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The effects of cloud aerosol interaction on earth albedo and radiation budget using Earth Observation Datasets and Numerical Weather Model Simulations.

Project Aim:    To combine earth observation datasets of albedo, cloud aerosol and cloud properties to examine changes in the earth’s radiation budget balance and analysis of numerical weather / climate model simulations for sensitivities in the cloud droplet characteristics; satisfying the research themes of atmospheric science and Earth Observation Datasets.

Background:    The official policy of getting to zero greenhouse gas emissions at some date in the future will leave concentrations higher than at present by an amount depending on how long the reduction takes.  This means that floods, droughts, storms, bushfires, ice melt, coral loss and sea level rise will all be worse, perhaps substantially worse, than at present when they seem quite bad enough.  It may be necessary to do direct world cooling despite the enormous amount of energy involved. One possible method, due to John Latham, exploits the Twomey effect to increase marine cloud reflectivity by increasing the concentration of cloud condensation nuclei.  This could be done by spraying submicron drops of filtered sea water into the turbulent marine boundary layer.  Computer models show sufficiently large cooling and benign effects on precipitation.

Engineering design of hardware of spray vessels at Edinburgh University is well advanced but we need to understand the best way to deploy them. The strength of the Twomey effect depends on initial nuclei concentration levels, the depth of the turbulent marine boundary layer, the solar input, the vertical gradient of humidity, the cloud fraction, the time between rain showers and the direction and speed of the wind.  These affect the extremes in, for example Sea Surface Temperatures (SSTs), which impacts on events such as the intensity of hurricanes developing between Africa and the Gulf of Mexico and SST dipoles in the Indian ocean are suggested to be connect to floods in Kenya and bush fires in Australia. Ocean cooling reverses sea level rise, half of which is caused by thermal expansion.

Remote sensing data from satellites provides useful data to examine the albedo of clouds and the droplet size. Latham 2012 ( shows in Figure 1 (from co-author Wood) how, in this case MODIS, can be used to determine the drop size distribution.  Approximately 15 papers by Latham, Salter and Gadian, discuss the technology and the process of modelling.  Wood and Rasch at PNNL / University of Washington, are developing high resolution modelling and experiments in parallel to this project.  Using the HadGEM, UK Met Office model and Earth observation data sets funded by NERC and UK Space Agency will update this approach by Wood and enable both correlation with current model data and  observations, and then interpret with model data sets where MCB has been applied.

Methodology:    The project will use existing datasets to produce a seasonal merit-order of ocean regions analogous to the list used by electricity generation boards to bring on different generation plant.  Information will be distilled and presented in a format that engineers can understand.   The objective is to develop a facility to develop pseudo-real time analysis from past earth observation data sets.  It will develop engineering useful data fields (Edinburgh) with derived meteorological and atmospheric cloud properties.  Previous work (Parkes, PhD, University of Leeds), using state of the art climate  and weather models detected teleconnections of cloud properties on temperature and precipitation fields.  Sensitivity studies, increasing and decreasing cloud aerosol properties in different random sequences and correlating each sequence with model results will lead to estimations of regional global temperature and precipitation patterns. The computations will be carried out on the ARCHER-2, for which computer time will be required.

The student will learn and use the earth observation data sets, creating tools for analysis and presentation of the relevant fields.  Using the state of the art UK Met Office HadGEM model, computer simulations will be conducted on the UK ARCHER computer system. The student can be hosted at either institution with Salter as the lead supervisor.

The work will be jointly supervised by Gadian (Leeds)  focusing on meteorological aspects and Salter (Edinburgh) on the engineering aspects of real time analysis and random sequencing and the data needed for vessel design. This project involves merging the meteorology and engineering aspects and hence the joint supervision.

The student has the potential to gain significant experience from working with leading edge organisations.  For the modelling and meteorological aspects, there is potential to visit and collaborate work with Phil Rasch Pacific North West Laboratory and the University of Washington and engage with scientists at the Met Office, Exeter and NCAS to develop HadGEM3 to modify CCN input data over 92 areas of the global oceans.  The student will also work with Artemis Intelligent Power.