
Level 2b Cloudnet product:Ice water content (radartemperature method) on ECMWF model gridData Home  Overview of Cloudnet products  Product list  Quicklooks  Conditions of useSummary
Dataset contentsSample NetCDF file: 20031001_chilbolton_iwcZTecmwfgrid.nc The following is a description of the variables in this product, produced automatically from the metadata in the sample file (using the nc2html unix utility): Dataset title: Ice water content at Chilbolton averaged to the ECMWF Integrated Forecast System (IFS) gridThis dataset contains ice water content derived using radar reflectivity and temperature, averaged on to the grid of a forecast model. It also contains the ice water content from that model, so may be used to calculate statistics quantifying the model performance.
Software version:1.1 Dimensions and coordinate variablestimeHours UTC
Type:singleprecision floatingpoint vector Height above ground
Type:singleprecision floatingpoint array Variableshorizontal_resolutionHorizontal resolution of model
Type:singleprecision floatingpoint scalar Height of radar above mean sea level
Type:singleprecision floatingpoint scalar Time since initialization of forecast For each profile in the file this variable contains the time elapsed since the initialization time of the forecast from which it was taken. Note that the profiles in this file may be taken from more than one forecast. Units:hoursType:singleprecision floatingpoint vector Height above ground The heights have been calculated using pressure, temperature and specific humidity. Units:mType:singleprecision floatingpoint array Latitude of site
Type:singleprecision floatingpoint scalar Longitude of site
Type:singleprecision floatingpoint scalar Observed mean ice water content, 1 hour sampling This variable is the observed mean ice water content derived from radar reflectivity factor and temperature using an empirical formula derived using aircraft data, averaged onto the model grid with height, and 1 hour in time. The formula has been applied where the "categorization" data has diagnosed that the radar echo is due to ice, but note that the phase of pixels is sometimes misdiagnosed. Where microwave radiometer liquid water path was available it was used to correct the radar for liquid attenuation when liquid cloud occurred below the ice, but there is some uncertainty in this prodedure. This variable does not include ice water content retrievals in situations of uncorrected attenuation (due to liquid water clouds beneath the ice cloud but no microwave radiometer data; rain and melting ice beneath the ice cloud; attenuation due to wetting of the radome when the rain reaches the surface); ice clouds being detected only by the lidar. In these situations the ice water content will be assigned "missing_value". Units:kg m^{3}Type:singleprecision floatingpoint array Observed mean ice water content, 40 km. This variable is the same as the observed mean ice water content, iwc, except that model winds were used to estimate the time taken to advect the cloud a distance equivalent to the model's horizontal resolution of 40 km (max 1 hour, min 10 minutes). Units:kg m^{3}Type:singleprecision floatingpoint array Observed mean ice water content (including attenuated profiles), 1 hour sampling This variable is the same as the observed mean ice water content, iwc, except that profiles with uncorrected attenuation of the radar reflectivity were included (although profiles with rain at the surface were still excluded) and should therefore only be used when the effect of attenuation is being studied. Units:kg m^{3}Type:singleprecision floatingpoint array Observed mean ice water content (including attenuated profiles), 40 km. This variable is the same as the advected observed mean ice water content, iwc_adv, except that profiles with uncorrected attenuation of the radar reflectivity were included (although profiles with rain at the surface were still excluded) and should therefore only be used when the effect of attenuation is being studied. Units:kg m^{3}Type:singleprecision floatingpoint array Observed mean ice water content (including attenuated and raining profiles), 1 hour sampling This variable is the same as the observed mean ice water content including attenuation, iwc_inc_att, except that profiles with rain at the surface were also included. It should only be used when the effect of attenuation is being studied. Radome attenuation is a serious problem for some of these profiles. Units:kg m^{3}Type:singleprecision floatingpoint array Observed mean ice water content (including attenuated and raining profiles), 40 km. This variable is the same as the advected observed mean ice water content including attenuation, iwc_adv_inc_att, except that profiles with rain at the surface were also included. It should only be used when the effect of attenuation is being studied. Radome attenuation is a serious problem for some of these profiles. Units:kg m^{3}Type:singleprecision floatingpoint array Model ice water content
Type:singleprecision floatingpoint array Model ice water content including snow The ECMWF model treats ice cloud and snow separately, with snow not contributing to cloud fraction or ice water content. This variable is model ice water content but with the contribution of model snow added. See Hogan et al. (2001, J. Appl. Meteorol., 40, 513525) for further discussion. Units:kg m^{3}Type:singleprecision floatingpoint array Model ice water content with undetectable cirrus removed using best guess of radar sensitivity This variable is model ice water content, filtered to remove ice cloud deemed to be too tenuous to be detected by the radar. The best guess of the radar sensitivity has been used, and the spread of IWC across the grid box assumed to be described by a gamma distribution (Hogan and Illingworth, 2003, J. Atmos. Sci., 60, 756767). Units:kg m^{3}Type:singleprecision floatingpoint array Model ice water content with undetectable cirrus removed assuming radar 3 dB less sensitive than best guess This variable is the same as "model_iwc_filtered" except that the sensitivity of the radar is taken to be 3 dB worse. It therefore provides an approximate estimate of the uncertainty associated with the removal of undetectable ice clouds from the model. Units:kg m^{3}Type:singleprecision floatingpoint array Model ice water content with undetectable cirrus removed assuming radar 3 dB more sensitive than best guess This variable is the same as "model_iwc_filtered" except that the sensitivity of the radar is taken to be 3 dB better. It therefore provides an approximate estimate of the uncertainty associated with the removal of undetectable ice clouds from the model. Units:kg m^{3}Type:singleprecision floatingpoint array Model ice water content with snow added and undetectable cirrus removed using best guess of radar sensitivity This variable is the same as "model_iwc_filtered" but with snow added in the same way as in "model_snow_iwc". Units:kg m^{3}Type:singleprecision floatingpoint array Model ice water content with snow added and undetectable cirrus removed assuming radar 3 dB less sensitive than best guess This variable is the same as "model_iwc_filtered_min" but with snow added in the same way as in "model_snow_iwc". Units:kg m^{3}Type:singleprecision floatingpoint array Model ice water content with snow added and undetectable cirrus removed assuming radar 3 dB more sensitive than best guess This variable is the same as "model_iwc_filtered_max" but with snow added in the same way as in "model_snow_iwc". Units:kg m^{3}Type:singleprecision floatingpoint array These pages are maintained by . 