Extreme dust storms evolving on sub-hourly timescales challenge conventional air-quality monitoring systems, as particulate matter (PM) sensors require sufficient aerosol accumulation before threshold exceedance is detected. The extent to which atmospheric potential gradient (PG) measurements can provide earlier indicators during rapidly evolving frontal dust intrusions remains insufficiently quantified. We evaluate PG detection latency during an unusually intense haboob-like dust outbreak that impacted Ica, Peru (14.07 degrees S, 75.73 degrees W), on 31 July 2025. Two ground-based stations separated by 13.6 km recorded PG and PM2.5 at minute-scale resolution. Frontal arrival times were independently constrained using GOES-19 ABI RGB imagery (10-min cadence) and 1-min ground-based cameras. Electrical detection was defined using objective seasonal baseline-departure criteria with multi-threshold persistence constraints. PG exhibited an initial statistically significant deviation (2 sigma) at 12:25 LT, more than 100 min prior to local particulate enhancement. A conservative rapid-growth onset (5 sigma) occurred at 13:48 LT, preceding both the PM2.5 increase at the urban station by 24 min and the camera-defined frontal impact by approximately 23 min. The event displayed a pronounced bipolar electrical structure, with PG amplification immediately before particulate onset followed by a sub-minute polarity reversal during frontal passage. These results indicate that high-resolution PG monitoring captures organized boundary-layer electrification associated with density-current dust fronts and may provide earlier detection than mass-based aerosol sensors in this extreme case. However, operational skill, false-alarm rates, and generality require evaluation using longer multi-event records.

The ground-level potential gradient (PG) or the atmospheric electric field, the air-Earth current density as well as the main Global Electric Circuit (GEC) parameters such as the ionospheric potential, global resistance and the total current, can be obtained from the EGATEC engineering model of the GEC (Odzimek et al. 2010) at the resolution of 3 hours. The model input data based on satellite cloud and lightning observation datasets from the period 1998-2006 for evaluating the activity of the GEC cloud generators, and the summer/winter and low/high solar activity conductivity model of Tinsley and Zhou (2006) allow calculating the GEC parameters in the summers and winters of the period. In this work we compare the modelling results to observations from the Stanislaw Kalinowski Geophysical Observatory in Świder, Poland (52°07' N, 21°14' E) of the ground-level potential gradient and conduction current density calculated from the newly digitised PG and positive conductivity data from 1965-2005. We also look for connections in the time variations of the model meteorological input and atmospheric electricity observational data. The work is supported by the Polish National Science Centre grant no 2021/41/B/ST10/04448.

The atmospheric potential gradient (PG) has been measured at ground level with a radioactive collector method in the Stanisław Kalinowski Geophysical Observatory in Świder (52.12° N, 21.23° E), Poland, for several decades. The long-term Świder measurements analysed previously revealed rather typical behaviour in the diurnal and seasonal variations of the PG of a land station, assumed to be controlled by pollution. Observations of the PG at such a station usually show a maximum at local winter months which are affected by anthropogenic pollution the most. A recently digitised series of 1965–2005 hourly data has been newly analysed to describe the Świder PG variations in greater detail, also in connection with an analysis of simultaneous measurements of condensation nuclei (CN) measured at 06:00, 12:00, and 18:00 UT. An attempt is made to calculate the diurnal and seasonal variations at the CN number concentrations below 10 000 cm−3. There is a decrease in the PG in the diurnal variation by up to 11 % in the winter and no significant change in the summer. The reduction in the annual variation is 11 %–26 %, with the biggest difference in February. In the summer months this difference is negligible. Despite the efforts to minimise the aerosol effect on the PG in the measured CN range, the character of the seasonal and annual variation of PG preserves its character with a maximum in the Northern Hemisphere winter and the minimum in the summer as observed at other mid-latitude stations in this part of the globe. When investigating the effect of reduced CN concentrations on the measured positive conductivity (PC), an increase of 7 %–17 % is found. In addition to an additional mechanism affecting the PG in the summer, there may be another aerosol fraction outside of the range of the condensation nuclei like dust, which affects the conductivity and indirectly the annual variation of the PG.

