Dependence of the precipitation intensity in mesoscale convective systems to temperature lapse rate

Abstract

The dependence of the structure and intensity of precipitation generated within squall lines to environmental temperature lapse rate is investigated by the use of a large set of numerical experiments under idealized model configurations. The lapse rate in a convectively unstable layer is used for the present analysis. The mean precipitation intensity during the simulated period generally increases with the increase in lapse rate, while the maximum precipitation intensity increases with the decrease in lapse rate. The precipitation mean is dependent on the intensity of cold pool resulting from organized convective clouds. In contrast, the precipitation maxima is regulated by relative humidity within the tropospheric lower layer. In an environment with higher lapse rate, a larger amount of CAPE is distributed in a deeper layer of the lower troposphere, which is beneficial for the development and intensification of convection and precipitation. Lapse rate in the troposphere is useful in comparing the characteristics of precipitation produced by mesoscale convective systems that occur in various climate regions of the world and also produced in a future climate under global warming.

Environmental Stability for Convective Precipitation Under Global Warming

“…In the environments projected in the future periods, temperature lapse rate decreases but CAPE increases. Consequently, convection intensity and mean precipitation does not decrease, according to the results of Takemi (2010). Precipitation amount will be maintained or even intensified in the future climates.…”

“…One of the interesting points in Takemi (2010) was that the maximum precipitation intensity increases with the decrease in temperature lapse rate while with CAPE being unchanged. On the other hand, the present analyses of the GCM data indicated that both static stability and CAPE increases.…”

“…He showed that a colder environment (which is more unstable) is favorable for generating stronger cold pool, which will highly control the scale and strength of convective updrafts and hence the organization and intensity of MCSs. Furthermore, Takemi (2010) concluded that temperature lapse rate in the convectively unstable troposphere is useful in comparing the characteristics of precipitation produced by MCSs that occur in various climate regions of the world. It should be pointed out that the experimental setup employed in those numerical studies was a highly idealized one which assumes horizontally homogeneous stratifications as basic environmental states.…”

“…This idealized setup is regarded as synoptically undisturbed, since only convective forcing is initial thermal and the resultant self-organizing effects. The weak shear condition (i.e., 5 m s -1 difference only in the lowest 2.5 km) examined in Takemi (2007b;2010) corresponds to the synoptically undisturbed conditions examined in this study. Their results indicated that with the same CAPE environment convection intensity (represented as updraft strength) and mean precipitation decrease as temperature lapse rate decreases.…”

“…The precipitation characteristics that will result from the projected changes in the environmental stability are discussed here. Takemi (2007b;2010) investigated the precipitation characteristics within the MCSs by changing temperature lapse rate and moisture content as well as shear profile in an idealized simulation setup where the basestate atmosphere is horizontally uniform without any external forcing. This idealized setup is regarded as synoptically undisturbed, since only convective forcing is initial thermal and the resultant self-organizing effects.…”