Temperature in the tropical tropopause layer (TTL) are closely related to the location and strength of tropical convection. As seen in Figure 1, temperatures are especially cold near the Maritime Continent region. The location of this cold extremum corresponds well to areas of low water vapor concentration and high TTL cloud frequency. Because this cold region tends to dehydrate air circulating into it, it is sometimes referred to as the "cold trap", as it plays an important role in limiting the amount of water vapor entering the stratosphere.

The location of the cold zone shifts depending on the phase of the  El Niño-Southern Oscillation (ENSO); during La Niña, it is closer to the Maritime Continent while during  El Niño this cold zone shifts into the Central Pacific. This is because the upwelling branch of the Walker circulation is shifted into the Central Pacific during  El Niño, The dependence of the cold zone location on the ENSO phase demonstrates the close relationship between tropical convection and TTL temperatures.

The temperature dependence on convection is a result of large-scale atmospheric response to latent heating. Latent heating in convection can be generally categorized into those from (1) convective and (2) stratiform precipitation; an example is shown in Figure 2. Convective precipitation forms during the early stage of storm development, and as the storm matures, a large area of outflow forms, and in it, the weak updrafts form significant amounts of stratiform precipitation.

The key goal of this study is to assess how the atmospheric response depends on vertical variation of vertical heating. One of the key figures is shown below in Figure 3, showing that stratiform heating is more closely related to temperatures in the lower stratosphere and upper troposphere. The implication from our study is that top-heavy tropical latent heating may be a key component of TTL cooling.