Model profiles at satellite locations, 09 - 21 UTC, 7th September, 2017

• Main Author: Geer, Alan J.
• Format: Dataset
• Language: English
• Published: Zenodo 2022
• Subjects: Sea ice
• Online Access: https://dx.doi.org/10.5281/zenodo.6362200; https://zenodo.org/record/6362200

Summary This dataset contains atmospheric profiles generated from an experimental run of the ECMWF integrated forecast system (IFS), interpolated to the observation locations and times of various satellite observations using the internal IFS observation operator (known as 'the GOM arrays'). The date and time range gives a snapshot of Hurricane Irma, 2017. Satellite observations Two satellite instruments are included: The Global Precipitation Mission (GPM) Microwave Imager (GMI): The profile locations are at the centres of boxes of roughly 40 km by 40 km. These boxes are used for superobbing the data, combining a minimum 15 raw GMI observations. The process of superobbing is used at ECMWF for a number of reasons including to colocate the various channels of GMI level 1b data, which are at different locations. Note that the 40 km superobbing resolution used here is different from the operational ECMWF superobbing resolution for this data (which is 80 km). The Advanced Technology Microwave Sounder (ATMS) on the Suomi NPP satellite. All locations in the raw level 1B dataset are included (note that the 3 x 3 averaging that is normally applied at ECMWF was switched off) The satellite observations themselves are not included in this dataset and must be obtained from the relevant data providers. The profiles are provided in a semi-random order and must be colocated to the relevant observations by the user. Model details IFS cycle 47r1 has been used; further information is at https://www.ecmwf.int/en/publications/ifs-documentation. The model profiles are generated from a run of the atmospheric forecast model that is initialised from the operational analysis at 00 UTC 7th September 2017. The profiles are hence based on a short forecast of 9 - 21 hours duration that is equivalent to the 'background forecast' in the data assimilation cycle. The model uses a horizontal resolution of T1279co (equivalent to 8 - 9 km) and 137 hybrid pressure levels in the vertical. Profiles represent slabs of atmosphere that are centred on the 'full' pressure levels and are bounded by 'half' pressure levels. Hence, half pressure level 1 is 0 hPa and half pressure at level 138 is the surface pressure. The dataset contains most of the necessary inputs for driving a radiative transfer model to simulate satellite-observed radiances. One important input that is not included is the surface emissivity, which may be estimated using a physical model integrated into the radiative transfer model, or it may be obtained from an emissivity atlas (in the context of the IFS data assimilation is in some cases estimated with a dynamic emissivity retrieval, which is not supplied in this dataset). There are 6 hydrometeors represented by the IFS. The large-scale condensation scheme represents cloud water, cloud ice, rain and snow as prognostic variables. Relating to these are a sub-grid cloud fraction which applies to cloud water and ice, and a precipitation fraction that applies to the large-scale rain and snow. Additionally, the mass flux convection scheme represents rain and snow generated by convection. The sub-grid fraction occupied by convection is not given in the file, since it is assumed to be a constant 0.05. The convection scheme does not represent convective cloud (e.g. non-precipitating particles) but it does represent the convective anvils via detrainment into the large-scale condensation scheme (hence convective anvils are represented in the large-scale cloud ice). Rain and snow were originally obtained as fluxes and converted to mixing ratios using assumptions of fall-speed and particle size distribution, as is standard within the all-sky satellite data processing at ECMWF. All mixing ratios [kg kg-1] are given relative to the moist atmosphere. The profile times are those of a model timestep close in time to when the observation was made. The model timestep is 7.5 minutes, but only every fourth timestep is available to the IFS observation operator, meaning that profile times are quantised at 0, 30 60 minutes (and so