Preprints
Filtering by Subject: Meteorology
Evaluating forecast baselines and network representativeness for daily PM2.5 in the Kathmandu Valley, Nepal
Published: 2026-09-03
Subjects: Atmospheric Sciences, Climate, Environmental Indicators and Impact Assessment, Environmental Monitoring, Meteorology
An order-fair attribution of daily PM2.5 predictability in the Kathmandu Valley assigns 72% of achievable error reduction to persistence, 19% to meteorology and 9% to day-of-year climatology, with the latter two largely redundant; no fitted model, including random forests and gradient boosting tuned by nested chronological cross-validation, outperforms an unfitted lag-1 forecast (11.22 µg m-3). [...]
The Super El Niño–Polar Vortex Paradox QBO Modulation and a Testable Hypothesis for Winter 2026/27
Published: 2026-08-30
Subjects: Atmospheric Sciences, Climate, Earth Sciences, Meteorology, Oceanography and Atmospheric Sciences and Meteorology, Other Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
The absence of major midwinter sudden stratospheric warmings (SSWs) during the three strongest El Niño winters in the instrumental record—1982/83, 1997/98, and 2015/16—poses an open question at the high-amplitude end of the canonical ENSO–stratosphere pathway. Motivated by the exceptionally strong El Niño developing in 2026, this study re-examines that relationship using publicly available ONI, [...]
Boxology: the isobar–thickness box count as an exact advection integral, and its rendering
Published: 2026-08-24
Subjects: Atmospheric Sciences, Meteorology, Oceanography and Atmospheric Sciences and Meteorology
“Boxology” is the hand-analysis practice of reading thermal advection from the angle at which mean-sea-level-pressure isobars cross 1000–500 hPa thickness contours: steep crossings cut the chart into small quadrilaterals and imply strong advection, while parallel families imply none. This note shows the practice is an identity rather than a rule of thumb, and implements it as a rendered chart [...]
Source-composition sensitivity in historical marine wind observations: a CLIWOC case study, 1750--1855
Published: 2026-08-15
Subjects: Climate, Earth Sciences, Environmental Monitoring, Environmental Sciences, Environmental Studies, Library and Information Science, Meteorology, Oceanography and Atmospheric Sciences and Meteorology, Other Applied Mathematics, Other Computer Sciences
Recovering Climate’s History with Artificial Intelligence used the CLIWOC ship-logbook database to argue that sailors’ wind observations reveal a previously undetected shift in global atmospheric circulation between the late eighteenth and early nineteenth centuries. We reproduce the article's principal annual aggregate from CLIWOC release 2.1 and find that this unstandardized, record-weighted [...]
Large-Scale Modulation of Mesoscale Convective System Propagation and Diurnal Rainfall over the Western Maritime Continent
Published: 2026-08-14
Subjects: Atmospheric Sciences, Climate, Meteorology
The western Maritime Continent exhibits a pronounced regional diurnal cycle of rainfall, to which the propagating Mesoscale Convective Systems (MCSs) make a significant contribution. Using an automated tracking algorithm based on brightness temperature, we quantify the contribution of MCSs to the regional diurnal cycle over Singapore and the South China Sea. MCSs affecting the Singapore sector [...]
Hydroclimatic Regime Shifts and Compound Heat–Dry Events in Rajshahi Division, Bangladesh: Integrating Thermal Gradients, Change-Point Detection, and Heat-Driven Dryness Dynamics (1992–2022)
Published: 2026-08-07
Subjects: Climate, Environmental Indicators and Impact Assessment, Environmental Monitoring, Hydrology, Meteorology, Other Earth Sciences, Other Oceanography and Atmospheric Sciences and Meteorology, Statistical Models
Hydroclimatic variability and compound climate extremes are increasingly affecting monsoon-dominated regions of South Asia, particularly drought-prone northwestern Bangladesh. However, integrated assessments of thermal dynamics, atmospheric moisture, land–atmosphere coupling, and compound heat–dry events remain limited in the regional context. Therefore, this study investigated long-term [...]
Stress-Conditioned Lightweight Flash-Drought Detection in the US Corn Belt Using MODIS NDVI and ERA5-Land
Published: 2026-07-29
Subjects: Hydrology, Meteorology
Flash-drought monitoring by classical indices averages predictive signal across calm and stressed years, blunting the signal exactly where it matters. We show empirically that the coupling between precipitation, soil moisture, vapor pressure deficit (VPD), and NDVI is stress-conditional: the hydrological pathway is visible when vegetation is already under stress (Spearman rho of about 0.18 for [...]
