Wessinger et al. (2025) An Unexpected Peak in Daytime Convection Initiation Weakens Diurnal Amplitude of Tropical Oceanic Precipitation and Cloud Cover

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Journal of Geophysical Research Atmospheres
• Year: 2025
• Date: 2025-11-08
• Authors: Sarah E. Wessinger, Anita D. Rapp, Gregory S. Elsaesser
• DOI: 10.1029/2025jd044399

Research Groups

Information not available in the provided abstract.

Short Summary

This study investigates the diurnal cycle of deep convective system (DCS) initiation and subsequent rainfall over tropical oceans to address deficiencies in Earth system models. It identifies two peaks of DCS initiation—an overnight peak and an unexpected late morning peak—and demonstrates that daytime-initiated DCSs significantly contribute to afternoon rain and cloud cover, suggesting that Earth system models may underestimate these daytime initiations.

Objective

• To better understand the diurnal cycle of tropical oceanic rain and cloud cover by analyzing the diurnal cycle of deep convective system (DCS) initiation and the subsequent later-stage accumulation of rainfall.
• To evaluate morphological characteristics and contributions of DCSs initiated at different times to the diurnal cycles of rain and cloud cover.

Study Configuration

• Spatial Scale: Tropical oceanic regions.
• Temporal Scale: Diurnal cycle (hourly resolution for initiation and accumulation).

Methodology and Data

• Models used: Tracking Of Organized Convection Algorithm through 3D segmentatioN (TOOCAN) for Lagrangian tracking of DCSs. Earth System Models (ESMs), specifically the NASA-GISS ESM, are used for comparison.
• Data sources: Integrated Multi-satellitE Retrieval for GPM (IMERG) rainfall product.

Main Results

• Two distinct peaks of deep convective system (DCS) initiation were observed: an anticipated overnight peak and an unexpected late morning peak, which occurs earlier than the expected afternoon peak in surface heating.
• DCSs initiated during the daytime peak exhibit similar morphologies to those initiated overnight.
• Daytime-initiated DCSs significantly contribute to the afternoon rain and cloud cover, which is likely important for explaining the decreased amplitude of the over-ocean diurnal cycle.
• When daytime-initiated DCSs are excluded from the computation of the precipitation diurnal cycle, the resulting amplitude more closely resembles that simulated by the NASA-GISS ESM.
• This suggests that current ESMs may either simulate too few daytime DCS initiations or fail to maintain them, leading to an over-ocean diurnal cycle amplitude that exceeds observational estimates.

Contributions

• Identifies and characterizes an unexpected late morning peak in tropical oceanic deep convective system (DCS) initiation.
• Demonstrates the significant contribution of daytime-initiated DCSs to the afternoon rain and cloud cover diurnal cycle over tropical oceans.
• Provides a potential explanation for discrepancies in the diurnal cycle amplitude of tropical oceanic precipitation between Earth system models (ESMs) and observations, specifically highlighting a possible underrepresentation or lack of maintenance of daytime DCSs in ESMs.
• Utilizes Lagrangian tracking of DCSs to disentangle initiation times from subsequent rainfall accumulation, offering a novel perspective on the diurnal cycle.

Funding

Information not available in the provided abstract.

Citation

@article{Wessinger2025Unexpected,
  author = {Wessinger, Sarah E. and Rapp, Anita D. and Elsaesser, Gregory S.},
  title = {An Unexpected Peak in Daytime Convection Initiation Weakens Diurnal Amplitude of Tropical Oceanic Precipitation and Cloud Cover},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2025},
  doi = {10.1029/2025jd044399},
  url = {https://doi.org/10.1029/2025jd044399}
}