Lowest events in Lake Titicaca’s water level (LTWL) significantly impact local ecosystems and the drinking water supply in Peru and Bolivia. However, the hydroclimatic mechanisms driving extreme lake-level lowstands remain poorly understood. To investigate these low lake-level events, we analyzed detrended monthly LTWL anomalies, sea surface temperature (SST) datasets covering the period 1921–2023. ERA5 reanalysis covers the period 1940–2023. A multiple linear regression model was developed to compute detrended LTWL anomalies, excluding multidecadal and residual components. Interdecadal Pacific Oscillation (IPO) and Pacific Decadal Oscillation (PDO) indices were also analyzed for the same period. Results indicate that 25% of all LTWL minima events have a short duration of <5 months, while the remaining 75% of all events have a long duration of more than 9 months, respectively. All long-lived LTWL minima events are associated with reduced moisture flow from the Amazon basin toward Lake Titicaca, but the large-scale forcing varies with the phase change of the decadal component in the 11–15 years band of the PDO (PDO11–15 years). Under warm PDO11–15 years phases, LTWL minima are driven by an enhanced South American low-level jet (SALLJ) caused by warm SST anomalies over the eastern Pacific Ocean. Warm SST anomalies over tropical North Atlantic and central Pacific cold events, which reinforce the cold PDO11–15 years phases, driving long-lived LTWL minima through the reduction of SALLJ. Conversely, long-lived LTWL minima events under neutral PDO11–15 years phases are caused by westerly flow anomalies confined to the Peruvian Altiplano. Therefore, PDO and IPO do not drive long-lived LTWL minima events because their relationship does not remain consistent over time. In conclusion, long-lived LTWL minima events exhibit a regional nature and are not driven by the PDO or IPO, as LTWL shows no consistent relationship with these decadal SST modes over time.

The water disponibility of Lake Titicaca is important for local ecosystems, domestic water, industry, fishing, agriculture, and tourism in Peru and Bolivia. However, the water level variability in Lake Titicaca (LTWL) still needs to be understood. The fluctuations of LTWL during the 1921–2018 period are investigated using continuous wavelet techniques on high- and low-pass filters of monthly time series, ERA-20C reanalysis, sea surface temperature (SST), and water level. We also built multiple linear regression (MLR) models based on SST indices to identify the main drivers of the LTWL variability. LTWL features annual (12 months), biennial (22–28 months), interannual (80–108 months), decadal (12.75–14.06 years), interdecadal (24.83–26.50 years), and multidecadal (30–65 years) signals. The high- and low-frequency components of the LTWL are triggered by the humidity transport from the lowland toward the Lake Titicaca basin, although different forcings could cause it. The biennial band is associated with SST anomalies over the southeastern tropical Atlantic Ocean that strengthen the Bolivian High-Nordeste Low system. The interannual band is associated with the southern South Atlantic SST anomalies, which modulate the position of the Bolivian High. According to the MLR models, the decadal and interdecadal components of the LTWL can be explained by the linear combination of the decadal and interdecadal variability of the Pacific and Atlantic SST anomalies (r > 0.83, p < 0.05). In contrast, the multidecadal component of the LTWL is driven by the multidecadal component of the North Atlantic SST anomalies (AMO) and the southern South Atlantic SST anomalies. Moreover, the monthly time series of LTWL exhibits four breakpoints. The signs of the first four trends follow the change of phases of the multidecadal component of LTWL, while the fifth trend is zero attributable to the diminished amplitude of the interdecadal component of LTWL.

