THE MERIDIONAL CIRCULATION PLAYS A CRITICAL ROLE IN THE TRANSPORT OF ANGULAR MOMENTUM AND MAGNETIC FLUX ACROSS A WIDE RANGE OF LATITUDES WITHIN THE CONVECTION ZONE AND IS A MAJOR COMPONENT OF MODELS OF THE DYNAMICS OF ROTATING STELLAR CONVECTION ZONES DYNAMOS AND THE SOLAR CYCLE. WE PROPOSE TO DETERMINE THE PHYSICAL PROPERTIES OF THE SUBSURFACE MERIDIONAL CIRCULATION THROUGH THE APPLICATION OF TWO LOCAL-HELIOSEISMIC PROCEDURES TO DOPPLERGRAMS FROM THE HELIOSEISMIC MAGNETIC IMAGER (HMI) ONBOARD THE SOLAR DYNAMICS OBSERVATORY (SDO) AS WELL AS ARCHIVED DATA FROM THE MICHELSON DOPPLER IMAGER (MDI) ONBOARD THE SOLAR AND HELIOSPHERIC OBSERVATORY (SOHO). THE TWO MAIN METHODS WE WILL EMPLOY ARE LEGENDRE FUNCTION DECOMPOSITION AND HELIOSEISMIC HOLOGRAPHY. INVERSE AND FORWARD MODELING WILL BE CARRIED OUT TO INFER DEPTH LATITUDE AND TEMPORAL PROPERTIES OF THE MERIDIONAL FLOW OVER A SPAN OF ALMOST TWO SOLAR CYCLES. THE TWO MAIN CHALLENGES TO A RELIABLE DETERMINATION OF THE MERIDIONAL FLOW - NAMELY A POOR SIGNAL-TO-NOISE RATIO AND THE PRESENCE OF SYSTEMATIC ARTIFACTS - WILL BE ADDRESSED BY 1) USING SUFFICIENTLY LONG DATASETS 2) IMPLEMENTING CONTROL MEASUREMENTS 3) PERFORMING COMPARISONS BETWEEN MULTIPLE METHODS AND INSTRUMENTS AND 4) CARRYING OUT VALIDATION TESTS WITH ARTIFICIAL DATA. OF PARTICULAR IMPORTANCE IS THE IDENTIFICATION AND REMOVAL OF SYSTEMATIC ARTIFACTS WHICH CAN MIMIC LARGE-SCALE FLOWS AND DETRIMENTALLY IMPACT THE MEASUREMENT OF THE LOW-AMPLITUDE MERIDIONAL CIRCULATION. THIS INVESTIGATION IS TIMELY IN THAT THE SUBSTANTIAL INVESTMENT OF RESOURCES INTO THE SOHO AND SDO MISSIONS IS NOW YIELDING THE DECADES-LONG DATASET REQUIRED FOR THE RELIABLE DETERMINATION OF THE PROPERTIES OF THESE FLOWS. THE PROJECT IS APPROPRIATE AND OF HIGH PRIORITY FOR THE HELIOPHYSICS SUPPORTING RESEARCH PROGRAM USING DATA FROM CURRENT NASA SPACECRAFT (SOHO AND SDO) IN COMBINATION WITH THEORY (INVERSIONS AND FORWARD MODELING) TO DIRECTLY ADDRESS THE GOALS OF THE HELIOPHYSICS DECADAL SURVEY. SPECIFICALLY THE DETERMINATION OF THE TEMPORAL AND SPATIAL CHARACTERISTICS OF THE SOLAR MERIDIONAL CIRCULATION IS CRITICAL FOR KEY SCIENCE GOAL 1: "DETERMINE THE ORIGINS OF THE SUN S ACTIVITY AND PREDICT THE VARIATIONS IN THE SPACE ENVIRONMENT." THE ROLE OF THE MERIDIONAL CIRCULATION IS SPECIFICALLY CALLED OUT IN THE DECADAL SURVEY REPORT WHICH NOTES THAT "THE DEEP PONDEROUS FLOWS THAT CARRY PATTERNS OF MAGNETIC FLUX TO THE POLES REGULATE THE SEEDING OF THE DEEP-SEATED DYNAMO THAT GENERATES SUBSEQUENT SOLAR CYCLES."