Not listed EFFICIENT AND ACCURATE CALCULATION OF SINGLE SCATTERING PROPERTIES OF REALISTIC HYDROMETEORS FOR BETTER INTERPRETATION OF MICROWAVE OBSERVATIONS $0 4/3/24 P00007 EFFICIENT AND ACCURATE CALCULATION OF SINGLE SCATTERING PROPERTIES OF REALISTIC HYDROMETEORS FOR BETTER INTERPRETATION OF MICROWAVE OBSERVATIONS Other Administrative Action $0 4/3/24 Not listed CHARACTERIZING THE SINGLE SCATTERING PROPERTIES (SSPS) OF REALISTIC HYDROMETEORS IS IMMEDIATELY AND INCREASINGLY NEEDED FOR A BETTER INTERPRETATION AND ANALYSIS OF PASSIVE AND ACTIVE MICROWAVE PRECIPITATION OBSERVATIONS. A FAITHFUL REPRESENTATION OF THE EM BEHAVIOR OF PRECIPITATION PARTICLES REQUIRES A NUMERICALLY EFFICIENT MODEL TO RIGOROUSLY CALCULATE THE SCATTERING BY ELECTRICALLY LARGE PARTICLES WITH REALISTIC COMPLEX SHAPES AND DIELECTRIC PROPERTIES AND THIS OVER A SUFFICIENTLY LARGE NUMBER OF PARTICLE ORIENTATIONS. THE DISCRETE DIPOLE APPROXIMATION (DDA) IS ONE OF THE MAIN APPROACHES THAT HAS BEEN USED TO THIS END IN THE LAST DECADE BEING A GEOMETRY-FLEXIBLE AND NUMERICALLY LOW-COST TECHNIQUE FOR COMPUTING SCATTERING AND ABSORPTION OF LIGHT BY PARTICLES OF ARBITRARY GEOMETRY AND INTERNAL DIELECTRIC COMPOSITION. THE DDA IS A POWERFUL TECHNIQUE BASED ON MAPPING THE COMPLEX-SHAPED PARTICLE INTO AN ARRAY OF N DIPOLES THAT TOGETHER REPRODUCE THE SHAPE AND INTERNAL OPTICAL RESPONSE OF THE ORIGINAL PARTICLE. NEVERTHELESS THE DDA PRESENTS TWO MAJOR LIMITATIONS. FIRST THE ACCURACY OF THIS APPROXIMATION STRONGLY DEPENDS ON THE PRECISION OF THE PARTICLE DISCRETIZATION NAMELY THE INTER-DIPOLE DISTANCE D WHICH MUST FULFILL THE VALIDITY CRITERIA M KD < 0.5 WHERE M IS THE COMPLEX REFRACTIVE INDEX AND K IS WAVELENGTH NUMBER. THEN SINCE THE CURRENT IMPLEMENTATIONS OF THE DDA (DDSCAT AND ADDA) ARE ITERATIVE-SOLVER BASED THE CALCULATION OF ORIENTATIONALLY-AVERAGED SSPS REQUIRES REPEATEDLY SOLVING COMPUTATIONALLY DEMANDING LINEAR EQUATIONS FOR EACH PARTICLE ORIENTATION. IN AGGREGATE TERMS BEING BASED ON ITERATIVE METHODS THE DDA IS TODAY EXCESSIVELY SLOW FOR LARGE PARTICLE SIZE PARAMETERS (XKA) LARGE VALUES OF THE REFRACTIVE INDEX LARGE NUMBERS OF DIPOLES AND LARGE TARGET ORIENTATIONS. FOR EXAMPLE TH CALCULATION OF THE SCATTERING PROPERTIES OF ONE SINGLE MEDIUM SIZE SNOW AGGREGATE (X24) COMPOSED OF N 140 896 DIPOLES OVER ONLY 2000 TARGET ORIENTATIONS AT F 200 GHZ REQUIRES ALMOST 1 YEAR OF CPU TIME WITH DDSCAT. TO OVERCOME THIS LIMITATION WE HAVE CHOSEN TO APPLY RATHER A DIRECT SOLVER-BASED METHOD KNOWN AS THE CHARACTERISTIC BASIS FUNCTION METHOD (CBFM). THIS DOMAIN DECOMPOSITION METHOD IS BASED ON THE GENERATION OF A NEW SET OF BASIS FUNCTION ADAPTED TO THE GEOMETRY OF THE SCATTERER IN ORDER TO SIGNIFICANTLY REDUCE THE NUMERICAL SIZE OF THE INITIAL EM PROBLEM. THIS ENABLES US TO USE A DIRECT SOLVER FOR THE RESOLUTION OF THE FINAL COMPRESSED SYSTEM OF LINEAR EQUATIONS WHICH IS BETTER ADAPTED THAN AN ITERATIVE SOLVER FOR MULTIPLE RIG HAND SIDES PROBLEMS. NAMELY THE CBFM WILL ENABLE US TO TRANSFORM THE ORIGINAL PROBLEM OF SIZE 3N 3N TO A COMPRESSED ONE OF SIZE