Notes Sensing Hadley cell with space-borne lidar

Some recent studies reported expansion of the Earth's tropical regime in the past few decades. The poleward expansion of the Hadley cell is a strong indication of the warming of the globe. The extent of Hadley cell also has very important implications to the climate of dry subtropical regions because of the prevalence of precipitation in the deep tropical belt. Determination of the Hadley circulation especially its extent has great significance for monitoring global climate change and for the subtropical climate studies. Although many methods have been developed in recent years, reliable measurement of the extent of Hadley cell is still an issue in climate studies. This letter shows that the extent of the Hadley cell could reliably be estimated by measuring the height of the uppermost super-thin clouds in the troposphere with space-borne lidar. Through consecutive multi-year measurements of the height of the uppermost super-thin clouds, a good estimation of the expansion of the Hadley cell could be obtained.