Storm in the System: How Tropical Cyclones Supercharge Summer Weather
A new study reveals how typhoons act as hidden engines driving atmospheric energy and shaping seasonal climate in the Western North Pacific.
Breaking the Ice:
In a groundbreaking paper published in the Journal of Climate, a team of researchers has unraveled the profound impact that tropical cyclones (TCs) have on the summer climate of the Western North Pacific (WNP). Spanning four decades of data (1979–2019), their study examined how TCs influence atmospheric perturbations — those swirls and eddies that characterize intraseasonal and shorter weather systems.
Using a novel “TC-removal” method that strips cyclonic signatures from reanalysis datasets, the researchers compared normal atmospheric behavior to a “TC-free” world. The results were striking: when TCs are removed, the monsoon trough weakens, the subtropical high expands westward, and key weather oscillations — such as intraseasonal oscillations (ISOs), submonthly waves, and synoptic patterns — lose up to 80% of their kinetic energy.
This comprehensive analysis doesn’t just map out how TCs respond to larger climate systems — it flips the perspective. Tropical cyclones, it turns out, are powerful agents that actively shape regional weather and atmospheric energy cycles.
Quick Melt:
Most existing climate models treat tropical cyclones as consequences of larger-scale climate variability. But the data presented here argue the opposite: TCs are major contributors to the system’s energy, particularly in the lower and upper troposphere. When cyclones are active — especially during the westerly phase of the ISO, when monsoon winds are strongest — they inject massive amounts of perturbation kinetic energy (PKE) into the atmosphere. This energy reinforces other weather waves, allowing them to grow stronger and persist longer.
In practical terms, this means that TCs may amplify other meteorological events, contributing to longer rain periods, altered wind patterns, and increased storm durations in East Asia. For regions like Taiwan, Japan, and southern China — already vulnerable to typhoon damage — this added atmospheric energy complicates forecasting and disaster planning.
Equally important, the study found that removing TCs caused ISOs to shift southwestward and weaken significantly, suggesting that TCs help anchor and guide these broader oscillations. Barotropic and baroclinic energy conversions, mechanisms by which energy is transferred through atmospheric layers and flows, also saw drastic reductions in TC-free simulations. These energy transfers are fundamental to storm formation and atmospheric dynamics, so their suppression indicates a deep interdependence between cyclones and the surrounding environment.
The Thaw:
How do Barotropic and Baroclinic Processes Impact Atmospheric Energy Flows? AccumulationZone Explains.
The atmosphere is a fluid system, where energy flows both horizontally and vertically. Barotropic conversion describes the transfer of energy from large-scale, steady background winds into smaller, turbulent eddies and waves — think of a river current spinning off into whirlpools. Tropical cyclones act like high-speed mixers in this system. Their presence boosts barotropic conversion, especially in the lower troposphere (around 850 hPa), helping fuel submonthly and synoptic-scale waves.
Baroclinic conversion, by contrast, operates vertically. It describes how differences in temperature and pressure between atmospheric layers (particularly in the upper troposphere, near 250 hPa) get converted into motion. This is crucial for storm intensification. The study shows that TCs play a key role here too — removing them slashes baroclinic energy by up to 90% in affected areas.
These energetic contributions from tropical cyclones vary significantly across seasonal and intraseasonal timescales, particularly in relation to phases of the intraseasonal oscillation (ISO). During the ISO's active (westerly) phase, the deepened monsoon trough creates a dynamically favorable environment for cyclone genesis and intensification, resulting in more frequent TCs with stronger feedback loops into the atmospheric system. In contrast, the suppressed (easterly) phase features a more stabilized and anticyclonic flow, which inhibits convection and reduces both the frequency and energy contribution of TCs—though the influence remains non-negligible.
Rather than serving solely as passive outcomes of broader climatic patterns, TCs actively reorganize atmospheric energy by enhancing kinetic energy transport and altering pressure and wind structures across multiple spatial and temporal scales. This study reframes TCs as dynamic agents of climate modulation, rather than as byproducts, challenging a long-standing paradigm in atmospheric science.
Final Thoughts
Tropical cyclones are not just destructive weather events, but integral components of the summer climate engine in the Western North Pacific. As climate change alters the frequency and intensity of these storms, understanding their feedback loops will be crucial for accurate forecasting, disaster resilience, and regional climate modeling. In the complex ballet of the atmosphere, typhoons may well be leading the dance.