The Rain in Cumulus over the Ocean (RICO) was a US-led international project to study trade wind cumulus clouds in the Caribbean. The main objective was to characterise and understand the properties of trade wind cumulus at all scales, with particular emphasis on understanding the warm rain process and determining its importance. The field campaign took place near Antigua and Barbuda from the 17th of November 2004 to the 24th of January 2005. The UK participation to RICO involved ground-based measurements and the use of the FAAM aircraft based at Antigua, from the 5th to the 28th of January 2005.

Chemistry of the Antarctic Boundary Layer and the Interface with Snow (CHABLIS) is a Natural Environment Research Council (NERC) and Antarctic Funding Initiative (AFI) funded project, aimed at studying the chemistry of the Antarctic Boundary Layer in greater detail, and for a longer duration, than has previously been attempted. Fieldwork was carried out at the new Clean Air Sector Laboratory (CASLab) at Halley station . The team from UK universities and the British Antarctic Survey brought to the project a suite of state-of-the-art instruments and models and a track record of successfully running major campaigns together in remote locations. The field campaign started during the austral summer in January 2004 and continued throughout the winter culminating with an intensive study during the summer of 04/05. Major foci for CHABLIS included detailed studies of seasonal oxidant chemistry, annual variation in the boundary layer NOy budget and elucidating air/snow transfer processes. The dataset includes mixing ratios (Ozone, CO, HCHO, NO2, and HONO), accumulation and isotope (Na, K, Mg, Ca, F, CH4, Cl, and NO3) concentrations of snow, and meteorological measurements (relative humidity, visibility, dew point, wind speed, and wind direction). Access to this dataset is now public.

The AUTEX / WINTEX (Autumn and Winter Experiments) project was a Met Office campaign on board the Facility for Airborne Atmospheric Measurements (FAAM) aircraft, that collected cloud physics and radiation data over the UK, from October 2004 to February 2007. The dataset collection contains measurements of water vapour distribution in both the horizontal and the vertical, mixed phase cloud structure and ice initiation in cumulus clouds. They also included studies into sea surface reflectance at low solar zenith angles, cirrus cloud radiative properties, microwave signature of 'bright band', clear air spectroscopy at night, clear air spectroscopy in the infrared and far infrared, land surface emissivity studies and the effect of inhomogeneity in clouds at low solar zenith angles. FAAM Bae-146 non-core data is now public, but raw Bae-146 core data is restricted to the FAAM staff.

The FLUXEX (Flux Experiment) project was an experiment to establish the fluxes of many ozone depleting gases (CFCs, HCFCs, halons) and greenhouse gases (HFCs, PFCs, SF6) from the UK. Its aim was to assess regional emission inventories of these gases to feed the UNEP/WMO Ozone Assessment and the UNFCCC. Attempts were also made to measure for the first time "new" ozone depleting gases, such as n-propyl bromide and hexachlorobutadiene, and to estimate UK emissions. To achieve this purpose, the FAAM aircraft, fitted with air sampling bottles, was flown in the boundary layer upwind and downwind of the UK. A total of 9 flights took place between 30. March and 29. September 2005.

An international long-term collaboration to study the climatic and environmental feedback mechanisms involved in the African monsoon, and in some of its consequences on society and human health. The programme, which started in 2004, has developed a network of ground-based observation stations over Sub-Saharan West Africa to measure heat flux and, for some stations, CO2 and H2O vapour fluxes. Files also include concomitant meteorological measurements (wind, temperature, pressure, humidity, rainfall) and soil physics parameters (soil temperature and moisture). The UK branch of AMMA makes use of several instruments provided by the UK Universities Facility for Atmospheric Measurement (UFAM) which are centred on the Niamey meso-site. The Facility for Airbourne Atmospheric Measurements (FAAM) aircraft was used during the July-August 2006 campaign.

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.

The Aberystwyth Egrett Experiment: Gravity Waves, Turbulence, Mixing and Filamentation in the Tropopause Region is a Upper Troposphere Lower Stratosphere (UTLS) Round 2 project led by Dr J. Whiteway and Dr G. Vaughan, Department of Physics, University of Wales, Aberystwyth. Dataset contains: airborne measurements, by the Egrett aircraft, of turbulence, ozone, water vapour, CH4 and CFCs; ground based measurements, by the NERC MST Radar, of atmospheric structure, mesoscale dynamics, and turbulence; balloons measurements of ozone, water vapour, wind, temperature and pressure; Lidar of ozone, water vapour, temperature and cirrus clouds. Airborne measurements: A unique stratospheric research aircraft, the Egrett aircraft, performed 10 separate flights in the UTLS region above Aberystwyth. The Egrett was equipped with advanced instrumentation for measurements of turbulence, ozone and water vapour. Ground based measurements: The ground based facilities at Aberystwyth were operated to their full capacity during the Egrett campaign. The NERC MST Radar provided measurements of atmospheric structure, mesoscale dynamics, and turbulence. Balloons carryed instruments for measuring ozone, water vapour, wind, temperature and pressure. Three separate lidar systems provided measurements of ozone, water vapour, temperature and cirrus clouds. Analysis of gravity waves and turbulence: The above measurements were conducted when gravity waves were breaking and causing turbulence. The combination of the Egrett and ground based measurements have been used to determine if this process is significant for transport of chemical constituents in the UTLS region. These measurements also provided a new basis for testing theories and models of the wave breaking process. Analysis of filamentation: The Egrett aircraft was directed to fly through regions of filamentation in the lower stratosphere. This provided new data to test theories and models of mixing through turbulence at the edges of filaments.

