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Assessing historical variability of South Asian monsoon lows and depressions with an optimized tracking algorithm

Cyclonic low-pressure systems (LPS) produce abundant rainfall in South Asia, where they are traditionally categorized as monsoon lows, monsoon depressions, and more intense cyclonic storms. The India Meteorological Department (IMD) has tracked …

Feedbacks and Eddy Diffusivity in an Energy Balance Model of Tropical Rainfall Shifts

Radiative feedbacks are known to strongly modify horizontal shifts of the intertropical convergence zone (ITCZ) produced by remote atmospheric energy sources. This study uses a one-dimensional moist energy balance model to understand how radiative …

Quasigeostrophic controls on precipitating ascent in monsoon depressions

South Asian monsoon depressions are convectively coupled cyclonic vortices that form and intensify in a region of easterly vertical shear of the horizontal wind. Observations of maximum precipitation downshear of the cyclonic center have led to prior …

Monsoon depression amplification by moist barotropic instability in a vertically sheared environment

This study makes the case that monsoon depressions over South Asia can form from a variant of moist barotropic instability. Using an idealized numerical framework in which the atmosphere is partitioned into a basic state and a perturbation, we …

Aquaplanet models on eccentric orbits: effects of the rotation rate on observables

Rotation and orbital eccentricity both strongly influence planetary climate. Eccentricities can often be measured for exoplanets, but rotation rates are currently difficult or impossible to constrain. Here we examine how the combined effects of …

Understanding the vertical structure of potential vorticity in tropical depressions

Potential vorticity (PV) has been used to understand the intensification and motion of a variety of tropical vortices. Here, atmospheric reanalyses and idealized models are used to understand how the vertical structures of moist convective heating …

Using atmospheric energy transport to quantitatively constrain South Pacific Convergence Zone shifts during ENSO

The South Pacific Convergence Zone (SPCZ) exhibits well-known spatial displacements in response to anomalous sea surface temperatures (SSTs) associated with the El Niño/Southern Oscillation (ENSO). Although dynamic and thermodynamic changes during …

Barotropic growth of monsoon depressions

Although monsoon depressions are a principal synoptic-scale element of the South Asian monsoon, producing extreme rainfall over India and surrounding regions, there exists no widely accepted mechanism explaining their occurrence. This study presents …

Sensitivity of subtropical stationary circulations to global warming in climate models: a baroclinic Rossby gyre theory

Time-mean, zonally asymmetric circulations maintain an intense hydrologic contrast between monsoon regions and subtropical drylands in Earth’s present climate. Climate model simulations suggest that this hydrologic contrast will increase in …

Global energetics and local physics as drivers of past, present and future monsoons

Global constraints on momentum and energy govern the variability of the rainfall belt in the intertropical convergence zone and the structure of the zonal mean tropical circulation. The continental-scale monsoon systems are also facets of a momentum- …