Journal Club MTG9: Land Use and Land Cover Change

My topic of research while in Michigan is on Land Use and Land Cover Change which made today's paper which I had to present especially interesting. The paper "Evaluating the effects of historical land cover change on summertime weather and climate in New Jersey: Land cover and surface energy budget changes" by Paul Wichansky et al (2008), investigates the sensitivity of a warm season climate of New Jersey to land cover change from 1880s versus 1990s. The areas of specific interest include the magnitude of land cover change and sensitivity on near surface air temperature, rainfall, dew point temperature, heat fluxes and climatological episodes.

Previous studies have shown that deforestation causes an increase in temperature and rainfall shifts, while reforestation causes cooling in the region. Urbanisation also causes an increase in temperatures and changes to the diurnal cycle. The interesting thing to note is that all three processes have occurred in the state of New Jersey within the last century. Reconstructing the land cover from historical topographical maps and land consensus, a full land cover map was available for direct comparison with NLCD data from 1992. Aggregated to 1km and combined into 8 vegetation classes, the researchers used RAMS and LEAF2 to compare atmospheric responses to land cover change.

They nested the grid in 3 levels (above-purple) and 3 ensemble members per land cover scenario, they used a 2 month period in June/July 1999. From NCEP data to force atmospheric boundary conditions, they used June as a spinup and July as a month for analysis. The soil moisture was described from observation.

The model comparisons showed an increase in near surface air temperature and dew point temperature in urban and deforested areas and cooler in reforested areas, just as previous research stated. The results overall come as no surprise but they way they use the ensemble without giving the spread or error is slightly weird.

Journal Club MTG8: Isoprene emissions

Today's article "The effect of elevated CO2, soil and atmospheric water deficit and seasonal phenology on leaf and ecosystem isoprene emission" by Emiliano Pegoraro describes an experimental biosphere laboratory in that looks at stresses to cottonwood plantations and their responses with respect to isoprenes. The experiment ran over a few years, and looked specifically at the fall of 2000, fall of 2002 and spring of 2003 to cover the range of phenological influences. The plantations were controlled, one with present day CO2 levels and one with elevated CO2 levels. The plantations were both stressed as a result of a vapour pressure deficit (VPD) and drought conditions. The idea was to measure the isoprene emissions under various conditions. The results show a correlation between photosynthetic photon flux density (PPFD) which makes sense as isoprene emissions shutdown with the absence of light. It was interesting that as the drought conditions continued, no matter the CO2 concentration, the isoprene levels tailored off to roughly the same emission rate.

As a side note, I am finally learning all that high school biology I didn't take.

First Snow

It snowed for the first time today. Apparently it won't "stick" but just fall for the next few weeks. I think the locals thought I was crazy, I was dancing around outside in the snow catching snowflakes :) I am sure I will hate the snow soon, but its still a novelty. Next time it snows enough to collect on the ground its snow angels and snowmen time.

In other news, the Engineering Graduate Symposium took centre stage on Friday. The day started with an overview of what to expect doing Engineering at Michigan and then department talks. This event is directed at undergrads looking to join Michigan and is sort of like UCT Open Day but for students already in university. The AOSS grads presented topics ranging from regridding climate models for translation from cubes to lat/long, Venus and its oxygen and nitrogen nightglow, Aerosol composition and cloud formation and Mars's middle atmosphere. Afterwards we went to dinner and drinks on Friday night and we took over 2 tables in the end. Dinner was nachos, salsa, burgers, beer and a Cookie-tini! The girls shared it, the thing is huge, 7 cookies and 5 scoops of ice-cream.

CUDA with NVIDIA

CUDA by NVIDIA is a new C language environment for developers to solve numerical processing problems on Graphical Processing Units(GPUs). The speedup of certain problems in astronomical such as an N-body problem can get up to a 100x faster. The GTX200 has 1.4 billion transistors and can reach 1000 GFLOPS as opposed to a quad core Xeon which reaches 96 GFLOPS. The reason is the difference in architecture. The CPU is designed for minimum latency, not throughput, something a GPU excels at and number crunching is essentially a throughput problem.The speaker Jonathan Cohen believes the scientific community and their problems are ideal for the GPU architecture. A few interesting features of the GPU include 240 processors split into groups of 8 to create shader multiprocessors(SM). Each SM has 6 SPs, 2 SFUs and and a DP. Note that Double precision (DP) processors are not needed for graphics/games and included for scientific reasons. The SFUs are optimised for sine/cosine/sqrt/exp operations, all common in scientific computing.

One application is transferring the cloud microphysics subroutine from WRF into CUDA and John Michalakes at NCAR reported a 1.3 speedup. This shows that it might be possible to build much cheaper clusters with more powerful GPUs and run climate models faster and for far less. Cohen is building up to a ROMS-like system for GPUs. A group in Italy built a computer with 8 GPUs (8 TFLOPS) for $6000. Think of the possibilities...

Journal Club MTG6: Global Change and Ozone Air Quality

This week we delve back into organic chemistry with an article on ozone quality over the United States. Titled "Effects of 2000-2050 global change on ozone air quality in the United States" by Shiliang Wu et al (2008), the paper looks at various changes in climate and anthropogenic emissions of ozone precursors using the GEOS-Chem model. Looking into the sensitivity of ozone to climate events, one can see minimal changes in the southeast, but large increases in ozone as the cyclone tracks change and don't protrude inland as far as presently occurs. The anthropogenic emissions are looked at under the A1B scenario from IPCC and has a decrease in emissions in the US and as a result a significant decrease over southeast. The final consensus is that the emissions cap currently in place at 40% needs to be increased to 50% to take into account the effects of climate change by 2050.

An interesting question at this point is, given that decreases are going to have different effects in different regions, should we have one solution at a federal level(in the US) or a state level?

