Three-dimensional cloud structure observed during DOE ARM's 2009 cloud tomography field experiment

The major objective of DOE Atmospheric Radiation Measurement (ARM)'s cloud tomography Intensive Observation Period (IOP) is to demonstrate the feasibility of the cloud tomography method for long-term 3D observation of cloud and water vapor. During the Summer of 2009, five scanning microwave radiometers were deployed along an eight-kilometer line at the Southern Great Plains site and programmed to continuously scan the upper hemisphere. The quality of the radiometric data is evaluated by examining radiation closure during clear sky conditions. The calculated brightness temperatures agree with the observed ones within 1.0 K when concurrent radiosonde measurements are used. Using a constrained cloud tomography retrieval algorithm, we are able to obtain a 2D slice of both the cloud liquid and the water vapor fields every two minutes. We then can construct 3D images of cloud and water vapor by combining sequential 2D slices in the same way as a spiral CT scanner reconstructs a 3D human image from multiple 2D slices. We will present the cloud and water vapor retrieval results for a variety of sky cover conditions. The high-resolution tomographic retrievals provide a unique opportunity for investigating the life cycle of warm clouds, the diurnal evolution of water vapor fields, and the interaction between them.