Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 5
Variations in land surface characteristics directly alter surface biophysical properties like albedo, roughness length, and canopy resistance, leading to changes in surface radiative and turbulent fluxes. These changes influence sensible and latent heat fluxes, which can further regulate surface temperature, evapotranspiration, and near-surface moisture transport. Thus, variations in surface fluxes associated with changes in land-surface properties can regulate convective instability, moisture convergence, and can modulate short-range rainfall characteristics and their predictability. Such land–atmosphere feedbacks are particularly important over the Indian region, where strong seasonal contrasts and heterogeneous land surfaces play a critical role in shaping rainfall variability. Hence, this study investigates the sensitivity of short-range precipitation forecasts over India to decadal changes in land use and vegetation during the pre-monsoon and monsoon periods. USGS 24-category land use data based on the 1994 landscape is used as the control run. Seven different simulation experiments are conducted using WRF model with various land use and vegetation data from MODIS and ISRO; ie: Experiment1 (MODIS 2001, USGS LAI and VF default), Experiment 2 (MODIS 2001, LAI and VF default), Experiment 3 (MODIS 2019, LAI and VF default), Experiment 4 (MODIS 2001, with Urban Class of 2019, LAI, and VF default), Experiment 5 (MODIS 2001, with water bodies of 2019, LAI, and VF default), Experiment 6 (MODIS 2019, LAI and VF of 2019), Experiment 7 (ISRO 2018-2019, VF and LAI default). A comprehensive assessment based on quantitative error metrics and categorical forecast skill scores demonstrates statistically significant improvements in rainfall forecast performance following the assimilation of updated land-use and vegetation datasets. These statistically robust improvements indicate that realistic representation of land-surface conditions contributes meaningfully to enhanced short-range precipitation predictability. The computed Extreme Dependency Index (EDI) values indicate an enhanced ability of the model to capture rare extreme rainfall events following the incorporation of updated land-use information. The incorporation of realistic land-use classifications derived from MODIS and ISRO datasets led to improved simulations of surface meteorological variables, including temperature, wind speed, relative humidity, surface pressure, and surface fluxes. Corresponding improvements were also observed in the vertical atmospheric profiles for wind, temperature, and specific humidity profiles. These enhancements indicate a more realistic depiction of land–atmosphere interactions and boundary-layer processes in the model.
How to cite: Putatunda, I., Vasudevan, R., and Singh, R.: Effect of decadal land use change on WRF model-simulated surface meteorological parameters over the Indian region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8881, https://doi.org/10.5194/egusphere-egu26-8881, 2026.
Reanalysis products, which blend weather model output with observations are commonly used as substitutes for observations to assess numerical weather prediction model forecast skill, the accuracy of climate model historical realizations, and AI training. However, the quality of reanalysis output is not uniform across all variables, times of day, seasons, or geographic settings. This study evaluates the strengths and weaknesses of ERA5 reanalysis (0.25° grid) over a multi-year period by comparing them to worldwide hourly surface observations from over 1200 stations, buoys, and radiosonde vertical profiles.
Our analysis focuses on several metrics across the diurnal cycle (7 AM and 3 PM local time) and during temperature outlier events (< 10th percentile and > 90th percentiles for the 30-year climatology). Results indicate that ERA5 provides reliable 2-meter air temperatures in most regions, but shows a frequent dry bias in dewpoint of greater than 3 ℃ more than 5% of the time for many stations in the Dry and Mediterranean climate zones. ERA5 often underestimates warm events (> 90th percentile), with the largest cold biases, less than -3 ℃ occurring more than 11% of the time in the Mediterranean climate zone. Temperature and dewpoint biases are amplified in complex terrain, and dewpoint biases tend to be larger near coastal locations. To investigate whether higher spatial resolution mitigates these issues, we also examine the performance of the ERA5-Land product (0.1° grid). These findings emphasize the importance of evaluating the adequacy of purpose when using reanalysis for specific applications, since performance can vary significantly by variable, time of day, season, and climate zone.
How to cite: Lewis, W., Yuter, S., and Miller, M.: Is ERA5 Fit for Purpose? A Global Multi-Variable Evaluation of Reanalysis Strengths and Weaknesses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15265, https://doi.org/10.5194/egusphere-egu26-15265, 2026.
