The Copernicus Climate Change Service (C3S), operated by ECMWF on behalf of the European Commission, provides climate services built around a comprehensive suite of data products. These products include multidecadal estimates of the atmospheric state, based on atmospheric reanalysis, and a range of observational datasets on Essential Climate Variables (ECVs).
Atmospheric reanalyses are now regarded as valuable sources of information for monitoring trends in the global atmospheric state and employ highly optimised methods for combining observations of meteorological variables, both in-situ and satellite. The most recent C3S global atmospheric reanalysis, ERA5, covering the period 1979-2019 (to be extended to 1950) is now available and since its release in early 2019 has a rapidly growing user base, currently numbering more than 30,000. It uses a recent version of the ECMWF Numerical Weather Prediction (NWP) system to assimilate observations (87 billion for the period 1979 - 2018) in order to analyse the atmospheric state. Satellite observations are a key input to reanalyses and the range of observations assimilated are reviewed.
ECVs derived from satellite and in-situ observations, spanning land, atmosphere, ocean and biosphere domains, produced as part of international collaborations, are available via the C3S Climate Data Store (CDS). The aspiration of C3S is to further develop the CDS to include a wider range of (∼ 35) ECVs in the next phase of the Copernicus programme (2021-2027).
Some aspects of the CubeMAP mission (also known as ESP-MACCS) are presented: its science objectives, and the primary choices made to address them from small satellite platforms. The science case, addressing some key scientific questions related to global change, is elaborated in four objectives focused on upper troposphere and stratospheric composition and its change. The sounding methodology and the associated observation concept retained is a constellation of miniature limb solar occultation thermal infrared sounders, offering the advantages of limb solar occultation, whilst mitigating the inherent lack of coverage of this geometry. The mission focuses on tropical regions as the gateway to the upper troposphere, and the stratosphere. The miniaturized instrument payloads developed for the mission are briefly presented: the High resolution InfraRed Occultation Spectrometer (HIROS) and the Hyperspectral Solar Disk Imager (HSDI). Lastly, the nanosatellite 12U platform and its subsystem are described, completing the overview of the mission space segment.
Assimilation of a new observation dataset in an NWP system may affect the quality of an existing observation data set against the model background (short forecast), which in-turn influence the use of an existing observation in the NWP system. Effect of the use of one data set on the use of another data set can be quantified as positive, negative or neutral. Impact of the addition of new dataset is defined as positive if the number of assimilated observations of an existing type of observation increases, and bias and standard deviation decreases compared to the control (without the new dataset) experiment. Recently a new dataset, Megha Tropiques SAPHIR radiances, which provides atmospheric humidity information, is added in the Unified Model 4D-VAR assimilation system. In this paper we discuss the impact of SAPHIR on the assimilation of hyper-spectral radiances like AIRS, IASI and CrIS. Though SAPHIR is a Microwave instrument, its impact can be clearly seen in the use of hyper-spectral radiances in the 4D-VAR data assimilation systems in addition to other Microwave and InfraRed observation. SAPHIR assimilation decreased the standard deviation of the spectral channels of wave number from 650 -1600 cm-1 in all the three hyperspectral radiances. Similar impact on the hyperspectral radiances can be seen due to the assimilation of other Microwave radiances like from AMSR2 and SSMIS Imager.
This work describes the use of a He:Ne laser based test rig, developed at NPL, and a low pressure gas cell containing CO to measure the instrument line shape (ILS) function of a Unicam Research Series FTIR spectrometer, which has been extensively used for the detection and measurement of fugitive gas emissions. During the ILS function measurements minor optical misalignments were introduced into the optical system, and their effect on the measured ILS function observed. The ILS functions obtained using the laser system and low pressure gas cell containing CO were in good agreement, both having a full width at half maximum of 0.3 cm-1. The minor optical misalignments had a significant effect on the ILS function. The initially symmetric function became more asymmetric as the degree of misalignment was increased. Gas concentrations have been retrieved using a symmetric and an asymmetric ILS function, and the differences presented.
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