Tropical Upper Tropospheric Trough
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A Tropical Upper Tropospheric Trough (TUTT) is a trough situated in upper-level (at about 200 hPa) tropics. Its formation is usually caused by the expansion of the Trough of Westerlies Wind to the tropics. It can also develop from the inverted trough adjacent to an upper level anticyclone. TUTTs are different from mid-latitude troughs in the sense that they are maintained by subsidence warming near the tropopause which balances radiation cooling.
TUTTs sometimes brings a large amount of vertical wind shear over tropical disturbances and cyclones and thus hinder their development. On the contrary, there are cases that TUTTs assist the genesis and intensification of tropical cyclones by providing additional forced ascent near the storm center and an efficient outflow channel in the upper troposphere. Moreover, under specific circumstances, TUTTs can grow into upper cold lows and may enhance the development of low level disturbances.
