Tropical tropopause layer clouds: their properties and influences on tropopause and cloud top temperatures
Abstract
Frequent convections over the tropics could bring clouds up to the tropopause and even higher, inducing cold anomalies around the tropopause. Those clouds above tropical tropopause layer (TTL) play an important role in Earth's radiation balance and troposphere-to-stratosphere transport. We quantify the macro- and micro-physical properties of TTL clouds (i.e., clouds with tops higher than tropopause) and characterize the vertical motion induced by cloud radiative heating near the tropopause, using four years (2007-2010) of multi-source data, especially collocated CALIPSO and CloudSat. Considering that TTL clouds are composed of diverse cloud types, detected TTL clouds are classified into deep convective clouds (DCCs), anvil clouds, and cirrus clouds. TTL cloud tops (i.e., 16.83 km) exceed the tropopause (i.e., 16.36 km) by approximately 0.5 km, but cloud top temperature is similar to tropopause temperature; TTL cirrus cloud tops (i.e., 17.03 km) are generally above DCC tops (i.e., 16.78 km) by approximately 0.25 km. Considering that oceanic convections are normally weaker than those over land, TTL clouds over ocean (western Pacific) are expected to be lower. Contrary to such expectation, our analysis shows that cloud top heights between land and ocean appear similar to each other. On the other hand, cloud top temperature is colder over ocean (by as larger as ~1.5 K) than over land, which is consistent with colder tropopause temperature over ocean. Colder temperatures noted at both tropopause and cloud top over ocean are thought to be associated with larger oceanic cloud-induced radiative heating near the tropopause. It is noted that the heatings are largely attributed to more abundant cirrus and anvil clouds over the western Pacific area. Such land-ocean contrasts are thought to be related to different cloud-induced radiative heating. It is because the vertical motion induced by cloud's heating should help to maintain the colder tropopause and TTL cloud top temperatures through the adiabatic cooling of the rising air.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.A14C..06L