African Climate Dynamics: Convection Over the Congo Basin

The Congo Basin, hosting the world's second-largest tropical rainforest, plays a critical role in global climate circulation, carbon sequestration, and biodiversity conservation. Despite its significance, the basin's climate dynamics have received less attention compared to its counterpart, the extensively researched Amazon, and other regions in Africa. In this context, there is a pressing need for in-depth research to unravel the basin's complex regional dynamics, especially in terms of rainfall, which suffers from significant discrepancies and uncertainties in climate models and satellite retrievels due to a lack of ground-based observations (Washington et al., 2013; Dosio et al., 2019; Vondou & Haensler, 2017). This project aims to narrow the gap by focusing on Mesoscale Convective Systems (MCSs), now recognized as the primary contributor to the region's rainfall (Nesbitt et al., 2006). a. General MCS characteristics over the Congo Basin
The Congo Basin is known as a global hotspot for convective activity, characterized by remarkably high Convective Available Potential Energy (CAPE) throughout the year. Like in other tropical regions, convective activity in the basin exhibits a robust diurnal cycle due to solar heating during daytime, with peaks in the late afternoon and early evening and decreasing to the minimum in the morning. Seasonal migration of solar heating leads to annual variations in large-scale convective activity (Hart et al., 2019). Strong orographic effect (i.e., the differential of solar heating) has been well recognized (e.g., Hartman 2020; Laing et al., 2011; Vondou et al., 2010; Jackson et al., 2009), which leads to the most frequent convection initiation near elevated terrain and areas affected by sea-/lake-breeze patterns. These convective systems typically move westward, steered by background winds, and develop into organized MCSs in environments
conducive to their upscale growth. Compared to individual convective systems, MCSs exhibit distinct lifecycle of genesis, growth, mature, and decay stages and tend to have profound impacts on global circulation. According to statistical information provided by Hartman (2020), MCSs would last 10 hours on average and tend to grow larger when moving over the Congo Basin than in the surrounding area. It should be noted that various global, synoptic, and regional climate features interact with the orographic effect and modulate the regional MCS lifecycle and tracks at various scales. Current understanding of their potential influence on MCSs over the Congo Basin could draw upon advances in knowledge of these features over other parts of Africa. Nonetheless, the unique environmental conditions of the basin mean these climate features may evolve and interact with the regional dynamics in a distinct way. Unfortunately, the Congo Basin
still remains one of the least researched large-scale convective regions in the global tropics, leaving key questions pertaining to MCS mechanisms in the basin unanswered. In the past few decades, the frequency, intensity, and areal extent of MCSs have seen an increasing trend (e.g., Hartman, 2020; Raghavendra, 2018; Taylor et al., 2018). Over the same period there is also an observed drying trend (Jiang et al., 2019; Hua et al., 2016; Zhou et al., 2014). However, much of what is known about MCS characteristics is derived from satellite observations of cold cloud. Insights into the dynamics associated with the systems are sparse.

This project will mainly focus on the modulation of the MCS environment by various Convectively Coupled Equatorial Waves (CCEWs) that are shown to impact convection and rainfall over the Congo to a varying degrees and with regional dependency. This project has several specific research goals:
1. Investigate favourable environmental conditions for MCS formation over the Congo Basin;
2. Investigate modulation of MCS formation and characteristics by tropical waves in the basin:
3. Explore the contributi