Applications of Water Vapour channel data

Imaging in the water vapour channel greatly enhances insight into atmospheric circulation and humidity in the middle atmosphere. The physical basis of water vapour band is the strong absorption of emitted terrestial radiation by atmospheric water vapour. The water vapour channel peaks at 400 mb and the radiance is used for computation of mid-tropospheric moisture content (Velden et al., 1997; Joshi et al., 2001). Water vapour structure also correlates very well with atmospheric motion and thus can be used to delineate jet cores. Thick CB clouds with anvil appear prominently in both water vapour and thermal data. Water vapour appearing as plumes are indicators of heavy rainfall regions, leading to flash floods. IMD has also started using water vapour images. Some of the applications are:

• Water vapour plumes appearing as a tongue or stream of moisture indicating cyclonic circulation leading to heavy rainfall.

• Forecasting track of cyclones, such as recurvature indicated by the moisture envelop around the cyclone field (Bhatia et al., 1999).

• Filling of gap in upper air observations (low density of radiosonde stations in tropics).

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