Recent radio occultation measurements using Global Positioning System satellite transmitters and an orbiting receiver have provided a globally distributed set of high-resolution atmospheric profiles, suggesting that the technique may make significant contribution to global change weather prediction programs. Biases in temperatures relative radiosonde model data are about 1 kelvin or less tropics generally than 0.5 at higher latitudes. Data quality is sufficient quantify errors remote...

Abstract In recent years difficulties have been experienced in exploiting satellite sounding data numerical weather prediction (NWP) the form of independently retrieved temperature and humidity profiles. Attention has now focused on methods through which information radiance measurements may be assimilated more directly into NWP system%. A scheme known as ‘one‐dimensional variational analysis’ (1DVAR) developed at European Centre for Medium‐range Weather Forecasts a method extracting from...

Abstract Using collocations of three different observation types sea surface temperatures (SSTs) gives enough information to enable the standard deviation error on each type be derived. SSTs derived from Advanced Along-Track Scanning Radiometer (AATSR) and Microwave for Earth Observing System (EOS; AMSR-E) instruments are used, along with SST observations buoys. Various assumptions made within theory, including that errors not correlated, which should case independent data sources. An...

Abstract Structure functions for the 3D‐Var assimilation scheme of European Centre Medium‐Range Weather Forecasts are evaluated from statistics differences between two forecasts valid at same time. Results compare satisfactorily with those reported in existing literature. Non‐separability correlation is a pervasive feature. Accounting non‐separability necessary to reproduce geostrophic characteristics statistics, such as increase length‐scale height horizontal mass variable, sharper vertical...

Abstract The direct use of TOVS (TIROS Operational Vertical Sounder) cloud‐cleared radiances in a three/four‐dimensional variational data assimilation scheme is described. This uses fast radiative transfer model and its adjoint. Radiances are used together with all the other observational data. Global spectral fields mass, wind humidity analysed simultaneously under certain mass/wind balance constraints which control degree to gravity waves enter into analysis. In this way need for...

Until January 2013, data from the high‐resolution sounder IASI were assimilated with a diagonal observation‐error covariance matrix within Met Office 4D‐Var assimilation scheme, assuming no correlation between channels. The errors inflated to account indirectly for known inter‐channel error correlations. This is sub‐optimal as it artificially down‐weights observations these instruments. true nature of correlations are estimated here using scheme and posteriori diagnostics based on analysis...

Abstract Developments in the assimilation of satellite data numerical weather prediction (NWP), from first experiments late 1960s to present day, are presented a two‐part review article. This part reviews early years, up about year 2000. It includes summaries relevant remote sensing technologies, theoretical and practical challenges faced when assimilating their within NWP systems, impacts on forecast skill. An important this story concerns developments information atmospheric temperature...

Abstract The role of observations in reducing 24-h forecast errors is evaluated using the adjoint-based sensitivity to (FSO) method developed within Met Office global numerical weather prediction (NWP) system. impacts various subsets are compared, with emphasis on space-based observations, particularly those from instruments board European Organisation for Exploitation Meteorological Satellites Operational-A (MetOp-A) platform. Satellite data found account 64% short-range error reduction,...

Abstract Developments in the assimilation of satellite data numerical weather prediction (NWP), from first experiments late 1960s to present day, are presented a two‐part review article. This part, Part II, reviews progress recent years, about 2000. It includes summaries advances relevant remote‐sensing technologies and methods assimilate observations these instruments into NWP systems. also summarises impacts on forecast skill. Continued has been made passive infrared (IR) sounding...

Abstract A one‐dimensional variational retrieval for the assimilation of refractive‐index profiles derived from radio occultation (RO) measurements has been developed. The method is tested by using simulated data to assess accuracy and information content measurements, various realistic estimates assumed error distributions. Theoretical retrieval‐error given a solution covariance matrix are in good qualitative agreement with those statistically comparison precisely defined ‘true’ values. It...

Abstract A new approach is proposed for inverting satellite sounding data use in numerical weather prediction (NWP). It may be considered two ways: either as a retrieval scheme which uses forecast profile background or ‘first guess’ and the covariance of error constraint order to produce retrieved profiles compatible with subsequent NWP analysis; module within analysis perform vertical radiances at observation points (i.e. project information on levels vertical). The performs an inversion...

