Influence of topography on temperature variations in the tropical tropopause layer

• Published in: Journal of geophysical research. Atmospheres 2016-10, Vol.121 (19), p.11,556-11,574
• Main Authors: Kubokawa, Hiroyasu, Satoh, Masaki, Suzuki, Junko, Fujiwara, Masatomo
• Format: Article
• Language: English
• Subjects: Atmospheric models; Big Bang theory; Computer simulation; Convection; Coordinate systems; Coordinates; Dehydration; Elevation; Equatorial waves; extreme events; Geophysics; Gravitational waves; Gravity waves; High temperature; Kelvin waves; Lower stratosphere; Madden-Julian oscillation; Mathematical analysis; Mathematical models; Mountain regions; Mountains; NICAM; Radiosonde data; Radiosondes; Regions; Satellite data; Sensitivity analysis; Stratosphere; Studies; Temperature; Temperature variations; Topography; Transistor logic; Tropical climate; Tropical tropopause; tropical tropopause layer; Tropopause; Troposphere; Upper troposphere; Variation
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2016JD025569

Temperature variations in the tropical tropopause layer (TTL) play an important role in dehydration in the upper troposphere and lower stratosphere. Equatorial Kelvin waves associated with the Madden‐Julian Oscillation (MJO) are known to induce remarkable temperature variations in the TTL. In this study, the influence of topography on temperature variations in the TTL is investigated by using radiosonde data, satellite data, reanalysis data, and numerically simulated data. When MJO convection passes over the radiosonde sites, temperature variations near mountainous regions are larger than those measured in regions of lower elevation. The difference in temperature amplitude reaches ~1–2 K. Large temperature variations over mountainous regions were also found in other data sets. Numerically simulated data from the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) are also used to investigate the temperature variations in the TTL. The results show that the temperature variations associated with Kelvin waves become large over mountainous regions. A sensitivity test using the stretched version of NICAM gave two important results: (i) the height of mountains affects the magnitude of the temperature variations in the TTL, and (ii) the terrain‐following coordinate system used in the model produces the artificially high‐temperature variation in the TTL. When Kelvin waves pass over mountainous regions, topographic gravity waves are excited and superimposed on the Kelvin waves, thereby producing large temperature variations over these regions. The mountainous region of the Indonesian Maritime Continent is a favorable location for large temperature variations in the TTL. Key Points Mountainous regions are favorable locations for large temperature variations in the TTL Superposition of gravity waves and Kelvin waves has the potential to produce the coldest region Terrain‐following coordinate system may produce unrealistic temperature variations in the TTL