Head in a Cloud

troposphere and stratosphere meet blogosphere

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Biological Particles Including Bacteria as Ice Nucleators

March 19th, 2008 by inansel · No Comments

In the article “Ubiquity of Biological Ice Nucleators in Snowfall” Christner et al., it is made clear how important biological particles are as ice nucleators and how many of these particles are bacteria. One thing that I found interesting is how high of a temperature bacteria can act as an ice nucleator, -2C. It is known that aerosols in the atmosphere act as catalysts for ice nucleation, but what Christner found was that 69 to 100% of these ice nucleators are biological. Since the atmospheric ice nuclei concentrations at temperatures above -10C are so small 19 samples of fresh snowfall were taken from multiple places in both the high and mid latitudes. These samples were then analyzed by a heat treatment, which inactivated the biological ice nucleators, and then these could be seperated from ice nucleators of mineral origin. This showed that out of all the ice nucleators, the biological ones represented the majority if not all of the nucleators. This was then further broken down to find the bacterial nucleators by adding lysozyme to the sample to disrupt the cell wall and reduce ice-nucleation activity in bacteria. The experiment found 0 to 85% of the ice nuecleators were susceptible to lysozyme and thus bacteria, but do to incomplete hydrolysis or resistance to lysozyme this could be underestimating the bacteria concentration. The one amazing finding to me was that biological ice nucleators were found in Antarctica albeit at the lowest concentration of the 19 samples, but it shows these particles had to have traveled long distances and stayed active as an ice nucleator. Christer believes this research can be used for further discovery of the connections between the biosphere and climate, and also aid in improving climate forecast models.

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“The Role of Cloud-Top Brightness Temperatures in the Production of Heavy Precipitation”

March 7th, 2008 by miller · 3 Comments

“The operational meteorological community is increasingly realizing the important role of cloud microphysics in the production of heavy precipitation, especially snow(e.g., Roebber et al. 2003)”. This is a direct quote from the journal article “Cloud-Top Temperatures for Precipitating Winter Clouds” by Jay W. Hanna, David M. Schultz, & Antonio R. Irving, of which I will summarize. I chose this quote because it reveals why the authors wrote this particular paper. Understanding cloud microphysics can greatly increase operational meteorologist’s understanding of heavy precipitation events. This paper relates cloud-top brightness temperatures to observed surface precipitation types(snow, rain, freezing rain & sleet) in order to better understand the microphysical processes within clouds.

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Aerosol Effects on Clouds, Precipitation, and Organization of Cumulus Convection

March 1st, 2008 by JonathanS · No Comments

I reviewed the article titled “Aerosol Effects on Clouds, Precipitation, and the Organization of Shallow Cumulus Convection” from the Journal of The Atmospheric Sciences, Volume 65, February 2008. The authors had a desire to study the aerosol effects on clouds and climate. Using large eddy simulations they investigated the effects of aerosol on clouds, precipitation, and organization of trade wind cumuli. The conceptual structure for this study follows the idea of greater aerosol loading suppresses precipitation formation, increases cloud liquid water, and leads to a long lived cloud with larger cloud fractions. Recent field studies have had a theme in focusing on the interaction between precipitation, boundary layer dynamics, and cloud organization with illustrative findings that precipitation is often associated with mesoscale variations. This article focuses mainly on using simulations to help understand ways in which precipitation effects the organization and structure of trade wind cumuli. Data collection during the ATEX (Atlantic Trade Wind Experiment) is used as reference and comparison data.

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Mountain-triggered cumulus evolving from shallow to deep convection.

February 24th, 2008 by cianca · 2 Comments

This post is a summary of “The Cumulus, Photogrammetric In Situ, And Doppler Observations Experiment 0f 2006″ published by R. Damiani, J. Zehnder, B. Geerts, J. Demko, S. Haimov, J. Petti, G.S. Poulos, A. Razdan, J. Huh, M. Leuthold, and J. French in the January 2008 issue of Bulletin of the American Meteorological Society (BAMS).

I have a sincere interest in this subject based on an old article that I read in National Geographic. The article concerned the “sky islands” or mountain ranges of Arizona and New Mexico, that erupted from the floor of the desert, into diverse and different ecosystems. What differentiated these areas from the normally arid portion of the country, was the elevation and the weather.

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Global Warming and Radiative Forcing

February 14th, 2008 by atripp3 · 5 Comments

As I’m sure many of you are aware, the issue of global warming has been deeply embedded within the concerns of nations across the world. With an issue that is so widespread, you would think that the causes would be common knowledge to everyone. However, from my experience over the past few years, I have found that most people are rather confused about the warming of the climate and whether it is a problem or not. Typically, some are convinced that climate warming is a natural process, and the “global warming” issue doesn’t really exist. Others seem to think that it is an issue and humans are accelerating it by the burning of fossil fuels. Because of the confusion, I have decided to explore the issue further to get an idea whether climate warming is due more to nature or humans.

The following is a brief overview of the section entitled “Concept of Radiative Forcing” that appears in the report “Climate Change 2007: The Physical Science Basis” written by Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). It discusses what is referred to as Radiative Forcing and how it is used to determine whether or not a specific agent, such as Carbon Dioxide, affects the global climate.

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