Persistent extreme weather anomalies lasting several weeks to months can lead to drought and compound dry–hot extremes, posing serious socio-economic risks in the Indian monsoon region. Although subseasonal-to-seasonal (S2S) prediction systems have advanced, the extent to which these models represent drought-relevant hydroclimatic variability over India has not been adequately quantified. Here, we focus on evaluating the hindcast quality of weekly accumulated precipitation and temperature from multiple S2S models with lead times up to six weeks during the JJAS season over India. These model hindcast outputs and IMD observations are regridded to a common 0.5° resolution and analyzed using deterministic forecast skill metrics at various lead times, statistical bias correction is then applied to isolate systematic model errors, followed by SPI-based drought diagnostics, and compound dry–hot extreme indices are derived and computed. The analysis reveals modest forecast skill at early lead times, followed by a systematic decline as lead time increases, with precipitation predictability deteriorating more rapidly than temperature predictability. Although the models generally capture the large-scale spatial distribution of drought-prone regions, they significantly underestimate the frequency and spatial extent of compound dry–hot conditions, exhibiting pronounced regional dependence across India. These results highlight key limitations and identify opportunities to enhance subseasonal drought early-warning systems.
Keywords: Subseasonal-to-seasonal predictability, Indian Summer Monsoon, Drought, Climate extremes, Hindcast evaluation
How to cite: Sukumaran, S. and Agarwal, A.: S2S Forecast Skill Assessment for Summer Monsoon Drought Warning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16394, https://doi.org/10.5194/egusphere-egu26-16394, 2026.
In Eastern Africa, subseasonal forecasts are critical for early warning systems as climate extremes severely impact food security and livelihoods. ECMWF Artificial Intelligence Forecasting System (AIFS ENS v1.0) , an ensemble-based probabilistic data-driven forecast model developed by ECMWF offers unprecedented opportunities for regional applications through AI-driven weather prediction, but GPU compute costs and data access challenges limit deployment. As participants in the ECMWF AI Weather Quest, we developed solutions enabling cost-effective, cloud-based AIFS ensemble forecasting tailored for regional climate centers.
We implemented a workflow (https://github.com/icpac-igad/ea-aifs) leveraging Google Cloud Platform infrastructure. Initial conditions are accessed via ECMWF's IFS data stored at AWS (Amazon Web Service) open data program at S3 Cloud storage using GRIB index-kerchunk, and VirtualiZarr methods for efficient data streaming without local storage overhead. The workflow employs experimental FP16 (half-precision) inference on AIFS ensemble models along with the standard FP32, evaluating GPU memory requirements and enabling deployment on cost-effective T4/L4 GPUs rather than expensive A100 instances.
Verification results from the SON (September-October-November) 2025 season as part of the AI Weather Quest demonstrates that Team Fahamu's submission using AIFS ensemble forecasts for temperature and mean sea-level pressure outperforms climatology benchmarks. Regional evaluation over East Africa reveals promising subseasonal skill for temperature at lead times of 2-4 weeks—critical timescales for agricultural planning and anticipatory drought/flood action—while evaluation of precipitation forecasts is ongoing. This method provides a scalable template for regional climate centers globally to operationalize state-of-the-art AI weather models cost-effectively, advancing the democratization of advanced forecasting capabilities.
How to cite: Koech, E., Kalladath, N., Mwanthi, A., Ogelo, A., Kinyua, J., Koros, H., Lelaono, M., Misiani, H., Bekele, T., Seid, H., Gudoshava, M., and Amdihun, A.: Cost-Effective ECMWF AIFS Ensemble Inference for Subseasonal Forecasting in East Africa , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20505, https://doi.org/10.5194/egusphere-egu26-20505, 2026.
Tropical deep convection evolves as a cyclic process, but most observational and modeling studies diagnose convection through regional or domain-based contrasts, obscuring how key physical processes vary across different stages of the convective life cycle. The convective life cycle in the tropics is frequently conceptualized through recharge discharge processes. While valuable, this framework can be extended with more granular, phase specific diagnostics to better understand the distinct physical processes governing each stage of convection. Here, we build on existing phase-plane approaches to represent convection as a cyclic process, using column-integrated moist static energy (MSE) and its temporal tendency as the primary state variables. The phase plane is constructed with column integrated MSE along the horizontal axis and its temporal derivative along the vertical axis. While adhering to the established recharge–discharge paradigm, we extend this terminology by defining four distinct, cycle-consistent stages on the phase plane: Build-up, Cresting, Decay, and Recovery. Applying this framework to the Indian Summer Monsoon (ISM) core region, we map quasi-geostrophic (QG) omega-scaled precipitation components onto the MSE phase plane to investigate the relative contributions of diabatic heating and adiabatic forcing across the convective life cycle. These stage dependent signatures demonstrate the utility of the MSE phase plane for attributing and relative importance of dynamical and diabatic processes across the convective life cycle. Final results and extended analyses will be presented and discussed at the conference.
How to cite: Chakraborty, S., Nikumbh, A., Maithel, V., and Zore, T.: A Phase-Plane Representation of the Convective Life Cycle: Characterizing Diabatic and Adiabatic Drivers during the Indian Summer Monsoon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19311, https://doi.org/10.5194/egusphere-egu26-19311, 2026.
