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Abstract
In an effort to disentangle the “orographic barrier” and “high-level heat source” effects, as they may combine to lead to the development of summer convective clouds over mountains, a series of measurements was undertaken in Arizona. With use of an instrumented airplane, measurements of temperature and dew point were obtained for a series of passes up- and downwind across a 9000-ft mountain range. Passes ranged in altitude from 10,000 to 14,000 ft. Data obtained at sunrise show very clearly the barrier effect which forced air to ascend about 1000 ft in crossing the ridge. After the mountain slopes became heated by insolation, a convection core formed over and slightly downwind from the ridge. This core served as the root of several small cumulus clouds which developed during the time of measurement.
Abstract
In an effort to disentangle the “orographic barrier” and “high-level heat source” effects, as they may combine to lead to the development of summer convective clouds over mountains, a series of measurements was undertaken in Arizona. With use of an instrumented airplane, measurements of temperature and dew point were obtained for a series of passes up- and downwind across a 9000-ft mountain range. Passes ranged in altitude from 10,000 to 14,000 ft. Data obtained at sunrise show very clearly the barrier effect which forced air to ascend about 1000 ft in crossing the ridge. After the mountain slopes became heated by insolation, a convection core formed over and slightly downwind from the ridge. This core served as the root of several small cumulus clouds which developed during the time of measurement.
Abstract
Using aircraft data collected during the University of Chicago Lake-Effect Snow Storm project, the results of a case study of the convective thermal internal boundary layer (TIBL) over Lake Michigan are presented. An intense cold air outbreak on 20 January 1984 featured a rapid growth of the convective TIBL thickness and the concurrent development of cloud and snow. The average slope of the TIBL top over a fetch of 123.7 km was 1.0%. Microphysical characteristics of cloud and snow along with the TIBL development are also presented. Results of the TIBL integrated budgets of heat and total water (including cloud and snow water) are given in detail. Over the surface of Lake Michigan the average downward snow flux (snow precipitation rate) was 0.79 mm (water) per day. The average sensible and latent heat fluxes at the water surface were 323 and 248 W m−2, respectively. About 13 percent of the total warming of this cloud-topped TIBL was due to radiation.
Abstract
Using aircraft data collected during the University of Chicago Lake-Effect Snow Storm project, the results of a case study of the convective thermal internal boundary layer (TIBL) over Lake Michigan are presented. An intense cold air outbreak on 20 January 1984 featured a rapid growth of the convective TIBL thickness and the concurrent development of cloud and snow. The average slope of the TIBL top over a fetch of 123.7 km was 1.0%. Microphysical characteristics of cloud and snow along with the TIBL development are also presented. Results of the TIBL integrated budgets of heat and total water (including cloud and snow water) are given in detail. Over the surface of Lake Michigan the average downward snow flux (snow precipitation rate) was 0.79 mm (water) per day. The average sensible and latent heat fluxes at the water surface were 323 and 248 W m−2, respectively. About 13 percent of the total warming of this cloud-topped TIBL was due to radiation.