The northwestern Peruvian Amazon (NWPA) basin (78.4–75.8° W, 7.9–5.4° S) is an important region for coffee and rice production in Peru. Currently, no prediction models are available for estimating rainfall in advance during the wet season (January–February–March, JFM). Hence, we developed multiple linear regression (MLR) models using predictors derived from sea surface temperature (SST) indices of the Pacific, Atlantic, and Indian Oceans, including central El Niño (C), eastern El Niño (E), tropical South Atlantic (tSATL), tropical North Atlantic (tNATL), extratropical North Atlantic (eNATL), and Indian Ocean basin-wide with E and C removed (IOBW*) indices. Additionally, we utilized large-scale convection indices, namely, the eastern Pacific intertropical convergence zone (ITCZe) and South American Monsoon System (SAMSi) indices, for the 1981–2018 period. Rainfall in the lowland NWPA exhibits a bimodal annual cycle, whereas rainfall in the highland NWPA exhibits a unimodal annual cycle. The MLR model can be used to accurately capture the interannual variability during the wet season in the highland NWPA by utilizing predictors derived from the C and SAMSi indices. In contrast, regarding rainfall in the lowland NWPA, the Pacific SST variability, SAMS and tropical North Atlantic index were relevant. For long lead times, the MLR model provided reliable forecasts of JFM rainfall anomalies in the highlands (R3, approximately 2700 m asl) as these regions are governed by Pacific variability. However, the MLR model exhibited limitations in accurately estimating the wettest JFM season in the highlands due to the absence of a predictor for the amplified effect of the Madden–Julian Oscillation on rainfall.

AbstractThe suppression of high‐energy cosmic rays, known as Forbush decreases (FDs), represents a promising factor in influencing the global electric circuit (GEC) system. Researchers have delved into these effects by examining variations, often disruptive, of the potential gradient (PG) in ground‐based measurements taken in fair weather regions. In this paper, we aim to investigate deviations observed in the diurnal curve of the PG, as compared to the mean values derived from fair weather conditions, during both mild and strong Forbush decreases. Unlike the traditional classification of FDs, which are based on ground level neutron monitor data, we classify FDs using measurements of the Alpha Magnetic Spectrometer (AMS‐02) on the International Space Station. To conduct our analysis, we employ the superposed epoch method, focusing on PGs collected between January 2010 and December 2019 at a specific station situated at a low latitude and high altitude: the Complejo Astronómico El Leoncito (CASLEO) in Argentina (31.78°S, 2,550 m above sea level). Our findings reveal that for events associated with FDs having flux amplitude (A) decrease ≤10%, no significant change in the PG is observed. However, for FDs with A > 10%, a clear increase in the PG is seen. For these A > 10% events, we also find a good correlation between the variation of Dst and Kp indices and the variation of PG.

Measurements of the potential gradient (PG) under fair weather conditions at new locations are crucial for monitoring the global electric circuit. In this study, we analyzed the variations in PG recorded in Ica city, Peru, during the period from March 2018 to December 2022. Our analysis involved a detailed comparison of PG with various meteorological parameters such as rainfall, wind speed and direction, dust storms, dust devils and fog to establish the characteristic PG curve under fair weather conditions (referred to as the standard curve). We identified a significant threshold of 3.5 m/s for strong winds, which helps prevent the influence of sea breeze and dust lifting on PG. Our results showed the impact of 'Paracas' dust storms on PG, which aligns with patterns observed in other arid regions worldwide. Subsequently, we calculated monthly, seasonal, and annual averages of the standard curve which showed a response likely associated with local convective processes on the PG diurnal variation. Furthermore, the seasonal variation of PG reveals higher values during June, July, and August compared to December, January, and February. These differences are attributed to seasonal changes in aerosol concentrations, potentially influenced by biomass-burning activities in Peru. Additionally, we performed a wavelet transform analysis of PG hourly values. We found the periodicities of 1 day, similar to 188 days, and 360 days which are related to the diurnal, semiannual and annual periods. During the months between January and March 2018 was found an intense period of similar to 45-day likely associated with one of the strongest Madden-Julian Oscillation events. Through this comprehensive investigation, we deepen our understanding of the intricate relationships among meteorological conditions, sea breeze, dust storms, and the PG in arid regions like Ica.

