Cloud influence on radiative cooling over the Tibetan Plateau during the summer monsoon period
The spatial and temporal variations of tropospheric longwave cooling, shortwave heating and cloud effects on these processes over the Tibetan Plateau during the summer monsoon season of 1988 are studied using infrared and visible measurements from the Indian geosynchronous satellite (INSAT). Estimates of surface temperature, surface albedo, cloud amount, cloud height, cloud water content, and effective radius of cloud drops are incorporated in a 27-band infrared model and a 38-band solar model to calculate radiative divergence profiles. The effects of cloudiness are parameterized in terms of water/ice contents and effective radius. Cloud effective radius is obtained through an optimization scheme which minimizes the top-of-atmospheric shortwave flux differences between INSAT visible measurements and estimates from the solar model. A theoretically consistent parameterization scheme is developed for calculating the cloud asymmetry parameter as a continuous function of wavelength and effective radius. The mean radiative effect of cloudiness over the large-scale elevated plateau during the course of the summer monsoon is to cool the atmosphere. However, the cooling takes place by virtue of cloud-induced longwave cooling dominating cloud-induced shortwave heating. This is completely opposite of the conventional view in which cloud causes infrared warming and solar cooling. Vertically, cloud-induced radiative cooling is strongest in the middle troposphere with weaker cooling rates in the lower troposphere. Therefore, clouds contribute indirectly to an increase in atmospheric heating through reducing static stability and thus aid the release of latent heat by cloud systems. Plateau radiative cooling rates vary significantly through different monsoon phases, primarily due to variations in cloud forcing.
- Research Organization:
- Florida State Univ., Tallahassee, FL (United States)
- OSTI ID:
- 6194358
- Resource Relation:
- Other Information: Ph.D. Thesis
- Country of Publication:
- United States
- Language:
- English
Similar Records
Surface forcing of the infrared cooling profile over the Tibetan Plateau. Part II: Cooling-rate variation over large-scale plateau domain during summer monsoon transition
Impact of Dust-Cloud-Radiation-Precipitation Dynamical Feedback on Subseasonal-to-Seasonal Variability of the Asian Summer Monsoon in Global Variable-Resolution Simulations With MPAS-CAM5