This study provides the first high-resolution polarimetric radar observations of Overshooting Convective Storms (OCS) over the Western Ghats (WG), India using the newly installed SSPA-based X-band Radar at HACPL, Mahabaleshwar. Three post-monsoon OCS events (15, 23, and 24 October 2025) were analysed using PPI, RHI, CFAD products and ERA5 Atmospheric fields. All storms exhibited strong vertical growth, with echo-top heights of 17.6–19.8 km (15 Oct), 16.5 km (23 Oct), and 17.8 km (24 Oct), and peak reflectivity values of 59.6, 63.3, and 52.1 dBZ, respectively. Notably, significant reflectivity (>40 dBZ) persisted above 16 km, confirming deep overshooting intrusions. Polarimetric signatures showed clear mixed-phase and ice-growth processes, including KDP up to 3–4° km⁻¹, enhanced ZDR in the rainy regions, and reduced ρhv (0.92–0.96) within convective cores, indicating liquid water content, riming, and graupel/hail production. ERA5 diagnostics revealed favorable conditions for deep convection, with strong mid-tropospheric ascent (–0.6 to –0.8 Pa s⁻¹), high moisture, and pronounced convergence over the WG. These results demonstrate intense post-monsoon overshooting convection in complex terrain and highlight the capability of X-band Polarimetric radar to reveal the storm microphysics and vertical structure in an orographically challenging environment.
How to cite: Devisetty, H., Uriya Veerendra, M. K., Tyagi, B., Das, S. K., Chakravarty, K., Survase, C., and Burrala, P. K.: Radar Polarimetry to Characterize Overshooting Convection in the Western Ghats of India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-676, https://doi.org/10.5194/egusphere-egu26-676, 2026.
With the intensification of global warming, deep convective system(DCS) precipitation over the Tibetan Plateau(TP) has become increasingly frequent, which plays a vital role in regulating the regional hydrological cycle. Previous studies have focused on instantaneous convective activity, little elaborating on the evolutionary processes and rainfall of DCSs throughout their whole lifecycle. Here, based on the continuous observations from the FY-4A geostationary satellite, this study investigates the characteristics and evolution of DCSs over TP from 2022 to 2023 through our previous full-lifecycle tracking algorithm from initiation to dissipation. Furthermore, the effects of key meteorological factors on DCSs evolution are revealed.
Results indicate that DCSs are mostly short-lived (3–6 h lifecycle), and more than 85% of convective precipitation occurs during summer from June to August. DCSs concentrate in the central-eastern TP, with an occurrence probability exceeding 12% in summer. Additionally, the area and rainfall rate of DCSs typically reach their peaks at the middle stage of the lifecycle. After the dissipation of the convective core, the persistence time of cirrus can reach 5%–28% of the core’s lifecycle. Controlled variable analysis reveals that convective available potential energy (CAPE) and precipitable water (PW) synergistically regulate the development of convective systems: under conditions of high CAPE (500-103 J kg-1) and high PW (>50 mm), the area of cores expands to the largest extend. However, the maximum lifecycle and peak precipitation of DCSs occur under conditions of moderate wind shear (5-10 m s-1).
This study explores the full-lifecycle evolutionary patterns of DCS over the TP and the regulatory effects of meteorological conditions over TP, laying a theoretical foundation for future research on regional precipitation and climate change in the region.
How to cite: Guo, C., Yin, J., Pan, Z., Zang, L., and Mao, F.: Observed Lifecycle of Convective Precipitation over Tibetan Plateau Based on the FY-4A Geostationary Satellite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1839, https://doi.org/10.5194/egusphere-egu26-1839, 2026.
This study develops a novel framework within the Weather Research and Forecast Model for modeling aerosol-cloud-lightning interactions. The framework explicitly represents aerosol-cloud interactions by prescribing aerosols with two configurations: an idealized setup, where both cloud condensation nuclei (CCN) and ice nucleating particles (IN) are assumed to have a single chemical composition and spatially uniform distributions; and a quasi-realistic configuration, with multi-species aerosols assigned spatially varying distributions, where hygroscopic components act as CCN, dust particles act as IN, and all aerosol species influence radiative transfer. Cloud microphysics is coupled with detailed charge separation and discharge processes to enable the lightning simulation. The framework is evaluated using two thunderstorms in Guangdong, China. For an isolated storm, the model successfully reproduces the observed tripolar charge structure (positive–negative–positive), demonstrating its capability in simulating cloud electrification. For a frontal storm, it captures well the observed precipitation and lightning, and shows that increasing CCN suppresses the rainfall while enhancing the lightning. Higher CCN concentrations produce more numerous but smaller cloud droplets, which suppresses the coalescence into rain droplets, allows a greater number of droplets to loft into the upper troposphere, and forms more but smaller cloud ice particles. This boosts graupel–ice collisions, intensifies non-inductive charging, strengthens the upper positive charge and the vertical electric-field gradient, ultimately increasing the lightning frequency. In contrast, no significant aerosol-induced invigoration of updrafts is observed. These results highlight the dominant role of aerosol microphysical effects over dynamical invigoration in modulating thunderstorm electrification and lightning activity.