Abstract. The ground-level atmospheric potential gradient (PG) has been measured with a radioactive collector method in Stanisław Kalinowski Geophysical Observatory in Świder (52.12° N, 21.23° E), Poland, for several decades. Long-term measurements analysed previously revealed rather typical behaviour in the diurnal and seasonal variations of the PG of a land station controlled by pollution. Observation of the potential gradient at such a station usually show a maximum at local winter months which are mostly affected by anthropogenic pollution. The 1965–2005 series has been newly analysed to describe the Świder PG variations in greater detail, also in connection with an analysis of simultaneous measurements of condensation nuclei measured at 6, 12, 18 UT. An attempt is made to calculate the diurnal and seasonal variations at condensation nuclei number concentrations below 10000 cm-3. There is a decrease of the PG in the diurnal variation by up to 11 % in the winter, and no significant change in the summer. The reduction in the annual variation is 11–26 % with the biggest difference in February. In the summer months, this difference is negligible. Such differences can be predicted with a simplified model of electrical conductivity including the aerosol composition of water soluble and soot particles, the main components of continental aerosol. With this model we obtained changes in the conductivity and the PG in up to 30 % in the winter, and 6 % in the summer. Despite the efforts to minimise the aerosol effect on the PG, the character of the PG seasonal and annual variation preserves its character with a maximum in the Northern Hemisphere winter and the minimum in the summer.

&lt;p&gt;The ground-level atmospheric potential gradient (PG) has been measured with a radioactive collector method in Stanislaw Kalinowski Geophysical Observatory in &amp;#346;wider, Poland, for several decades. The observations have been previously analysed by Kubicki et al. (ICAE 2003, ICAE 2007) revealing rather typical behaviour in the diurnal and seasonal variations of the PG of a land station controlled by pollution. Electric field measurements at such station usually show a maximum at local winter months which are mostly affected by anthropogenic pollution. The whole series has been newly analysed to describe the &amp;#346;wider PG variations in greater detail, also in connection with an analysis of simultaneous measurements of cloud condensation nuclei. Fair-weather potential gradient course is calculated in different time scales (annual, seasonal and diurnal) with taking into account local meteorological and air pollution conditions. An attempt is made to calculate the diurnal and seasonal variations at very low cloud condensation nuclei counts. The work is supported by Poland National Science Centre grant no 2021/41/B/ST10/04448.&lt;/p&gt;

&lt;p&gt;Analysis of the variation of the potential gradient (PG) at ground level is important to monitor the global electric circuit and the different solar and geophysical phenomena affecting it. However, this is challenging since several factors (e.g., meteorological) produce perturbations in the potential gradient. For this reason, timeseries and spectral analysis of PG at several stations are required. In this work, for the first time we performe the spectral analysis of the potential gradient recorded at several sites located at Vostok, Concordia, Halley and Casleo (South Hemisphere), and Sodankyla and Reading (North Hemisphere). In order to find the main periodicities and how the amplitude of those periods change as a function of time we use the Lomb-Scargle Periodogram and the Wavelet Transform, respectively. For all PG sites the periodicities of 0.5, 1, ~180 and 365-day were found. It was also found evidence of the ~27- and ~45-day periods. Further analysis using the cross-wavelet transform for PG versus cosmic rays, PG versus Madden-Julian Oscillation index, and PG versus meteorological parameters, shows that the 27- and 45-day periods are likely related to the solar rotation and Madden- Julian Oscillation, respectively. Moreover, for the 27-day period we found that the relationship is stronger during the occurrences of co-rotating interaction regions.&lt;/p&gt;

Analysis of the variation of the potential gradient (PG) at ground level is important to monitor the global electric circuit and the different solar and geophysical phenomena affecting it. However, this is challenging since several local factors (e.g., meteorological) produce perturbations in the potential gradient. Time series and spectral analysis of PG at several stations can help to minimise local effects so that global effects may be more clearly observed. In this work, for the first time we performed spectral analysis of the potential gradient recorded at several sites located at Vostok, Concordia, Halley and Casleo (Southern Hemisphere), and Sodankyla and Reading (Northern Hemisphere). In order to find the main periodicities and how the amplitude of those periods change as a function of time we use the Lomb-Scargle periodogram and the wavelet transform, respectively. For all PG sites we found periodicities of 0.5-, 1-, -180- and 365-day. Our results show that the 0.5-day (1-day) periodicity is more prominent during the months of June-July-August (December-January-February). Evidence of -27- and - 45-day periods was also observed at multiple sites. Further analysis using the cross-wavelet transform for PG versus cosmic rays, PG versus Madden-Julian Oscillation index, and PG versus meteorological parameters, show clues that the 27- and 45-day periods are likely related to the solar rotation and MaddenJulian Oscillation, respectively. Furthermore, our results show that during the passages of co-rotating interaction regions, the 27-day period for PG vs cosmic rays XWT is stronger than for the other XWT analysis.

