Large scale fluctuations of the Continental Tropical Convergence Zone (CTCZ) during pilot CTCZ phase-2009 and the evolution of monsoon drought in 2009

Summer monsoon season of the year 2009 resulted in a major drought on the scale of India with rainfall deficiency of 23% from the normal. This was the monsoon season when a pilot phase of the programme Continental Tropical Convergence Zone (CTCZ), a planned multiyear programme to understand the complex interactions among the land, ocean, atmosphere, biosphere components of the regional monsoon climate system, was undertaken. The paper attempts to document the major features in the evolution of monsoon 2009 and provides a preliminary diagnosis of the causes for monsoon drought.

Influence of land surface aridification on regional monsoon precipitation in East Asian summer monsoon transition zone

The East Asia summer monsoon transition zone, a unique area of transition from humid monsoon to arid continental climate, has the most prominent aridification in the world, and has experienced land surface aridification (LSA) in recent years. To investigate the influence of LSA on regional monsoon precipitation, two numerical experiments were run for vegetation degradation over a long period (30 years). Then, precipitation variation of different magnitudes was analyzed. After that, the mechanism of LSA influence on precipitation was studied. The results show that aridification reduced average summer precipitation by 5%. Additionally, LSA considerably changed the frequency of precipitation. Unlike aridification in North Africa caused by albedo variation, LSA in our study area mainly reduced surface thermal capacity, increased surface temperature, sharply increased the transport of surface sensible heat, and raised the atmospheric convective boundary layer. This reduces atmospheric moist static energy, which is not conducive to the generation of precipitation. LSA also increases the surface landscape gradient, local horizontal gradient of land surface turbulent flux, and probability of heavy convective precipitation. This paper reveals the mechanism by which land surface anomalies affect precipitation, which lays a foundation for follow-up studies.

Future changes in monsoon duration and precipitation using CMIP6

Future change in summertime rainfall under a warmer climate will impact the lives of more than two-thirds of the world’s population. However, the future changes in the duration of the rainy season affected by regional characteristics are not yet entirely understood. We try to understand changes in the length of the rainy season as well as the amounts of the future summertime precipitation, and the related processes over regional monsoon domains using phase six of the Coupled Model Intercomparison Project archive. Projections reveal extensions of the rainy season over the most of monsoon domains, except over the American monsoon. Enhancing the precipitation in the future climate has various increasing rates depending on the subregional monsoon, and it is mainly affected by changes in thermodynamic factors. This study promotes awareness for the risk of unforeseen future situations by showing regional changes in precipitation according to future scenarios.