How to cite: Wang, W., Chen, G., and Zhang, Y.: A framework for modeling aerosol-cloud-lightning interactions: Validation of charge structure and aerosol effects, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6493, https://doi.org/10.5194/egusphere-egu26-6493, 2026.
In this study we analyze the occurrence of cold pools in the tropical Atlantic during the ORCESTRA field campaign (August to September 2024), using data collected from over 2000 soundings. We first tested whether the method to detect cold pools based on the mixed-layer height, developed for shallow convective cold pools in the winter trades during EUREC4A, is applicable to the deep convective regime of the ITCZ. The validation by a surface-based detection method and the investigated recovery behaviour of the mixed layer after a cold pool demonstrates its applicability to this environment. On this basis, we examine the distribution and properties of cold pools within the tropical Atlantic. A total of 26% of all ORCESTRA soundings detected cold pools, compared to only 7% during the EUREC4A campaign in the winter trades. The ITCZ region with the highest moisture content and presumably deepest convection features the largest number of cold pools. This presentation will further discuss how the cold pool strength and frequency correlate with wind, moisture and stability.
How to cite: Vogel, R., Mann, L., Robbins-Blanch, N., and Rochetin, N.: Characterizing cold pools in the ITCZ using soundings from the ORCESTRA campaign, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14298, https://doi.org/10.5194/egusphere-egu26-14298, 2026.
Satellite data sets are the primary source of observations of cloud characteristics, but downward-looking passive sensors cannot see lower-level clouds obscured by higher clouds nor cloud bases. Observations of low clouds with downward-looking satellite IR are hampered by the small brightness temperature differences between the low cloud top and the underlying surface. In contrast, upward-looking thermal IR can readily distinguish warm clouds against the cold sky. By sampling thermal IR cloud characteristics across the diurnal cycle, upward looking thermal IR observations have the potential to yield improved understanding of transitions in cloudiness at sunrise and sunset and differences in the relative importance of different cloud processes with and without SW fluxes.
Our thermal IR all-sky camera was assembled from commercially available, off-the-shelf parts. The key components are a FLIR Boson thermal IR camera and a FLIR PTU-5 pan-tilt mount. The IR camera has a 50° field of view and a resolution of 640x500 pixels. To obtain imagery of the entire sky, the pan-tilt mount points the camera at 14 different directions, each varying in azimuth and elevation. The volume coverage pattern is executed once per minute, and the entire sky is sampled in less than 30 seconds. The images are then stitched together in software to yield a hemispherical array of IR brightnesses from horizon to horizon.
From the imagery we can infer cloud fraction, cloud coverage characteristics relating to the size and shapes of cloud elements, and estimate the altitude of cloud bases at all times of day. Sequences of images reveal the evolution of individual cloud elements and provide information on the phase space of cloud properties across the diurnal cycle and to related to air mass changes, such as the passage of fronts. Combined with other data from lidar and visible all sky cameras, the upward-looking thermal IR data on cloud outer surface temperature details at small spatial scale (10s of meters) and few minute time scale have high potential to yield new insights on cloud initiation and dissipation.
We will detail the performance of the thermal IR all-sky camera and analyze derived cloud characteristics in the context of data from visible wavelength all-sky imagery and additional atmospheric observations.
How to cite: Miller, M. and Yuter, S.: All-Sky Camera Upward-looking Thermal Infrared Cloud Characteristics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15029, https://doi.org/10.5194/egusphere-egu26-15029, 2026.
