JET STREAMS ARE RELATIVELY NARROW BANDS OF STRONG WEST-TO-EAST WINDS IN THE UPPER TROPOSPHERE AND ARE IMPORTANT CHARACTERISTICS OF THE ATMOSPHERIC CIRCULATION. AVERAGING OVER ALL LONGITUDES THERE ARE TWO JET STREAMS THE SUBTROPICAL JET (STJ) AND POLAR FRONT JET (PFJ) LOCATED IN BOTH THE NORTHERN AND SOUTHERN HEMISPHERES. UNDERSTANDING VARIABILITY IN THE POSITION AND STRENGTH OF THE JET STREAMS IS IMPORTANT AS THEY DIRECTLY INFLUENCE IMPACTFUL SURFACE WEATHER EVENTS SUCH AS HEATWAVES COLD AIR OUTBREAKS AND EXTRATROPICAL STORM.TRACKS AND THEIR ASSOCIATED HEAVY PRECIPITATION EVENTS. HOWEVER THE DOMINANT PHYSICAL MECHANISMS CONTROLLING THE MEAN-STATE JET STREAMS AND THEIR VARIATIONS IN POSITION AND/OR STRENGTH REMAIN AN AREA OF ACTIVE RESEARCH..SOME RECENT STUDIES HAVE HYPOTHESIZED THAT MOIST PROCESSES HAVE SIGNIFICANT IMPACT ON THE JET STREAMS IN THE CURRENT CLIMATE AND IN RESPONSE TO CLIMATE CHANGE. HOWEVER THE SEPARATE INFLUENCE OF LATENT HEATING AND CLOUD RADIATIVE HEATING ON THE JET STREAMS AND THEIR RELATIVE IMPORTANCE HAS NOT BEEN EXAMINED IN DETAIL YET. IN ADDITION PREVIOUS STUDIES WHICH FOCUSED ON VERTICALLY-INTEGRATED LATENT HEATING/CLOUD RADIATIVE HEATING OR ZONAL-MEAN JETS MAY FAIL TO CAPTURE SOME SIGNIFICANT RELATIONSHIPS AT INDIVIDUAL LONGITUDES AND AT SPECIFIC VERTICAL LEVELS. THIS STUDY WILL EXAMINE THE REGIONAL CHARACTERISTICS OF THE JET STREAMS AND THE ROLE OF MOIST PROCESSES IN.MODULATING THE MEAN-STATE AND VARIABILITY OF THEIR POSITIONS AND STRENGTHS..THE PROPOSED PROJECT HAS TWO PARTS. THE FIRST PART OF THE PROJECT WILL EXAMINE HOW THE MEAN-STATE JET STREAMS ARE INFLUENCED BY MOIST PROCESSES IN TWO WAYS: LATENT HEAT RELEASE AND CLOUD RADIATIVE EFFECTS. LATENT HEATING AND CLOUD RADIATIVE EFFECTS WILL BE DEFINED FROM MERRA-2 REANALYSIS AND NASA SATELLITE PRODUCTS FROM THE GPM AND CLOUDSAT MISSIONS. EXPERIMENTS WILL BE CONDUCTED USING A STATIONARY WAVE MODEL TO PARTITION THE INFLUENCE OF LATENT HEATING AND CLOUD RADIATIVE HEATING ON THE MEAN-STATE JET STREAMS. A SERIES OF EXPERIMENTS WILL BE CONDUCTED WITH THE STATIONARY WAVE MODEL WITH DIFFERENT LATITUDES OR VERTICAL LEVELS OF LATENT HEATING OR.CLOUD RADIATIVE HEATING ABSENT AS PERTURBATION EXPERIMENTS. THE SECOND PART OF THE PROJECT WILL EXAMINE THE RELATIONSHIP BETWEEN JET VARIABILITY AND LATENT HEATING/CLOUD RADIATIVE HEATING IN OBSERVATIONS AND TRY TO UNDERSTAND THE DIRECTION OF CAUSALITY BETWEEN THEM USING VARIOUS REGRESSION TECHNIQUES.