The decadal variability in summer precipitation over the Central Andes (10°–30°S) is investigated from 1921 to 2010 using low‐pass filtered time series of the central and eastern El Niño–Southern Oscillation (ENSO) Pacific (C and E) indices, the South Pacific Convergence Zone (SPCZ) index, the Atlantic SST indices, Atlantic Multidecadal Oscillation (AMO) index, North Atlantic Oscillation (NAO) index, and ERA‐20C reanalysis. Additionally, an empirical‐statistical downscaling (ESD) model was built. A rotated empirical orthogonal function (REOF) analysis shows that the first leading mode of precipitation (RPC1) represents 38.2% of the total decadal variance. RPC2, RCP3, and RPC4 represent 18.8, 12.8, and 9.7% of the total decadal variance, respectively. Furthermore, RPC1 features highest loadings over most of the region. RPC2 features a dipole of highest loadings over the southernmost Bolivian Altiplano and lowest loadings over the northwestern Argentinian Andes. Conversely, RPC3 presents highest loadings over the eastern‐central Bolivian Altiplano and northwestern Argentinian Andes. RPC4 features highest loadings over the southern Bolivian Andes. RPC1 and RPC3 wet summers are associated with moisture transport from the Amazon basin, but RPC1 features the strengthening upper‐level Bolivian high‐Nordeste low system over South America. Conversely, RPC2 and RPC4 wet summers are associated with local processes induced by southward displacement of the South Atlantic Convergence Zone and warm sea surface temperature ( SST) anomalies over the Indian Ocean, respectively. According to the ESD model, the decadal variability in the central and eastern Pacific (CP and EP) and Atlantic Ocean reproduces the decadal component of the DJF precipitation over most of the Central Andes.

High‐energetic charged particles, such as solar protons, and phenomena such as Forbush decreases are eligible candidates to affect the global electric circuit. These effects have been studied by analyzing disturbances of the potential gradient in ground‐based measurements in fair weather regions. In this paper, we investigate deviations in the potential gradient diurnal curve, during solar proton events, and Forbush decreases, from the mean values obtained in fair weather conditions. In each situation, we select only events which are not accompanied or followed by the other. Using the superposed epoch analysis, in order to enhance the visualization of small effects, we study the potential gradient data recorded between January 2010 and December 2019 at two stations located at low and middle‐latitudes, and at two different altitudes: the Complejo Astronómico El Leoncito (CASLEO), Argentina: 31.78°S, 2550 m a.s.l., and the Geophysical Observatory in Świder (SWIDER), Poland: 52.12°N, 100 m a.s.l., respectively. For intense solar proton events (>100 MeV) we found a statistically significant increase of the potential gradient after solar proton events recorded at CASLEO and no such deviation in the potential gradient recorded at SWIDER. For Forbush decrease events (greater than 4%), no significant deviation of the potential gradient after the start of the event was found in both stations, however for very intense Forbush decreases (>7%) we found an increase of the potential gradient recorded at CASLEO.

The description and technical characteristics of the gamma-spectrometer installation for the detection of cosmic rays, as designed at the Dolgoprudny scientific station of the Lebedev Physical Institute in cooperation with the Mackenzie University (Sao Paulo, Brazil), are presented. This installation has operated continuously in the CASLEO astronomical complex since 2015. The detector modules of the setup are based on the NaJ (Tl) scintillator, which is 76.2 mm × 76.2 mm high, a Hamamatsu R1307 photomultiplier tube, a high voltage power supply, and a preamplifier. The technique of the experimental calibration of the spectrometer is also presented.