Rising global warming is accelerating climate extremes at regional scales worldwide. Capturing these extremes at the regional level requires high resolution climate modeling capable of representing complex topography and strong land atmosphere interactions. In this study, a high-resolution Non-Hydrostatic Regional Climate Model (NHRCM) is configured at a kilometer scale resolution (5 km) through dynamic downscaling of the MRI AGCM 3.2 outputs developed by the Meteorological Research Institute of Japan (MRI). Daily precipitation and temperature (maximum and minimum) data are generated at 5 km resolution for the historical period (1980–2000) and the future period (2081–2100) under the high emission climate scenario SSP585. The performance of the downscaled climate variables is evaluated against ERA5 Land data after resampling to the same resolution as the NHRCM. Statistical metrics and extreme climate indices are used to quantify model skill and biases at regional and sub regional scales over Pakistan. The results reveal a strong correlation in high elevation regions of Pakistan compared to the plains. After evaluating model performance, precipitation and temperature extreme indices are calculated for both historical and future periods. The findings indicate an increase in precipitation in the southern regions of Pakistan, accompanied by rising temperatures. These trends are also associated with an increase in short-duration intense rainfall events during summer and prolonged dry conditions in winter. Furthermore, the frequency of heatwaves is expected to rise by the end of the century across Pakistan, along with increasing temperatures in snow fed regions. Overall, this study highlights the added value of high-resolution nonhydrostatic regional climate modeling in understanding and assessing climate extremes over Pakistan, providing a robust foundation for future climate impact assessments and adaptation planning.
How to cite: Mamoor, M., Rahim, A., Yaseen, M., Naz, R., Kosar, T., Tariq, N., and Akif, A.: Kilometer Scale Climate Modeling of Extremes: Evaluation of the NonHydrostatic Regional Climate Model (NHRCM) over Pakistan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9211, https://doi.org/10.5194/egusphere-egu26-9211, 2026.
African Easterly Waves (AEWs) are a dominant synoptic-scale feature of the tropical atmosphere, widely recognized for their role as precursors of tropical cyclones and for modulating summertime rainfall over the Atlantic basin and adjacent regions. However, their potential influence on the transport of Saharan dust across the Atlantic and its impacts on air quality has received comparatively less attention. In this study, we investigate the role of AEWs in modulating Saharan dust transport and its relationship with high PM2.5 concentration episodes over the Yucatán Peninsula. Using reanalysis data, we document a pronounced seasonal cycle in dust transport, with maximum concentrations during boreal summer (June–August), coinciding with the peak activity of AEWs. Spectral analysis reveals a significant contribution at periods of 4–9 days, consistent with the characteristic timescales of AEWs. To quantify their impact on air quality, intense dust events associated with AEWs were identified based on anomalies exceeding one standard deviation and compared with episodes of poor air quality driven by particulate matter. Our results indicate that AEWs account for approximately 26–31% of PM2.5 pollution episodes linked to dust over the Yucatán Peninsula, with event durations ranging from 1 to 8 days. These findings highlight the important role of AEWs in shaping the synoptic-scale variability of aerosol transport and surface air quality in the Yucatán Peninsula and southern Mexico, underscoring their relevance beyond tropical cyclogenesis and precipitation, particularly during the boreal summer.
How to cite: Jaramillo-Moreno, A. and Vázquez-Jiménez, C. S.: African Easterly Waves as Drivers of Saharan Dust Transport and PM2.5 Extremes in the Intra-Americas Region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4071, https://doi.org/10.5194/egusphere-egu26-4071, 2026.
The Madden–Julian Oscillation (MJO) is the dominant mode of intraseasonal variability (30–90 days) in the tropical atmosphere, characterized by eastward-propagating convective and circulation anomalies that strongly modulate tropical and regional climate. Through its large-scale dynamical perturbations, the MJO influences moisture transport, low-level circulation, and precipitation over regions far removed from its primary convective center. However, its role in regulating low-level moisture fluxes over northwestern South America has received comparatively limited attention. In this study, we investigate the influence of the MJO on moisture transport toward Colombia, with particular emphasis on its modulation of the Chocó Low-Level Jet. Using MERRA-2 reanalysis, we characterize intraseasonal variability in low-level moisture advection and wind fields associated with different MJO phases defined by the Real-time Multivariate MJO (RMM) index. The analysis examines changes in low-level moisture transport, wind intensity, and large-scale convergence associated with the zonal displacement of the MJO convective envelope. Results show that the strength of the Chocó Jet depends strongly on the longitudinal position of the MJO convective center. Certain MJO phases enhance moisture transport from the eastern Pacific toward Colombia, favoring orographic ascent along the Andes and organized convection over the Colombian Pacific region, while other phases are associated with weaker moisture fluxes and reduced convergence. These findings highlight the role of the MJO in regulating intraseasonal moisture transport and low-level circulation over northwestern South America.
How to cite: Toro-Arenas, J., Jaramillo-Moreno, A., Carvajal-Serna, L. F., and Mesa-Sanchez, Ó. J.: Intraseasonal Modulation of the Chocó Low-Level Jet by the Madden–Julian Oscillation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4128, https://doi.org/10.5194/egusphere-egu26-4128, 2026.
