We highlight recent progress in and discuss future plans for the OpenSSP particle and scattering property database. Ongoing work has focused on expanding the types of particles to include polycrystals and melting snowflakes. Future expansion will include rimed particles, hail, and aligned snowflakes.

To address the acute challenge posed by the melting layer to accurate surface precipitation retrievals from space, we ensure the compositional consistency in ice, liquid, and total masses of synthetic melting hydrometeors with a method of stochastic compensation. The method is applied to simulated melting hydrometeors prior to calculating their scattering properties using the discrete dipole approximation (DDA). We investigate the impact of this stochastic compensation to calculated scattering properties by contrasting it with a naïve approach and report our findings.

Presents a computationally simple technique for retrieving the precipitation and vertical hydrometeor profiles from downward viewing radiometers. The technique is computationally much less expensive than previous profiling schemes and has been designed specifically to allow for tractability of assumptions. In this paper, the emphasis is placed upon passive microwave applications, but the combination of passive with active microwave sensors, infrared sensors, or other a priori information can be adapted easily to the framework described. The technique is based upon a Bayesian approach. The authors use many realizations of the Goddard Cumulus Ensemble model to establish a prior probability density function of rainfall profiles. Detailed three-dimensional radiative transfer calculations are used to determine the upwelling brightness temperatures from the cloud model to establish the similarity of radiative signatures and thus the probability that a given profile is actually observed. In this study, the authors show that good results may be obtained by weighting profiles from the prior probability density function according to their deviation from the observed brightness temperatures. Examples of the retrieval results are shown for oceanic as well as land situations. Microwave data from the Advanced Microwave Precipitation Radiometer (AMPR) instrument are used to illustrate the retrieval structure results for high-resolution data while SSM/I is used to illustrate satellite applications. Simulations are performed to compare the expected retrieval performance of the SSM/I instrument with that of the upcoming TMI instrument aboard the Tropical Rainfall Measuring Mission (TRMM) to be launched in August 1997. These simulations show that correlations of /spl sim/0.77 may be obtained for 10-km retrievals of the integrated liquid water content based upon SSM/I channels. This correlation increases to /spl sim/0.90 for the same retrievals using the TMI channels and resolution. Due to the lack of quantitative validation data, hydrometeor profiles cannot be compared directly but are instead converted to an equivalent reflectivity structure and compared to existing radar observations where possible.

The authors describe and apply a correction technique for matching the resolution of all the frequencies of the Special Sensor Microwave/Imager (SSM/I) to the 25-km spatial resolution of the 37-GHz channel. To accomplish this, it is necessary to increase the spatial resolution of the 19- and 22-GHz channels while degrading that of the 85-GHz channel. It is found that the approach produces adequate enhancement of the spatial resolution to make such a correction worthwhile. Results suggest that this technique decreases brightness temperature differences stemming solely from spatial resolution differences by over 50% for the low resolution channels with only a modest increase in random noise. The correction can also help to better resolve small features which would otherwise be lost due to the lack of resolution.>

A constrained iterative image restoration method is applied to multichannel diffraction-limited imagery. This method is based on the Gerchberg-Papoulis algorithm utilizing incomplete information and partial constraints. The procedure is described using the orthogonal projection operators which project onto two prescribed subspaces iteratively. Its properties and limitations are presented. The effect of noise was investigated and a better understanding of the performance of the algorithm with noisy data has been achieved. The restoration scheme with the selection of appropriate constraints was applied to a practical problem. The 6.6, 10.7, 18, and 21 GHz satellite images obtained by the scanning multichannel microwave radiometer (SMMR), each having different spatial resolution, were restored to a common, high resolution (that of the 37 GHz channels) to demonstrate the effectiveness of the method. Both simulated data and real data were used in this study. The restored multichannel images may be utilized to retrieve rainfall distributions.