Journal Club MTG5: Urban Parameterization for CCSM Part II

The paper this week is "An Urban Parameterization for the Global Climate Model. Part II: Sensitivity to Input Parameters and the Simulated Urban Heat Island in Offline Simulations" by Oleson et al. The paper builds on the previous paper and looks at the sensitivity to changing parameters within the model. The split the parameter types in 3 categories, morphological, radiance and thermal. Each category was combined using every possible combination within its own category. The results of this highlight that previous surfaces, or the lack thereof, greatly influence the latent heat available and the sensible heat is very sensitive to both the morphological and radiance parameters. The paper moves on to simulating heat islands and compared this is Oke(1981) who derived a logarithmic equation based on measurements of heat islands in US and European cities. The model simulates the increased diurnal cycle and temperature difference between urban and rural environments. The sensitivity studies also real that parameter uncertainty mainly effects the amplitude of the diurnal cycle and not the phase. Overall the paper has a few confusing parts and many graphs that could be simplified or removed, but I felt this study did a much better job than some sensitivity studies of other areas in the past.

Phoenix Mars Mission Talk

The seminar in AOSS this afternoon included preliminary work and results from the Phoenix Mars Mission. The speaker, Professor Nilton Renno, reviewed the mission goals of the Phoenix Mars Mission and the procedures involved in selecting a landing sight. Never trust interpolation of images was the take home message, an apparently flat surface from satellite imagery contained 10m diameter boulders. He went on to show some of his students, notably Manish Mehta whose doctoral thesis investigated the effects of the lowering rockets on the surface dust of Mars. Pretty cool work. Renno proceded to show some of the images from the Lander (inset picture) and explained some of the experiments run. It appears if you look at the images closely that there is sublimation happening on the legs of the lander with saline water settling on the mud kicked up from the landing on Mars. Apparently not everyone in the program which is shared between JPL, University of Arizona and Locklead Martin Space Systems. It is going to be interesting to see what research is published and what happens when NASA releases the data to the public in February next year.

Journal Club MTG4: Atmospheric Feedbacks

The article today was "Atmospheric / vegetation feedbacks: A mechanism for abrupt climate change over northern Africa" by CM Patricola and KH Cook. The paper discusses the sensitivity to the latitude of the desert border in the Sahara and the atmospheric feedbacks in the African easterly jet (AEJ). The idea is that if the desert border is located below 17.9N the climate becomes sensitive and the summer precipitation and a weakening in the AEJ. There are a few concerns with the paper as they use prescribed soil moisture and do not discuss the land cover model used.

Journal Club MTG3: Ozone Interannual Variability

Today is yet again journal club day. We are reviewing a paper by S Koumoutsaris et al. "Influence of El-Nino-Southern Oscillation on the Interannual Variability of tropospheric ozone in the northern midlatitudes". It is a rather long and figure intensive article that documents CO and O3. The author used the Goddard Earth Observing System Chem (GEOS-Chem) model to explore the correlation between El-Nino and O3. The model accurately captures the sensitivities to biomass burning and the meteorology for CO but not completely for O3. The study is conducted at 4 x 5 degrees that disregards the regional features. It is important to note that the article explains the shortfalls in capturing all the O3 from stratospheric dynamics and intrusions.

Down and Out

I have been sick since Friday, not an enjoyable experience but I suppose being sick never is. I attended the Ballroom Team BBQ against my better judgement, it was literally across the road, but stayed maybe 15 minutes. Long enough to have my picture taken and get hit by a volleyball, meh.

I felt marginally better on Saturday and went to the football match between Michigan and Illinois. Michigan lost, badly. I left in the third quarter when the noise from the crowd made my headache worse. I dragged Oswald (the other UCT exchange student) along to the game.

In other news, I was shown what has got to be the nerdiest landscaping in history: A wave field, the ground is a 3D sinusoidal wave. We took our research group photos there



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Journal Club MTG2: Urban Parameterization for CCSM

As part of the journal meetings we are reviewing "An Urban Parameterization for a Global Climate Model. Part 1: Formulation and Evaluation for Two Cities" by KW Oleson et al. The paper reviews efforts to capture land use change in urban areas and the effects this has on the atmosphere. The global models currently divides the world into a grid and each grid cell is further divided into various plant function types and wetland, urban etc. Each is dealt with separately however there is no scheme for urban areas. This paper presents an "urban canyon" solution that supposedly captures the urban climatology. There are separate energy balances and surface temperatures for each canyon facet. I really appreciate the added heat sources from waste (air conditioners) and traffic. A 1D heat conduction is solved numerically for fluxes in and out of surfaces. The paper then describes an experiment looking at two different cities areas, Mexico City and Vancouver. The results suggest an increased understanding of fluxes but says that the timing is off in the model, but note that no one has perfected the urban diurnal cycle. I want to note that the observations are rather sparse though. The paper also states that implementing this system globally might be problematic as no urban map yet exists categorising urban types. Something to look forward to in the future. Lastly a relevant question is, at what resolution does this actually matter? Perhaps a global view is not the answer but maybe regional is.

Journal Club MTG1: Atmospheric Chemistry

I attended my first ever Journal Club today with my supervisor here and fellow officemates. The topic: Atmospheric oxidation capacity sustained by a tropical forest by Lelieveld et al. Interesting paper from Nature that explores a theory which opposes known science in atmospheric chemistry. The idea is that OH is recycled through some mechanism in a low NOx environment like a rainforest. The paper is not great, requires a lot of supplementary material but it has jumpstarted my organic chemistry understanding, last attempted in high school. It also started to fill in the gaps of knowledge I have about various plugins in global climate models. However unless you are an organic chemist or have one handy (my officemate Ahmed very kindly spent an hour patiently explaining things) don't bother.