The Indian Summer Monsoon Rainfall (ISMR), occurring from the month of June to September, is characterized by intraseasonal variability in the form of active and break spells. Monsoon breaks are periods of sparse to no rainfall, marked by positive outgoing longwave radiation anomalies, above-normal pressures, and clear-sky conditions. These monsoon breaks can have socioeconomic impacts due to their effect on crop growth stages, irrigation planning, and water management. This study aims to investigate the synoptic-scale systems responsible for the onset and sustenance of monsoon breaks over the Western Ghats and other parts of India to improve future predictability of the same. Rainfall data from 1901 to 2025 is used to identify break spells and classify them into short, moderate, and long-duration events. Subsequently, decadal rainfall composites are constructed. These composites reveal patterns of rainfall suppression and enhancement over the Indian subcontinent, equatorial Indian Ocean and West Pacific. Although the spatial structure of rainfall anomalies remains consistent, slight decadal variabilities are observed. Composite analyses of outgoing longwave radiation, and upper and lower tropospheric winds are used to diagnose the synoptic features associated with monsoon breaks. Case studies of recent drought years, 2002 and 2015, highlight the role of upper tropospheric anticyclones, northward displacement of the monsoon trough, and dry air intrusion from West Asia in sustaining and prolonging the breaks, confirming previous studies. The influence of large scale climate oscillations such as ENSO, EQUINOO, and the Boreal Summer Intraseasonal Oscillation (BSISO) on monsoon break frequency and duration is investigated using statistical and machine learning tools, with the aim of informing the development of improved predictive frameworks for monsoon breaks.
How to cite: Aboobaker, J. and Singh, Dr. S.: Synoptic-Scale Mechanisms And Climate Oscillation Influences On The Monsoon Breaks Of The Indian Summer Monsoon System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4971, https://doi.org/10.5194/egusphere-egu26-4971, 2026.
How to cite: Liu, Z.: Global-scale compound Droughts and heatwaves: inland/coastal type grouping, diversity of temperature extremes, and dynamically-based Interpretable reconstruction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2053, https://doi.org/10.5194/egusphere-egu26-2053, 2026.
Persistent heatwaves across South Asia impose severe and growing impacts, yet the atmospheric processes that sustain extreme heat over multiple days remain incompletely understood. This study aims to determine whether heatwave persistence is driven by failures of nocturnal boundary-layer ventilation, rather than by daytime temperature extremes alone. We analyze pre-monsoon (March–May) heatwaves across South Asia (65°E–98°E, 5°N–35°N) from 1981 to 2024 using ERA5 hourly reanalysis, which includes near-surface air temperature, boundary-layer height, near-surface winds, and surface sensible heat flux. Heatwaves are identified using a percentile-based definition of daily maximum temperature, and nighttime conditions are diagnosed consistently using local solar time. Nocturnal ventilation is quantified through a physically interpretable ventilation potential combining nighttime boundary-layer height and near-surface wind speed, complemented by diagnostics of turbulent mixing and nocturnal cooling. We find that heatwave nights are consistently characterized by suppressed nocturnal ventilation, including shallow boundary layers, weak winds, and reduced turbulent exchange, and that reductions in nighttime ventilation are more strongly associated with heatwave duration and nighttime heat accumulation than daytime temperature anomalies. Composite analyses further indicate that ventilation and turbulent mixing weaken before heatwave onset and remain suppressed throughout the persistence phase, with particularly pronounced effects in humid regions such as Bangladesh. Our findings demonstrate that nocturnal boundary-layer ventilation failure is a central physical mechanism controlling heatwave persistence and suggest that incorporating nighttime atmospheric processes into heatwave monitoring and early-warning frameworks is essential for anticipating prolonged and high-impact heat extremes.
How to cite: Laskor, Md. A. H., Dipu, S. U. A., Bhuiyan, F., and Islam, A. K. M. S.: Nocturnal boundary-layer ventilation failure governs heatwave persistence in South Asia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21148, https://doi.org/10.5194/egusphere-egu26-21148, 2026.
Carbon dioxide removal (CDR) is critical to net-zero pathways achieving the Paris Agreement 1.5°C target, yet its effectiveness in reducing humid heat stress risks remain uncertain. Here we examine the hysteresis and reversibility of humid heat stress in China under CDR scenarios. Humid heat responds asymmetrically during warming and CO2 removal especially in eastern and southern China, producing a hysteretic and partially reversible trajectory. This results from unequal adjustments of temperature and relative humidity, which constrain heat-stress recovery even as global temperatures decline. Moist static energy analysis indicates suppressed vertical energy export over eastern China and enhanced transport of warm moisture from tropical oceans, sustaining humid heat during CO2 removal. Consequently, severe humid heat stress persists, with over 6.4 billion people affected, more than 66% of which is due to hysteresis. These findings highlight enduring heat-related risks and the urgent need for adaptation alongside mitigation.