A multi-indicator framework for assessing the likelihood of ENSO impacts across southern Africa
Published: 2026-07-02
Subjects: Atmospheric Sciences, Climate, Meteorology, Oceanography and Atmospheric Sciences and Meteorology
The El Niño-Southern Oscillation (ENSO) is the dominant source of seasonal predictability for southern Africa, yet operational guidance rarely conveys which agriculturally relevant variables it can skillfully predict, or where ENSO impacts are most likely. We present an operational analysis framework that converts an ENSO state, classified by phase and strength, into gridded, analogue-composite [...]
A State-dependent Error Covariance Model of Surface Atmospheric Forcings over the Arctic Sea Ice
Published: 2026-07-01
Subjects: Atmospheric Sciences, Meteorology, Oceanography, Other Oceanography and Atmospheric Sciences and Meteorology
This paper presents a state-dependent error covariance model of surface atmospheric forcings over Arctic sea ice for constraining atmospheric influences on short-range sea ice forecast errors. Atmospheric influences are argued to be a dominant source of sea ice forecast errors at shorter lead times and thus need to be properly accounted for in generating ensemble sea ice forecasts relevant for [...]
Resolving microscale near surface temperature variability during a heatwave using a dense sensor network
Published: 2026-06-29
Subjects: Climate, Environmental Monitoring, Environmental Sciences, Meteorology, Oceanography and Atmospheric Sciences and Meteorology
High-resolution measurements of near-surface temperature are essential for understanding environmental responses to extreme weather events, yet are rarely available from dense, regularly spaced in situ measurement grids. Here, we analyse temperature measurements derived from a dense network of over 3,000 nodal seismometers deployed across a 6 km² area in North Yorkshire, UK, during the July 2022 [...]
Measurement and Tracking of Blowing and Falling Snow Particles Using an Automotive 1550 nm LiDAR
Published: 2026-06-26
Subjects: Atmospheric Sciences, Fresh Water Studies, Glaciology, Hydrology, Meteorology
The prevalence and affordability of fast-scanning commercially available LiDARs are increasing due to the rapid expansion of the autonomous vehicle industry. These LiDAR units can provide >1 Hz measurements of millions of laser reflections at ranges of hundreds of meters with high precision. In this study we investigate the often overlooked 1550 nm wavelength LiDAR for measurements of airborne [...]
Dress Rehearsal: 2023 El Niño Anticipatory Action Somalia, in the Shadow of 1997
Published: 2026-06-10
Subjects: Atmospheric Sciences, Climate, Earth Sciences, Environmental Studies, Human Geography, Meteorology, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Other Geography, Physical and Environmental Geography
In 2023 Somalia saw the largest-ever scale of anticipatory action (AA) linked to a seasonal forecast. $24m was spent on preparedness and early response, based on forecasted flooding driven by El Niño and a positiveIn 2023 Somalia saw the largest-ever scale of anticipatory action (AA) linked to a seasonal forecast. $24m was spent on preparedness and early response, based on forecasted flooding [...]
ENSO Modulation of the Amazonian Low-Level Jet: More Moisture, Less Rain, and the Role of Land Surface Reception
Published: 2026-05-30
Subjects: Climate, Hydrology, Meteorology
The Amazonian Low-Level Jet (ALLJ) carries moisture from the tropical Atlantic coast into the basin interior, sustaining wet-season convection. Here we analyze 45 years of ERA5 reanalysis (1979–2023), 44 years of CHIRPS precipitation (1981–2024), GRACE terrestrial water storage (2002–2025), and SMAP root-zone soil moisture (2015–2024) to determine how ENSO modulates this transport pathway and its [...]
Analysis of sub-regional climates in the European Alps based on the EEAR-Clim observational dataset
Published: 2026-05-22
Subjects: Atmospheric Sciences, Climate, Meteorology
The European Alps exhibit a complex geomorphology and undergo the influences of different climate regimes, resulting in high spatial variability of climatic variables and their changes. To provide a detailed analysis of climate regions and climatic changes occurring at a sub-regional scale during the 1961-2020 period, we exploited an updated regionalization of the European Alps that benefits from [...]
First Observational Evidence That Biological Giant CCN Control Urban Rainfall Character: A Natural Experiment from Islamabad's Paper Mulberry Removal
Published: 2026-05-22
Subjects: Atmospheric Sciences, Earth Sciences, Hydrology, Meteorology
Modeling studies predict that biological aerosol, specifically pollen acting as giant cloud condensation nuclei (GCCN), can modify precipitation character by initiating collision-coalescence and warm rain in shallow cloud (Steiner et al., 2015; Wozniak et al., 2018; Paukert et al., 2025). No observational study has tested this prediction. We exploit a natural experiment, the removal of ~29,000 [...]