Water vapour concentration in the upper troposphere

E. Linacre and B. Geerts

3/’02

There is evidence (1) that the net effect of the updraughts and downdraughts in tropical mesoscale convective systems is to remove moisture from the upper troposphere, whereas small convective clouds result in moisture uplift. In particular, the upper troposphere tends to dry by convection when:

  1. the average size of very cold cloud clusters (less than -50°C) is greater than 68,000 km2;
  2. less than 20% of the very cold cloud clusters (less than -50°C) have diameters less than 70 km;
  3. the rain rate is greater than 2 mm/hr (2).

 

References

  1. Barr-Kumarakulasinghe, S.A., and K. M. M. Lwiza, 1998. Deep convective cloud scales and direct adjustment of upper troposphere moisture in the tropical Western Pacific environment. Meteorology and Atmospheric Physics, 66, 35-50.
  2. Barnes, G. and M. Garstang. 1982. Subcloud layer energetics of precipitating convection. Mon. Wea. Rev. 110, 102-117.