How to cite: Ma, Q.: Committed and Irreversible Humid Heat Stress Risk in China Despite Carbon Dioxide Removal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2384, https://doi.org/10.5194/egusphere-egu26-2384, 2026.
Delhi is one of the most polluted megacities in the world. Since the ancient era, Delhi has been known for its rich heritage sites like the Red Fort, Humayun’s Tomb, and Qutub Minar, which are UNESCO World Heritage Sites. In this study, we investigate urban pollution-linked alterations at the heritage buildings (HBs) of Delhi, India, through a comparative characterization of deposited black crust (BC) and the underlying red sandstone (RS) collected from the exposed surfaces of the HBs. The BC on HBs can act as an integrative passive sampler of urban pollution, recording particulate matter, reactive gases (SOx/NOx), and associated heavy metal deposition. To achieve this objective, we applied a multi-analytical workflow combining X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR), carbonaceous analysis, and inductively coupled plasma mass spectrometry (ICP-MS) resolved phase assemblages, morphology, major-elemental composition profiles, and signatures of trace elements. The outcome suggests that the urban pollution sources, including vehicular emissions, road/construction/soil dust, industrial activity, and biomass burning, were identified as fingerprints of calcium (Ca) and sulfur (S) in the formed BC at the RS substrate. In this scenario, BC was enriched with Ca and S, which may cause sulfation phenomena to occur at the RS substrate as it contains low intrinsic Ca. Therefore, gypsum was identified as a dominant deteriorating agent, along with weddellite, bassanite, while carbon and heavy metals were also embedded in BC relative to the RS substrate. Additionally, in this work, a modeling approach is also utilized to assess the pollution dispersion impacts on the built HBs and linkage with BC deposition, which was employed using coupled WRF (Weather Research and Forecasting) and AERMOD (the American Meteorological Society/Environmental Protection Agency Regulatory Model) technique. Hence, considering these analytical and modelling approaches contributes to applying the site-specific conservation and preservation interventions in similar urban polluted environments.
How to cite: Kumar, G., Gurjar, B. R., Sharma, M., and Ojha, C. S. P.: Black crust as a passive sampler of urban pollution on the heritage buildings in Delhi, India: An analytical and modelling approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18929, https://doi.org/10.5194/egusphere-egu26-18929, 2026.
Western Disturbances (WD) are key atmospheric phenomena over northern India, Pakistan, and the Western Himalayas, especially during winter months (December to February). In recent years, increasing variability in these systems has been observed across all seasons, notably pre-monsoonal months (March to May), although thorough investigation remains underexplored. The study evaluates the shifting behaviour and structure in WDs across two climatologically distinct periods – 1950 to 1976 and 1977 to 2022, corresponding to the well-documented 1976-1977 climate shift. In this study, vorticity-based WD track data, coupled with the ERA5 reanalysis dataset, have been utilised to analyse the shift. Behavioural changes are quantified through frequency trends, maximum vorticity distribution and mean track, while structural evolution is examined through composite vertical profiles of key atmospheric variables. The study unravels notable increase in WD frequency during the pre-monsoon season in recent decades, accompanied by a westward shift in WD origins and longer track durations, thereby enhancing the potential for moisture transport. Furthermore, substantial strengthening of upper-level zonal winds, intensified mid-tropospheric convection, and atmospheric moisture availability have been observed through structural analysis. Such transformations indicate a transition of WD towards hybrid systems with enhanced convective features, thereby elevating the potential for extreme precipitation events during the pre-monsoon period. This improved understanding of the evolving WD dynamics is critical for hydrological planning, climate action, strategies and disaster preparedness in the highly vulnerable Himalayan and adjoining regions.
How to cite: Mitra, S., Sardana, D., and Agarwal, A.: Evolving Characteristics in Western Disturbances over the Hindu Kush Himalayas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-731, https://doi.org/10.5194/egusphere-egu26-731, 2026.
This work investigates a prominent dust event that occurred over Nainital, Uttarakhand, during 14-18 May 2025. Continuous micro pulse lidar (MPL) observations provided evidence of significant aerosol enhancement during the event. Distinct elevated aerosol layers were observed between 1 and 2.5 km above ground level, where backscatter coefficients increased to approximately 5×10⁻³ km⁻¹ sr⁻¹ and extinction values ranged between 0.8 and 1.2 km⁻¹. The persistence of these layers indicated long-range transport rather than local sources. Satellite-based aerosol optical depth (AOD) data from MODIS confirmed these enhancements, showing values doubling from 1.1-1.5 to above 2.2 during the peak dust intrusion. Meteorological observations documented elevated daytime temperatures between 20.1 ± 1.3 and 26.8 ± 1.6 °C and a marked reduction of relative humidity to below 50%, suppressing aerosol scavenging. Wind speeds intensified, with nocturnal maxima up to 5.6 ± 1.1 m/s and predominantly westerly to northwest directions (230°- 265°), favoring dust transport from western source regions. Synoptic-scale 850 mb wind analyses further corroborated persistent strong westerlies guiding mineral aerosols from the Thar Desert and Indo-Gangetic plains into the Himalayan foothills. The results highlight the importance of integrating lidar measurements with meteorological and reanalysis datasets to capture both vertical and horizontal characteristics of dust intrusions in mountainous regions.
