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Convective Available Potential Energy and Precipitation in a Cloud-Resolving Model Simulation of Indian Summer Monsoon

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Abstract

Relationship between convective available potential energy (CAPE) and precipitation is explored in a season-long cloud-resolving model (CRM) simulation of Indian summer monsoon. The location of maximum precipitation and CAPE does not always coincide in a CRM simulation. The diurnal land surface heating is shown to have an effect on CAPE and precipitation over ocean. Convective inhibition energy is shown to have a significant effect on the location of precipitation. It is shown that mass flux parameterizations which depend on CAPE consumption do not get the location or magnitude of precipitation right at CRM resolution. It is emphasized that once the model resolution starts approaching cloud scale, the basic assumption of convective quasi-equilibrium is not sufficient and representation of organized mesoscale convective systems becomes imperative. Present-day cumulus parameterizations do not include any representation of organized mesoscale convective systems. We show that CAPE consumed by these systems not only triggers vertical motion but also contributes to horizontal motion of the system.

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... The variations in monsoon rainfall are also influenced by CAPE, which is considered as the positive buoyancy to be available for an air parcel to rise. The consumption of CAPE is associated with convective activity (Jain et al. 2019) and is essential for the formation of convective clouds. The association between CAPE and summer monsoon rainfall over central India and the Bay of Bengal (BoB) on a diurnal scale was studied by Jain et al. (2019). ...
... The consumption of CAPE is associated with convective activity (Jain et al. 2019) and is essential for the formation of convective clouds. The association between CAPE and summer monsoon rainfall over central India and the Bay of Bengal (BoB) on a diurnal scale was studied by Jain et al. (2019). They found that the maximum CAPE occurs six hours prior to the precipitation over land (i.e., central India) and 3 h prior to the precipitation over the BoB. ...
... Most of the Indian regions including the northeast, northwest and central Indian regions associated with high values of CAPE (about 700-800 J kg −1 ) (Fig. 1c). Usually, the convection is likely to occur in the regions with a high value of CAPE (Jain et al. 2019). This is evident from Fig. 1c, that the regions with high values of CAPE (mainly the northeast, central India and foothills of Himalayas) are associated with a high amount of rainfall as shown in Fig. 1a. ...
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The present study explored the influence of different convective parameters such as lower tropospheric stability (LTS), low and medium cloud covers (LCC and MCC), and convective available potential energy (CAPE) on the regional variability of Indian summer monsoon rainfall (ISMR). The variabilities and trends of summer monsoon rainfall over the west coast (WC), central India (CI), northeast (NE) and northwest (NW) regions of India were analyzed during the period 1979–2015. The linkage of convective parameters and ISMR with ENSO were also examined based on spatial and 21-year sliding correlations. The ISMR shows considerable regional variability with maximum (moderate) rainfall in the WC and NE regions (CI) and minimum in the NW regions. The ISMR shows an increasing trend in all four regions, except in the NE region, where the trend is negative. All the convective parameters exhibit significant trends; however, the trend values highly vary from one region to another. A positive correlation is observed between LTS and ISMR in the WC and CI regions. The increase in specific humidity or LTS may cause more moisture to be trapped within the lower levels which increases the low-level clouds and thus rainfall. The rainfall and CAPE are exhibiting an in-phase (out-of-phase) relationship over the WC and NW (WC and CI) regions. The out-of-phase relationship may be due to the high and low orographic influence over the WC and CI regions, respectively. Both the LCC and MCC are positively correlated with ISMR over all regions; however, a robust relationship is observed in the case of LCC. An out-of-phase relationship between Niño 3.4 index with rainfall and LCC is observed over most of the Indian regions during the summer monsoon season. However, an out-of-phase relationship is observed between Niño 3.4 index and LTS over the eastern and southeastern parts of the country. On the other hand, in the case of CAPE, a significant out-of-phase relationship is dominated only over the CI region.
... This is why we considered the CAPE and CIN in this study. Ratnam et al. (2013), Riemann-Campe et al. (2009), Blanchard (1998) and Jain et al. (2019) presented the following expressions for the CAPE and CIN: ...
... The sharp decrease in the CAPE before the triggering operations implies that this is when the accumulated charges in the cloud are ready to discharge as lightning and the water particles to fall as precipitation. The CIN refers to the power involved in external lifting and plays an important part in controlling the location of precipitation (Jain et al., 2019). A small CIN means that the energy required from other sources to lift the parcel from the base of the atmosphere to level of free convection is small and there is a large probability of the convective weather system developing further (Barkiđija and Fuchs, 2013). ...
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National Centers for Environmental Prediction NUDoC National Weather Service
National Centers for Environmental Prediction NUDoC National Weather Service (2000) Ncep fnl operational model global tropospheric analyses, continuing from
  • L J Donner
  • V T Phillips
[Donner and Phillips(2003)] Donner LJ, Phillips VT (2003) Boundary layer control on convective available potential energy: Implications for cumulus parameterization. Journal of Geophysical Research: Atmospheres 108(D22) [NCEP (2000)] National Centers for Environmental Prediction NUDoC National Weather Service (2000) Ncep fnl operational model global tropospheric analyses, continuing from july 1999. https://doi.org/10.5065/D6M043C6