Surface Convective Precipitation Research Articles

Differences among three types of tropical deep convective clusters observed from A-Train satellites

Deep convective clusters (DCCs) constitute a complex regime with a variety of types of cloud parameterization in multiple global climate models (GCMs). This study develops a method to identify tropical DCCs and presents regional differences in cloud occurrence, surface precipitation and a vertical survey of ice water content among separated DCCs, connected DCCs and mesoscale convective systems (MCSs) determined by collocating data from MODIS, AMSR-E, CPR and CALIOP instruments on board A-Train satellites. The results reveal that separated DCCs and MCSs occur frequently over East Asia, while connected DCCs are more common over the warm pool of the West Pacific in June-August and over South America in December-February. Higher surface convective precipitation rates occur more frequently in MCSs than in separated and connected DCCs in non-monsoon areas. However, connected DCCs have a large ice water content (IWC) at 10–15 km similar to that of MCSs, and these clusters are more intense than those in separated DCCs. Remarkably large anvil-stratiform clouds connected with multiple deep convective cores in connected DCCs can be easily confused with MCSs if the cloud top brightness temperature in the horizontal view is the only parameter being considered. Combined observational data of surface precipitation of DCCs will be helpful for distinguishing connected DCCs and MCSs.

On the association of lightning activity and projected change in climate over the Indian sub-continent

The association of lightning activity with the long-term as well as seasonal spatio-temporal distribution of convective available potential energy (CAPE), surface convective precipitation, vegetation cover and anthropogenic aerosol loading over the Indian sub-continent has been studied for the period 2000–2014. The north-east to north-west arc including the foothills of the Himalayas is the primary seats of lightning occurrences. The correlations of lightning activity with each of aerosol loading, vegetation cover, convective instability and convective precipitation helps us in understanding the definite entity that is responsible for changing the lightning activity in different parts of this tropical region. Lightning flash rate (LFR) has significant positive correlations (r ~0.5–0.7) with AOD, CAPE and surface convective precipitation but significant negative correlation (r ~−0.4) with Normalized Difference Vegetation Index (NDVI). Using global circulation models from the Climate Model Intercomparison Project Phase 5 (CMIP5), time-series of observed and projected upper tropospheric water vapor, surface convective precipitation and aerosol optical depth (AOD) from the historical simulations (1996–2005) and RCP8.5 emission scenario (2036–2045) are analyzed over the Indian region that are vulnerable to climate change in terms of occurrence of convective events and associated hazardous lightning phenomena. This study indicates that upper tropospheric water vapor (300hPa) has a significant linkage with the lightning occurrences associated with convective activities and strong updraft. During the mid- 21st century, AOD, surface convective precipitation and specific humidity are projected to increase by 1.42%, 2.01% and 1.40%, respectively which may result in regional changes in lightning activity over the Indian sub-continent.

Analysis of convective precipitation in the western Mediterranean Sea through the use of cloud-to-ground lightning

The monthly convective precipitation (CP) and convective precipitation rate (CPR) over the western Mediterranean Sea are estimated using cloud-to-ground lightning flashes for the June to October period using data of 3 years (1992–1994). Rain yield was computed using the precipitation data from seven observing stations (all equipped with rain gauges) located on the Mediterranean coast of the Iberian Peninsula and in the Balearic Islands. The values obtained were 0.93×10 8 kg/fl for the negative flashes and 20.63×10 8 kg/fl for the positive flashes. Convective precipitation over sea was estimated from the rain yield using the cloud-to-ground (CG) lightning activity detected by a lightning detection network. Because no measured data on precipitation over sea are available, the estimated convective precipitation was compared with the monthly diagnostic surface convective precipitation data from the NOAA NCEP/NCAR climate data assimilation system. Analysis of the results revealed that convective precipitation over the western Mediterranean Sea is maximum in the months September and October and near the northeastern coast of the Iberian Peninsula (maximum in the order of 240 mm/month). The convective precipitation rate exhibits less time variability than convective precipitation, although its spatial distribution is similar.

A GCSS model intercomparison for a tropical squall line observed during toga‐coare. II: Intercomparison of single‐column models and a cloud‐resolving model

AbstractThis paper presents single‐column model (SCM) simulations of a tropical squall‐line case observed during the Coupled Ocean‐Atmosphere Response Experiment of the Tropical Ocean/Global Atmosphere Programme. This case‐study was part of an international model intercomparison project organized by Working Group 4 ‘Precipitating Convective Cloud Systems’ of the GEWEX (Global Energy and Water‐cycle Experiment) Cloud System Study.Eight SCM groups using different deep‐convection parametrizations participated in this project. The SCMs were forced by temperature and moisture tendencies that had been computed from a reference cloud‐resolving model (CRM) simulation using open boundary conditions. The comparison of the SCM results with the reference CRM simulation provided insight into the ability of current convection and cloud schemes to represent organized convection. The CRM results enabled a detailed evaluation of the SCMs in terms of the thermodynamic structure and the convective mass flux of the system, the latter being closely related to the surface convective precipitation. It is shown that the SCMs could reproduce reasonably well the time evolution of the surface convective and stratiform precipitation, the convective mass flux, and the thermodynamic structure of the squall‐line system. The thermodynamic structure simulated by the SCMs depended on how the models partitioned the precipitation between convective and stratiform. However, structural differences persisted in the thermodynamic profiles simulated by the SCMs and the CRM. These differences could be attributed to the fact that the total mass flux used to compute the SCM forcing differed from the convective mass flux. The SCMs could not adequately represent these organized mesoscale circulations and the microphysicallradiative forcing associated with the stratiform region. This issue is generally known as the ‘scale‐interaction’ problem that can only be properly addressed in fully three‐dimensional simulations.Sensitivity simulations run by several groups showed that the time evolution of the surface convective precipitation was considerably smoothed when the convective closure was based on convective available potential energy instead of moisture convergence. Finally, additional SCM simulations without using a convection parametrization indicated that the impact of a convection parametrization in forced SCM runs was more visible in the moisture profiles than in the temperature profiles because convective transport was particularly important in the moisture budget.