In recent years the analysis of the variability of the natural gamma radiation and its relationship with high atmospheric electric fields in disturbed weather, e.g., thunderstorms, have been important, as well as the relationship between these parameters in fair weather conditions. In this paper we analyze the diurnal variation of the atmospheric electric field and natural gamma radiation, in fair and disturbed weather conditions, recorded in the Argentinian Andes mountain (2552 masl) between April 2018 and February 2019. In fair weather conditions, it was found a higher linear correlation coefficient (R) between the atmospheric electric field diurnal curve and the universal Carnegie curve (R=0.93), and a high negative correlation between the atmospheric electric field and natural gamma radiation diurnal curve (R=-0.9). On the other hand, in disturbed weather conditions, we reported thirteen events where it was found intense natural gamma radiation enhancements associated with high atmospheric electric field variability. A maximum of 35 % excess in the natural gamma radiation was detected, which was associated with thunderstorms and rain precipitation. It was observed a high correlation between the excesses of the gamma natural radiation enhancement with the atmospheric electric field values (R=0.80) and with the rain precipitation rate (R=0.59).

Previous research has shown that the study of the global electrical circuit can be relevant to climate change studies, and this can be done through measurements of the potential gradient near the surface in fair weather conditions. However, potential gradient measurements can be highly variable due to different local effects (e.g., pollution, convective processes). In order to try to minimize these effects, potential gradient measurements can be performed at remote locations where anthropogenic influences are small. In this work we present potential gradient measurements from five stations at high latitudes in the Southern and Northern Hemisphere. This is the first description of new datasets from Halley, Antarctica; and Sodankyla, Finland. The effect of the polar cap ionospheric potential can be significant at some polar stations and detailed analysis performed here demonstrates a negligible effect on the surface potential gradient at Halley and Sodankyla. New criteria for determination of fair weather conditions at snow covered sites is also reported, demonstrating that wind speeds as low as 3 m/s can loft snow particles, and that the fetch of the measurement site is an important factor in determining this threshold wind speed. Daily and seasonal analysis of the potential gradient in fair weather conditions shows great agreement with the “universal” Carnegie curve of the global electric circuit, particularly at Halley. This demonstrates that high latitude sites, at which the magnetic and solar influences can be present, can also provide globally representative measurement sites for study of the global electric circuit.

Energetic particles are potential candidates to affect the Global Electrical Circuit. This is supported by theoretical models that propose that these events can modify the conductivity profile above thunderstorms. If very strong, they can change the conductivity at low altitudes. We can study these effects through potential gradient measurements in fair weather regions. In this study, we investigate the potential gradient daily curve departures from the standard curve (mean curve in fair weather conditions) during very intense solar proton events and Forbush decrease. The superposed epoch analysis was utilized in order to enhance weak effects. Potential gradient data corresponds to the period between January 2008 and July 2019, and were recorded at two different stations located in different latitudes: CASLEO (Argentina, South Hemisphere) and Swider (Poland, North Hemisphere).

Continuous global monitoring of lightning has been important in recent years to study a possible relationship with global warming. Consequently, several networks to detect lightning have been installed at various spatial scales (regional and global). One of these networks is the World Wide Lightning Location Network (WWLLN), which has been monitoring lightning since 2003. It is also important to monitor the occurrence of thunderstorms and this can be roughly archived by detecting lightning clusters. In this work, we propose a lightning grouping methodology, in order to estimate the global number of thunderstorms. Our methodology consists of grouping the WWLLN data into a density matrix with a spatial resolution of 0.1° x 0.1° (1 pixel) and a temporal resolution of one hour, then the algorithm identifies the pixels with lightning and groups these pixels with the adjacent pixels to form the thunderstorm. Then, we calculate monthly, seasonal and annual averaged daily curves of the number of thunderstorms. The data set under study includes years 2012 and 2013. Our methodology is validated by calculating the linear correlation coefficient (R) between the annual daily thunderstorm curve and the "universal" Carnegie curve (R = 0.97) and with the Vostok electric field measurements (R = 0.98). Additionally, we found higher correlation in September–October–November months (R = 0.98) compared with June–July–August months (R = 0.75) for Carnegie and for Vostok station (R=0.99 and R=0.88, respectively).