Estimation of Liquid Water Amount in an Extended Cloud by Nimbus-5 Microwave Data

摘要

The possibility of estimating liquid water amount in the atmosphere from satellite microwave data was studied numerically by making use of a cloud model in which the size distribution of water drops and other factors were varied, and integrated liquid water amount in an extended cloud over the AMTEX area was estimated by using Nimbus-5 microwave data at 19.35 GHz (ESMR). Numerical calculations show that integrated liquid water amount can be estimated from satellite microwave data with the error less than 10% even in consideration of the effect of different size distribution of water drops on estimated value, if it is less than 0.30 g/cm2. In the atmosphere over the AMTEX area integrated liquid water amount was smaller than 0.12 g/cm2 during the period of cold-air outbreak from the Asian Continent (Feb. 25 to 27 in 1974). It was smaller than 0.03 g/cm2 in the system composed of only low-level clouds and it was between 0.05 and 0.12 g/cm2 in the two-layers cloud system composed of low-level clouds and middle-level clouds. The rate of conversion of cloud water into rainwater in an extended cloud was discussed on the basis of integrated liquid water amount derived from satellite microwave data and rainfall intensity measured on the ground.