Anthropogenic influence on Upper Tropospher-Lower Stratosphere (UTLS) clouds and aerosol (CIRRUS) UTLS round 5 project led by Prof. Tom Choularton. The dataset contains the total number of Condensation Nuclei (CN), CCN, IN and the size distribution of optically active particles in clean and polluted air in the UTLS region over the UK, the number, size distribution, phase and morphology of droplets and crystals in cirrus cloud.

Objectives

-To measure the total number of Condensation Nuclei (CN), CCN, IN and the size distribution of optically active particles in clean and polluted air in the UTLS region over the UK. Assessment of their spatial distribution and their likely source based on tracer measurements and air mass history.

-To use a unique suite of state of the art instruments to quantify the extent to which air mass history, and gas and particle loading can affect the microphysical properties of cirrus clouds in the UTLS region, in particular, the size distribution, phase and morphology of cloud particles.

-To obtain estimates of HNO3 loss to cirrus clouds and the subsequent effect on the aerosol population after the cloud has evaporated using case studies involving one or more wave clouds.

-To make observations of the number, size distribution, phase and morphology of droplets and crystals in cirrus cloud and the number and size distribution of interstitial particles and correlate these with measurements of tracers that identify anthropogenic anthropogenic influence. Hence building on objective 3 to investigate the influence of cirrus on the distribution of aerosol and gases in the UTLS region as cloud and precipitation evaporate.

-To make an assessment of the chemical composition of the particulate in the UTLS region as a function of their size, their spatial variability and the effect different sources have on their composition.

-To use measurements of the masses of key components as a function of size of cirrus particle dry residues and interstitial particles to determine if there are distinct chemical differences between activated and unactivated particles.

-To establish the partitioning of oxidised nitrogen between the gas and aerosol phases as a function of air mass history and source region.

Methodology

These studies were performed during the spring/summer of 2005 over the UK using the BAE 146 aircraft for in situ sampling Experiments were undertaken in a wide range of meteorological conditions i.e. in frontal cirrus, in convective conditions and in anticyclonic conditions. The aircraft made measurements below and within the cirrus cloud.