2 points each => 6 points ● Report due two weeks after the experiment ● Prepare lab report closely following guidelines – One report per group ● Grading scheme out of 20 ● Submit one report per group per experiment – No re-submissions allowed

Grading Scheme 5/30 ● Preparedness before experiment – 3 – Institute for Atmospheric and Climate Sciences IACETH ● Clear that lab manual was read and questions were thought about Appropriate abstract/intro/background – 5 – Not too brief, having appropariate amount of theory and not a copy-paste version from lab report – Abstract presents a good succinct summary of report ● Tutorial questions/discussion – 9 ● Overall presentation/style/language – 3

Lab Reports: Page Structure 6/30 ● ● Institute for Atmospheric and Climate Sciences IACETH ● 10 pages of single spaced text including figures and tables (excludes title page, abstract, references) 1 title page Background/introduction should be no more than 1. 5 pages (excl. eqns. ) ● Margins (min 0. 75 inches on all four sides) ● Font: 12 pt Times New Roman or similar ● ● Anything above 10 pages will not be read or considered for grading Important: Proof Read Reports before handing in

Structure of Lab Report Institute for Atmospheric and Climate Sciences IACETH 7/30 ● Title Page – 1 page ● Abstract – 150 -200 words ● Introduction/Background (1 -1. 5 pg) ● Materials and Methods ● Results ● Discussion ● Conclusion ● References ● No Need for: – Can combine List of figures/tables and table of contents 10 pages

Contents in Each Section (1/4) 8/30 Title Page (1 page) ● Institute/department, title of experiment, supervisors, author(s), course, date Abstract (150 -200 words) Institute for Atmospheric and Climate Sciences IACETH ● Summary of four aspects – – Purpose, key findings, significance of results and major conclusion(s) Often can include brief reference to theory/introductory statement and to methodology Introduction (1 -1. 5 pages, excl. equations) ● ● More focussed than abstract, provide background of experiment, should not be identical to lab manual State clear objective(s) at the beg. or end of introduction – should state end goal, not pedagogical goal

Contents in Each Section (2/4) 9/30 Materials and Methods ● ● Institute for Atmospheric and Climate Sciences IACETH ● Describe the central instruments and their functions used Any standard analysis methods, software that was used In some cases it is sufficient to refer to the lab manual – but important to judge what to include in the lab report Experimental Procedure ● ● Report the chronology of how the experiment was conducted, conditions, time and date If you made an exception to the procedure, changed something or something did not work Results ● Dominated by figures, table and graphics, but still have to explicitly state the results in verbal/text form.

Contents in Each Section (3/4) 10/30 Discussion (give an analysis and interpretation) ● An analysis – ● Interpret your results Institute for Atmospheric and Climate Sciences IACETH – – – ● ● Compare expected results with what you observe Analyse experimental error Explain results in context of theory (against, or predicted by) Relate your results to your objective(s) Discuss limitation/strength of experiment design Discuss aspects not obvious from just viewing your results Discuss errors/uncertainties. Consider having 1 -2 subsections: – – ● What you have found and is clearly indicated that you know with certainty “estimation of uncertainties/errors” “Limitations of experiment/results” Make use of sub-sections if it helps organize your thoughts and interpretation

Institute for Atmospheric and Climate Sciences IACETH 11/30 sp, sq and sr can also be uncertainties (instead of standard deviations)

Institute for Atmospheric and Climate Sciences IACETH 12/30 Example ●

Contents in Each Section (4/4) 13/30 Conclusions ● This can be short, simply summarise what you did and what you know for sure from the results Institute for Atmospheric and Climate Sciences IACETH Referencing ● ● Wikipedia references not allowed Feel free to use any style referencing just but be consistent, APA, numbered referencing No footnotes for referencing but allowed for specific messages/information If using websites (other than Wikipedia) give website and date visited in reference list

Institute for Atmospheric and Climate Sciences IACETH 14/30 Example Report: Title Page

Institute for Atmospheric and Climate Sciences IACETH 15/30

Dos and Don’ts Institute for Atmospheric and Climate Sciences IACETH 16/30 • • Do not repeat what is in the manuscript word for word Do not copy word for word anything from a reference Always paraphrase When in doubt ask your TAs first – they are a valuable resource

