TRANSMISSION SPECTRA OF SHORT-PERIOD EXOPLANETS WITH SIZES COMPARABLE TO NEPTUNE AND BELOW ("WARM NEPTUNES MINI NEPTUNES AND SUPER EARTHS") REVEAL LARGE VARIATIONS BETWEEN DIFFERENT PLANETS. SOME SPECTRA SHOW CLEAR MOLECULAR FEATURES WHILE OTHERS REMAIN FEATURELESS OR HAVE STRONGLY MUTED FEATURES. WHILE PART OF THIS DIFFERENCE COULD BE ATTRIBUTED TO SOME ATMOSPHERES HAVING A HIGHER MEAN MOLECULAR WEIGHT AEROSOLS LIKELY PLAY A STRONG ROLE IN MUTING SPECTRAL FEATURES AND ARE NECESSARY TO EXPLAIN SOME OF THE SPECTRA. VERTICAL MIXING PLAYS A CRUCIAL ROLE IN SHAPING THE DISTRIBUTION OF AEROSOLS - IT DETERMINES WHETHER CLOUD OR HAZE PARTICLES CAN STAY ALOFT AT ALTITUDES HIGH ENOUGH TO AFFECT TRANSMISSION SPECTRA AND IMPACTS PARTICLE GROWTH. IN THE PROPOSED STUDY WE WILL USE A 3D GENERAL CIRCULATION MODEL TO STUDY HOW THE ATMOSPHERIC CIRCULATION SHAPES VERTICAL MIXING AND THE DISTRIBUTION OF CLOUDS AND HAZES IN THE ATMOSPHERES OF WARM NEPTUNES MINI NEPTUNES AND SUPER EARTHS. WE WILL FOCUS ON QUESTIONS THAT HAVE NOT BEEN ADDRESSED SUFFICIENTLY IN PREVIOUS LITERATURE: HOW DOES THE CIRCULATION AND WITH IT THE MIXING OF AEROSOLS CHANGE OVER THE WIDE RANGE OF PLANET PROPERTIES SUCH AS RADIUS MASS EQUILIBRIUM TEMPERATURE AND COMPOSITION (HYDROGEN-DOMINATED H2O CO2)? ARE PHOTOCHEMICAL HAZES PRODUCED AT THE TOP OF THE ATMOSPHERE EXPECTED TO HAVE A DIFFERENT DISTRIBUTION IN THE ATMOSPHERE THAN CONDENSATE CLOUDS? HOW DOES THE RADIATIVE FEEDBACK FROM CLOUDS AND HAZES ALTER THE ATMOSPHERIC CIRCULATION AND HOW DOES THIS DEPEND ON THE PARTICLE PROPERTIES? TO ANSWER THESE QUESTIONS WE WILL UTILIZE THE GENERAL CIRCULATION MODEL DEVELOPED IN OUR RESEARCH GROUP A STATE-OF-THE-ART MODEL THAT HAS BEEN SUCCESSFULLY APPLIED TO A WIDE RANGE OF EXOPLANETS. AS A FIRST STEP WE WILL EXPLORE A BROAD PARAMETER RANGE WITH PASSIVE TRACER PARTICLES. THEN WE WILL EXTEND OUR MODELING TO RADIATIVELY ACTIVE TRACERS WITH DIFFERENT OPTICAL PROPERTIES REPRESENTATIVE FOR PHOTOCHEMICAL HAZES AND DIFFERENT SPECIES OF CLOUD PARTICLES. THIS WORK WILL SIGNIFICANTLY ADVANCE OUR UNDERSTANDING OF THE CONDITIONS UNDER WHICH PARTICLES CAN BE LOFTED TO ALTITUDES HIGH ENOUGH TO AFFECT TRANSMISSION SPECTRA OF EXOPLANETS AND THUS HELP ANSWER THE QUESTION WHY SOME OF THE OBSERVED SPECTRA SHOW MOLECULAR FEATURES WHILE OTHERS DO NOT