Lawrence Livermore National Laboratory
The ARM cloud radar simulator is a ground-based cloud radar simulator developed to facilitate the comparison of climate model-simulated clouds with ARM observations from its vertically pointing radars. The simulator converts model-calculated cloud properties to what can be directly observed by a cloud radar (i.e., radar reflectivity). The ARM simulator output are joint histograms of radar reflectivity and altitude [i.e., the Contoured Frequency by Altitude Diagrams (CFADs)].
To compare with ARM cloud radar simulator outputs, observational reflectivity-height joint histograms, i.e., CFADs, are constructed from the operational ARM Active Remote Sensing of Clouds (ARSCL) Value-Added Product. The reflectivity-height data were produced for every hour with the vertical resolution of 100 m to capture both the diurnal variability and detailed vertical structures of clouds. The reflectivities (in dBZ) are binned in 5 dBZ increments from -50 dBZ to 25 dBZ. The daily- and monthly-mean data can be easily calculated from the hourly data. To date, ARM CFADs have been generated for multiple years at the ARM permanent sites.
The climate modeling community can easily and routinely compare the model-simulated clouds with ARM cloud observations and evaluate their model performance.
The ARM cloud radar simulator cannot be applied to identify model issues in simulating high thin cirrus clouds. Small cirrus cloud particles are not detectable due to the limitations of cloud radars. As a result, the cloud-top height of high thin cirrus clouds is usually underestimated by the ARM cloud radar simulator. Another big data issue is that the historical ARM cloud radar were not well calibrated when the data was created. The data will be reprocessed once the calibrated radar reflectivity is available. We recommend that users refer to the technical report or contact the relevant ARM Translators for more information on the data limitation and uncertainties for this data product.