K K WITH K $0 4/17/23 P00006 CHARACTERIZING THE SINGLE SCATTERING PROPERTIES (SSPS) OF REALISTIC HYDROMETEORS IS IMMEDIATELY AND INCREASINGLY NEEDED FOR A BETTER INTERPRETATION AND ANALYSIS OF PASSIVE AND ACTIVE MICROWAVE PRECIPITATION OBSERVATIONS. A FAITHFUL REPRESENTATION OF THE EM BEHAVIOR OF PRECIPITATION PARTICLES REQUIRES A NUMERICALLY EFFICIENT MODEL TO RIGOROUSLY CALCULATE THE SCATTERING BY ELECTRICALLY LARGE PARTICLES WITH REALISTIC COMPLEX SHAPES AND DIELECTRIC PROPERTIES, AND THIS OVER A SUFFICIENTLY LARGE NUMBER OF PARTICLE ORIENTATIONS. THE DISCRETE DIPOLE APPROXIMATION (DDA) IS ONE OF THE MAIN APPROACHES THAT HAS BEEN USED TO THIS END IN THE LAST DECADE, BEING A GEOMETRY-FLEXIBLE AND NUMERICALLY LOW-COST TECHNIQUE FOR COMPUTING SCATTERING AND ABSORPTION OF LIGHT BY PARTICLES OF ARBITRARY GEOMETRY AND INTERNAL DIELECTRIC COMPOSITION. THE DDA IS A POWERFUL TECHNIQUE BASED ON MAPPING THE COMPLEX-SHAPED PARTICLE INTO AN ARRAY OF N DIPOLES THAT TOGETHER REPRODUCE THE SHAPE AND INTERNAL OPTICAL RESPONSE OF THE ORIGINAL PARTICLE. NEVERTHELESS, THE DDA PRESENTS TWO MAJOR LIMITATIONS. FIRST, THE ACCURACY OF THIS APPROXIMATION STRONGLY DEPENDS ON THE PRECISION OF THE PARTICLE DISCRETIZATION, NAMELY THE INTER-DIPOLE DISTANCE D WHICH MUST FULFILL THE VALIDITY CRITERIA |M|KD < 0.5 WHERE M IS THE COMPLEX REFRACTIVE INDEX AND K IS WAVELENGTH NUMBER. THEN, SINCE THE CURRENT IMPLEMENTATIONS OF THE DDA (DDSCAT AND ADDA) ARE ITERATIVE-SOLVER BASED, THE CALCULATION OF ORIENTATIONALLY-AVERAGED SSPS REQUIRES REPEATEDLY SOLVING COMPUTATIONALLY DEMANDING LINEAR EQUATIONS FOR EACH PARTICLE ORIENTATION. IN AGGREGATE TERMS, BEING BASED ON ITERATIVE METHODS, THE DDA IS TODAY EXCESSIVELY SLOW FOR LARGE PARTICLE SIZE PARAMETERS (XKA), LARGE VALUES OF THE REFRACTIVE INDEX, LARGE NUMBERS OF DIPOLES AND LARGE TARGET ORIENTATIONS. FOR EXAMPLE, TH CALCULATION OF THE SCATTERING PROPERTIES OF ONE SINGLE MEDIUM SIZE SNOW AGGREGATE (X24), COMPOSED OF N 140 896 DIPOLES, OVER ONLY 2000 TARGET ORIENTATIONS AT F 200 GHZ REQUIRES ALMOST 1 YEAR OF CPU TIME WITH DDSCAT. TO OVERCOME THIS LIMITATION, WE HAVE CHOSEN TO APPLY RATHER A DIRECT SOLVER-BASED METHOD, KNOWN AS THE CHARACTERISTIC BASIS FUNCTION METHOD (CBFM). THIS DOMAIN DECOMPOSITION METHOD IS BASED ON THE GENERATION OF A NEW SET OF BASIS FUNCTION ADAPTED TO THE GEOMETRY OF THE SCATTERER, IN ORDER TO SIGNIFICANTLY REDUCE THE NUMERICAL SIZE OF THE INITIAL EM PROBLEM. THIS ENABLES US TO USE A DIRECT SOLVER FOR THE RESOLUTION OF THE FINAL COMPRESSED SYSTEM OF LINEAR EQUATIONS, WHICH IS BETTER ADAPTED THAN AN ITERATIVE SOLVER FOR MULTIPLE RIG HAND SIDES PROBLEMS. NAMELY, THE CBFM WILL ENABLE US TO TRANSFORM THE ORIGINAL PROBLEM OF SIZE 3N 3N TO A COMPRESSED ONE OF SIZE K K, WITH K Other Administrative Action $0 4/17/23 P00005 CHARACTERIZING THE SINGLE SCATTERING PROPERTIES (SSPS) OF REALISTIC HYDROMETEORS IS IMMEDIATELY AND INCREASINGLY NEEDED FOR A BETTER INTERPRETATION AND ANALYSIS OF PASSIVE AND ACTIVE MICROWAVE PRECIPITATION OBSERVATIONS. Other Administrative Action $0 3/16/22