Evaluation of the Ozone and Water Vapour Datasets of the 40-Year European Re-analysis of the Global Atmosphere Upper Troposphere Lower Stratosphere (UTLS) Round 2 project led by Prof. A. O Neill, Dr W. Lahoz and Prof. B. Hoskins, Centre for Global Atmospheric Modelling, Department of Meteorology, University of Reading. Re-analyses datasets, such as the 40-year re-analysis dataset (ERA-40), have been produced by the European Centre for Medium Range Weather Forecasts. This has provided an invaluable tool for a wide range of modelling, theoretical and observational studies of the atmosphere, including the UTLS region. This was because they have the advantage of being global, self-consistent and relatively long-term. It was vital that the ERA-40 dataset was carefully evaluated before projects studying the UTLS region, for example, draw conclusions based on its use. This project undertook an evaluation of the ERA-40 dataset by comparing ozone and water vapour fields (important for climate, radiation and dynamics) in the UTLS region using independent satellite data from the Upper Atmosphere Research Satellite (UARS), aircraft data from the Measurements of Ozone by Airbus In Service Aircraft (MOZAIC) programme, measurements from fields campaigns (e.g. the European Arctic Stratospheric Experiment (EASOE), and the Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME). The objectives of the UTLS-Ozone ERA40 Validation project were: To evaluate the ozone and water vapour datasets in ERA-40, including the identification of shortcomings and suggestions for improvements. To gain intimate knowledge of the data quality and shortcomings of ERA-40 datasets other than ozone and water vapour, via membership of the ERA-40 data evaluation team. To provide users with quality-controlled, three dimensional ozone and water vapour datasets from the ERA-40 analyses, together with error statistics on the reliability of the fields. To provide support for measurement campaigns associated with the study of chemistry/ climate interactions. To provide support to the scientific community in the form of climatologies for studies of atmospheric variability and predictability. To provide interdisciplinary training in data evaluation and analysis techniques, earth observation sciences and atmospheric modelling.

The ACTIVE (Aerosol and chemical transport in tropical convection) Natural Environment Research Council (NERC) funded consortium project, combined field measurements and a range of modelling tools at different scales to address questions related to the composition of the tropical tropopause layer (TTL). Field measurements were conducted in Darwin, Australia in two phases: November-December 2005 (pre-monsoon convection), in collaboration with the SCOUT-O3 project funded by the European Commission, and January-February 2006 (monsoon convection), in collaboration with the US/Australian TWPICE project. ACTIVE utilised the Australian Egrett aircraft operated by Airborne Research Australia (ARA) and the NERC Dornier 228 operated by the British Airborne Research and Survey Facility (ARSF) to measure chemical species and aerosol in the inflow and outflow of tropical storms. Cloud-scale and large-scale modelling studies assisted in the interpretation of the measurements to distinguish the different contributions to the TTL composition. The dataset contains the before-mentioned aircraft measurement as well as ozonesondes. Institutions involved in ACTIVE include The University of Manchester, UK. The University of Cambridge, UK. The University of Wales at Aberystwyth, UK. The University of York, UK. The Deutsches Zentrum fur Luft- und Raumfahrt (DLR), Germany. The Forschungzentrum Julich (FZJ), Germany. The York University, Canada. The Bureau of Meteorology (BOM), Australia. The Airborne Research, Australia (ARA).

The HadAT data are global radiosonde gridded temperature anomalies at standard levels (850, 700, 500, 300, 200, 150, 100, 50, and 30hPa) in the troposphere and in the lower stratosphere from 1958 to December 2012. This monthly timeseries are available on a 10 degree longitude by 5 degree latitude basis. This dataset supersedes the HadRT dataset. All values are anomalies relative to the monthly 1966-95 climatology. The gridded product is derived from 676 individual radiosonde stations with long-term records. Because of the criteria of data longevity the resulting dataset is limited to land areas and primarily Northern Hemisphere locations. Radiosondes are single launch instruments and there have been many changes in instruments and observing practices with time. HadAT has used a neighbour-based approach to attempt to adjust for these effects and produce a homogeneous product suitable for climate applications. Zonal averages were created by averaging all available gridbox values in each 5 degree latitude band. Large scale mean timeseries for the globe and the tropics (defined here as 20N to 20S) are simply cos(lat) weighted zonal mean field values. This reduces the spatial sampling bias towards Northern Hemisphere mid-latitudes. Other plausible large-scale averaging techniques would impact the timeseries values calculated. Cautionary note from the Met Office Hadley Centre It is important to note that significant uncertainty exists in radiosonde datasets reflecting the large number of choices available to researchers in their construction and the many heterogeneities in the data. To this end we strongly recommend that users consider, in addition to HadAT, the use of one or more of the following products to ensure their research results are robust. Currently, other radiosonde products of climate quality available from other centres for bona fide research purposes are: - Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC) - RAdiosonde OBservation COrrection using REanalyses and Radiosonde Innovation Composite Homogenization ) - IUK (Iterative Universal Kriging) Radiosonde Analysis Project Also see a comparison with Microwave Sounding Unit (MSU) data by Remote Sensing Systems (see links under Docs tab below) .