Motivation – Trace Species 17/30 ● Institute for Atmospheric and Climate Sciences IACETH ● ● ● Gas molecules absorb radiation of a given wavelength only if the energy can be used to increase in the internal energy level of the molecule Gases that absorb in the wavelength (λ) 5 – 50 µm where most terrestrial radiation (longwave) is emitted are called greenhouse gases (GHGs) Absorption corresponds to vibrational and rotational transitions in a molecule Vibrational transitions are allowed only if the change in in vibrational state changes the dipole moment, p of the molecule

Institute for Atmospheric and Climate Sciences IACETH 18/30 Normal vibrational modes of CO 2 and N 2 Fig. 7 -10 (Jacob 1999)

Importance of Trace Species 19/30 ● Institute for Atmospheric and Climate Sciences IACETH ● ● Generally molecules that can acquire a charge asymmetry by stretching or flexing are GHGs (CO 2, H 2 O, N 2 O, O 3, hydrocarbons) Molecules that cannot acquire a charge asymmetry by flexing or stretching (N 2, O 2, H 2) are not GHGs Principal atmospheric constituents are not GHGs but trace species are GHGs with most important being those present with high enough concentrations to absorb a significant fraction of the radiation emitted by the Earth – Including H 2 O, CO 2, CH 4, N 2 O, O 3 and CFCs

Water Vapor as a GHG 20/30 ● Institute for Atmospheric and Climate Sciences IACETH ● ● ● By far the most important is water vapor because of its abundance and is extensive absorption features in the IR spectrum Water vapor is the most important GHG in the Earth's atmosphere Anthropogenic perturbations are minor compared to large natural source from oceans But water vapour can provide a positive feedback by precipitating and forming clouds

Institute for Atmospheric and Climate Sciences IACETH 21/30 O 3– perfect absorption Figure 7 -11 (Jacob, 1999): Efficiency of absorption of radiation by the atmosphere as a function of wavelength. Major absorbers identified

Optical Depth 22/30 Institute for Atmospheric and Climate Sciences IACETH ● ● ● The absorption or scattering of radiation by an optically active medium such as the atmosphere is measured by the optical depth (δ) of the medium Gas molecules can absorb or scatter radiation but the scattering is inefficient at visible and IR wavelengths because of similar size of the gas molecules and the wavelength Scattering more important for aerosol (next lecture) – One reason to study physical properties of aerosols

23/30 Optical Depth (2) Institute for Atmospheric and Climate Sciences IACETH Figure 7 -17 (Jacob, 1999): Transmission of radiation through and elemental slab

Institute for Atmospheric and Climate Sciences IACETH 24/30 Optical Depth (3) ●

Institute for Atmospheric and Climate Sciences IACETH 25/30 Optical Depth (4) ●

26/30 Optical Depth (5) Institute for Atmospheric and Climate Sciences IACETH Figure 7 -18 (Jacob, 1999): Effect of incident angle on the transmission of radiation through a slab

27/30 Determining Concentration of Trace Species ● Use absorption and scattering of gases at different wavelength to determine the concentration of species Institute for Atmospheric and Climate Sciences IACETH – ● i. e. determining n (the number density in the equation) Similar formulation using intensity of radiation at given wavelength – use to determine concentration of H 2 O(g) and O 3 – two abundant GHGs

28/30 Other Factors Influence Optical Depth ● In addition to gasses in the atmosphere what other scatterers and absorbers are there? Institute for Atmospheric and Climate Sciences IACETH – Aerosols and Clouds Figure 8 -2 (Jacob, 1999): Production, growth and removal of atmospheric aerosols

Aerosol – Radiation Interactions 29/30 Institute for Atmospheric and Climate Sciences IACETH ● ● Aerosols can scatter and absorb visible radiation therefore limiting visibility and affecting Earth’s climate directly – Can have a cooling effect if aerosols reflect incoming short wave back to space – Warming effect if aerosols (e. g. black carbon) absorb shortwave and remit longwave Aerosols also affect Earth’s climate indirectly by serving as nuclei for clouds Can be respiratory health hazard in the high concentrations found in urban environments Provide sites for surface and condensed phase chemistry to take place in the atmosphere

Aerosol Effects 30/30 ● Which properties are important for scattering, visibility reduction and climate perturbation? Institute for Atmospheric and Climate Sciences IACETH – Size or chemistry? Figure 1 -4 (Boucher, 2015): Temperature evolution of the global mean surface temperature (observed black line) and simulated by a range of models in response to natural factors