| Tropical tropopause layer(TTL)clouds play important roles in Earth’s radiation balance and troposphere-to-stratosphere transport.TTL clouds are defined as cloud pixels with cloud top height higher than tropopause height using the combined Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations(CALIPSO)and Cloud Sat data,then we investigate and quantify TTL cloud properties,i.e.,cloud top,cloud base,cloud depth,cloud layer,cloud phase,cloud classification and etc.This study classifies TTL clouds into three types(i.e.,deep convective cores,anvil clouds,and thin cirrus clouds)and characterizes the TTL cloud properties,radiative heating and induced vertical velocity for the classified cloud types over tropical continental and oceanic convection regions(i.e.,Central Africa and South America continental regions vs.the central and western Pacific oceanic regions).The occurrence frequency of TTL clouds during the nighttime is found to be almost 13%and can reach ～50–60% in areas with frequent convections.The presence of TTL clouds causes tropopause temperature in clouds to be ～3–4°C colder than that in the all-sky condition.It also lifts the tropopause heights by ～160 m during the nighttime and lowers the heights by ～84 m during the daytime.Among the three types of TTL clouds,cirrus clouds are the most abundant(almost four-fifths),and approximately 17% and 6% of TTL clouds are anvil and deep convective core types,respectively.The heating rate and derived vertical motion indicate that the dominant contribution to shaping the overall heating rate and vertical velocity profiles is from cirrus clouds(～48.4%)due to their greater abundance.Contributions by anvil clouds and deep convective cores are also found to be significant in the regional discrepancy of TTL cloud radiative heating and induced vertical motion.The resulting mean heating rate and corresponding vertical velocity profiles show that TTL clouds can lower the level of zero net radiative heating of clear sky by ～400–900 m and result in enhanced upwelling motion throughout the TTL,supporting the mechanism that the radiative effect of TTL clouds can enhance the gas transport from the troposphere to the stratosphere.Our findings are important to better understand the contributions of different types of TTL clouds in Earth’s radiation balance and troposphere-to stratosphere transport. |