How to cite: Singh, S. K., Singh, N., Rawat, V., Chauhan, M., and Debnath, S.: Variation of atmospheric properties during a dust episode over central Himalayan region using Lidar observation and auxiliary data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1290, https://doi.org/10.5194/egusphere-egu26-1290, 2026.
There is consensus that forcing due to Northern Hemispheric anthropogenic aerosols has played a significant role in the decline of South Asian monsoon precipitation since the mid-20th century. However, the future trajectory of regional aerosol emissions remains highly uncertain, particularly in light of potentially stricter air-quality regulations that could lead to reductions in aerosol loading across South and East Asia. Understanding how such changes may influence the near-term evolution of the monsoon is therefore critical. Here, we investigate the response of the South Asian summer monsoon to regional aerosol reductions using a suite of sensitivity experiments conducted with the IITM Earth System Model (IITM-ESMv2). Our simulations reveal a widespread intensification of monsoon precipitation over South and Southeast Asia following aerosol reductions. This response is driven by the combined effect of increasing greenhouse gas concentrations and declining absorbing aerosols over the subcontinent, which together enhance the land–sea thermal contrast. The strengthened thermal gradient promotes strengthened cross-equatorial low-level flow, leading to enhanced moisture transport and a sustained buildup of moisture across the monsoon region. The thermodynamic and dynamical changes favor widespread increases in precipitation. Our findings suggest that future air-pollution mitigation efforts across South and East Asia may play a critical role in shaping the near-future intensification of the monsoon, with important implications for regional hydroclimate over the coming decades.
How to cite: Dey Choudhury, A., Dhara, C., and Krishnan, R.: Rapid regional aerosol reductions drive near future intensification of the South Asian Monsoon , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7763, https://doi.org/10.5194/egusphere-egu26-7763, 2026.
The Amazon Basin (AB) is experiencing an intensification of hydroclimatic extremes, with droughts becoming more frequent, widespread, longer, and severe in the 21st-century. While precipitation deficits have historically been the primary driver of these events, the role of rising air temperatures and the consequent increase of atmospheric evaporative demand (AED) remains poorly quantified. Understanding the relative contributions of these factors is crucial for assessing AB resilience and potential tipping points under ongoing global warming. Here, we analyzed drought evolution across the AB over 45 years (1980–2024) using the Standardized Precipitation-Evapotranspiration Index (SPEI) derived from ERA5-Land reanalysis data. To isolate the contribution of atmospheric evaporative demand (CAED) to drought severity, we compared the standard SPEI with a modified SPEI version based on constant climatological AED.
Furthermore, we applied a rarity index to systematically rank drought events by intensity and spatial extent, enabling a standardized comparison of the exceptional 2023/24 event with historical benchmarks. Our analysis reveals that the 2023/24 drought (AD-23/24) was the most extreme event on record, affecting over 88% of the basin’s area and having a magnitude four times that of the average of the previous top-5 droughts. Notably, the recurrence of high-ranking drought years since 2020 underscores a persistence of extreme conditions in the 2020s. Crucially, the CAED analysis uncovers a distinct temporal regime shift occurring after 2005. While earlier droughts were primarily precipitation-driven, the post-2005 era is characterized by a predominantly evapotranspiration-driven regime, in which climate change-induced warming significantly amplifies drought intensity through increased AED. This intensification is further linked to sea surface temperature anomalies in the Tropical Indian, Tropical Pacific, and North Atlantic oceans. These findings demonstrate that the AB has entered a new hydroclimatic phase in which temperature-driven AED is overtaking precipitation deficits as the primary driver of exceptional drought events. This shift suggests that warming is likely exacerbating drought severity, posing unprecedented challenges for ecosystem stability and water security in the region.
How to cite: Albuquerque, R., M. dos Santos, D., F. V. V. Miranda, V., F. Peres, L., M. Trigo, R., M. B. Nunes, A., L. R. Liberato, M., M. Gouveia, C., and Libonati, R.: Temperature-driven shift intensifies 21st-century Amazon droughts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-557, https://doi.org/10.5194/egusphere-egu26-557, 2026.