on) through the forecast range. Essentially, there should be no more than a 15 minute time mismatch between the validity time of the profile and the satellite observation time. Licensing and copyright Copyright statement: Copyright "© 2022 European Centre for Medium-Range Weather Forecasts (ECMWF)". Source: www.ecmwf.int Licence Statement: This data is published under a Creative Commons Attribution 4.0 International (CC BY 4.0). https://creativecommons.org/licenses/by/4.0/ Disclaimer: ECMWF does not accept any liability whatsoever for any error or omission in the data, their availability, or for any loss or damage arising from their use. Where applicable, when redistributing the data, give an indication if the material has been modified and an indication of previous modifications. Full ECMWF licence terms are given at https://apps.ecmwf.int/datasets/licences/general/ : Example ncdump -h from the GMI profiles, in order to illustrate the contents of the files: dimensions: LEVELS_FULL = 137 LEVELS_HALF = 138 OBSERVATIONS = 198880 JULIAN_DAY_START = 1 variables: short LEVELS_FULL(LEVELS_FULL) string LEVELS_FULL:units = NIL string LEVELS_FULL:description = NIL short LEVELS_HALF(LEVELS_HALF) string LEVELS_HALF:units = NIL string LEVELS_HALF:description = NIL int OBSERVATIONS(OBSERVATIONS) string OBSERVATIONS:units = NIL string OBSERVATIONS:description = NIL double JULIAN_DAY(OBSERVATIONS) string JULIAN_DAY:units = "fractional days" string JULIAN_DAY:description = "Days since noon on January 1, 4713 BCE" double JULIAN_DAY_START(JULIAN_DAY_START) string JULIAN_DAY_START:units = "fractional days" string JULIAN_DAY_START:description = "Reference julian day at 0900 UTC, 7th September 2017" float LON(OBSERVATIONS) string LON:units = "degrees" string LON:description = "Longitude" float LAT(OBSERVATIONS) string LAT:units = "degrees" string LAT:description = "Latitude" float OROGRAPHY(OBSERVATIONS) string OROGRAPHY:units = "m" string OROGRAPHY:description = "Altitude of surface" float TSFC(OBSERVATIONS) string TSFC:units = "K" string TSFC:description = "Skin temperature" float LSM(OBSERVATIONS) string LSM:units = "0-1" string LSM:description = "Land-sea mask" float SEAICE(OBSERVATIONS) string SEAICE:units = "0-1" string SEAICE:description = "Sea ice fraction" float U10(OBSERVATIONS) string U10:units = "m s-1" string U10:description = "10m wind speed zonal component" float V10(OBSERVATIONS) string V10:units = "m s-1" string V10:description = "10m wind speed meridional component" float PRESSURE_FULL(OBSERVATIONS, LEVELS_FULL) string PRESSURE_FULL:units = "Pa" string PRESSURE_FULL:description = "Full level pressure" float PRESSURE_HALF(OBSERVATIONS, LEVELS_HALF) string PRESSURE_HALF:units = "Pa" string PRESSURE_HALF:description = "Half (bounding) level pressure including surface pressure at level 138" float GEOPOTENTIAL(OBSERVATIONS, LEVELS_FULL) string GEOPOTENTIAL:units = "m2 s-2" string GEOPOTENTIAL:description = "Geopotential height (divide by g for approximate level altitude)" float T(OBSERVATIONS, LEVELS_FULL) string T:units = "K" string T:description = "Temperature" float Q(OBSERVATIONS, LEVELS_FULL) string Q:units = "kg kg-1" string Q:description = "Specific humidity" float O3(OBSERVATIONS, LEVELS_FULL) string O3:units = "kg kg-1" string O3:description = "Ozone" float CLW(OBSERVATIONS, LEVELS_FULL) string CLW:units = "kg kg-1" string CLW:description = "Cloud liquid water (large scale)" float CIW(OBSERVATIONS, LEVELS_FULL) string CIW:units = "kg kg-1" string CIW:description = "Cloud ice (large scale)" float CC(OBSERVATIONS, LEVELS_FULL) string CC:units = "0-1" string CC:description = "Cloud cover (large scale)" float RAIN_LS(OBSERVATIONS, LEVELS_FULL) string RAIN_LS:units = "kg kg-1" string RAIN_LS:description = "Rain (large scale)" float SNOW_LS(OBSERVATIONS, LEVELS_FULL) string SNOW_LS:units = "kg kg-1" string SNOW_LS:description = "Snow (large scale)" float PRECIP_FRACTION_LS(OBSERVATIONS, LEVELS_FULL) string PRECIP_FRACTION_LS:units = "0-1" string PRECIP_FRACTION_LS:description = "Preciptitation fraction (large scale)" float RAIN_CV(OBSERVATIONS, LEVELS_FULL) string RAIN_CV:units = "kg kg-1" string RAIN_CV:description = "Rain (convective)" float SNOW_CV(OBSERVATIONS, LEVELS_FULL) string SNOW_CV:units = "kg kg-1" string SNOW_CV:description = "Snow (convective)" ;