Abstract A practical technique for the assimilation of cloud‐affected infrared radiances is presented. The best suited to advanced sounders such as AIRS and IASI. Radiances are first pre‐processed by a one‐dimensional variational analysis (1D‐Var) scheme, where cloud parameters (cloud‐top pressure effective fraction) retrieved simultaneously with atmospheric profile variables. then passed data system, they used constrain radiative transfer calculation in reduced set channels. channel...

Abstract Observations from the Infrared Atmospheric Sounding Interferometer (IASI), onboard EUMETSAT's MetOp satellite, have been assimilated at Met Office in global and regional numerical weather‐prediction systems since 27 November 2007. Pre‐operational trials of IASI assimilation model during summer 2007 delivered a positive impact on forecasts approximately twice as large that shown by InfraRed Sounder (AIRS) EOS‐Aqua satellite. A series observing system experiments confirmed relative...

Abstract The optimal utilisation of hyper‐spectral satellite observations in numerical weather prediction is often inhibited by incorrectly assuming independent interchannel observation errors. However, order to represent these observation‐error covariance structures, an accurate knowledge the true variances and correlations needed. This structure likely vary with type assimilation system. work this article presents initial results for estimation IASI when data are processed Met Office...

Observation bias correction schemes are important components of the data assimilation (DA) systems used in operational numerical weather prediction (NWP). They at present mainly to correct for biases satellite radiance observations and their observation operators. These attempt remove relative NWP model background or analysis field. The presence itself can substantially complicate this process. Using a very simple scalar forecast DA system, study explores extent which leads states. Theory is...

Abstract The Advanced TIROS Operational Vertical Sounder (ATOVS) was launched on the NOAA‐15 satellite in May 1998. This provided a very significant improvement information available from meteorological polar‐orbiting satellites compared with previous system, particularly for humidity and vertical resolution of temperature cloudy areas. In preparation assimilation observations into three‐dimensional analysis atmospheric humidity, have been calculated top‐of‐atmosphere brightness temperatures...

An optimal estimation inverse method is presented which can be used to retrieve simultaneously vertical profiles of temperature and specific humidity, in addition surface pressure, from satellite‐to‐satellite radio occultation observations the Earth's atmosphere. The a nonlinear, maximum posteriori technique accommodate most aspects real problem found stable converge rapidly cases. has two distinct advantages over analytic that it accounts for some effects horizontal gradients able optimally...

Abstract The observation‐error covariance matrix used in data assimilation contains contributions from instrument errors, representativity errors and introduced by the approximated observation operator. Forward model arise when operator does not correctly observations or can resolve spatial scales that cannot. Previous work to estimate for particular observing instruments has shown it signifcant correlations. In particular, correlations humidity are more significant than those temperature....

Abstract Aircraft reports are an important source of information for numerical weather prediction (NWP). From March 2020, the COVID‐19 pandemic resulted in a large loss aircraft data but despite this it is difficult to see any evidence significant degradation forecast skill global NWP systems. This apparent discrepancy partly because very variable, showing both day‐to‐day noise and lower frequency dependence on mean state atmosphere. The definitive way cleanly assess impact using denial...

Abstract Four‐dimensional variational (4D‐Var) assimilation forecast impact experiments were conducted with CHAMP radio occultation measurements from 1st June to 31st July 2004. The bending angles assimilated one‐dimensional (1D) and two‐dimensional (2D) angle observation operators, enabling the potential benefits of latter be investigated. Two computationally affordable 2D operators considered. first can viewed as a straightforward generalisation 1D operator. second is based on fourth order...

Abstract The potential of the TIROS Operational Vertical Sounder (TOVS) and Advanced TOYS (ATOVS) for providing information on vertical profiles atmospheric temperature humidity is investigated. theoretical performances these systems are examined primarily in terms their ability to contribute a numerical weather prediction (NWP) system. covariance retrieval error expected from an optimal nonlinear inversion scheme, which retrieves simultaneously all surface variables significantly affect...