Research Project by Undergraduate Shira Zingman-Daniels
The following is a short research summary on an SIO 199, or independent research project, undertaken by Shira Zingman-Daniels throughout the 2011-2012 academic year. Shira Zingman-Daniels was a third year environmental engineering student at the time and focused her research project on analyzing a climate run forced by climatalogical sea surface temperature. This was done as a part of the EaSM, or Aerosol-Cloud-Earth Feedbacks Project. Help with preparing the data and with animations throughout the 199 process was given by Minghuai Wang at PNNL.
Multidecadal simlulations of aerosol effects on clouds, namely stratocumulus, shallow cumulus, and deep cumulus clouds, were run in order to analyze the influence of aerosol indirect effects on decadal climate variability. These simulations were run over the continent of North America, from a latitude of 130 to 60 degrees West and 15 to 75 degrees North. Observations for the simulations used in these models were run from June 1 to June 11 with new observations taken exactly every 30 minutes.
A major part of this independent research project was creating animations of data taken as a partof the overall EaSM Project. This data was taken using the Cloud Resolving Model with 4km grid spacing as well as three other aerosol optical depth models. All aerosol measurement simulations were subject to gaps in data throughout the night, since the instruments were not able to measure the presence of aerosols during the night. The models are able to determine the amount of aerosols present as a result of their reflectivity and absorption of light, neither of which can be measured with no sunlight. The following models were plotted using a MATLAB program and were animated using a combination of Quicktime Animator and ULead GIF Animator.
All models and animations created as a part of this project can be seen here. Each sub-section on the animations page reflects either a different mode or model used to create the data or different sections of data to be analyzed.
Although there are many animations to be analyzed, most of the important data from this set falls under 5 categories: aerosol measurement, water present in clouds, water present in the atmosphere, cloud forcing, and temperature. Some observations and results are listed below along with examples of each type of animation.
An example of aerosol measurements can be found here. This model was created to analyze the aerosol optical depth using the Accumulation Mode. Aerosol Optical Depth is the measurement of the degree to which aersols impact the transmission of light throughout the atmosphere. This can be used to measure the amount of aerosols present and quantify the distribution of aerosols around the planet. Aerosols absorb and reflect light, so areas with low optical depth indicate low aerosol levels and, conversely, areas with high optical depth indicate high levels of aerosols present. The animations show high aerosol optical depth levels around the Georgia area during the first part of June, which would be expected because of the high levels of aerosols present in the area throughout the summer. All aerosol optical depth measurements on the animations page linked above use this same theory to model the amount of aerosols present in the atmosphere. Although the three aerosol optical depth animations use different modes to quantify the optical depth, all show related results and all results show similarities to the model animating the aerosol absorption in the atmosphere, found here. This is expected, since the measurement of the prevention of light transmission through the atmosphere should be closely related to the absorption of light by aerosol particles.
Water in Clouds
The amount of water present in clouds was measured through numerous types of simulations focusing on cloud water droplet numbers, rain and snow particle numbers, cloud ice numbers, cloud ice, and cloud water, among others. The amount of water present in clouds, whether it is in liquid or ice form, can help to determine the amount of aerosols present in the clouds. Since aerosols commonly serve as cloud condensation nuclei, they can begin the process of cloud formation if enough moisture accumulates on them. Therefore, the amount of water present in clouds helps to not only analyze the type and composition of clouds but also to determine the amount of aerosols present. An animation of cloud water measurements can be found here. Cloud water is the water content in all phases present in a cloud. This animation shows a variability in the location of clouds with high water content. This signifies that the location of cloud water changes throughout the day and from day to day. It also shows the uncertainties still present in the animation's estimate of where high levels of cloud water will be located, since clouds with high water content can move across the continent. The other animations show expected results, with high levels of snow and ice content in the northern latitudes and similar distribution of cloud water droplets throughout the atmosphere as with cloud water measurements.
Water in Atmosophere
The amount of water in the atmosphere can be related the amount of water present in clouds. This can be analyzed by observing precipitation rates, water vapor, and atmospheric humidity. High atmospheric water content can be related to cloud water content because high cloud water content leads to water in the atmosphere from precipitation and evaporation. An example simulation of atmospheric water content in the form of precipitation can be seen here. These models show similar results to cloud water content, with maximum precipitation rates varying throughout the atmosphere over time. As with cloud water, this shows the variability in the location of precipitation over time and the uncertainties present in the estimation of the location of atmospheric water content.
Cloud forcing is defined as the difference between actual and cloud-cleared outgoing radiant fluxes in the atmosphere. This is essentially a measure of the energy change in the atmosphere. It is related to aersols present in the atmosphere because cloud forcing shows the the amount of energy being reflected in the atmosphere. Locations of high cloud forcing shows where the model predicts clouds will occur and energy will be reflected. Shortwave cloud forcing takes place at the top of the atmosphere, while longwave fluxes and cloud forcing happens at the top of the atmosphere and at the surface. An example of shortwave cloud forcing can be seen here. This model shows some changes over time. However, each day follows a similar trend with the location of high shortwave cloud forcing moving from the Southwest area of the screen to the Northeast and finally to the Southeast area, ending back at the Southwest portion of the model. This shows the energy reflected throughout the day and how the location of clouds changes throughout the day.
Temperature was measured in these models by simulating the temperature in the atmosphere, surface temperature, and CRM model temperature. As expected, all models show maximum temperatures in the areas corresponding to Mexico and the southern United States and minimum temperatures in the Canada, Alaska, and northern United States areas. An example of temperature models can be seen here. This model ranges from values of 270 to 310 degrees Kelvin.